User Guide
Contents
1. i oS EA aud oft dud oe m oe eoe 17 5 1235 7 Naas a 0 oO Comp Listen Dynamic sl al Je al comp U oN i0 N20 2NA O Dynamic Ea oct Hz dB SIDE CHAIN BANDWIDTH FREQUENCY GAIN SIDE CHAIN a Figure 13 Active controls in Linked Mode Stereo Linking in Compressor Mode Linked Compressors use the rms sum of the two channels side chains and display this summed result on the side chain dBr meters of both channels The Master channel settings determine the actual gain reduction characteristics Linked Controls in Dynamic EQ Mode When channels are linked in Dynamic EQ mode both channels use the Master channels control settings but the dynamic EQ essentially functions independently for each channel Combin ing the rms values of broadband and bandpass signals as is done in Compressor mode is of no advantage in Dynamic EQ mode Stereo Linked Limiters When channels are linked the Master channel Limit Threshold setting determines the maximum output level for both chan nels However the greater of the two peak detected signals is used to control the gain of both Master and Slave channels For example if the Slave channel signal exceeds the Mater channel s Limit Threshold by 3 dB both channels are limited by 3 dB The Limit Headroom meters remain independent for both chan nels as the dynamics of the Master and Slave channels may be quite different When channels are Linked e By2. based on this difference there fore it is our experience that Relative Threshold Dynamic EQ as described above is the best dynamics processor for this task as it is able to maintain proper sibilant to non sibilant balance regardless of level A good de esser looks at the average level of the broadband signal 20 Hz to 20 kHz and compares it to the average level of a bandpass filter in the side chain The threshold setting defines the relative threshold or difference between broadband and bandpass levels which result in compression of sibilants Because de essing depends on the ratio of sibilant to broadband signal levels it is not affected by the absolute signal level allowing the de esser to maintain the correct ratio of broadband to sibilant material regardless of signal level as shown in Figure 4 25 E Ap lt 0 83 De essing 20 50 100 200 500 1k 2k 5k 10k 20k Frequency Hz Figure 4 The C4 s De essing performance remains consistent with varying input levels This means that the de essing performance is consistent and predictable regardless of how loud or quiet the singer talker is Taming sibilance when the talker is quiet is just as important as when the talker is at a fevered pitch Figure 5 shows what happens using a primitive de esser with a side chain EQ
3. of the transmit ted signal in broadcast Figure 8 shows the effect of limiting a signal The top line is the original full volume input signal we need to limit perhaps the unfortunate blast of noise when the vocalist inadvertently unplugs the phantom powered mic The bottom line shows the limited output At no point does the output signal ever exceed the threshold demonstrating the limiter s brick wall capability Contrast this with Figure 9 which shows a compressor set to a high ratio co 1 and a fast attack time Due to the compressor s averaging effect the output easily overshoots the threshold and transient peaks are missed altogether And it s these peaks which can potentially ruin your speakers or the perfect recording take and possibly your reputation THRESHOLD RELEASE SIDE CHAIN Figure 7 Peak Limiter Block Diagram cmogectoecoO vi Limit Threshold Output Limit Threshold Overshoot Output i Figure 9 Compressor used as a limiter Signal peaks can still exceed threshold even at high ratio settings 15 10 5 s 5 E 10 15 20 25 30 Threshold 35 40 AAU 40 35 30 235 20 15 10 5 0 5 10 15 20 Input dBu Figure 10 Peak Limiter Response Graph Manual 5 Making Connections The C4 features auto balanced unbalanced XLR and 14 TRS input and ou
4. ratio of 3 1 Set the threshold high enough so when the person is the normal distance there is no response and only when they move closer to the mic does the threshold kick the filter into action 2 The second application compensates for the loss of proximity effect as the person moves the microphone away from their mouth typical of most hand held mics Solve this problem by perform the opposite routine as the po dium mic example above Have the person hold the microphone at the farthest distance from their mouth that can occur Set the Dynamic EQ so that it is just below threshold Once they move the mic closer to their mouth it will reduce the low frequency boost Since we have become accustomed to hearing the proxim ity effect try low ratios so that the tonality change is slight but remains more consistent than without the Dynamic EQ Use appropriate EQ on the input channel to add back in any missing warmth this warms the signal while the Dynamic EQ keeps the tonality consistent Typical starting points are a frequency of 100 250 Hz a band width of 2 0 octaves and a ratio of 2 1 depending on the desired change in tonality 2 3 456789 1000 Hz Figure 6 Microphone Proximity Effect courtesy of Shure Inc Low 2 3 456789 10000 20000 frequencies rise as the sound source gets closer to a cardioid microphone Manual 4 Auto EQ Changing Sound Sources A great example is evening out the tone or timbre of a gu
