Yamaha White Paper (Installation Series Speakers) Reference Guide
Contents
1. We could minimize the phase change over the whole range and obtain the gentle descending phase characteristics with no sudden phase change as well as obtain the smooth amplitude characteristics 5 Phase characteristics of the Installation series The following graphs show the phase characteristics of the Installation series and the competition model From these graphs you can see that the phase characteristics of the Installation series are almost the same regardless of directivity drive mode and model A White Paper Of The Installation Series Loudspeakers lt Figure 11 Phase characteristics comparison gt YAMAHA INSTALLATION SERIES Competition model Comparison between different directivity patterns Comparison between different directivity patterns Orange IF2115 64 bi amp Blue IF2115 95 bi amp Orange Competitor s 15 LF 2way 60x40 bi amp Red IF2115 99 bi amp Green IF2115 AS bi amp Blue Competitor s 15 LF 2way 90x50 bi amp Comparison between different drive modes Comparison between different drive modes Orange IF2115 64 bi amp Orange Competitor s 15 LF 2way 60x40 bi amp Purple IF2115 64 passive Red Competitor s 15 LF 2way 60x40 passive Comparison between models Comparison between models Orange IF2115 95 bi amp Blue IF2112 95 bi amp Orange Competitor s 15 LF 2way 60x40 bi amp Green IF2208 Purple IF2108 Green Competitor s 12 LF 2way 60x40 bi amp Red IF2205 13 62. Designing and developing style Designing as well as developing a prototype was made in three separate stages In the first stage Proto 1 for the first sound evaluation was developed In the second stage Proto 2 was developed reflecting the result of the Protol evaluation The basic designing of the enclosure and horn as well as driver selection was done by Audio Composite Engineering Yamaha made the detailed data measurement and listening test not only in the anechoic room but also in the practical environment Then the analyzed results as well as summaries of issues and resolutions were reported to Audio Composite Engineering for feedback In the third stage based on Proto 2 the preproduction was made in the factory where the final products were produced using the parts and materials for mass production This was the trial production stage for checking the quality of the final mass production products Various enclosures using different materials or paints were made Various components were mounted to these enclosures and tested The following reports the current situation for each component Horn We evaluated horns by measuring data such as the phase response and amplitude response as 11 A White Paper Of The Installation Series Loudspeakers well as giving listening tests to check clearness resolution audio image size etc The horn with 1 4 inch throat used for 15 inch and 12 inch mode
3. Summary In the autumn of 2004 we invited the estimators and had the meeting at Audio Composite Engineering for evaluating the tone quality of the final prototype Using CDs and microphones that were brought by estimators evaluation was carefully made The meeting finished amid a storm of applause In Japan we also had the similar meeting for evaluating the tone quality Both meeting ensured us that the Installation series realized our design concept and offered top quality sound Especially realizing the family sound concept was well received Through the speech test in English and Japanese using a microphone it was proven that the series could amplify voices in both languages very clearly Yamaha Installation series speakers for facilities solve the problems caused by using multiple speakers together We really hope you confirm its tone quality tone color matching when using more than one speaker together linear reaction of EQ etc Yamaha is planning to add the 3 way model and 2 way middle power model to the series in the future Yamaha is also planning to introduce the digital speaker processor at the end of 2005 Regarding DSP processing for driving the Installation series you can use general speaker processors because no special crossover filter and 14 A White Paper Of The Installation Series Loudspeakers EQ are used However we believe that the Yamaha DME24N 64N are the best combin
4. 3 dB As the phase difference increases the area ib A White Paper Of The Installation Series Loudspeakers affected by the dip caused by the interference expands as well as the dip frequency lowers When the phase difference is 90 degrees if 0 is 15 degrees or less the level difference at 1kHz or below is within 3 dB When the phase difference is 150 degrees even if O is 0 degrees or less the level difference at 1kHz or below is more than 6 dB These results show that when using more than one speaker it is very important to match the phase characteristics of the speakers in order to get the same response at any position in the room lt Figure 7 Test condition gt 0 degree lt Figure 8 Characteristics in the overlapped area gt Phase 0 degree Relative SPL dB S 100 1000 Phase 90 degrees Relative S P L dB 100 1000 10000 Phase 120 degrees Relative S P L dB 100 1000 Frequency Hz 10000 Relative S P L dB Frequency Hz 10000 In actual speaker installation to a theater etc it is common to use several speaker models with different directivity according to the necessary cover range Also there may be several speaker handling power combinations see Figure 9 A White Paper Of The Installation Series Lo
