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Yamaha Multichannel Monitoring Booklet

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1. Rec ITU R BS 775 1 Multi channel Stereophonic Sound System With and Without Accompanying Picture was produced by the radio communication sector of the ITU under the impetus of the advent of HDTV 1992 1994 For this reason most broadcast stations take Rec ITU R BS 775 1 as the standard for their playback environment This speaker placement is also acknowledged as the standard one for a wide range of playback environments including music production If you want to apply a uniform standard to your production environment or if you do not have special intentions regarding the playback sound field it is desirable to adopt the ITU R placement for your playback environment 3 1 1 ITU R speaker placement Fig 19 Rec ITU R BS 775 1 in case of using one loudspeaker for each LS and RS The main features of the ITU R placement are as follows Note In addition to a layout placing one surround speaker each for LS and RS Rec ITU R BS 755 1 also describes layouts that place multiple speakers However in this document we will discuss only the first of these 1 L R angle of separation 60 This emphasizes compatibility with conventional audio listening environments an equilateral triangle consisting of L lt gt R lt gt listener 2 Surround speakers LS RS placement angle 110 10 with C located at 0 in the plane 32 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corp
2. 3dB 0 500 6dB 0 000 codB Ra Default Atti Att2 0 707 3dB Fixed DTS Atti Att2 0 707 3dB Fig 14 Flow of a Down mixing DVD Video Dolby DIGITAL DTS Lo Ro downmix 5 1ch Master 2ch Down mix L oO O O O Lt L 0 707 xX C 0 707 X LS RS O Rt R 0 707 XC 0 707 x LS RS Fig 15 Flow of a Down mixing DVD Video Dolby DIGITAL DTS Lt Rt downmix In DVD Video Dolby Digital DTS the above two types of down mixing Lo Ro down mixing Fig 14 Lt Rt down mixing Fig 15 are possible and the DVD player and AV receiver must have these down mixing circuits One advantage of Lo Ro down mixing Fig 14 is that the production engineer is able to select the attenuation values The playback device performs down mixing according to the attenuation values recorded as meta data on the DVD however in the case of DTS Attl Att2 3 dB fixed On the other hand Lt Rt down mixing Fig 15 allows Dolby Pro Logic Dolby ProLogic I x or DTS NEO 6 decoding to play back surround such as 3 1 5 1 6 1 or 7 1 from the two channels Lt Rt In the Lt Rt down mix the surround signals LS RS are mixed in reverse phase with the L channel signal This means that if the surround portion and L portion contain a similar signal the signal may disappear when down mixed To prevent this 5 1 productions in DVD Video often apply a 90 degree phase shift to the LS RS channels when encoding 29 74 Multichannel Monitoring Tutoria
3. 85 dBC The sound pressure level displayed by the sound level meter is this all pass level 85 dBC and an RTA Real Time Analyzer is required in order to determine the band level approximately 71 dB 1 3 octave of each frequency 63 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation at Seas AIl pass level 85dBC a lL uss octave band level Te 1 3 octave band center frequency HA Fig 50 All pass level and band levels Please note that it is NOT the right way to determine the playback level of the speakers only from the all pass level Fig 51 is an example showing the response of two types of pink noise whose all pass level is 85 dBC The black shows the response of 20 Hz 20 kHz broad band pink noise and the grey shows the response of 80 Hz 8 kHz narrow band pink noise Wide band Narrow band All pass level 85dBC QOAIl pass level 85dBC T 1 3 octave band level approx 71dB T 1 3 octave band level approx 72dB SPL dB Fig 51 Difference of the band level between the wide band pink nose and the narrow band pink noise 800 1 25k 2 1k j 125k 1 3 octave band center frequency Hz When the all pass level is adjusted to the identical 85 dBC the narrow band pink noise has a higher band level than the broad band pink noise 71dB gt 72dB This means that if the playb
4. A all speakers are placed at the same height Examples B and C place the surround speakers higher than the front speakers B shows the surround speakers placed closer to the listening point as seen in the horizontal plane in order to make the monitoring distance identical to the other speakers C shows the surround speakers placed at the same distance as the other speakers in the horizontal plane resulting in a longer monitoring distance for the surround speakers Best A Good Not Bad Fig 34 Heights of the loudspeakers and time alignment In the case of A O playback response O surround sound field Since all speakers are placed at equal distances in the horizontal plane the surround playback sound field is a perfect circle which is ideal Since the actual distance from each speaker to the listening point is identical there is no danger that comb filtering or the Haas effect will occur between channels and the playback frequency response is also good In the case of B playback response A surround sound field Since the actual distance from each speaker to the listening point is identical there is no danger that comb filtering or the Haas effect will occur between channels and the playback frequency response is also good However in the horizontal plane the surround speakers are closer meaning that the surround sound field is not a perfect circle N
5. Cutoff frequency The identical cutoff frequency used by the low pass filter is also used by the high pass filter Slope The slope must be such that it will cross optimally with the low pass filter Here it is important to consider not only the response of the respective filters but also the response of the speakers that are used In other words filter response speaker response crossover response Here we will discuss the slope of the high pass filter with the assumption that the following specifications have already been determined e LPF fe 80 Hz 24 dB oct e HPF fe 80 Hz The playback bandwidth of the sub woofer usually extends above the cutoff frequency of the low pass filter that is applied This means that the low frequency response played back from the sub woofer will be identical fc 80 Hz 24 dB oct to the specifications of the low pass filter Therefore this same fc 80 Hz 24 dB oct will apply to the low range response of the sub woofer playback The cutoff response of the main speakers played via the high pass filter must be targeted to this fc 80 Hz 24 dB oct Example 1 If the main speakers are a small type whose response falls off at 12 dB octave below 80 Hz the high pass filter response 12 dB octave Thus filter 12 dB oct speakers 12 dB oct crossover 24 dB oct Example 2 If the main speakers are large speakers that are able
6. DTS Organization Surround processing method a Matak Encoda Compression g method response media S 100Hz 7kHz Playback response Level L CSR SS RS sss speaker amp L C R full range amp S 100Hz 7kHz amp Method 5 1 discrete Name Dolby DIGITAL DTS SDDS Manufacturer Organization Dolby lab DTS Sony Surround i i i processing method Compression Dolby AC 3 APT X100 ATRAC method Recording L C R LS RS full range L C R full range L C R LS RS full range response media LFE lt 120Hz SMPTE standard e ok LFE lt 120Hz LS RS 80Hz 20kHz Full band is theoretically possible LFE lt 80Hz LS amp RS information below 80Hz is summed into the LFE channel during the encoding process Level L C R Playback response LS RS 3dB amp speaker amp LFE 10dB in band gain amp L C R LS RS full range LFE 20Hz 120Hz L C R full range LS RS 80Hz 20kHz LFE 20Hz 80Hz L C R full range LFE 20Hz 120Hz Remarks Also possible are 7 1ch 8 ch which adds the two channels LC between L and C and RC between R and C Table 2 2 Multi channel formats typical examples Film 11 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Method 6 1 matrix Name Dolby DIGITAL Surround EX DTS ES Matrix Manufactu
7. DTS or film production Dolby DTS SDDS adjust the amp gain so that the band level of the LFE channel is 10 dB relative to the main channel Note that it is a mistake to adjust the amp gain so that the pink noise playback level shown by the sound level meter is 95 dBC 85dBC 10dB The most reliable way is to use the RTA and make adjustments so that the 1 3 octave band levels are approximately 81 dB In this case the all pass level indicated by the sound level meter will be approximately 89 dBC not 95 dBC 85dBC 10dB In cases such as DVD Audio or Super Audio CD where you set the band level of the LFE channel to the same level as the band level of the main channels 0 dB the all pass level shown by the sound level meter will be approximately 79 dBC if we assume the LFE playback bandwidth to be 20 120 Hz Main channels LS Pe eae RS for 3 1 and Movie program LFE channel All pass level 85dBC O Allpass level 82dBC O All pass level approx 89dBC T 1 3 octave band level approx 71dB Pe eae 1 3 octave band level approx 68dB T 1 3 octave band level approx 81dB O m o g Fink eer i EE f ij AON o TAAL ii POA HA 1 3 octave band center frequency Hz Fig 54 Playback level of LFE channel DVD Video Movie Main channels LFE channel 20 120Hz All pass level 85dBC O All pass level approx 79dBC f 1 3 octave band level approx 71dB 4 1 3 octave band level approx
8. Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 6 5 Delay adjustments Even in an environment in which all speakers are placed at an equal distance from the listening point it is best to measure and adjust the time alignment In addition to differences in the distance to each speaker the time at which the playback sound arrives can often be delayed slightly by the electrical rigidity of the individual speaker other materials or wiring and monitoring problems such as impaired highs can occur due to these reasons For time alignment adjustments the first step is to apply a delay based on the differences in the distance to each speaker Whether the distance difference is calculated based on the distance difference within the horizontal plane or the actual distance difference will depend on how the surround sound field and the playback response affect each other see p 47 section 3 8 4 Distance difference mm Delay time msec ______ _ Sound speed 344 m sec or Delay time msec 0 9 x Distance difference ft msec millisecond 1 1000th of a second Next check whether any comb filtering effects are occurring due to slight time differences between channels Play back the same pink noise at the same timing from the two channels being adjusted and use an RTA to check the frequency response If dips that wer
9. POM GZOSLOBUSSSASSSSARL Par Q RnR Fig 38 LFE vs C with Bass Management Fig 39 and Fig 40 are examples showing the difference in values when the center channel playback level is subtracted from the LFE playback level 4 Fig 39 shows examples of ten different studios without bass management controllers while Fig 40 shows examples of eleven different studios with bass management controllers Since both groups are adjusted as DVD Video playback environments it is necessary that the low frequency range show a 10 dB difference in values It can be seen that the studios not using a bass management controller exhibit a greater disparity Fig 39 than studios that are using a bass management controller N N w A a Q gaii e gt o ol fo fo w Q on jo 1 80ct band frequency z Fig 39 LFE vs C 10 studios without Bass Management GLE f 0 L L L 1 L L Y Q amp 2 Reg o o O 2 1 Boct band frequency Hz Fig 40 LFE vs C 11 studios with Bass Management 53 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation If bass management is to be applied in a professional playback environment the filter response
10. This method is based on a two channel system L R and adds a center channel C and surround channel S Although there are two surround speakers one each at left and right the playback is monaural The 3 in 3 1 indicates L C and R and the 1 indicates S Note that if 3 1 is expressed as 3 1 this means L C R LFE 1 2 2 5 1 ch This method is based on the 3 1 ch system but changes the surround to stereo LS RS and adds an LFE Low Frequency Effect channel for low frequency effects The LFE channel is played back through a dedicated subwoofer designed for low frequency playback 1 2 3 6 1 ch This method is based on the 5 1 ch system and adds a new back surround channel BS If two speakers are provided to play back the back surround channel these are sometimes called BS and BSr but the signal that is played back is a monaural signal where BSI BSr 1 2 4 Other As other formats there is 3 2 without LFE and 2 2 without C and LFE which are based on 5 1ch but do not use specific channel s of them As a format with a greater number of channels than 6 1ch we have 7 1ch 7 1ch can be subdivided into the SDDS format which is used in film and Dolby ProLogic IIx which is used in DVD Video etc SDDS is a discrete 7 1ch format which adds LC and RC channels between L and C and between R and C respectively and is used in applications such as supplementing the center gap b
11. 1 discrete Name Dolby Pro Logic II Dolby DIGITAL DTS Manufacturer Organization Dolby lab Dolby lab DTS Surround processing method 5 2 Matrix Encode Compression method Dolby AC 3 DTS Coherent Acoustic Recording response L C R full range L C R LS RS full range a media LS RS 100Hz 20kHz LFE lt 120Hz e LFE none oradded to L R 120Hz Playback response Level L C R LS RS Level L C R LS RS e speaker amp LFE none LFE 10dB in band gain ge L C R LS RS full range L C R LS RS full range lt LFE none LFE 20Hz 120Hz amp Method 6 1 matrix 6 1 discrete Name Dolby DIGITAL Surround EX DTS ES Matrix DTS ES Discrete Manufacturer Organization Dolby lab DTS DTS Surround processing method LS RS 3 2 Matrix encode LS RS 3 2 Matrix encode Compression method Dolby AC 3 L C R LFE DTS Coherent Acoustic DTS Coherent Acoustic Surround back channel Encode LS RS eT es response L C R LS RS BS full range A ge LFE lt 120Hz e amp Playback response Level L C R LS RS amp eu Wego gen LFE 10dB in band gain 7 ee a Pes an a a eee a ss ee LFE 20Hz 120Hz Table 2 3 Multi channel formats typical examples DVD Video 13 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Media Method Music 5 1 6 ch discrete Name DVD Audio Super Audio
12. Promotion Conference makes the following references to the handling of the LFE channel Regarding LFE bandwidth limitations Excerpted and summarized from the DVD Audio Software Production Guidebook Supplemented Edition The DVD Audio specification document does not obligate bandwidth restriction of the signal recorded on the LFE channel This means that the LFE recording bandwidth can be determined by a decision at the time of production In general some DVD Audio players apply an LPF to the LFE output while some do not The same is true as to whether or not an LPF is present in the amp This means that whether an LPF is applied to the signal reaching the speaker in the end user s playback environment will depend on the individual situation It is possible that in some end user environments no LPF will be applied at any point in the player amp speaker chain and in this case unneeded high frequency signals will be included in LFE and may be played back Thus if LFE is to be used for its intended purpose of low frequency effects appropriate filtering applied at the time of production will make it easier to obtain the same playback result in differing environments It is typical for the filter cutoff frequency to be in the range of 80 Hz 150 Hz Limiting the bandwidth of the LFE has the additional benefit of improving MLP compression efficiency 26 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporati
13. R BS 1116 1 43 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Fig 32 shows a comparison between a small room and large room illustrating how the playback level from speakers decreases by distance and how movement of 25 cm one head from the listening point will affect the playback level from each speaker 4 8 We assume that the speakers are flush mounted into the wall directivity coefficient Q 2 and that they are placed according to Rec ITU R BS 775 1 L R 30 LS RS 110 We assume a monitoring distance of 1 5 m for the small room and 4 0 m for the large room and the conditions of each room are as follows e Small room 3 5 m x 4 0 m x 2 2 m floor area 14 m room volume 31 m total surface area 61 m Average absorption coefficient Owe 0 6 e Large room 10 0 m x 15 0 m x 6 0 m floor area 150 m room volume 900 m total surface area 600 m Average absorption coefficient Owe 0 6 Small room r 1 5m 3 5mx4 0mx2 2M4 a 0 6 __ Large room r 4 0m 10mWx4 0mx2 2mH 0f 0 6 Reduction of SPL SPL r dB Monitoring distance r m rity Small room r 1 5m 0 0 0 5 1 0 1 5 2 0 2 5 3 0 35 40 4 5 5 0 Large room r 4 0m Distance from the loudspeaker m Fig 32 Variation of the monitoring level caused
14. Three keys of multichannel monitoring In addition to the above three points this document will discuss the construction of a monitor system and the measurements and adjustments that are necessary in order to create a multi channel playback environment It should be noted that this booklet is written for medium to small multichannel studios and that much of the material e g speaker placement delay adjustment bass management will not apply to surround monitoring in a large space such as in a movie theater or in a dubbing studio where the final mix of a film is being made 8 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 Multi channel formats At present multi channel playback is supported by numerous types of consumer media of which DVD is one The playback response for each of these types of media is defined by the organizations or manufacturers listed below Media Playback TO po BSE Storage method used Note Media anaes specification organization Film SMPTE ices secre re aa SMPTE ISO DVD Video Dolby lab DTS Pee ee DYD Rerum Wal DVD Audio DVD Forum WG4 Paes s DVD Forum WG4 ee Audio Sony Philips DST coded DSD Sony Phillips Digital ARIB MPEG 2 AAC lt ISO IEC broadcast Dolby lab Dolby DIGITAL DTS DTS Administrative body MP