5. ANE OPERATORS MANUAL C4 QUAD COMPRESSOR LIMITER o oy o 2 yas o5 12 SIDE CHAIN W SIDE CHAIN SIDE CHAIN Quick Start Rejected Rane advertising slogan 1743 C4 It ll blow your mind We re not entirely sure why the marketing department didn t like the idea but be assured unlike its explosive material namesake the C4 Quad Compressor will not blow up Heck it won t even spark or sizzle under normal circumstances The only thing smokin will be your mix thanks to the C4 s smooth compression precise dynamic EQ and ultra fast limiting Each of the C4 s four channels offers a full featured compressor with selectable Compressor and Dynamic EQ modes In ad dition an oversampled brick wall LIMITER is included for catching signal peaks COMP THRESHOLD RATIO ATTACK RELEASE and KNEE give full control over the audio envelope The compressor is toggled on and off using the ACTIVE BYPASS switch the Limiter is engaged at all times and is not affected by this switch Limiter operation is completely independent of the com pressor with its own LIMIT THRESHOLD control and Headroom meter Channels 1 amp 2 and 3 amp 4 can be LINKed to maintain a proper left right stereo image with channels 1 and 3 acting as the MASTERs respectively For the ultimate in dynamics processing flexibility the C4 includes both internal and external side chain functions with a full PEQ parametric EQ section included for good measure Ex
6. ATTACK RELEASE and KNEE 100 i25 32 50 250 i 50 2s 25 500 25 Auto ms ms J ATTACK RELEASE Auto Hard Soft KNEE ATTACK determines how fast the gain is turned down once the signal exceeds Threshold and is adjustable from 25 ms fast to 500 ms slow The W pointer at 25 ms shows the typical setting for De essing RELEASE determines the rate of gain increase as less gain reduction is required and is adjustable from 25 ms fast to 2 seconds slow It is important to understand the difference between release rate as determined by this control and release time The Release setting determines how long it takes for the gain to change by 10 dB not how long it takes to return to unity gain no gain reduction Example with the Release control set to 1 s when a signal with 5 dB of gain reduction presently applied suddenly drops below threshold the release time is 0 5 s calculated as follows Gain Reduction x Beta 5dBx a 0 5s Auto Attack and Release Unsure about how to set the Attack and Release controls Venue doors opening in 15 minutes and you need to speed through sound check No problem Simply rotate the Release control fully clockwise until Auto is lit indicating the Attack and Re lease settings are appropriately fixed for most types of program material The C4 s not entirely on auto pilot though you still have full control over the Threshold Ratio Gain and Knee set tings We are t
7. Dynamic EQ Relative Threshold Dynamic EQ is a special form of dynamic EQ where the rms level of the bandpass signal in the side chain is compared to the rms level of the broadband signal The differ ence between the bandpass and broadband levels is compared to the threshold rather than the absolute rms value of the bandpass signal The advantage of this type of dynamic EQ is that the relative amplitude of a band of frequencies as compared to the broadband level is maintained regardless of broadband ampli tude The typical topology is shown in Figure 3 THRESHOLD RATIO ATTACK RELEASE FREQ BW SIDE CHAIN Figure 3 Relative threshold dynamic EQ block diagram De essers De essing limits or controls the sibilant content of speech Sibilance produces a hissing sound English sibilant speech sounds are s sh z or zh De essing is often confused as a type of dynamics processor It s actually a specific application that is accomplished using many different types of dynamics processors And contrary to popular belief successful de essing is not as simple as placing a bandpass or treble boost filter in the side chain and calling it done Frequency Sensitive Compression Split Band Compression Dynamic EQ and Relative Threshold Dynamic EQ are all used for de essing True de essing involves comparing the relative difference between the troublesome sibilants and the overall broadband signal then setting a threshold
8. IDE CHAIN Parametric EQ 2 e 640 e 0 e Q Q Q 0 5 10 20 20k 12 12 oct Hz dB BANDWIDTH FREQUENCY GAIN PEQ The Side chain PEQ filter operates in one of two ways depend ing on whether the channel is operating in Compressor mode or Dynamic EQ mode PEQ in Compressor Mode In Compressor mode the PEQ section operates as a normal 2 _order parametric filter with independent BANDWIDTH FREQUENCY and GAIN controls The GAIN control has a center detent position indicating 0 dB or unity gain Use the PEQ to adjust the sensitivity of the rms detector to specific frequencies Boosting a particular frequency makes the detector more sensitive to this frequency while cutting makes it less sensi tive Broadband compression still takes place the filter does not directly affect the frequency response of the main signal as is done with the Dynamic EQ used in de essing Example reducing detector sensitivity to low frequencies helps avoid the pumping and breathing often associated with compressing an overall mix of instruments Start by engaging Listen mode and set the PEQ Gain to 12 dB with a bandwidth of 1 to 2 octaves Adjust the frequency and bandwidth controls until most of the low frequency sound disappears 125 Hz is a good start Oh and don t forget to dis engage Listen mode when you re done PEQ in Dynamic EQ Mode In Dynamic EQ mode the PEQ controls define a bandpass filter in the side chain and a Dynamic EQ in the main s