5. between the different speaker models For example in a live concert it is common to make speaker arrays using the multiple same speaker systems However in a facility it is common to use different speaker models together agi A White Paper Of The Installation Series Loudspeakers Yamaha thought that even if different speaker models are used in a system we should offer a white canvas and paid attention to the phase characteristics aiming for the unification of the phase characteristics through the series As for sound quality we aimed for both the clearness of speech PA and the high fidelity sound reinforcement of vocals musical instruments while the unification of the tone color Family Sound Concept of all products in the series was the basic concept Also we made a great effort to reproduce the natural dimensions of the sound image In other words the size of image must be an accurate representation ofthe source particularly with regard to speech In short the design concept of the Installation series is to realize the concepts for the phase characteristics and tone color The following explains the details of our concept as well as how to realize the concept 2 Consideration of speaker phase characteristics In a design of the installation series we investigated the influences of phase characteristics of speakers into their responses at receiving points at first 1 About phase char
6. type though the phase significantly changes over the whole range lt Figure 10 Minimum phase change type and same phase slope type 180 Phase degree 180 Minimum phase change type Frequency 180 2 bh oO g oO S a a 180 Frequency Same phase slope type Before starting designing the Installation series we made prototypes of both minimum phase change and same phase slope types and gave a listening comparison test The following shows the result When testing with a bi amp speaker using the DSP though there was a different nuance in the crossover range it was hard to say which one was better When testing with a passive speaker the minimum phase change type with a simple 9 A White Paper Of The Installation Series Loudspeakers network circuit sounded better Also there was a fear that each model may have the different delay time of the low frequency driver if all the Installation series speakers were adjusted by applying the same phase slope method This might cause the problem when using more than one speaker together By these reasons above we decided to use minimum phase change type 2 Tone quality control 1 Target sound We set the main targets of the installation series to halls theaters and churches Such facilities might have conferences music concerts musicals lectures etc Therefore for the SR system offering clear and good sound wa
7. 7 Hz 1 626Hz 1 626 Hz 15 0 517 0 517 0 518 1 087 Hz 1 086Hz 1 085 Hz 20 0 683 0 684 0 684 817 Hz 816 Hz 816 Hz Phase difference 90 degrees 0 L 6 m L 12m L 24m 5 0 087 0 087 0 087 4 336 Hz 4 332 Hz 4 331 Hz 10 0 174 0 174 0 174 2 170 Hz 2 168 Hz 2 167 Hz 15 0 261 0 261 0 261 1 449 Hz 1 448 Hz 1 447 Hz 20 0 347 0 347 0 347 1 089 Hz 1 088 Hz 1 088 Hz Phase difference 120 degrees To confirm the validity of our consideration we made the following test Using the Yamaha SREV1 we created the phase differences of 90 120 and 150 degrees at 2 kHz by simulating the impulse response that has a different inclination of phase characteristics in the frequency range Then we compared the frequency response at the testing point Figure 7 shows the test condition while Figure 8 shows the result The testing point is fully apart from the wall We use a boundary microphone in order to avoid the effect of the reflected sound from the wall and floor All the results are standardized by the result under the condition where 8 0 and no phase difference Both speakers have a 60x40 directivity and the degree of their side taper is 15 degree When there is no phase difference if 0 is 15 degrees or less the level difference at 2 kHz or below is within 3 dB If 6 is 25 degrees or less the level difference at 1 kHz or below is within
8. A White Paper Of The Installation Series Loudspeakers YAMAHA CORPORATION PA DMI Division Advanced System Development Center 1 Introduction The ease with which a speaker system can be adjusted to match the characteristics of a facility is of the utmost importance to sound contractors and engineers In the same way that a painter s canvas must be white in order to show the true colors of his paints a speaker system must be a white canvas in the sense that it accurately reproduces the waveforms provided as input and responds in a linear fashion to equalization in audio terms it needs to provide a flat response The two most common causes of such uneven response are comb filter caused by the installation or architectural condition and difference between the phase characteristics of the speakers The former must be considered in the aspect of the system design such as speaker angle etc The latter should be considered as the important matter for making the Yamaha speaker system as white canvas lt Figure 1 Speaker measurement condition gt A White Paper Of The Installation Series Loudspeakers We made the simple test for measuring the phase characteristics using two 2 way speaker systems Figure shows the setting Speaker system A has 60 degrees x 40 degrees horizontal x vertical of the high frequency directivity while speaker system B has 90 x 50 The amplitude response is almost the same When driving