15. distribution across the width W axis of the room than a case in which only one sound source is used If two sub woofers are placed across the width of the room in this way changes in sound pressure level will be mainly limited to the depth D axis of the room In this case design methods for conventional two channel studios can easily be applied such as applying sufficient acoustical treatment to the rear wall Using two sub woofers placed across the front of the room will also contribute to the quality of the playback by improving the connection between L R when bass management playback discussed below is used Single source BOHZ Double source oe 2am Rebtive Level dB Relative Level dB Fig 30 Low frequency response reproduced by the single source the double source 80Hz Examples of numerical calculations The Yamaha DM2000 DM1000 and 02R96 digital consoles allow the phase of the sub woofer output to be reversed making it possible to manage the phase of the sub woofer appropriately for the placement location 42 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 7 Monitoring distance The playback sound field becomes more stable as the monitoring distance the distance from the listening point to each speaker increases In other words surround playback tends to be more stable in a larger room and less
16. frequency response of the main speakers but also improves the low frequency playback response and allows checking of how the material will play back on consumer equipment Major advantages of a bass management controller are listed below A The low frequency response of the main channels L C R LS RS can be made consistent By ensuring that the low frequency response which is most prone to inconsistency is consistent the bass management makes it easier to ensure that all channels have the same response Regardless of whether the response is good or poor consistency of response between all channels is the most important point for a professional monitoring environment whether it be two channel or multi channel In the case of two channel monitoring it is fairly easy to make the response of all channels L and R identical by making the listening environment symmetrical between left and right However in the case of multi channel monitoring simply making the listening environment symmetrical between left and right is not usually enough to ensure consistency in particular for low frequency response B By placing the sub woofer in the optimal location the low frequency response of all channels can be improved In small to medium sized rooms there is a very limited range of speaker locations that produce good low frequency response Since there is a high degree of freedom in placing the sub woofer can be positioned in the location to o
17. in the vicinity of 100 Hz acoustical measures must be applied to the room Bass management is a very useful way to improve the low range playback response in a mid to small scale surround monitoring environments but it is by no means a cure all Its use must be considered for each individual case depending on the acoustical conditions of the studio and the content of the production In general the advantages are greater when it is used during post production and for musical applications the decision must be taken in view of the acoustical conditions of the room However for music slight phase differences in the playback speakers can affect the production meaning that there may be cases in which bass management becomes a liability The same applies to LFE due to fears of phase change or delay resulting from the LPF LFE is not usually used for music However regardless of whether bass management is used in the playback environment during production a bass management controller is equipment that a production studio should have for purposes such as verifying the playback in the end user environment and checking for ultra low frequency noise The Yamaha DM2000 DM1000 and 02R96 digital consoles contain a cutting edge bass management system that is able to respond immediately to a variety of audition environments and production media In order to match a variety of speakers it allows the selection of either Butterworth or Linkwitz Riely filter
18. larger TV screen Screen A 33 HDTV or B 13 5 HDTV or d 3xXH HDTV or 2XH H Height of the screen Fig 20 Placement of the video image Rec ITU R BS 775 1 33 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 1 3 Center speaker placement Rec ITU R BS 775 1 recommends that the L C and R speakers all be placed at the same height ear level Thus if the playback environment includes video an acoustically transparent screen is recommended If an acoustically transparent screen is not used it is stated that the center speaker should be placed immediately above or below the screen CRT 3 1 4 LFE sub woofer placement Rec ITU R BS 775 1 mentions systems that include an added LFE system optional but does not specify the placement of the sub woofer speaker for playback However the playback bandwidth is specified as 20 Hz 120 Hz Annex 7 Also while the playback level is said to be under consideration it is stated that it is useful to provide gain in the range of 10 12 dB as with film 3 1 5 Monitoring distance The distance from the listening point to each speaker the monitoring distance is not explicitly stated in Rec ITU R BS 775 1 but the Rec ITU R BS 1116 1 cited as a reference does recommend a monitoring distance of two to three meters for a multi channel playback environ
19. level maintain a gain equal to the low frequency response of the other channels plus an additional 10 dB such as DVD V and film Thus ensuring that the low frequency response of each channel is consistent is one of the most important points for constructing a multi channel monitoring environment This is why we need to consider some type of bass management In a small to medium sized studios we can consider three methods of bass management acoustical treatment of the room speaker placement and electro acoustic methods 4 1 Acoustical treatment of the room Room acoustics can be treated by adding thick acoustically absorptive material or by significantly inclining the walls In theory an 85 cm or greater thickness of absorptive material is required in order to completely absorb low frequencies in the 100 Hz region However as the room size becomes smaller physical considerations often make it more difficult to add thicker absorptive material 4 2 Speaker placement The low frequency response of a speaker has a closely linked effect on the room acoustics Thus consideration of the speaker placement is a useful way to improve the low frequency playback response In many cases we are able to consider only the placement of the sub woofer which allows a high degree of freedom in its placement Consideration of the sub woofer placement in conjunction with the use of a bass management controller discussed later is one of the
20. management may cause those low frequency signals to be lost This suggests the possibility that low frequency components that were heard in a production environment not using bass management can become inaudible in the end user environment Using bass management during production to check the playback sound is an effective way to prevent this type of lost low frequency playback Fig 37 is an example of the playback response in a studio that does not have a bass management controller while Fig 38 is an example of the playback response in a studio that has a bass management controller 4 Since both are adjusted for use as a DVD Video playback environment it is necessary that the playback level of the LFE channel maintain 10 dB of gain relative to the main channels In the studio that uses a bass management controller 10 dB of gain is maintained in the entire low frequency range even though there is unevenness in the low frequency response Fig 38 In contrast in the studio that does not use a bass management controller this difference is not consistent some regions have a 10 dB difference while other regions do not Fig 37 85 80 75 70 65 60 55 SPL dB Fig 37 LFE vs C without Bass Management 52 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation n NV RUMOATFFANNWOAUMROiLMApNYRDP MAHFN SHAdhHA25GBO r
21. most effective ways in which a small or mid sized studio can improve its low frequency response 4 3 Electro acoustic methods The bass management controller shown in Fig 19 can be applied to a monitor system to implement electro acoustic compensation In general bass management refers to processing by a bass management controller LS O H HPF HP LS RS O HPE HPN RS Fig 35 Bass management controller 1 50 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Oo Relative SPL dB 10 OFER HE HEE AMAIN SPEAKERS E z A 3 80Hz N 1 25k 1 3 octave band center frequency Hz Fig 36 Playback characteristics using Bass management controller 1 A bass management controller is a crossover filter that routes the low frequency component to a sub woofer This means that the sub woofer will output the low frequency components combined from each of the main channels as well as the LFE signal making it impossible to adjust the gain of only the LFE channel after bass management the sub woofer amp occurs Thus the bass management controller must also provide functionality for switching the gain of the LFE playback sound 10 dB DVD Video and movies etc 0 dB DVD Audio and Super Audio CD etc The bass management controller includes not only the simple function of supplementing the low
22. playback is also important in order to check compatibility with the end user environment Bass management functionality is built into the Yamaha DM2000 DM1000 and 02R96 digital consoles This means that bass management which can be switched on off can be applied without any problems of tonal change that might be a concern when using external bass management devices The bass management that is built into the DM2000 DM1000 and 02R96 provides not only conventional bass management functionality but also the ability to adjust the playback level of the LFE and surround thus filling the roles of a monitor system that supports a variety of media 5 3 Monitor alignment In order to precisely measure the time alignment of each channel it is desirable to provide an electrical delay for each speaker Considering the actual adjustment process attenuators and GEQ PEQ will usually be necessary as well The Yamaha DM2000 DM1000 and 02R96 digital consoles provide monitor alignment functionality consisting of an adjustable delay and attenuator for each speaker This means that monitor alignment can be performed without any problems of tonal change that might be a concern when using external alignment devices The delay can be adjusted in 0 02 msec steps and the attenuator can be adjusted in 0 1 dB steps providing sufficiently precise adjustment even for professional monitoring environments 60 74 Multichannel Monitoring T
23. responses as well as 12 dB octave or 24 dB octave slopes for each speaker L amp R C LS amp RS Monitoring conditions can be adjusted for a variety of media for example with variable LFE or LS RS playback levels In addition bass management can easily be switched on off making it easy to audition the effect of bass management This THX pm3 Approved bass management can instantly support the monitor system of a THX pm3 Certified Studio simply by recalling a THX preset DM2000 02R96 Ver 2 1 or later DM1000 Ver 2 0 or later 56 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 4 4 Monitoring the decoder output The inclusion of a bass management controller is required for consumer DVD players and AV receivers As mentioned in the preceding section the ability to adjust the gain of the LFE channel is indispensable for bass management and for this reason some consumer devices do not output LFE at unity gain Thus when the output of the decoder is being monitored in the studio it is necessary to pay attention to the LFE output level The examples shown in Fig 43 and Fig 44 are simplifications of a portion of the output processing in a consumer player and AV receiver Fig 43 shows bass management turned on and Fig 44 shows it turned off Dolby DTS OR MPEG 2 AAC Pecode etc Oc DVD Audio O LS Super
24. stable in a smaller room However as the monitoring distance increases the influence of the room also increases so it is important to pay attention to the acoustics of the room Fig 31 shows calculations for each speaker simulating an off axis deviation of 25 cm one head forward and backward from the listening point relative to the Rec ITU R BS 775 1 speaker placement 4 8 Even if speaker angles are adjusted precisely L R 30 LS RS 110 the L R spread will narrow 01r 30 gt R if the listener moves backward from the listening point causing the surround speakers to change from a rear placement to a sideways placement 0 rsrs 110 0 srs The graph in Fig 31 describes such changes The upper half shows the angle difference when moving forward 25 cm and the lower half shows the angle difference when moving backward 25 cm The dashed lines show the angle difference for L and R A 0 pg Oir and the solid lines show the angle difference for LS and RS A isprs Otsps The horizontal axis indicates the monitoring distance 8 0 degree Backward 25cm Off axis error A 1 5 4 35 4 45 5 Monitoring distance r m Critical robust Monitoring distance r m Fig 31 Variation of the placement angle of the loudspeaker caused by the movement of the listening position From Fig 31 we can determine the following points regarding how forwar
25. studio the same flat response as described for DVD Video is generally used even when creating film productions The X curve is designed so that playback with a flat response in a small to medium space produces the same perceptual impression even in a large space This means that the perceptual impression is that of flat response in a small to medium space X curve in a large space Thus if you apply the X curve ina small to medium space the result will often be an unnatural sounding lo fi playback If you absolutely must compensate the high frequency region when playing back a film production in a small space you could conceivably use an LPF with a somewhat gentler curve than the X curve for example fe 2 kHz 1 2 dB oct However due to the additional requirement of being able to hear perceptual differences caused by the size of the playback space it is necessary that final mixing of a film production be performed in a large dubbing studio Curve X of B Chain SMPTE 202M 1998 4 toe Et FF FF YH a ee lel eet el cl te st GGG S Zn r a o rie n4 mO mia E oe a aa a a a xe 8 otefee eT ESS a oo oo t 165 H o oe oe oe ee EEE E EE E E E e r ore EE FF FF FFF YF ERSS E Oooo OOO OOOO ASALA a Fig 12 X Curve of B chain SMPTE 202M 1998 25 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 4 3 Musi
26. that because the 500 Hz 2 kHz band limited pink noise has a narrower bandwidth than the broad band pink noise its all pass level is 80 dBC which is 5 dB lower Thus when using the 500 Hz 2 kHz narrow band pink noise to adjust the level of each channel you must set the all pass level the value indicated by the sound level meter not to 85 dBC but to 80 dBC which is 5 dB lower Wide band 500Hz 2kHz All pass level 85dBC O All pass level approx 80dBC T 1 3 octave band level approx 71dB T 1 3 octave band level approx 71dB es PR 80 1 ce CA A A A H E a A A A A A A A A A A E E m EET TT AE EGT co D 70 FF Pane m H H i a THT E 50 40 E x x x x x O 2 BA 2 886 a4 oH oO bo Oo WwW Oo N ha a N xt m m 1 3 octave band center frequency Hz Fig 52 500 2kHz Pinknoise and Broadband Pinknoise Most of the pink noise built into consumer receivers and players is band limited pink noise of this type However since its level is not precise you must use caution when making adjustments targeted at an absolute value such as 85 dBC or 80 dBC Some devices such as the Dolby Laboratories DP564 professional decoder have built in band limited pink noise to which level compensation has already been applied and in such cases you can make adjustments to 85 dBC not 80 dBC even when using band limited pink noise 65 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masatak
27. to create phantom sound images in a variety of directions In such cases it is desirable that the distance from each speaker to the listening point be identical so that loss of highs does not occur in the playback response In addition in order to obtain a good surround playback sound field it is necessary that all speakers be placed at the same height This means that A is ideal as a playback environment for musical productions but if for various reasons the height of the surround speakers must differ from the height of the front speakers you must decide whether the surround playback sound field or the playback response are of greater importance and choose either B or C as the playback environment For post productions such as DVD Video and film on the other hand it is customary to place the surround speakers higher than the front speakers and in this case it is best to construct environment C in which priority is given to the naturalness of the surround sound field In post productions it is usually the case that the acoustical roles can be divided between the three categories of L R C and LS RS and it is seldom the case that signals are highly correlated between these Thus even if the actual distance to the front channels differs slightly from the distance to the surround channels it is not likely that comb filtering effects between the two signals will cause problems in the playback response such as a loss of highs
28. to reproduce below 80 Hz then high pass filter response 24 dB oct Thus filter 24 dB oct speakers 0 dB oct crossover 24 dB oct 54 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Filter Types The type of filter used Butterworth Linkwitz etc depends on the matching between the type of low pass filter and the response of the main speakers Example For small types where the main speaker is attenuated below 80 Hz e LPF Linkwitz fc 80 Hz 24 dB oct e LPF Butterworth fc 80 Hz 12 dB oct In this way it is desirable for the specifications of the high pass filter to be selectable according to the response of the speakers that are used The bass management controller shown in Fig 35 is a type that is frequently used in consumer players and AV receivers When this type of bass management controller is used the upper limit of the LFE playback bandwidth is determined by the crossover frequency of the main channels as shown in Fig 36 Since the crossover frequency is generally set to 80 Hz bass management controllers such as shown in Fig 35 will limit the LFE playback bandwidth to 80 Hz In contrast DVD Video and film allow LFE signals up to 120 Hz to be recorded and played back and DVD Audio and Super Audio CD allow full range recording and playback In a production workplace wh