9. acteristics between drivers Even a single speaker system may have the out of phase problem for example between HF and LF drivers of a 2 way speaker system Figure 4 shows the phase response of a 2 way speaker system The cutoff frequency is 1 5 kHz for both the HPF 18 dB oct BW and LPF 18 dB oct BW Let s focus on 1 5 kHz frequency now From the graph of the amplitude response you can see that 1 5 kHz frequency sound is reproduced both by the HF and LF drivers From the graph of the phase response you can see that the phase difference between HF and LF is 180 degrees Both signal levels are equal so both cancel each other and in result the dip is created in the amplitude characteristics Also in the overall phase response graph you can see that the phase suddenly changes between kHz and 2 kHz In result the speaker system has a bad phase characteristics around the crossover point Figure 5 shows the phase response of the same 2 way speaker system as Figure 4 however the speaker system is adjusted for reducing the phase difference in the range between 1 kHz and 2 kHz within 90 degrees The slope of the phase characteristics is constant over the whole range so the bad influence to the amplitude characteristics is minimized The installation series has smooth phase response that has the constant slope over the whole range A White Paper Of The Installation Series Loudspeakers lt Figure 4 Influence of the p
10. ation in terms of tone quality We are planning to show you the DSP setting data and EASE data at the Yamaha web site in the near future Note that we used the Yamaha PC OIN series power amplifier in the final process of tone adjustment Currently in parallel with hardware developing for these items we are developing a simulation software application that can be used easily in the designing stage of the sound system All you have to do is to enter data of the room shape room size sound pressure level at the listening position Based on the data this application will recommend you the best array configuration It also allows you to simulate equalization for compensation of the array characteristics The result of equalizing simulation can be stored to the Yamaha DME24N 64N as a library file By using this simulation software application with the Yamaha Installation series you can dramatically save time for setting adjustment Finally we would like to extend our heartfelt thanks to Audio Composite Engineering and Mr Michael Adams Reference 1 G Davis and R Jones Sound Reinforcement Handbook Second Edition Yamaha 1989 2 D Davis and C Davis Sound System Engineering Second Edition Focal Press 1997
11. both speaker systems that have the same phase characteristics simultaneously the relative S P L increases by 6dB at all frequencies as shown in Figure 2 We then changed the phase characteristics of speaker system B and made measurement The result is shown in Figure 3 In the frequency range where the phase difference is more than 120 degrees significant cancellation is observed in the amplitude response you can see the cancellation in the range where the phase difference is between 120 and 240 degrees In the frequency range where cancellation is observed the equalizer does not respond in linear so it is very difficult to improve the frequency characteristics using the equalizer lt Figure 2 Driving two speaker systems that have the same phase characteristics gt Amplitude Speaker A HH Speaker B A B Relative S P L dB 100 1000 10000 Frequency Hz Phase Degree Speaker A Speaker B A B lt Figure 3 Driving two speaker systems that have different phase characteristics gt Amplitude m D A As u o 2 5 Speaker A m Speaker B A B 100 1000 10000 Frequency Hz Phase Phase Degree Speaker A Speaker B A B 100 This problem happens not only between the same speaker models but also
12. el Unification of the tone color between the high power and middle power models using the same enclosure Unification of the tone color between the different enclosure models 10 A White Paper Of The Installation Series Loudspeakers 3 Minimizing the electronic compensation The equalizing operation compensates the amplitude response on the other hand it causes deterioration of the phase characteristics The more you compensate the amplitude response the more the phase changes So we aimed for minimizing the electronic compensation using the equalizer Especially for the crossover range we aimed not to use the equalizer at all 4 Cooperation with an outside speaker designer We decided to design the speakers in cooperation with an outside speaker designer The leader of the Yamaha speaker developing team was Akira Nakamura He was the developer of the NS1000M long seller hi fi speaker the NS10M de facto standard speaker in the studio and the MSP series powered monitor speakers We appointed Mr Michael Adams as the outside speaker designer He is not only a veteran speaker designer but also has a long experience as an SR engineer and currently he is the chief designer of Audio Composite Engineering a speaker designing company in U S A He understood and Yamaha s concept that seemed to be very difficult to make it realize He is one and only speaker designer who has golden ears of an SR engineer 4
13. hase difference to the amplitude response gt Relative S P L dB Low High T T 100 1000 10000 Phase Degree 2 o 12 High RE i 151 Low High TY T 180 100 10000 1000 Frequency Hz lt Figure 5 Response of a speaker system that has in phase units gt Relative S P L dB Low High 100 1000 10000 Phase Degree High Low High 2 Discussion on phase response when multiple speaker systems are used For installation to a hall theater church ete multiple speakers may be stacked in arrays In such conditions there may be a problem in the overlapped area where more than one speaker covers That is as described in 2 1 above there may be a dip in the amplitude response This is because of the phase difference that is caused by the distance difference between the speaker position and the listening position Therefore from the view point of the system design it is very important to reduce the overlapped area but actually it is very difficult to perfectly eliminate it Under the condition where two speakers are used as shown in Figure 6 Table 1 shows the relation between the distance difference and out of phase frequency The distance difference shows the difference between the d
14. istances from these speakers to the testing point The frequency shows the point where the phase difference caused by the distance difference is 90 degrees The parameter 6 is the angle with the center axis Table 1 indicates the following When the overlapped area is within 10 degrees the phase difference caused by the distance difference in the overlapped area is within 90 degrees at 1 kHz or less frequency regardless of the distance from the sound source When the overlapped area is within 20 degrees A White Paper Of The Installation Series Loudspeakers the phase difference is within 120 degrees at 1 kHz or less frequency It is thought that under this amount of phase difference interference can be ignored Therefore in this condition it is very important to match the phase characteristics of two speakers in order to get the amplitude characteristics with no dip as with the discussion of phase characteristics between drivers described earlier Note that practically because the directivity of a speaker changes depending on frequency you have to consider frequency directivity and distance lt Figure 6 Considering the characteristics in the overlapped area gt lt Table 1 The relation between the distance difference and out of phase frequency in the overlapped area gt 0 L 6m L 12 m L 24m 5 0 174 0 174 0 174 3 3252 Hz 3 249 Hz 3 248 Hz 10 0 347 0 347 0 347 1 62
15. ls improved sound penetration and resolution This is the maximum size horn that can be fitted in the enclosure The material is FRP that is enhanced using glassfiber and deadened by adding the anti vibration material All horns are rotatable within the 90 degree range Compression driver for high frequency range After repeated listening tests for pursuing the family sound we selected drivers In result all selected drivers are made by the same manufacturer The driver used for the 15 inch or 12 inch model features the 3 inch voice coil and titanium diaphragm The edge and diaphragm are integrated The edge is tangentical type for higher durability and better tone quality Woofer for low frequency range To prevent collapsing the sound image at high power the 15 inch and 12 inch woofers use 4 inch voice coils The woofer has been carefully selected by considering the following Offering both the high damping factor and smooth low frequency response Sonic matching with the enclosure Smooth crossover to high frequency The magnetic circuit uses a large ferrite magnet for enhancing the magnetic density resulting clear and crisp sound Enclosure After the listening tests we decided to use 11 ply Finnish Birch for the enclosure material The tuning frequency is set to the point where the sound pressure from the port affects the low frequency response most effectively We made prototype in which the