29. 1 m If there is more than 1 meter of difference between the distance from the sub woofer to the listening point and the distance from the other speakers to the listening point dips are likely to occur in the combined response Severe dips occur in the region of the sub woofer cutoff frequency If the monitor system uses bass management discussed below special care must be taken to avoid significantly impairing the frequency response of the main channels If the above monitoring problems occur you will need to reconsider the speaker placement and try adjusting the speaker phase in particular the sub woofer If improvements cannot be expected from the above adjustments it will be necessary to apply electrical delays to each speaker In addition to delay designing your monitor system so that an attenuator or GEQ PEQ can be applied to each speaker often provides useful ways to adjust the monitoring response 46 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 8 4 Speaker placement height and time alignment If delay compensation is to be applied in an environment in which all of the speakers are not placed at the identical height we must consider how this will interact with the playback sound field and the playback response Fig 34 shows how the height of the surround speakers is related to the monitoring distance In example
30. 5 1 to 3 1 etc For example the surround speaker output level is changed by 0 dB in the case of 5 1 or 3 dB in the case of 3 1 as appropriate for the channel format of the consumer input source Thus when the decoder output of a consumer device is being monitored in a studio it is often unnecessary to adjust the surround monitor 57 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation level according to the channel format However there is no guarantee that the playback of all consumer devices is being processed as described in Fig 43 Fig 44 It is desirable to obtain the output levels and output diagram for each device you are using Some Dolby DIGITAL decoders for professional use also have bass management or surround attenuation functionality Fig 45 and Fig 46 are simplified depictions of a portion of the output processing within the Dolby Laboratories DP564 professional decoder Fig 45 shows the processing with bass management on and Fig 46 with it off iw 5 gog P gt Q o gt L gt O Dolby AC 3 etc Decode Fig 46 Example of a signal flow of a professional decoder Dolby DP564 Bass management OFF The difference with the consumer device shown in Fig 43 and Fig 44 is that regardless of whether bass management is on or off the input output of all channels including LFE is c
31. 625 50 regions DVD Video players must have Dolby Digital AC 3 playback capability e Optional audio signals for DVD Video DTS MPEG SDDS Examples of lossless reversible compression formats Table 3 2 Examples of lossy compression formats Media CH DVD Audio 1 5 1 6 ch Super Audio CD 2 5 1 6 ch Compression PPCM Packed PCM MLP DST Direct Stream Transfer fs Hz 44 1k 88 2k 176 4k 48k 96k 192k 2 8224M Qb bit 16 20 24 Bitrate bps Max 9 6M Max 14 99136M Dynamic range dB Max 144dB More than 120dB Only one or two channels at fs 176k or 192 k Value in the audible bandwidth Includes the effect of noise shaping from Delta Sigma modulation e Super Audio CD requires that a two channel source be stored discs containing only a multi channel source are not allowed e DVD Audio allows either of two methods storing both a two channel source and a multi channel source or storing only a multi channel source together with downmixing coefficients provided as meta data Table 3 3 Examples of lossless compression formats 21 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 3 Recording response By recording response we mean the response allowed when the master tape produced by the studio is recorded onto th
32. 71dB 90 REESE H 80 ere Aa S N AS EA SEE EE A S E a S 70 RSE a 60 1 25k Seen 20k PTTL 1 3 octave band center frequency Hz Fig 55 Playback level of LFE channel DVD Audio Super Audio CD 67 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Main channels e All pass level 85 dBC e Band level 1 3 octave approx 71 dB LFE band level 1 3 octave e Approx 81 dB 10 dB DVD Video film e Approx 71 dB 0 dB DVD Audio Super Audio CD LFE all pass level 20 Hz 120 Hz e Approx 89 dBC approx 4 dBC DVD Video film e Approx 79 dBC approx 6 dBC DVD Audio Super Audio CD When the LFE playback bandwidth is assumed to be 20 120 Hz Since the above all pass levels are the values with the LFE playback bandwidth assumed to be 20 Hz 120 Hz you will need to apply a 120 Hz LPF to the monitor output for the LFE signal reproduced by the subwoofer if you are relying on the all pass level to make adjustments Alternatively the pink noise used for adjustment could be bandwidth limited with 120 Hz as the upper limit The all pass level value is easily affected by the frequency response and playback bandwidth The low frequency response which is particularly liable to be affected by the acoustical character of the room is apt to become unstable Furthermore in many systems the main
33. Audio CD etc RS Att HPF O RS Fig 43 An example of output processing in a consumer player and receiver with bass management on Dolby DTS R MPEG 2 AAC Decode etc C SUB LFE DVD Audio LS Super Audio CD etc RS 10dB DVD V 0dB DVD A Super Audio CD Fig 44 An example of output processing in a consumer player and receiver with bass management off Consumer devices that have this type of bass management circuit automatically switch the AMP gain of Fig 43 and Fig 44 according to the input source in order to produce an LFE output appropriate for a wide range of media formats For example 10 dB of gain is applied for DVD Video sources such as Dolby DIGITAL or DTS while 0 dB is applied to DVD Audio or Super Audio CD On some consumer equipment this gain AMP is applied regardless of whether bass management is on or off while for other consumer equipment this gain depends on the bass management on off status Thus you should be aware that on some consumer devices the LFE output is already at 10 dB when playing back DVD Video When monitoring the decoder output of this type of consumer device in the studio the LFE playback level must be set to 0 dB or the LFE channel of the decoder output must be input at 10 dB Incidentally the Att in Fig 43 Fig 44 is an attenuator that automatically adjusts the playback level of the surround speakers when the surround format is changed such as from
34. CD Manufacturer Organization Surround processing method DVD Forum WG 4 Sony Phillips Compression method PPCM Packed PCM MLP Max 96kHz 24bit 6ch LCPM uncompressed Max 96kHz 24bit 4ch Max 96kHz 20bit Sch Max 96kHz 16bit 6ch DST Direct Stream Transfer Recording response media L C R LS RS full range LFE full range Playback response speaker amp Other methods Level L C R LS RS LFE L C R LS RS full range LFE Not prescribed full range is possible 2 1 2 1 1 3 3 1 3 1 3 1 1 2 2 2 2 1 3 2 etc 3 3 1 2 2 2 2 1 3 2 Table 2 4 Multi channel formats typical examples Music 14 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Media Digital broadcast Method 5 1 discrete Main countries Japan Europe etc Name Manufacturer Organization Signal format ISO IEC Signal format ISO IEC Playback response etc Each administrative body Playback response etc ARIB Surround processing method Compression method MPEG 2 AAC MPEG 2 Recording response media L C R LS RS LFE full range L C R LS RS full range LFE lt 125Hz Playback response Level L C R LS RS Level L C R LS RS k Gpeaken aimp LFE Prescribed by ARIB LFE Prescribed by administrative body L C R LS
35. D Audio Software Production Guidebook Supplemented Edition it is desirable that an LPF be applied during production to the LFE master source in order to maintain compatibility for a variety of end user playback environments Attention must be paid to the playback level of the LFE signal particularly when producing DVD Audio and DVD Video hybrid multichannel discs For example in order for an LFE signal produced in a DVD Audio environment to be converted for use with DVD Video the LFE master signal must be recorded at a level 10 dB lower Front channel Level L C R Playback bandwidth Full range Surround channel Level 3 1 S LS RS L C R LS RS L C R 3dB DVD Audio 5 1 LS RS L C R Playback bandwidth 3 1 Full range DVD Audio 5 1 Full range LFE channel Level Band level 0 dB same as main channels Playback bandwidth Not specified full range is possible Monaural surround in DVD Audio and Super Audio CD Monaural surround in DVD Audio DVD Audio provides monaural surround S LS RS formats of which 3 1 L C R S is an example In this case the LS and RS playback levels are LS RS L C R and LS RS L C R 3dB Thus in DVD Audio it is necessary to re adjust the LS and RS playback level depending on whether you are producing for 5 1 or 3 1 This is the same for DVD Video In other words in DVD Audio multi channel production can use the same playback environment DVD Video with the exception of LFE B
36. EG 2 lt ISO IEC Other matrix methods such as Dolby Surround Dolby ProLogic I x and Circle Surround GAME Dolby lab DTS Dolby DTS lt lt Hardware manufacturers Notes lt lt Within the recording format specified by the standards organization the actual recording method and playback response are provided by another party lt The recording method specified by the standards organization is used and the applying organization considers the playback response The standards organization directly specifies the recording method and the playback response 1 DVD Video also allows LPCM multichannel recording 2 The PPCM algorithm is provided by Meridian Audio Ltd 3 For PPCM maximum 96 kHz 24 bit 6ch For LPCM maximum 96 kHz 24 bit 4ch 96 kHz 20 bit 5ch 96 kHz 16 bit 6ch For 2ch maximum is 192 kHz 24 bit 4 For 2ch Plain DSD uncompressed DSD is also possible 5 J apan 6 Europe USA and Korea 7 Europe etc 8 Europe etc 9 xK Can also be applied to analog broadcast Indicates that this is not a broadcast media standard but a recording format standard Table 1 Multi channel formats and standards organizations 9 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Each format of multi channel media is characterized by a combination of surround processing method encoding and co
37. M2TB rev 3 5 2 Multichannel Monitoring Tutorial Booklet 2 Edition With Reference to the surround monitoring functions of the Yamaha DM2000 DM1000 and 02R96 digital consoles May 2005 rev 3 5 2 2005 YAMAHA Corporation YAMAHA 2005 SONA Corporation SONA Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Multichannel Monitoring Tutorial Booklet Second edition rev 3 5 2 May 2005 First edition rev 230 June 2002 Contents Fore Word sssssscsssssseesecssessscsseesecsseesessessecssessacsseseeseseseesssesesssseseesesesessscssessssesessesesseessseesessseeseseseesessssesesess 3 Prefa sa sescsiseccnesiescecacdoccebetdeseccescstbssenedscecsssesoecdecseeesestedeseddaencbagussdsscodsronseadsssesenecesococbdsoscc edebeacssuatansuacseccdecse 4 0 Introd uction scscccssssssssssssssssssssesesesessssssssssssesesesesesesesesesssssesesesesesesesesessssesesesesessseseseseseseseseseseseseseses 5 1 What is SUTTOUNA cccscesescscccsscsesesssssecscssssssssssssesesesesesesesescssssesesesesesesesesesesesesesesesesesesssesessesesesesesees 6 TAT cS CELeO ANG SULTOUNG ORAE AEAEE SEA EE E A AE 6 1 2 Channel conficuration nesre sr riar A Ereti I EKETA SEE ENEE EEN ET EO 6 1 3 Key points for multi channel monitoring sssessesssissessesserssresesesresesesresesesresenesee 8 2 Multi channel fo
38. NA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Playback bandwidth 3 1 In the case of matrix 100 7 kHz it is best to use full range speakers In the case of discrete full range 5 1 Full range 5 0 In the case of matrix 100 Hz 20 kHz it is best to use full range speakers In the case of discrete full range 6 1 Full range LFE channel Level Band level is 10 dB compared to the main channel Playback bandwidth 20 Hz 120 Hz 2 4 2 Film Dolby DTS All pass level 1 3 octave band level Input Signal O LFE approx 89dBC LFE approx 81dB Wide band Pink Noise L C R 85dBC Tt L C R approx 71dB approx OVU OLS RS 3aB 82dBC T LS RS approx 68dB 20dBrms F 80 10dB o L4C R JE 70 Fa LS RS 80Hz DT 60 0 120Hz Dolb 50 5 S 19 g S Lo ro Lo Q 2 x N x 5 x s xt x m y 1 3 octave band center frequency Hz Fig 11 Playback specification for Movie program In an environment for producing film for public performance in a theater the playback level of the surround speakers is not changed for 5 1 and 3 1 This means that even for 5 1 the LS and RS playback level are to be set 3 dB lower than the other main channels for 3 1 compatibility For LFE the level is 10 dB relative to the main channels just as for DVD Video SMPTE RP 200 Proposed SMPTE
39. ONA Corporation 3 5 Playback image compatibility with the playback environment Differences in surround speaker placement and the spread between the L R speakers rarely cause profoundly different results in the playback image when a surround production is played back Thus the end user can enjoy most surround productions even if their setup is not for example the ITU R configuration However compatibility of the speaker placement does become important when creating musical productions in which you intend to skillfully use the phase relationships between channels to generate a precise sound field Including situations in which such needs must be supported it is sometimes necessary that a certain standard be maintained in the production playback environment The typical example of this case is Rec ITU R BS 775 1 and it is important to consider ITU R as the primary basis for the surround playback environment On the other hand there are cases in which room shape room size and the production content cause disadvantages if you attempt to apply Rec ITU R BS 775 1 to the production environment and in such cases it is valuable to consider other placements For example in an extremely narrow environment the ITU R surround speaker placement immediately beside the listener s ears may create an unnatural sounding playback Although standard placement is an important element of the playback environment it is also important that the engin
40. RS full range L C R LS RS full range LFE Prescribed by ARIB LFE 20 125 Hz Main countries Europe USA Korea etc Europe etc Name Dolby DIGITAL DTS Manufacturer Organization Dolby lab DTS Surround processing method Compression method Dolby AC 3 DTS Coherent Acoustic Recording response L C R LS RS full range 2 media LFE lt 120Hz gs Level L C R LS RS a Playback response LFE 10dB in band gain amp speaker amp L C R LS RS full range LFE 20Hz 120Hz amp Discrete methods 3 1 5 0 etc Matrix methods Dolby Surround ProLogic II x Circle Surround etc In MPEG 2 AAC the LFE channel supports full band encoding but a bandwidth limitation may be applied in transmission Other methods Table 2 5 Multi channel formats typical examples Digital broadcast 15 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Media Games Method 5 1 discrete 5 0 matrix Name Dolby DIGITAL DTS Dolby Pro Logic II Manulachinet Dolby lab DTS Dolby lab Organization Surround 5 2 Matrix Encode processing method Compression DTS Coherent method Doly Absa Acoustic 7 Recording response L C R LS RS full range amp L C R full range media LFE lt 120Hz LS RS 100Hz 20kHz LFE none or added to L R lt 120Hz Playback response Level L C R LS RS qe L
41. Recommended Practice Relative and Absolute Sound Pressure Levels for Motion Picture Multichannel Sound Systems Front channels Level L C R 85 dBC The playback level of all channels is to be set identically Playback bandwidth Full range 24 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Surround channels Level For film productions set the playback level of surround channels at 3 dB relative to the front channels The film playback environment is designed based on the level balance for 3 1 L C R S LS RS 85dBC LS RS 82 dBC the surround playback level is not changed for 5 1 3 1 LS RS 82 dBC in other words S LS RS 85 dBC 5 1 LS RS 82 dBC 6 1 LS RS BS 82 dBC Playback bandwidth 3 1 For matrix 100 7 kHz it is best to provide full range speakers For discrete full range 5 1 Full range 6 1 Full range LFE channel Level Relative to the main channels the band level is 10 dB Playback bandwidth 20 Hz 120 Hz Dolby 20 Hz 80Hz DTS X curve X Curve of B chain SMPTE 202M 1998 SMPTE STANDARD for Motion Pictures Dubbing Theaters Review Rooms and Indoor Theaters B chain Electroacoustic Responses In a large space such as a movie theater or dubbing studio the X curve is generally used as the standard for playback frequency response B chain However in a medium or small
42. This means that we should give preference to environment C since the surround sound field will be well formed and gestures such as flyovers can be performed However if the distance difference between the front channels and surround channels is so great that the Haas effect results we need to consider an environment that falls between B and C The Yamaha DM2000 DM1000 and 02R96 digital consoles allow a delay in 0 02 ms steps 0 30 msec and a gain adjustment in 0 1 dB steps 12db 12 dB to be applied to each speaker output This allows precise adjustments to be made to eradicate comb filtering effects in the audible band lt 20 kHz 3 9 THX pm3 Certified Studios At present there is a profusion of multi channel playback environments L xX When deciding which playback environment you will ultimately construct you must take into account overall considerations such as the media you will be producing and J ofa ae the state of your room It is also important that the level balance and frequency response of each speaker in your multi channel monitoring system be adjusted according to the media you are producing Announced by THX Ltd in 1999 THX pm3 is a program for designing this type of small to medium size multi channel studio and is currently the only design program that provides a total solution The THX pm3 Certified Studio program allows the design of a multi channel studio accordin
43. a Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation The Yamaha DM2000 DM1000 and 02R96 internally provide two types of pink noise for use as monitor adjustment signals 20 dBrms broad band pink noise and 500 Hz 2 kHz narrow band pink noise The band level of the 500 Hz 2 kHz pink noise is approximately 5 dB greater than the band level of the broad band pink noise Thus you can use the DM2000 DM1000 and 02R96 to make adjustments referenced to 85 dBC to both broad band pink noise and 500 Hz 2 kHz pink noise dBr PLL MMS SY lt X lt vexrxe DONNHFHVSSOHOGS Neat Go rar w 1 3 octave band center frequency Hz Fig 53 Frequency response of the pink noise produced by the DM2000 DM1000 and 02R96 broad band and 500 2k The DM2000 DM1000 and 02R96 allow you to adjust the playback level of each speaker in a range from 12dB to 12dB with a precision of 0 1 dB steps Also the SET SPL 85 dB function lets you specify a desired position of the master volume as the 85 dB indication and the SANP TO SPL85dB function lets you instantly switch the volume from any master volume position to the reference playback level of 85 dBC 66 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 6 4 LFE channel level balance For a DVD Video Dolby
44. ack level is adjusted referring only to the all pass level for speakers with differing frequency ranges differences in band level will occur For example let us suppose that the front speakers are large speakers with a broad frequency response while speakers with a narrow frequency response are used for the surround channels In such an environment relying only on the all pass level 85 dBC to adjust the playback level of those speakers will mean that the playback band level of the surround speakers will be higher and as a result the surround channels will play back at a louder volume than the front channels Matching the speaker playback levels means that the band levels 71 dB 1 3 octave not the all pass level must be matched Adjustment based on the all pass level 85 dBC using only a sound level meter is an easy method that is possible only if all speakers have the same playback response and the room acoustics are sufficiently good In actual measurement it is desirable that you check not only the all pass level 85 dBC but also use an RTA to check the band levels 71 dB 1 3 octave 64 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 6 3 Narrow band pink noise We can consider the following factors as possible reasons for differences in frequency response between playback channels 1 Playback response of the speakers Pla
45. acoustic phenomena to lower the redundancy of the original signal thus compressing it Lossless compression allows the original signal to be completely recovered from the compressed signal that is recorded i e this is reversible compression This method is used to compress files on a computer It uses mathematical means to lower the redundancy of the original signal compressing it Thus lossless compression delivers a lower compression ratio than lossy compression Examples of lossy compression Examples of lossless compression Method Media Method Media Examples of uncompressed formats Dolby AC 3 DTS coherent acoustic ATRAC MPEG 2 AAC etc Film DVD Video digital broadcast games etc MLP PPCM Packed PCM DST Direct Stream Transfer DVD Audio Super Audio CD Dynamic range Media CH Encoding method fs Hz Qb bit Bitrate bps dB cD 2ch LPCM 44 1k 16 1 4112M 96dB DVD Video 1 8ch LPCM 48k 96k 16 20 24 Max 6 144M Max 144dB 1 44 1k 88 2k 176 4k DVD Audio LPCM 16 20 24 Max 9 6M Max 144dB 5 1 6 ch 48k 96k 192k DSD Super Audio CD 2ch 2 8224M 1 5 6448M ae Direct Stream Digital Within a maximum of 6 144 Mbps fs and Qb can be specified in a scalable manner according to the number of channels Example In the case of two channel maximum 96 kHz x 24 bit x 2 channels 4 608 Mbps lt 6 144 Mbps Within a maximum of 9 6 Mbps fs and Q
46. aha DM2000 DM1000 and 02R96 digital consoles contain virtually all of the monitoring system required for multi channel playback and allow a professional level playback environment to be easily constructed without the use of special external equipment Consideration has been taken for specialized operability for surround playback and changes in playback format for a variety of media can be performed intuitively Measurement signals such as pink noise are also built in making this a surround console that provides all around support for the establishing of a playback environment 71 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Reference materials References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Multichannel stereophonic sound system with and without accompanying pictures Recommendation ITU R BS 775 1 1992 1994 Method for the subjective assessment of small impairments in audio systems including multichannel sound systems Recommendation ITU R BS 1116 1 1994 1997 Koichiro Hiyama Setsu Komiyama Kimio Hamasaki The minimum number of loudspeakers and its arrangement for reproducing the special impression of diffuse sound field AES 113th Convention Los Angels preprint 2002 Masataka Naka
47. allows surround panning to move an audio source in a 360 path and is therefore often used as the production environment for multi channel media that accompanies video Its compatibility with both 6 1ch playback and 5 1ch playback is a reason why it is favored as a post production environment In particular this playback environment is a necessity for film productions Due to the fact that most productions created in diffused surround do not exhibit significantly different playback images when different surround speaker placements are used diffused surround is often used as the environment for efficiently producing general purpose program material As standard the Yamaha DM2000 DM1000 and 02R96 digital consoles support both direct surround and diffused surround by allowing up to two speakers be used for each of LS and RS you can also use one speaker for each In addition these surround speakers can be automatically routed to appropriate surround channel following any changes in the channel format 3 1 5 1 6 1 39 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 4 C If a visual image is not used or if an acoustically transparent screen is used the center speaker should be placed at the same height as the L R speakers If it is important to match the sound and the image it is good to place the center speaker
48. argely dependent on two parameters the sampling frequency fs Hz which corresponds to the sampling precision of the time axis frequency axis and the number of bits used for quantization Qb bit which corresponds to the sampling precision of the amplitude loudness For both fs Hz and Qb bit higher values allow the occurrence of digital encoding noise to be minimized This means that for both fs Hz and Qb bit higher values are generally interpreted as higher audio quality In two channel media a CD is encoded at fs 44 1 kHz Qb 16 bit and DAT is encoded at fs 48 kHz Qb 16 bit The dynamic range for these types of media is approximately 96 dB In multimedia DVD Audio is encoded with six channels of fs 96 kHz Qb 24 bit giving a dynamic range of approximately 144 dB This type of encoding is known as multi bit encoding the upper limit of the frequencies that can be reproduced is determined by fs 2 and Qb essentially determines the dynamic range In contrast the single bit high speed sampling method uses the minimum number of quantization bits Qb 1bit and instead samples at an extremely high sampling frequency In the Super Audio CD SA CD developed by Sony and Phillips this is called the DSD Direct Stream Digital method Because single bit high speed sampling expresses the amplitude of the sound not as a stepwise amplitude of Qb but rather by the density of the sound pressure It is said that this encoding method is clos
49. aturalness of the surround playback field is obtained when the distance from each speaker to the listening point is the same in the horizontal plane In such cases the perceptual impression will be that the surround sound is being played back from a nearby but higher location and the surround playback will be lacking in depth If the surround is more distant than the front it will seldom be perceived as being unnatural but if it is closer the listener will usually sense that something is wrong Sometimes this type of sound field can be created by automatically adjusted delay compensation so caution is needed In the case of C A playback response O surround sound field Since equal distance in the horizontal plane is maintained the surround sound field is a perfect circle which is good On the other hand the actual distance from the surround speakers to the listening point is greater than the distance to the front speakers possibly causing problems with the playback response For example if the same type of signal is being played back from the front channels and the surround channels 47 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation comb filtering could cause highs to be attenuated in the playback sound In musical productions signals that are highly correlated between the front channels and surround channels are sometimes used
50. b can be specified in a scalable manner according to the number of channels However only one or two channels are possible for fs 176 4k or 192k Examples One or two channels max 192 kHz 24 bit 4 ch max 96 kHz 20 bit 5 1 6 ch max 96 kHz 16 bit Value in the audible bandwidth Includes the effect of noise shaping from Delta Sigma modulation Table 3 1 Examples of uncompressed formats 20 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Examples of lossy irreversible compression formats r r Dynamic Media CH Compression fs Hz Qb bit Bitrate bps range dB Dolby AC 3 44 1k 16 320k Film 5 1ch APT X100 DTS 44 1k 16 882k ATRAC SDDS 44 1k 16 2 4M 224k 256k 1 5 1ch Dolby AC 3 48k 16 20 24 320k 384k DVD Video 448k 1 7 1ch DTS coherent acoustic 48k 96k 16 20 24 TOLIR d am 1 50975M oi MPEG 2 AAC 32k 44 1k 144 256k 2ch aa 1 5 1ch More than 16 P LC profile 48k 96k 320k 384k Multi 8 channels L LC C RC R LS RS LFE backup Lmix Rmix C LFE 5 1ch or more channel e SDDS film ATRAC allows 7 1 ch 8 ch which adds LC between L and C and RC between R and C to 5 1 ch e Mandatory audio signals for DVD Video LPCM signal or Dolby Digital AC 3 signal MPEG signal is also required in TV system
51. by the movement of the listening position Small room r 1 5m vs Large room r 4m The solid line of the graph plots the decrease in playback sound pressure level for the Small room according to the distance from the speaker and the dashed line indicates the decrease in playback sound pressure level for the Large room When we leave the listening point the distance to each speaker is no longer identical meaning that we lose the playback sound pressure level balance between the channels Differences in playback level between speakers caused by forward backward movement 25 cm are plotted by circles O In the Large room where the monitoring distance is 4 0 meters the difference between speakers is approximately 0 8 dB However in the Small room where the monitoring distance is 1 5 meters it is greater 1 8 dB In this way the playback level balance between speakers tends to become unstable in a small playback environment leading us to consider ways to broaden the coverage area This tendency occurs even more markedly if the room is more dead and if the speakers are free standing rather than flush mounted To summarize the above considerations related to monitoring distance can be grouped into the following three situations with appropriate measures to be taken for each situation 3 meters or more Ideal Stable Attention to room acoustics is important 2 3 meters Typical Measures to reduce instability should be taken as appropriat
52. c DVD A Super Audio CD The 5 1 channel 6 channel playback response for DVD A or Super Audio CD is shown below All pass level 1 3 octave band level Input Signal OLFE approx 79dBC 20 120Hz wide pang ae ee C R C approx L C R LS RS 85dBC T L C R LS RS LFE approx 71dB eine 90 80 m 0dB ke F C R LS RS 5 1ch eh 1 70 a a if 20 120H A 60 Full raing 50 _ O Q O Ke Q LO Q Q x x x x O A 2 A amp 6 So 5 NAN FH H o F SF 1 3 octave band center frequency Hz Fig 13 Playback specification for Music program DVD Audio SACD A 5 1 playback environment for DVD Audio or Super Audio CD differs from the 5 1 playback environment for DVD Video in the playback level of the LFE channel For DVD Audio or Super Audio CD the LFE channel is treated exactly the same as other channels In other words DVD Audio and Super Audio CD are actually completely discrete six channel recording media rather than 5 1 channel media Thus in the format books for these types of media it is clearly stated that all channels including the LFE channel must be recorded and played back at the same specifications and no reference is made to special level balancing etc at the time of playback However for DVD Audio the DVD Audio Software Production Guidebook Supplemented Edition published by the DVD Audio
53. ccount the matching of the video with the audio The spread of 45 that we mention here is one example of a placement angle often used when consideration is given to matching video and audio Regarding the placement height it is desirable that elevation angle from the listening point be within 15 If the L R speakers are placed higher than 15 the phantom image generated by L and R tends to blur Fig 21 Wide angular spacing between L and R 60 degree and 45 degree 35 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 3 LS RS For the surround speakers LS RS we have two types a direct surround environment or a diffuse surround environment Fig 22 Direct surround is a method in which the pair of surround speakers is aimed directly at the listening point Diffused surround on the other hand does not have pin point sound source localization for the surround speakers It is a placement method for expanding the coverage area Movie theatres are an example of this Direct Surround Environment Diffuse Surround Environment ITU 100 120 135 qe Playback image Rear Broad surround area GOOD Surround stereo image NGA O GOOD NG Surround panning GOOD GOOD Shallow back Sound field Split front and back Smooth Advantages Precise sound field image Ambient Fly over dynamic I
54. channel and sub woofer differ in their ability to reproduce the low range and careful measurement and adjustment is necessary in order to adjust the band level according to specifications 10 dB 0 dB This means that in actual measurement it is desirable that not only a sound level meter but also an RTA must be used to check the level balance of each channel in octave band levels Using a sound level meter to adjust the all pass level is a simple method of measurement in which precision is guaranteed only if all speakers are in the ideal playback conditions In an environment in which bass management is being applied 10 dB of gain is already being applied before bass management LFE bus so the playback level adjustment must be performed after bass management the sub woofer The 85 dBC value used up to this point is based on adjustments for a movie theater SMPTE 202M 1998 SMPTE RP200 In other words by defining the relative value of the audio source signal level and the playback sound pressure level we can play back the same program anywhere at the same volume When this program is actually played back in this environment a maximum playback volume of approximately 110 dB is obtained Since it is not necessary to define the absolute level for other than movie theater productions the desired value may be used as the pink noise input level or the sound pressure level at the listening point The important thing is that the relative sound pr
55. channel format playback response may not be the same as the recording response The following pages describe playback response for typical media 2 4 1 DVD Video Dolby DTS All pass level 1 3 octave band level Input Signal O LFE approx 89dBC LFE approx 81dB Wide band Pink Noise L C R LS RS 85dBC Tt L C R LS RS approx 71dB approx OVU LS RS 3cB 82dBC T LS RS 3cB approx 68dB 20dBrms F 80 10dB S L C R _LS RS BS 5 1ch 6 tch a 70 ma N LSRS 8 1ch 60 2 120Hz SG amp amp 8 8 8 es amp we eS BS x z m n 1 3 octave band center frequency Hz Fig 10 Playback specification for DVD Video program In DVD Video Dolby DTS the playback level of the LFE channel 20 120 Hz is set so that it will be 10 dB relative to the level of the main channel bands In the case of 3 1 LS and RS are set approximately 3 dB lower so that the playback levels of L C R and S LS RS will be the same Front channel Level L C R 85 dBC Match the playback level of all channels Playback bandwidth Full range Surround channels Level 3 1 S LS RS L C R 85dBC Set the LS and RS playback levels lower than for 5 1 LS RS 82 dBC 5 1 LS RS L C R 85 dBC 6 1 LS RS BS L C R 85 dBC 23 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SO
56. ck that the master source does not contain unwanted ultra low frequency noise E The playback result on consumer playback methods can be checked DVD Video players or AV receivers that have Dolby DIGITAL decoding functionality are required to provide bass redirection functionality equivalent to Fig 35 and bass management is performed when the speaker setting is set to small This functionality is provided to deliver extended low frequency response for the small satellite speakers subwoofer playback setups that are common in consumer listening environments The bass redirection functionality of consumer equipment was originally provided as a requirement for Dolby DIGITAL but is recently being extended to function on a variety of sources such as DTS DVD Audio Super Audio CD and digital broadcasts Bass management is a process of electrical summation in which the low frequency signal of each channel is combined electrically In contrast low frequency signals played back without using bass management are combined by acoustical summation as they pass through the space of the room until they reach the ears of the listener In comparison to acoustical summation electrical summation is prone to cause interference between signals For example if the same low frequency signals are recorded on both the front channels and the surround channels and if they are being processed so as to be nearly out of phase with each other playback via bass
57. d backward movement will affect the speaker placement angle 1 As the monitoring distance is shorter the angle deviation increases rapidly gt Instability in the playback environment is more likely to occur in small rooms than in large rooms In other words the listening area becomes smaller as the monitoring distance becomes shorter 2 The LS RS angle deviation is greater than the L R angle deviation gt Sound field instability is more likely to occur for the surround speakers than for the front speakers 3 The L R angle deviation is greater when moving forward than when moving backward gt It is desirable that the front speakers be placed for broad coverage in front 4 The LS RS angle deviation is greater when moving backward than when moving forward gt It is desirable that the surround speakers be placed for broad coverage in the rear From the above points we can conclude that the playback sound field will tend to become unstable particularly for the surround speakers that are placed in a small room and that it is therefore important to give broad coverage area to surrounds In the experience of the author a fairly stable playback environment can be obtained with a monitoring distance of 3 meters or more and monitoring distances of less than 2 meters tends to produce an unstable sound field Most studios have a monitoring distance between these two in the range of 2 3 meters and this is the same as the values recommended in ITU