16. ower will be available in the autumn of 2005 models with the same enclosure Same phase characteristics between different enclosure models The phase difference between speakers at 2 kHz must be within 90 degrees 2 Using the minimum phase change type There are two methods of controlling the phase characteristics of multi way speaker systems A Minimum phase change type This method aims for minimizing the phase change between 20 Hz and 20 kHz It realizes the smoothly changed phase characteristics within one lap 180 degrees to 180 degrees It is likely to have the level down problem of the amplitude characteristics in the frequency range where low frequency and high frequency drivers are crossed over B Same phase slope type This method aims for the smooth phase change over the whole frequency range It does not aim for minimizing the phase change By adding a delay to the low frequency driver to match the phase slope of the low frequency driver to the slope of the high frequency driver the phase characteristics of two drivers are smoothly joined With this method at the boundary of the phase characteristics of the two drivers the phase difference is 360 degrees However from the view point of boost cut of the amplitude characteristics it can be regarded as the same phase which can avoid the level down problem in the crossover range This method is simpler and easier than the minimum phase change
17. s the minimum requirement as well as providing enough audible level at any position in the area Furthermore it was also required to offer high fidelity sound for vocal and music instruments as well as for playback of music or ambient sound Therefore for tone quality of the Installation series products we aimed for realizing the following in addition to the flat amplitude characteristics Speech intelligibility Well balanced and well separated tone for music Non coloration sound regardless of the total level Same timbre at any position within the directivity range Adequate audio image size of each source 2 Family Sound Concept For a facility in a hall theater or church auxiliary speakers such as under balcony speaker and frontfill speaker may be used for audience in addition to the main speakers The sounds generated by these speakers are mixed in the room hall space However it was very difficult to get the same timbre at any position in the room hall because the timbre of each speaker is different if the size or model is different even though the manufacturer is the same Now Yamaha introduces Family Sound Concept According to this concept all speaker models in the same series has the same tone color Unification of the tone color between the different directivity models using the same enclosure Unification of the tone color between the passive and bi amp modes of the same mod
18. tuning frequency point was calculated by computer simulation and gave the listening tests repeatedly for checking the matching between the enclosure and woofer then made change for improvement As for the enclosure shape to keep the clear sound we set the side panel and baffle to the same height This eliminates sound reflection by the side panel which may make the sound unclear We reinforce the inside by bracing considering the strength and resonance In result we ensure the clear tone quality with no speaker box noise 25 mm glass wool is used inside the enclosure as the sound absorption material resulting the well balanced low frequency sound that is tight but sustained To get the higher sound penetration 63 of the metal grille is open Network To prevent the sound deterioration by inserting the network the network is very simple 12 A White Paper Of The Installation Series Loudspeakers For the low frequency network of the 15 and 12 inch models a coil binding 15 gauge copper wire to the large silicon steel plate core and a large film capacitor with small Tan 0 ensuring the high resolution sound even at high power input To get the same phase response and amplitude response as those at the bi amp operation we made computer simulation and actual measurement repeatedly until we completed the network design As a whole we could accomplish both In Phase Concept and Family Sound Concept
19. udspeakers For designing the Installation series speakers Yamaha focused on this point and considered it very important to match the phase characteristics not only between the same speaker models but also between different models lt Figure 9 Variations of speaker combinations gt lt Same enclosures different directivities gt 60 x 40 90 x 50 lt Same enclosures different drive modes gt Bi Amped Passive Drive lt Same enclosures different power models gt High power model Middle power model lt Combination of different enclosure size models gt LS Tr 15 LF 2way 8 LF 2way 3 Design concept According to the experiment mentioned above we recognized a phase control as the one of the most important factor Then we especially focused on the balance of a phase and tone control and aimed to realize both the In Phase Concept and family sound concept The followings are details of each concept 1 Phase control 1 In Phase concept From the result described above the phase characteristics of all speakers in this series must be the same Same phase characteristics between the same enclosure models that have different directivities A White Paper Of The Installation Series Loudspeakers Same phase characteristics between passive and bi amp models with the same enclosure Same phase characteristics between high power and middle p
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