58. droom is set at 20 dB and 18 dBrms pink noise is used for a studio in which the headroom is set to 18 dB Pink noise changes significantly in amplitude and it is difficult to determine its input level by using the level meters of the console In the case of 20 dBrms pink noise there will be intensive change in the region of approximate 14 dBFS For this reason it is necessary that the actual value of the pink noise used for detection be known beforehand If 20 dBrms pink noise is to be used for a studio in which the headroom is set to 18 dB the playback level from each speaker must be adjusted so that it is 2 dB 20 dBrms 18 dBrms lower than the target level 61 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation When the headroom is 20 dB Reference signal Reference signal level Peak meter VU meter 1kHz Digital 20dBp p 23dBrms 20dBFS OdB Analog 17dBp p 20dBrms T T Pink noise DC 20kHz 20dBrms 14dBFS 0 1 5dB Table 4 1 The level relationship between 1 kHz and pink noise when referenced to 20 dB When the headroom is 18 dB Reference signal Reference signal level Peak meter VU meter 1kHz Digital 18dBp p 21dBrms 18dBFS OdB Analog 15dBp p 18dBrms T T Pink noise DC 20kHz 18dBrms 12dBFS 0 1 5dB Tab
59. e for the specific case Less than 2 meters Most likely to be unstable It is desirable that the coverage area of the surround speakers be expanded However the monitoring distance is often restricted not only by the size of the room but also by the capabilities of the speakers 44 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 8 Monitor alignment In some cases problems with the size or shape of the studio will mean that it is not possible to place all speakers at an equal distance from the listening point Such problems can occur particularly when partially renovating a two channel studio for multi channel support In general the center speaker is placed closer than the L R speakers and next the surround speakers are often placed closer Under such conditions the following three monitoring problems can occur Distance Time Omm Omsec _ gt dB 8mm 0 02msec iM i Panning 30cm imsec Diffuse surround area im 3msec 10m 30msec 1msec 1 1000sec Fig 33 Monitoring errors caused by differences in monitoring distance 45 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 8 1 Comb filtering Distance difference gt 8 mm If the same sound is played back from two speakers
60. e not seen for the individual channels occur when the two channels are played back simultaneously it is possible that a comb filter effect is occurring due to differences in delay Comb filtering effect 90 annoa A B Difterencelmm Erai msec 80 S 70 T a 60 50 40 1 3 octave band center frequency Hz Fig 56 Time alignment using an RTA checking for comb filtering Fig 56 shows an example in which dips not seen in channel A or channel B occur at 12 5 kHz when channels A and B are played back together In this case this means that there is a playback difference of approximately 0 04 msec between channel A and channel B 0 04 msec corresponds to a difference of approximately 14 mm in difference If you notice a dip caused by this type of comb filtering effect adjust the delay between channels so that the dip is shifted to a frequency higher than the audible limit of 20 kHz If dips are not seen in the region below 20 kHz this means that the two channels are time aligned with a precision of 0 025 8 mm msec or better If a highly correlated signal is reproduced from two speakers from which comb filtering effects have not been eliminated such as in Fig 56 a loss of highs will be perceived in the playback sound at the listening point This is a particularly important problem in a playback environment for musical material that uses signals that are highly correlated between differing channels in an attempt to reproduce prec
61. e production target media The response of each channel recorded on the media will depend on the encoding method and compression method as described above In the case of analog recording the response will depend on the specifications of the recording media However for lossy compression irreversible compression it is important to note that fs and Qb do not directly determine the recording response in particular the dynamic range Currently for most media full range recording is possible for all channels However in the case of LFE and surround channels there will be differences depending on the media 2 3 1 LFE channel For media that is recorded in Dolby DIGITAL such as film and DVD Video the bandwidth is restricted to 120 Hz at the time of encoding This also applies to DTS However in film the range to 80 Hz is the recording band for the LFE channel of DTS Similarly for the MPEG 2 used in digital broadcast Europe the upper limit of the LFE storage bandwidth is restricted to 125 Hz In MPEG 2 AAC digital broadcast Japan full range recording is possible for encoding but due to considerations of the propagation spectrum there may be a bandwidth limitation on the LFE channel Thus it is necessary to be aware of the recording bandwidth of the LFE channel when the propagation system is taken into account see ISO IEC and ARIB For music media DVD Audio Super Audio CD the LFE channel allows full rang
62. e recording in the same way as the main channels To be precise Dolby Digital can record signals of up to about 600 Hz on the LFE channel of DVD Video but since the LFE channel LPF fc 120 Hz is applied by default as an option during encoding it is best to consider 120 Hz as the upper frequency limit for recording and playback on the LFE channel except for special cases 2 3 2 Surround channels S LS RS BS For 3 1 matrix Dolby stereo Dolby surround DTS stereo the recording bandwidth of the S channel is restricted to 100 Hz 7 kHz For 5 0 matrix Dolby Pro Logic II the LS and RS recording channels are restricted to 100 Hz 20 kHz In DTS for film 5 1 6 1 the recording bandwidth of the surround channels LS RS BS is restricted to 80 Hz and above but since sound recorded on the master tape that is lower than this point is collectively recorded on the LFE channel the resulting playback is full range This is known as bass management described in section 4 22 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 4 Playback response By playback response we mean the desired recommended response of the playback system that plays back the media For example this corresponds to the frequency response of each speaker and the level balance It is important to be aware that depending on the media and the
63. e so a space for hearing multichannel audio in a correct playback environment is a requirement not only for commercial applications but also for personal applications This is a case of one hearing is better than a hundred views It is my hope that this booklet will be a step toward obtaining the hundred views that will give you the confidence to construct your own multichannel playback environment Masataka Nakahara author SONA Corporation 4 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 0 Introduction The most important consideration for a studio monitoring environment is that the response of all channels be consistent The second most important consideration is that this consistent response be good response We could list numerous parameters for deciding whether the response is good ranging from subjective to physical but the key point is that there be no large peaks or dips in the frequency response In the case of two channel it is fairly easy to create an environment in which the response of all channels i e L and R is consistent We simply need to ensure that the shape of the room and the placement of the speakers is symmetrical between left and right In the case of multi channel on the other hand it is often difficult to obtain a consistent playback response for all channels
64. eer find it easy to carry out the mixing process It is important that the mixing engineer engage in surround production in an environment in which he finds it easy to mix and creating the multi channel product with consideration of compatibility with other speaker placement To ensure this it is important to understand the characteristics of various speaker configurations Also in actual production variances in playback image due to differing speaker configurations can be minimized if signals highly correlated with other channels are kept out of channels speakers whose location is indeterminate For example in the case of L R it is easy to obtain equivalent playback even between a variety of playback environments so using highly correlated signals is not a problem However for L R and C or for L R and LS RS different environments will have these located in different positions so if highly correlated signals are used there is a danger that the playback image or playback response may be significantly different Caution is necessary if you re using a lot of delay processing to create a sound field or when using production methods in which the correlation between speakers channels is important Correlation of the playback signals L R vs C vs LS RS Compatibility between Robust S d Severe different listening environment Fig 28 Correlation images of the playback signals and Compatibility between different listening envir
65. el Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Relative SPL dB oO 3 soon S A 5 1 3 octave band center frequency Hz 31 5 1 25k Fig 42 Playback characteristics using Bass management controller 2 As discussed above bass management specifications must be determined on the basis of an overall evaluation of numerous factors including the speakers used and the purpose of the studio It is also important to carefully consider filter response and sub woofer placement taking into account how they match the speaker and to require the same quality of sub woofer as the woofer units of the main speakers The true value of bass management appears only when careful adjustments are made to a setup in which these factors have been taken into account However even in a carefully adjusted environment it is not the case that the low frequency portion below 80 Hz sent by the bass management controller to the sub woofer is completely devoid of directionality To some extent care taken in the placement of the sub woofer can improve the sense of directionality but depending on the content the low frequency portion of the surround may be heard from the sub woofer placed in front of the listener In particular for musical content this is often undesirable The region that can be improved by bass management is the region below 80 Hz and for the low range
66. eld including Mr Steven Martz from THX As the lessons I learned from them began to take root in me I have been acquiring valuable new strategies and techniques for studio design Initially I had doubts regarding techniques that seemed at first glance to conflict with a professional approach such as bass management and diffused surround but as I spent time with professionals of multi channel audio I came to see why many top ranked experts with far more experience than myself held these opinions and requirements for surround studios In the process I gradually obtained a glimpse of various problems and aspects of surround playback that lie behind such questions This publication is a valuable booklet that brings together much valuable information obtained from first rate professionals such as Steven from THX I consider myself to have been a ghost writer for these experts and think of them as the real authors of this booklet I would like to take this opportunity to extend my thanks to each of them In view of these intentions portions of this booklet dealing with various standards have been written so as to list the various multichannel formats as broadly fairly and accurately as possible I beg the indulgence of the reader for allowing me to include material that represents my own opinion as an acoustic designer In my opinion user experience as a listener is of great value in the production process In order for this to b
67. elow we summarize and excerpt from material on monaural surround in the DVD Audio Software Production Guidebook Supplemented Edition DVD Audio Promotion Conference 271 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation When reproducing monaural surround S from LS and RS DVD Audio Software Production Guidebook Supplemented Edition If no independent speaker is provided at a location corresponding to monaural surround S it is usual to adjust S by 3 dB and distribute it to LS and RS for playback In most cases at present the player does not have an analog output for the S channel separately from LS and RS so this distribution is performed within the player and the S signal is sent from the analog LS and RS outputs If the player does have an S channel output or if the S channel is being conveyed by a multi channel digital stream via IEEE 1394 etc the amplifier performs the above distribution processing Monaural surround in Super Audio CD Super Audio CD does not provide monaural surround as a format This means that if you are producing monaural surround for Super Audio CD you will need to mono mix the S channel to LS and RS at the appropriate level in the stereo surround LS RS environment 5 1 6 ch is the basic multichannel format for Super Audio CD other formats are supported by recording digital mute signals for unu
68. ent it is important that the mixing engineer understands the playback decoding process of consumer devices and the problems of speaker placement in the typical home To this end it is important not only to have an interest in constructing the ultimate surround playback environment in the studio but also to have a full consumer level experience of how the home surround user sets up his surround environment operates his equipment and listens In two channel production most engineers have mixing techniques that take into account playback on a radio cassette player TV car stereo or through headphones and this is due to their own experience as an end user Due to the above considerations consideration of the playback environment is important when creating multi channel productions and when constructing a monitoring environment for such work the acoustic design and selection of equipment must involve an overall consideration of the following factors 1 Understanding of the format for the media being produced 2 Consideration of the studio environment spaciousness acoustic absorption 3 Consideration of the end user environment compatibility with a variety of playback environments 4 The process of measurement and adjustment This document provides the basic items needed for this process and it is the hope of the author that it will be of assistance to those involved in constructing a multi channel monitoring environment The Yam
69. er to the physical characteristics of the sound wave itself However since Qb 1 bit the quantization noise when encoding is much greater than with multi bit methods and an extremely high sampling frequency is required in order to remedy this The Super Audio CD uses a very high sampling frequency of 2 8224 MHz with Delta Sigma conversion shifting noise shaping quantization noise outside the audible range and delivering better than approximately 120 dB of dynamic range in the audible range The recording bandwidth is said to be DC through 100 kHz In this way there are currently two ways to digitally encode an audio signal multi bit methods and single bit high speed sampling methods Generally PCM or LPCM indicate multi bit methods In contrast since the Super Audio CD is currently the only mass market media that uses single bit high speed sampling single bit high speed sampling and DSD are often used as synonyms 19 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2 2 2 Compression methods 2005 YAMAHA Corporation 2005 SONA Corporation Compression methods can be broadly divided into two types lossy compression and lossless compression With lossy compression the original signal cannot be recovered in its entirety from the compressed signal that is recorded i e this is irreversible compression This method generally takes advantage of psycho
70. ere it is necessary to reproduce all of the playback bandwidth that can be recorded on the media it is necessary to use the bass management controller shown in Fig 41 This type of bass management controller has two low pass filters a low pass filter for the main channel crossover LPF1 and a low pass filter for the LFE LPF2 and allows the cutoff frequency of LPF2 to be changed as needed Most professional bass management controllers are of the type shown in Fig 41 Example LPF1 HPF fc 80Hz LPF2 fc 120 Hz DVD Video movies etc Through DVD Audio Super Audio CD etc AMP 10dB DVD Video movies etc O0dB DVD Audio Super Audio CD Whether this type of bass management controller maintains 10 dB of gain for the region above 80 Hz DVD Video movies will depend on the room acoustics Fig 42 but it is an effective bass management controller for previewing and for work that requires all of the signal recorded on the master to be checked such as when mastering or authoring During the mixing production process on the other hand acoustical operations that would allow signals above 80 Hz which carry a sense of localization to be present in the LFE signal are normally avoided and a low pass filter at fe 80 Hz is usually applied to the master signal of the LFE In this case it is possible to use the bass management controller shown in Fig 35 Fig 41 Bass management controller 2 55 74 Multichann
71. essure balance be maintained If you want to play back at volumes typical of a household environment it is good to make adjustments at about 79 dBC Recently however the expression 85 dB of volume is often used for the playback of multi channel productions regardless of media and it is convenient to maintain an 85 dBC playback position as the reference for a studio The value of 85 dBC when playing back broad band pink noise is a reference value that assumes the speaker has a broad band playback response of 20 Hz 20 kHz This means that in this case the 1 3 octave band level of 71 dB is the true playback level reference value Since the LFE playback level is given as a relative value 10 dB 0 dB relative to the main channel band level a simple comparison of levels is difficult to make if the sub woofer and the main speakers have differing low range playback capabilities Due to considerations such as these it is important to use not only a sound level meter but also an RTA to make measurements and adjustments in order to ensure reliable monitor adjustments If this is difficult you can consider measures such as a simplified measurement using 500 2 kHz band limited pink noise However this cannot be used for adjusting the LFE It is also useful to use the bass management functionality temporarily to extend the playback range of all main channels to the full range of 20 Hz 20 kHz before making adjustments 68 74
72. etween screen speakers in large movie theaters Since the 7 1ch SDDS format is compatible with 5 1ch we can say that SDDS supports both 5 1ch and 7 1ch configurations Dolby ProLogic IIx uses matrix logic processing within the decoder to stereoize BS BSI BSr and at present is targeted for surround processing in the playback system of consumer decoders receivers Current multi channel systems were developed to maintain compatibility with previous systems and have not been researched or developed in order to reproduce a 360 virtual acoustic space This means that if you expect current multi channel systems to deliver full virtual acoustic playback capability you will be at your wits end In particular sound images directly to the side the phantom sound image of L and LS or the phantom sound image of R and RS are difficult to portray with current speaker configurations due to the physiology of hearing The key to multi channel production is how to make effective use of the newly obtained channels to create a product with the maximum entertainment value 7 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 1 3 Key points for multi channel monitoring In our consideration of multi channel monitoring it is important to understand the following three key points Multichannel formats Playback environment Fig 2
73. evel L C R LS RS speaker amp LFE 10dB in band gain LFE none L C R LS RS full range eK L C R LS RS full range LFE 20 120Hz amp LFE none Other methods Interactive etc Table 2 6 Multi channel formats typical examples Games 16 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 1 Surround processing methods There are two types of surround processing method matrix and discrete 2 1 1 Matrix This method uses phase synthesis technology to record a larger number of channels on a limited number of tracks This means that for some channels there may be restrictions in playback bandwidth and channel separation crosstalk Matrix processing is often used for analog recording where the number of tracks is limited such as for the analog tracks of a film or on video cassette tape However in principle it could also be applied to digital media such as CD Recently 5 0 matrix formats using Dolby Pro Logic II have been used frequently in game media Production Playback by end users Lt L total O C in phase signal of Lt and Rt anti phase signal of Lt and Rt Movie VHS etc Fig 4 3 1 Matrix Production Playback by end users Lt L total O Master l Surround processing Surround processing Game etc Fig 5 5 0 matrix If the master source of
74. g to the following guidelines 1 Achievement of room acoustic performance that meets standards for soundproofing NC values and reverberation time etc 2 Consideration of the ideal speaker placement as appropriate for the purpose of the studio and the room environment 3 Monitor adjustments and certification measurements performed by a specialized THX engineer 4 If the room acoustics and monitoring response satisfies the THX pm3 reference values certification as a THX pm3 Certified Studio 5 Following certification certification measures are performed at yearly intervals and monitor response is re adjusted if necessary This ensures that a monitoring environment in compliance with the regulations is maintained 48 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation In order to construct a reliable monitoring environment THX pm3 also requires that playback equipment such as speakers and amps be selected from a list of approved equipment that has met careful testing by THX In addition to this equipment equipment related to surround monitoring such as the bass management controller described in the following section must also be approved The combination of appropriate room acoustic design appropriate combination of playback equipment and a yearly check by dedicated staff makes a THX pm3 Certified Studio tha
75. hara Akira Omoto Room acoustic design for small multichannel studios AES 24th International Conference on Multichannel Audio Banff preprint 2003 Masataka Nakahara Atsuro Ikeda Shin ichi Ueoka Hisaharu Suzuki Akira Omoto On the loudspeaker layouts for multichannel studios AES 11th Regional Convention Tokyo preprint 2003 Hisaharu Suauki Akira Omoto Kyoji Fujiwara Diffuseness and the sound pressure distribution in an enclosure AES 11th Regional Convention Tokyo preprint 2003 Multichannel surround systems and operations AES Technical council document ESTD1001 0 01 05 Surround production handbook in Japanese Mick Sawaguchi editor Kenrokukan publishing 2001 Surround recording technical principles in Japanese Japan Association of Professional Recording Studios Kenrokukan publishing 2001 2004 Masataka Nakahara Acoustic design for multichannel studios in Japanese Prosound magazine vol 103 108 Stereo Sound Publishing 2001 2002 Dolby Digital Check Disc DVD Video All reagion in Japanese Geneon entertainment Inc 2003 AES http www aes org ARIB http www arib or jp Dolby lab http www dolby com DTS http www dtsonline com DVD Audio promotion conference http www dvdaudio net com in Japanese DVD Forum http www dvdforum org ISO http www iso ch ITU http www itu int SDDS http www sdds com Super Audio CD http www superaud
76. io cd com SMPTE http www smpte org THX http www thx com Surround Terakoya by Mick Sawaguchi http nw001 gate01 com mick sawa 721 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Acknowledgement Completion of this booklet was made possible by the cooperation of the following people I would like to take this opportunity to express my thanks to them Honorific titles are omitted e Hisayuki Nakayama e Roy H Onoyama e Mariko Konta e Bike H Suzuki Chairman of DVD Forum WG4 e Norihiko Fuchigami Member of DVD Forum WG4 e Akira Fukada e Shigeru Inoue e Muneyasu Maeda e Satoshi Yoneya e Toshiyuki Shirasu e Steven P Martz e Andrew M Poulain e Shigenobu Kanno e Hirochika Maegaki Tak T Shono Content Production Studio Services Dolby Laboratories International Services Inc Japan Branch Technical Support dts Japan KK Encoding Engineer dts Japan KK Integrated AV System Strategy Div Victor Company of Japan Ltd Technology Development Div Victor Company of Japan Ltd Music amp Entertainment Program Engineering Production Operations Center Broadcast Engineering Department Japan Broadcasting Corporation S Project Product Planning Dept Audio Group HENC Sony Corporation Storage Technologies Development Dept Optical System Development Division H
77. ise sound field expressions 69 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Adjusting the delay between channels is important not only for the broad purpose of correcting the speaker placement locations but also for the purpose of maintaining the playback frequency response in the production environment For this purpose it is desirable that you use monitoring equipment that allows the delay to be adjusted with a precision of greater than 0 025 msec one sample at fs 48k or 44 1k In a playback environment for which all channels are precisely time aligned at a certain point a focused surround playback sound field will be created with that point as its center Normally this point will be the listening point Once a focused surround sound field has been created a location appropriate surround sound field can be experienced even if you leave the listening point In this way creating a clear time aligned listening point does not limit the listening area to a single point but expands the listening area In contrast a surround playback environment whose focus is not defined will have an unsatisfactory sound field at all locations and the least worst point will be the listening point This means that the listening area is conversely narrowed In an environment in which bass management is being applied delay adjustments must be app
78. l Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 5 2 Two channel fold down for Digital broadcasting Japan MPEG 2 AAC 5 1ch Master 2ch Down mix L O _O _ O O Lo Att3 x L Att1 xX C Att2 x LS RO o Ro Att3 x R Att1 X C Att2 x RS C O Meta data LFEO HAt LS O 0 707 3dB MAti2 RS O 0 707 3dB 0 500 6dB 0 354 9 0dB 0 000 codB HAtt3 0 707 3dB WDefault Att1 Att2 Att3 0 707 3dB Fig 16 Flow of a Down mixing Digital broadcasting in Japan MPEG 2 AAC ARIB STD B 21 mandatory 5 1ch Master 2ch Down mix L ome O O O Lt 0 707 x L 0 707 x C Attx LS RS RO O Rt 0 707 x R 0 707 x C Attx LS RS C O LFEO Meta data BAtt ESO Att 0 707 3dB 0 500 6dB 0 354 9 0dB 0 000 codB RSO Fig 17 Flow of a Down mixing Digital broadcasting in Japan MPEG 2 AAC ARIB STD B 21 for external quasi surround processing option The MPEG 2 AAC format defined by ISO IEC is used as the audio format for digital broadcasts in Japan Down mixing is done according to ARIB STD B 21 as shown in Fig 16 and Fig 17 As in the case of Dolby Digital DVD Video the receiver is required to support two types of down mixing one type that provides the attenuation values as meta data Fig 16 mandatory and one type that is surround compatible Fig 17 optional This differs from the Lo Ro downmix Fig 16 of Dolb
79. le 4 2 The level relationship between 1 kHz and pink noise when referenced to 18 dB When the main channel playback level is referenced to 85 dBC Headroom setting of the Signal used for adjustment Speaker playback level studio 20dB 0VU 20dBrms pink noise 85dBC 18dB 0VU 18dBrms pink noise 85dBC 20 dBrms pink noise 82dBC Table 5 The relation between pink noise used for adjustment and the target playback level The Yamaha DM2000 DM1000 and 02R96 digital consoles contain built in 20 dBrms pink noise for purposes of monitor adjustment The pink noise playback bandwidth is cut at an upper limit of 20 kHz so that the power level of the pink noise does not change regardless of the sampling frequency mode 6 2 Main channel level balance Play back the above pink noise from the main speakers and adjust the gain of each amp so that the sound pressure level of each speaker is 85 dBC at the listening point The sound pressure level 85 dBC at the listening point is measured using a sound level meter slow response C weighted frequency curve The sound pressure level indicated by the SPL meter is the all pass level that is the sum of the levels of all bands If the all pass level is 85 dBC the band level of each band displayed in the RTA the 1 3 octave band level will be approximately 71 dB 62 74 sR A 30 M
80. lied after the bass management speakers sub woofer not before the bass management channel buses The Yamaha DM2000 DM1000 and 02R96 digital consoles allow delay compensation to be adjusted in detail for each speaker in steps of 0 02 msec max 30 msec 70 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 7 Summary At present multi channel productions are being released in numerous types of consumer media including film DVD Video DVD Audio Super Audio CD digital broadcast and games The multi channel playback specification is defined for each of these types of media and the construction of a playback environment that complies with these is required of studios in which such productions are being created This means that in order to construct a multi channel playback environment it is first necessary to understand the formats for the types of media that are being produced When compared with two channel systems end user playback environments are highly diverse involving factors such as down mixing and bass management Being mindful of compatibility with the end user environment is professional technique that is a requirement for any workplace that creates packaged media and on this point there is no difference between two channel and multi channel production In order to be mindful of the end user listening environm
81. ment Rec ITU R BS 775 1 is the basis of a surround monitoring environment but in cases such as the following it may be better to consider other speaker placements 1 When dynamic surround panning such as fly overs are an important means of acoustical expression such as in films 2 When many of the target end uses for your productions are at variance with the ITU R placement and you want to give consideration to compatibility with these end users 3 When it is difficult to implement the ITU R configuration in the room studio Or in cases in which forcibly implementing the ITU R configuration produces an unnatural sound field For example if you implement the ITU R configuration in an extremely narrow room the surround speakers would be placed directly beside your ears producing an unnatural feeling surround playback The ideal speaker placement will depend on the size of the room the monitoring radius the distance from the speakers to the listening point and the acoustical treatment of the room absorption diffuseness etc Thus decisions regarding speaker placement must take into account both the character of the media produced in the studio and the physical environment of the studio the size of the space the monitoring radius It is important for the production people to have an understanding of his or her own surround playback environment In particular if you are considering a configuration other than the ITU R which i
82. mix should be recorded on the disc Incidentally since Super Audio CD does not have a down mixing circuit as described above two channel mix material must always be recorded on the disc The surround monitoring functionality of the Yamaha DM2000 DM1000 and 02R96 digital consoles provides down mixing circuitry that complies with Lo Ro down mixing for DVD Video Dolby Digital DTS and digital broadcast Japan MPEG 2 AAC allowing you to check the down mix playback immediately The values of attenuation meta data for down mixing can also be adjusted allows you to determine the appropriate attenuation values for each production 31 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 Playback environment The playback environment consists of two aspects room acoustics which include the room shape absorptivity reflectivity and diffusivity characteristics and speaker placement This chapter will discuss speaker placement Discussions of music related media commonly refer to Rec ITU R BS 775 1 Fig 19 recommendations For other media as well references are often made to ITU R standards or to compliance with the above discussed DVD Video environment 3 1 Rec ITU R BS 775 1 The ITU R speaker placement is a recommendation Rec set forth by the International Telecommunication Union Radio Communication Section
83. mpression method recording response and playback response Most of these types of media provide downmixing functionality to allow two channel playback Multichannel media A D and D A Compression Record specification Surround processing Playback specification Fig 3 Factors that feature multichannel media Currently the following major multi channel formats exist as mass consumer media Media Video cassette tape etc Method 3 1 matrix 5 0 matrix Name Dolby Surround DTS Stereo Dolby Pro Logic II Manufacturer Organization Dolby lab DTS Dolby lab Surround processing method 4 2 Matrix Encode amp 5 2 Matrix Encode Compression method L C R full range Recording response media rai ea LS RS 100Hz 20kHz i S LFE none or added to L R lt 120Hz Piavback tespons Level Level L C R LS RS y p L C R S LS RS LFE none Speaker amp fener renner SS nea nnn nnn nnn nnn penne nea ae tee anne L C R full range gs L C R LS RS full range S 100Hz 7kHz a LFE none Table 2 1 Multi channel formats typical examples Video cassette tape etc 10 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Media Film Method 3 1 matrix Name Dolby Stereo DTS Stereo Manalan Dolby lab
84. must be meticulously matched between the bass management controller and speakers and a sub woofer of equivalent grade to the main channel woofer units must be considered taking careful thought for its placement Bass management that simply imitates Fig 35 is likely to cause various monitoring problems such as separation of sounds and unnatural localization of sound sources In the sections that follow we discuss filter response for bass management controllers E Low pass filter Cutoff frequency This must be set to a frequency low enough that the low frequency signal reproduced by the sub woofer will not have a sense of direction However if the cutoff frequency is set excessively low this will narrow the bandwidth that is handled by the sub woofer and the improvement in low frequency response will be less A frequency lower than 60 Hz is ideal if we give priority to spatialization but in view of how this affects the improvement of low frequency response a cutoff frequency of 80 Hz is usually specified Slope If the slope is gradual sounds higher than the above specified cutoff frequency may be heard and this will produce a sense of directionality from the sub woofer Conversely if the slope is too steep the sense of unity between the main speakers and sub woofer will be diminished and sounds will tend to split between the low range and the mid high range In most cases a slope of 24 dB octave is used E High pass filter
85. nterchangeability of various playback environments Drawbacks Narrow listening area Ambiguous phantom images Fig 22 Direct surround environment Diffuse surround environment 36 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 3 1 Direct surround In the case of direct surround the placement of the surround speakers involves a trade off between surround panning and sense of rear stereo Below we describe the characteristics of typical direct surround configurations 110 10 ITU R 135 150 Fig 23 Fig 23 Subtended angle for surround loudspeaker placement direct surround 110 degree 10deg 135 degree 150 degree 3 3 1 1 ITU R 110 10 In the ITU R placement which locates the surround speakers at the side rather than at the rear there is good left right separation for the surround and it is easy to produce a detailed sound field However surround panning is typically limited to expressions in which the sound image passes rapidly just behind the listener s head without the localization image having much depth and it is not easy to produce surround panning expressions that have a sense of depth In other words sound source movement via surround panning does not describe a circle 3 3 1 2 135 In order for a sound source to be perceived as being behind ra
86. ome Electronics Development Group HENC Sony Corporation Media and Systems Technology Development Department Technologies Development Division PSNC Sony Corporation Media Storage Systems Department Storage Systems Division PSNC B amp P Company Sony Corporation Design Engineering Manager THX Studio THX Ltd Professional Applications Engineer THX Ltd Commercial Audio Division CA Tokyo Branch Yamaha Corporation AV amp IT Business Group Home Theater Products Development Division Yamaha Corporation Marketing Group Commercial Audio Business Unit Yamaha Corporation 73 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Author Masataka Nakahara Engineering manager SONA Corporation http www sona co jp Director of the AES Japan section He graduated from the graduate school of the Kyushu Institute of Design in Fukuoka in 1995 And then he joined the SONA Corporation in Tokyo and is engaged in acoustic design for professional studios In 2005 he received Dr Design degree from the Kyushu University Since 2001 he has cooperated with YAMAHA in development of the monitoring functions for DM2000 DM1000 and O2R96 All product names corporate names and other trademarks appearing in this document are the property of their respective owners This document can also be downloaded from the following
87. on 2005 YAMAHA Corporation 2005 SONA Corporation Regarding LFE recording and playback levels Excerpted and summarized from the DVD Audio Software Production Guidebook Supplemented Edition Systems such as Dolby Digital prescribe the mechanism by which the LFE level is boosted during playback and LFE is boosted 10 dB by the playback system in the same way during production as well On the other hand in DVD Audio specification audio tracks LPCM MLP the LFE signal level not the signal amplitude itself but the playback reference level is handled in the same way as other channels and it is assumed that all channels will be at the same level This means that LFE does not require any special handling in the way of level adjustments at the time of production The final LFE volume obtained in the end user environment may be affected by numerous factors such as the bass management system applied by the user s system Ultimately if we are not taking bass management into consideration the signal level of all channels should be thought of as equal Thus for DVD Audio and Super Audio CD note that the LFE playback level must be 0 dB just as the other channels which is 10 dB in comparison to DVD Video playback environments such as Dolby or DTS The frequency bandwidth of the LFE signal also differs from DVD Video in that since an LPF is not applied during encoding full range recording and playback is possible However as stated in the DV
88. onment 41 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 6 SUB When placing the sub woofer we must take the acoustics of the room into account For example placing the sub woofer in the corner of the room will produce good results in terms of power but may produce problems in the frequency response due to disruptions caused by standing waves Fig 29 shows an example of the measured relationship between the sub woofer location in the listening room and the frequency response 4 It can be seen that the frequency response changes in various ways depending on the location of the sub woofer When placing the sub woofer we must consider both the playback power and the frequency response Frequency responses Room plan fi CK keed BY 5E 74 N yo gh Y a EFN Sub woofer Relative SPL dB Measured position I Y 3oct band frequency Hz Fig 29 Placement of the subwoofer and Frequency responses Measured examples In some cases placing two sub woofers in appropriate locations can stabilize the playback environment Fig 30 shows an example 6 of calculations performed to simulate the differences in sound pressure distribution between one sound source and two sound sources You can see that playback using two sound sources produces less variance of sound pressure
89. onstructed at unity gain and that the 10 dB for the LFE is obtained by the amp of the playback system This means that when using this type of professional decoder you merely need to use a DVD Video playback environment in which the LFE playback gain is adjusted by 10 dB For consumer devices that perform the same processing you will need to take the same actions In this way when monitoring the decoder output in a studio in which the monitoring environment has been adjusted for master production it is necessary to know the output diagram of the decoder you are using 58 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 5 Monitor systems As stated at the beginning of this booklet multi channel monitoring involves three key points multi channel format bass management and playback environment In order to meet the needs of these three points a multi channel monitoring system must contain three main structures monitor matrix bass management controller and monitor alignment In other words monitor matrix corresponds to multi channel format bass management controller to bass management and monitor alignment to playback environment It is not enough for a surround mixing console that the main buses simply provide multi channel support In addition to the reco
90. oration 2005 YAMAHA Corporation 2005 SONA Corporation 3 Height of each speaker 1 2 m listener ear height The surround speakers LS RS may be placed higher than L C and R as long as the elevation angle is within 15 Surround speakers LS RS are placed at the sides rather than at the rear It is said that this type of placement at the sides toward the rear is able to provide more information to the human auditory system It is one of the most effective placements in order to supply information that is lacking in conventional L R two channel playback However it is difficult for this type of horizontally located surround speaker placement to provide a sound image that has depth in the backward direction 3 1 2 Regarding placement of the image Rec ITU R BS 775 1 contains the following note regarding the relationship of the L R sound image width and the width of the video image The screen of a TV image has often been found to be the size shown in Fig 20 which is narrower than the width of the L R sound image 60 degrees The discrepancy B between the visual image and the sound image is 13 5 degrees HDTV or 6 degrees On the other hand in a film playback environment it is usually the case that the angle of L R sound image spread is the same as the angle of the visual image spread producing a difference in mixing for TV and for film For improved compatibility between TV mixing and film mixing it is good to use a
91. ound in a 360 path by surround panning in a circle This configuration is suitable when the front panning and the rear panning are both important We can say that while ITU R is better at portraying a sound field the 150 placement is better at localizing a sound image However as the surround speakers are placed farther to the rear the surround sound field will tend toward monaural and there will be a more distinct separation between the front and rear sound fields 3 3 2 Diffuse surround The most common method of creating diffuse surround is to use several surround speakers When multiple surround speakers are to be placed it is important that the speakers be placed in the side area lt 135 and the rear area gt 135 Fig 24 This makes it easy to construct a monitoring environment that provides the advantages of side placement and rear placement allowing both a sense of stereo separation in the surround the advantage of side placement and 360 surround panning the advantage of rear placement On the other hand when the surround channels consist of multiple speakers the sound intensity vector of the LS and RS has been found to be located at the phantom sound image of multiple speakers 4 5 For example if speakers are placed at 100 and 150 the sound intensity vector when the LS or RS channel is played will indicate the 125 direction which is the same as if a speaker were placed at 125 If compatibility with direc
92. ptimize the frequency response of all channels for that room C The 10 dB band gain for the LFE channel can be ensured By using bass management a playback gain of 10 dB relative to the main channels can be applied to the entire LFE bandwidth If the 10 dB playback gain is not consistently applied to the LFE the LFE effect will often be obscured by other channels and will not be heard correctly film DVD Video An environment in which the playback quality of the LFE channel is ensured is extremely important for LFE production for film or DVD Video 51 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation D All channels can be given a playback response equivalent to large monitors that reproduce the ultra lows starting at 20 Hz Most professional sub woofers are able to reproduce the low range down to about 20 Hz On the other hand virtually no main speakers are able to reproduce the low range down to 20 Hz with the exception of only a very few high quality models By using bass management all main speakers can be extended to allow low range playback down to 20 Hz This is particularly important for studios that produce material for theaters such as film In a movie theater L C and R are reproduced by enormous speakers that are able to play back the ultra low frequencies When creating productions for theaters it is important to che
93. rding buses that divide up the main buses it is desirable that monitor buses routed via the monitor matrix also be provided separately To Recorder Bass Monitor Monitor i management matrix alignment controller Multichannel Bass Playback formats management environment Fig 47 Flow of a multichannel monitoring system 59 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 5 1 Monitor matrix A monitor matrix circuit is required if you will need to perform both 5 1 and 3 1 processing or if you need to produce audio for different media such as DVD Video and film even though both of these are 5 1 A monitor matrix is also required in order to audition the down mixing functionality defined by DVD Video Dolby DIGITAL DTS The monitor matrix is normally part of the mixing console s functionality The monitor buses of the Yamaha DM2000 DM1000 and 02R96 digital consoles provide a monitor matrix that is optimized for surround monitoring This makes it easy to produce down mixes or to change the surround playback level attenuation when switching between 3 1 and 5 1 5 2 Bass management In order for a small to mid sized studios to obtain a monitoring environment in which the low frequency response is managed it is good to apply a bass management controller to the monitor system Checking the bass management
94. rer Organization Surround processing method Dolby lab LS RS 3 2 Matrix encode DTS LS RS 3 2 Matrix encode Compression method Dolby AC 3 L C R LFE APT X100 Surround back channel Encode LS RS Recording response L C R LS RS BS full range L C R full range LFE lt 120Hz LS RS BS 80Hz 20kHz media LFE lt 80Hz LS RS and BS information below 80Hz is summed into the LFE channel during the encoding process Playback response Me ae pa speaker amp LFE 10dB in band gain es L C R full range LS RS BS 80Hz 20kHz LFE 20Hz 80Hz L C R LS RS BS full range LFE 20Hz 120Hz Table 2 2 continued from preceding page Multi channel formats typical examples Film 12 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Media DVD Video Method 3 1 matrix 3 1 discrete Name Dolby Surround Dolby DIGITAL Manufacturer Organization Dolby lab Dolby lab Surround processing 4 2 Matrix Encode g method Compression method Dolby AC 3 Recording response media L C R full range S 100Hz 7kHz L C R S full range Playback response speaker amp Level L C R S LS RS L C R full range Level L C R S LS RS L C R S LS RS full range S LS RS 100Hz 7kHz Method 5 0 matrix 5
95. rmatsS sssesssesecosecosecsscosscoseosecosecosecosecsscosscosecsscosscosecsseosecosecsseosecosecosecsseosecsseosseossesseoe 9 2 1 Surround processing methodS sessessssssessessstesertstereststeseristesentstenetnsesenreresenesseses 17 2 2 Encoding and compression methodS e sssssesssssissersssssesistssesissssesesrssesesriseserssesee 19 2293 Recording TESPON SEn sessed no cusstcaveseusesescessuabeanssctstetecsueopsvastensbeosveestevendvesy 22 2A Playback respons Es ea R A A Aa 23 2 5 Down mixing 3 Playback environment ssesssessesesessescsessescssoscssssosossssoscssssosessssosossssosesessosessososessososessososessssoscssssosesessos 32 SEIA AIA NO E A o e EAE EA A E A E 32 DoD E E E E A E E IE RIE EE T eters 35 33 LS RS oienerenireana iia a i e 36 Det OEE EAA AA E EAA EA E E EAT 40 3 5 Playback image compatibility with the playback environment cece 41 37 Ou SUB ESAE AE AEE AATE AEE EET 142 3 7 Monitoring distance oc cesececseececsesesessesseecscsssseessessesssesecessessesseesaaeaees 43 3 8 Monitor Al SN MEN Css ssrin sen e o n EE EEEE A E 45 3 9 THX pm3 Certified Studios c cccccecssessessessesseessesseesuecsecsessecsecsnesuecseeseeneeneenes 48 4 Bass ManageMent cccccsssssssssssssesssssssssssssscsesesessssssssssesesesesesesesesesssessssssssesesesesssesesesesesesesesesesesees 4 1 Acoustical treatment of the room 4 2 Speaker placement cece escceccesecscsesscscsessescsesscsssesscss
96. s often called the standard for the playback environment it is important to understand the characteristics of your particular playback environment Speaker placement is determined largely by two factors the angle of L R separation and the placement of the surround speakers 34 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 3 2 L R We will consider two angles of separation for the L R speakers 60 and 45 If we want to emphasize compatibility with conventional two channel systems such as used for music playback we give priority to the 60 placement If the playback environment of the end use is primarily post production for TV or movie theater we usually give priority to the 45 placement However it is not the case that there is a clear division with film sound using a spread of 45 and music using a spread of 60 For example most production workplaces for broadcast programs are based on the ITU R playback environment 60 The placement of 45 for film and 60 for music is a principle that applies in most situations but in other post production or broadcast program production situations it is necessary to consider a placement that suits the intentions of the prodution In the case of audio playback that accompanies video it is important to consider not a numerical value of 45 but rather a placement that takes into a
97. sed In this case the playback environment will be as described for DVD Video The Yamaha DM2000 DM1000 and 02R96 digital consoles support these various playback environments by providing LFE boost functions and LS RS attenuation functions in the bass management section of their surround monitor functionality making it possible to switch instantly between playback environments 28 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 5 Down mixing Most multi channel media requires two channel playback There are two possible ways in which content equivalent to a multi channel production can be mixed to two channels One way is to generate a separate two channel mix using the individual musical materials stems that were used for multi channel mixing The other way is to use electrical circuitry to forcibly create the two channel program fold down The fold down algorithm is defined for each type of media and the production side must store attenuator values etc on the media as meta data Typical examples of two channel fold down are shown below 2 5 1 Two channel fold down for DVD Video Dolby DIGITAL DTS 5 1ch Master 2ch Down mix L O _ _O O Lo L Att1 X C Att2 x LS O Ro R Att1 x C Att2 x RS co Meta data Dolby DIGITAL mAttt LFEO 0 707 3dB 0 596 4 5dB 0 500 6dB LS O BAti2 0 707
98. sed channels as well as setting mute flags This means that the same playback environment can be applied for all channel formats of Super Audio CD 2 4 4 Broadcast Dolby DIGITAL DTS MPEG 2 MPEG 2 AAC In the case of Dolby DIGITAL or DTS the DVD Video playback response is used In the cases of MPEG 2 and MPEG 2 AAC the response is defined by the administrative body LFE channel handling in particular For MPEG 2 digital broadcast Europe the ISO standard limits the LFE recording bandwidth to 125 Hz but the playback level is defined by the administrative body For the LFE of MPEG 2 AAC digital broadcast Japan full band recording is possible according to the ISO IEC specification However in some cases bandwidth limitations may occur during propagation ISO IEC In actual operation bandwidth limitation and playback level is defined by the ARIB Association of Radio Industries and Businesses In the cases of MPEG 2 and MPEG 2 AAC the playback level of LS and RS for monaural surround the S LS RS channel in 3 1 must also be as specified by the administrative body 2 4 5 GAME Audio for games falls in two categories multi channel playback for the movie portion of role playing games etc and interactive multi channel playback that occurs in response to movements within the game These multi channel formats will depend on the audio processing method used by each manufacturer Currently Dolby DIGITAL or DTS are widely u
99. sessessseessesseeseessaseeeeaaegs 4 3 Electro acoustic methods resnie a a AE O NA 4 4 Monitoring the decoder output seeeseseseseesisrststsisrsrsrsisisisiststststststststsrstsrstsentnenenee 5 Monitor SYSteMS oisit aen ienasi aa aeiiae iae i iier Ee ea e ees 59 5 1 Monitor matrix ssenari 60 5 2 Bass mahagement ainesest eeeescsesessescsesseecsesesesesseessessesssesseseeessesesesaeseeeaaeee 60 5 3 Monit r alignments eriein seriei tara t A ETE E EAE EEE onevedebeseseceteaent 60 6 Measurement and adjustment ccccsssssccssssscsssssscsecsssesesessssesessssecessssecessssecersssssessssesesessesessesesers 61 Gle TESES SNAN aR A EAE AEN E A NNR 61 6 2 Main channel level balance seccare 62 6 3 Narrow band pink noise oo eee eee ce cs eseeeeecsesscscseseessesecsssesseeesesseseeesseeeeesaeee 65 6 4 LFE channel level balance cece cece ce EA CAAA RR 67 6252 Delay ACFUSHMENLS reeeo estre it iaca ness naststvasavessvensuseivanonesdvscsscebvaneyeatuncanetonaseyestrasanes 69 7 DUMMA Y oieee eaa ie ei a e E e E E A E e a a i ai Reference materials 2 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Foreword Surround sound has evolved into more than the experience heard in cinemas Through the introduction of the DVD it has invaded most every aspect of our lives our homes our cars and even our workplaces We now listen
100. simply by creating a symmetrical speaker placement and room shape Mixing of the final product must be done in a properly configured playback environment No matter how high the grade of your equipment it is impossible to create a final mix unless you have a good sounding playback environment The essential identity of a professional studio is in its good monitoring environment The arrival of multi channel is a good opportunity for us to reconsider the question of what is a studio monitoring environment 5 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 1 What is surround 1 1 Stereo and surround Multi channel is sometimes called surround and two channel is often called stereo The precise terms are as follows Correct term two channel stereophonic Abbreviation two channel Common term stereo Correct term multi channel stereophonic Abbreviation multi channel Common term surround Stereo phonic spatial acoustics 1 2 Channel configuration At present a variety of channel assignments have been proposed for various types of media The most popular of these are shown below Fig 1 2ch 3 1ch 5 1ch 6 1ch 6 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 1 2 1 3 1 ch
101. slightly above the middle of the screen This is because most people appearing in a film will be shot at bust level or standing so that the mouth from which dialog originates is usually located in the upper half of the screen By placing the center channel which is used mainly for dialog in the upper part of the image we can increase the fusion between the dialog and the image a for Audio Fig 26 Height of the center loudspeaker placement Acoustical transparent screen or without video images If an acoustically transparent screen is not used the center speaker should be placed above or below the video image If the center speaker is placed below the video image it will be easy to align the L C R speakers vertically allowing you to easily construct an environment with good acoustical playback response On the other hand placing the center speaker above the video image will provide good matching of the dialog and the visual image and will be better for the audio video programs In this case keeping the vertical difference between the L R speakers and the center speaker to less than 7 will make it easier for L lt gt C R panning to move the sound image smoothly for Audio with video images for Audio Fig 27 Height of the center loudspeaker placement Video Monitor 40 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 S
102. surround soundfield to be efficiently reproduced using a minimum number of channels There is also a commonality between the QUAD placement and the ITU R placement namely that the angle of spread between L and LS and between R and RS is 90 Thus it is thought that a placement of about 90 is favorable for the relationship between L R and LS RS In other words we can conclude that 37 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation because the ITU R configuration with its L R spread of 60 is based on maintaining compatibility with conventional two channel stereo its surround speakers were placed correspondingly further toward to the front comparison to QUAD If the naturalness of just the surround playback soundfield is to take priority over the relationship between L R and LS RS we can say that a placement of 135 which uses the rear half of the QUAD configuration is a good placement 3 3 1 3 150 If you require that the surround L and R have the same acoustical conditions as the front L and R placing the surround speakers at 150 will produce a placement that is completely symmetrical between front and rear However to be precise there must also be forward rear symmetry in the shape and other acoustical aspects of the room In such a placement the L R spread and LS RS spread are identical and it will be easy to move the s
103. t reliably delivers an accurate multi channel playback environment The Yamaha DM2000 DM1000 and 02R digital consoles are the first mixing consoles whose bass management and other surround monitoring controller functionality have been approved as THX pm3 Approved equipment DM2000 and 02R96 Ver 2 1 and later DM1000 Ver 2 0 and later In addition to being the first approved bass management controllers built into mixing consoles these are also the first full digital THX pm3 Approved bass management controllers This indicates that the surround monitoring functionality of the DM2000 DM1000 and 02R96 provides sufficient functionality to act as a stand alone monitor controller I EX m Mji v m o MHL For details regarding THX pm3 Certified Studios refer to http www thx com THX and THX pm3 are trademarks of THX Ltd which may be registered in some jurisdictions All rights reserved 49 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 4 Bass management In a small to medium sized studios room modes due to standing waves often become a problem and it is easy for inconsistencies to develop in the low frequency response of each speaker This can impair the following important requirements for multi channel monitoring 1 That all channels have a consistent response 2 That the LFE playback
104. t surround must be considered as a part of diffuse surround you should consider the positioning of the surround speakers phantom sound images Fig 24 Two loudspeakers placement for each surround channel Diffuse Surround 38 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Incidentally Rec ITU R BS 775 1 gives examples of multiple speakers used as surround speakers and it is stated that in this case these speakers should be placed in the range of 60 150 symmetrically between left and right Fig 25 Rec ITU R BS 775 1 Four surround loudspeakers 3 3 3 Direct surround and diffuse surround The advantage of direct surround is that it excels in precise reproduction of a sound field For example a placement such as ITU R is ideal for reproducing a live recording in a concert hall Recent research has confirmed the effectiveness of the ITU R placement in reproducing a diffuse sound field 3 For the above reasons direct surround and the ITU R placement in particular is often used as the production environment for musical content such as DVD Audio and Super Audio CD In broadcasting stations as well there is a tendency for a direct surround environment compliant with Rec ITU R BS 775 1 to be used as the production environment On the other hand diffused surround excels in delivering ambient or fly over sounds and
105. the LFE channel contains the important information and it needs to be played back it should be mixed into L amp R in advance 17 74 2 1 2 Discrete Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Playback by end users Production O BS in phase signal of LSt and RSt Surround processing Surround processing Movie DVD Video etc Fig 6 6 1 matrix This method allows each channel to be recorded as a completely independent track This became possible with the advent of high capacity media such as DVD and with the advance of digital compression technology Playback by end users Production O Master Surround processing Surround processing DVD Video DVD Audio DTV etc Fig 7 3 1Discrete Production Playback by end users Master Surround processing ji Surround processing Movie DVD Video DVD Audio Super Audio CD DTV GAME etc Fig 8 5 1 Discrete 18 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Production Playback by end users Master Reiss POR aa Surround processing Surround processing DVD Video Fig 9 6 1 Discrete 2 2 Encoding and compression methods 2 2 1 Encoding methods When encoding an analog signal into a digital signal the encoding performance is l
106. ther than beside the listener it is said that the surround speakers need to be placed at 135 or more toward the rear In most households it is common for the speakers to be placed not at the side as in ITU R but rather behind at approximately 135 If you want the surround speakers to have a character somewhere between placement at the side 100 120 and placement at the rear 150 it is good to place the speakers at a position of 135 In such a configuration of LS and RS the spread between LS and RS will be 90 which is the same as the speaker configuration for the four channel 2 2 QUAD format that appeared in the 1970 s and subsequently disappeared However in QUAD the L and R speakers were also spread at an angle of 90 and it was recommended that all four speakers be placed at equal conditions in other words the angle between L and LS and between R and RS is also 90 For this configuration it was said that its lack of compatibility with conventional stereo in which the L and R spread is 60 prevented its subsequent popularization but recent research has reported that it does have a high degree of sound field reproducibility and there are examples in which this configuration is still used today in research systems for virtual playback The QUAD placement is often seen with the single point microphones or IRT cross configurations often used to record a surround soundfield and is a method that allows a
107. to multi channel audio delivered via television programs video games and even by the music of our favorite bands With the introduction of the DM2000 DM1000 and O2R96 Digital Consoles Yamaha provides a platform that includes complete surround sound mixing and monitoring capabilities for studios of all types These consoles offer a vast array of features and functions that enable the user to create a world of multi channel content Masataka Nakahara the celebrated acoustician studio designer and the author of this booklet and SONA Corporation have designed and supported numerous THX pm3 Certified Studios As the THX pm3 representatives in Japan they continually inform and educate studios owners in the calibration and design of studio playback systems During the development of these consoles Mr Nakahara offered his years of experience to assist in the design of the surround monitoring capabilities In conjunction with THX engineers the release of the Version2 software expands their features even further This THX pm3 Approved revision includes the addition of THX presets for film DVD and music mixing These are the same settings used in THX certified studios Studios have a long track record in mixing mono and stereo content but for some industry professionals multi channel mixing is relatively new There are more channels more equipment and more techniques to be learned How do you set up your studio Do I use bass management There are man
108. ultichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation CH Media L c R LS RS BS LFE 3 1 S LS RS 85dBC DVD V 85dBC 85dBC 85dBC LS RS 82BC DVD A T T T Film T T T T Digital x EN aN Prescribed by 7 broadcast administrative body 5 1 DVD V 85dBC 85dBC 85dBC 85dBC 85dBC 10dB band gain 89dBC 20 120Hz Film T T T 82dBC 82dBC T DVD A T T T 85dBC 85dBC 0dB band gain 79dBC 20 120Hz Super an a ai Audio CD T T T Rec t T T T T T Prescribed by administrative body 6 1 DVD V 85dBC 85dBC 85dBC 85dBC 85dBC 85dBC 10dB band gain 89dBC 20 120Hz Film T T T 82dBC 82dBC 82dBC T Table 6 Playback level balances 0 terti TRS Te00000 HE g 10 HFH 3S O oHa x x x DO 5S oH Oo bo a N op 1 3 octave band center frequency Hz Fig 49 Frequency characteristics of the filters of the sound level meter A C F Fig 50 is a table showing the levels of each 1 3 octave band for pink noise whose all pass level is 85 dBC If the all pass level is 85 dBC the 1 3 octave levels will be approximately 71 dB In other words when C weighted filtering is applied to the thirty one bands 71 dB and the bands are summed the all pass level will be 85 dBC Incidentally all pass level with F weighted filtering will be 86 dB 71 dB 10 log 31 band 86dB F 86dB F 1dB energy loss of a C weighted filter
109. utorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 6 Measurement and adjustment In two channel playback placing the L and R speakers at the left and right of the listening point and playing them back at the same power will allow both L and R to be received at the same power and the same timing However for multi channel playback simply powering all speakers equally is not usually enough to ensure that all channels including LFE are received at the appropriate level balance and the same timing This means that in most cases a process of measurement and adjustment is required when setting up a multi channel listening environment To measure the monitor response and make adjustments we need pink noise as a source signal and a sound level meter to measure the playback sound pressure level of the speakers In addition a 1 3 octave analyzer RTA Real Time Analyzer is usually necessary when making the actual measurements Mixing Console RTA MAIN LFE Pinknoise 20dBrms i 20dB 0VU gt LFE SPL meter Recorder Fig 48 Measurement and tuning for DVD Video 6 1 Test signal Broad band pink noise of 20 Hz 20 kHz is used as the signal for measurement The level dBrms of pink noise used as the sound source shall be the reference for the headroom setting 0 VU of the studio In other words 20 dBrms pink noise is used for a studio in which the hea
110. websites http www yamahaproaudio com http www sona co jp Multichannel Monitoring Tutorial Booklet M2TB 2 Edition May 2005 rev 3 5 2 Copyright 2005 Yamaha Corporation Copyright 2005 SONA Corporation 74 74
111. whose distance to the listening point differs by 8 mm or more dips will occur in the frequency region below 20 kHz A distance of 8 mm corresponds to a minute time difference of approximately 0 025 msec when converted by the speed of sound and can be caused not only by differences in physical distance but also by the rigidity of the speaker the wiring and electrical delay produced by equipment 3 8 2 Haas effect Distance difference gt 30 cm This is also called the precedence effect which is the phenomenon that causes the perceptual sound source to be strongly localized around the closer of two sound sources The distance difference at which the Haas effect appears depends on the type of signal but in general is greater than 30 cm A monitoring environment in which the Hass effect is occurring may experience problems such as failure of the sound image to move smoothly when panning occurs For example if the surround speakers LS RS are placed more than 30 cm closer than the front speakers L C R the sound source movement when you surround pan from surround gt front will not be heard smoothly because the perceptual panning is pulled strongly toward the surround speakers Another problem is that in a diffuse surround environment the surround coverage area may not be wide enough causing the perceived sound image to be located only around the nearest surround speaker 3 8 3 Crossover with the sub woofer Distance difference gt
112. y Digital DVD Video in that some of the attenuation selection parameters are different and that 3 dB of attenuation is applied at the final stage In addition to the above two down mixing methods ARIB STD B 21 also allows a receiver to have within certain defined standards its own proprietary down mixing option for virtual surround 30 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation 2 5 3 Two channel fold down for DVD Audio 5 1ch Master 2ch Down mix o Lmix Atti XL Att2 x R Att3 x C Att4 x LFE Att5 X LS Att6 X RS Rmix Att7 X L Att8 X R Att9 X C Att10 X LFE Att11 X LS Att12 X RS Meta data MAtt1 Att12 1 000 OdB 0 001 60dB 0 000 codB lt 0 2dB step 0 40dB lt 0 4dB step 40 60dB MiDefault N A Fig 18 Flow of a Down mixing DVD Audio DVD Audio down mixing circuits have full matrix mixer functionality consisting of twelve attenuators and ten phase switches The attenuation values can be set in detailed steps of either 0 2 dB or 0 4 dB Since default values are not specified for each parameter the parameters must be specified as meta data when encoding and stored on the disc in order for the player to perform a down mix to two channels fold down DVD Audio on the other hand allows you to record meta data that prohibits down mixing by the player and in this case a separate two channel
113. y questions to be answered This booklet offers an excellent compilation of the knowledge required to construct a properly configured surround playback environment Much of this document shares the same principles as THX pm3 program We are proud of our association with Yamaha Mr Nakahara and SONA Corporation and their efforts to create a manual to help guide the user It is my sincere wish that engineers carefully read this guidebook in order to obtain an accurate understanding of the surround monitoring functionality provided by the Yamaha digital consoles Here are the tools Now it s up to you to create the perfect mix Steven P Martz THX Ltd 3 74 Multichannel Monitoring Tutorial Booklet M2TB rev 3 5 2 Masataka Nakahara SONA Corporation 2005 YAMAHA Corporation 2005 SONA Corporation Preface As one whose profession is the acoustical design of studios I place great value on the parting ceremony of handing over to its new owner my creation studio whose playback environment and acoustical response I have ensured In order to actualize these characteristics in a multichannel studio it is necessary to collect the fragmentary technical information provided by various standards organizations and manufacturers and then to organize and understand this information Doing so takes an enormous amount of time but one of the most valuable things I gained from the process has been friendships with many superb professionals in the fi
114. yback limitations at the low and high ranges 2 Acoustical response of the room Inconsistent low frequency response In addition to the above the results of adjustment can be affected by the margin of error in the measurement system such as 3 Response of the sound level meter mic Inexpensive units are not able to measure the high frequency range As described above there is a close relationship between frequency response and the all pass level This means that in an environment where there is inconsistency between the playback levels of each channel it is possible that major errors may occur if you make adjustments using only a sound level meter all pass level 85 dBC and that it is therefore desirable that you also use an RTA to check the band levels 71 dB 1 3 octave If you suspect that there is inconsistency between the frequency response of the channels but it is difficult to make adjustments using an RTA then you may be able to obtain good results in some cases by using 500 Hz 2 kHz band limited pink noise as the adjustment signal The reason is that 500 Hz 2 kHz band limited pink noise does not include the low frequency region which often causes instability in the frequency response of the playback environment nor the high frequency region which is easily affected by the quality of the sound level meter Fig 52 shows the response of broad band pink noise black and 500 Hz 2 kHz band limited pink noise gray You can see

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