9. Sibilance during loud passages is attenu ated but there is no gain reduction during quiet passages even though there may still be a significant amount of sss in the person s voice For a given threshold this often results in an overly aggressive effect during the loud choruses and a com pletely ineffective result during the hissy whispered verses al Ap ks De essing e 17 5 V 20 225 25 d 27 5 B No De essin u 30 32 5 35 37 5 40 42 5 20 50 100 200 500 1k 2k 5k 10k 20k Frequency Hz Figure 5 Primitive de esser with a simple side chain Varying input levels adversely affects de essing Manual 3 Dynamic EQ Applications Auto Correct Microphone Proximity Effect Use Dynamic EQ to automatically correct for timbre changes due to the low frequency boost caused by the proximity effect of cardioid microphones see Figure 6 which occurs when a singer speaker does not remain a consistent distance from the microphone Two opposite applications share this problem 1 The first occurs when the mic is located far enough from the person that the proximity effect has no bearing typically a podium situation then the speaker leans in closer to the microphone causing a low frequency boost Start with a 100 250 Hz center frequency a bandwidth of 2 octaves and a
10. actual gain cor rection value as determined by the THRESHOLD RATIO ATTACK RELEASE and KNEE controls Gain reduction may be indicated when the Threshold indicator is off as attack and decay rates may dictate continued gain reduction even when the rms level is below threshold MASTER SLAVE Stereo Link 1 LINK 2 3 LINK 4 MASTER SLAVE MASTER SLAVE The MASTER SLAVE switches link channels 1 amp 2 or channels 3 amp 4 for stereo operation When linked the associ ated LINK indicator lights and only the controls of the Master channel channel 1 or channel 3 are active with the exception of channel ACTIVE BYPASS switches This feature helps pre serves a stable left right image when compressing a stereo source such as a vocal or horn submix 1 uk 2 21 12 6 3 1 e421 ee MASTER SLAVE eeeoecneoeoeo di Reducti 2 o 12 6 e Br 20 ot 12 MTO A umit u nil dB COMP THRESHOLD RATIO GAIN COMPTHRESHOLD RATIO GAIN e 10 100 500 10 125 Is 2019 9 OF A 125 N 1s 2o o OF 500 25 J auto 50 250 oe Qe at 50 Jas of 30 x10 12 OH C 40 r2 24 25 50 25N auto WK 40 _A22 24 He ATTACK 2 RELEASE 7 KNEE ms m pJ ATTACK RELEASE KNEE Auto 0 5 oct BANDWIDTH FREQUENCY GAIN 18 12 es z di 5 a e 2 o 7 ion dB A D 209 0 AN 6 ACTIVE BYPASS 15 5 6 ACTIVE BYPASS ge a8
11. all W pointer next to a control indicates a typical set ting for De essing Listen routes the side chain signal to the channel output allow ing you to hear exactly what the detector hears and is especial ly useful when making precise PEQ adjustments for frequency sensitive compression or de essing The yellow indicator flashes when Listen is engaged as a friendly reminder to toggle back to Comp or Dynamic EQ mode before show time The Listen source depends on the selected mode Comp or Dynamic EQ so the switch operates as follows when switch ing from Comp to Listen the Comp indicator remains lit and the Listen indicator flashes which signifies you are listening to the Compressor side chain PEQ response When the switch is moved to Dynamic EQ the Listen and Comp indicators are turned off and the Dynamic EQ indicator is lit When the switch is then moved from Dynamic EQ to Listen the Dynamic EQ indicator remains lit and the Listen indicator flashes which signifies you are listening to the Dynamic EQ response Remember once the show begins the audience never hears the filtered side chain signal unless you accidentally leave Listen mode engaged of course If something sounds a bit odd during the gig look over at the C4 and see if any of the yellow Listen lights are flashing If so casually saunter over to the rack and toggle the side chain out of Listen mode as if you meant to have it engaged for the first six songs S
12. e if you added treble boost to the side chain audio either by using the C4 s built in PEQ or an outboard EQ it would not affect the high frequencies in the main signal path but it would cause them to cross the threshold sooner and more often Large peaks of treble would cause heavy compression with no compres sion at other times This example is the basic de esser a circuit to remove excess sibilance There is a much more sophisticated and effective de esser built into the C4 but more on that later With a bass boost you can make a de thumper and with a midrange boost a de nasaler There are a number of parameters governing side chain activ ity but the four primary ones are Threshold Ratio Attack time and Release time THRESHOLD BW GAIN RATIO ATTACK RELEASE SIDE CHAIN Figure 2 Frequency sensitive compressor block diagram Dynamic EQ Dynamic EQ differs from the forms of compression listed above in that it dynamically controls the boost cut of a parametric filter rather than broadband frequency gain The basic dynamic EQ uses a bandpass filter in the side chain with variable center frequency and bandwidth The side chain detector is sensitive only to the passband frequencies A parametric filter with match ing bandwidth and center frequency is placed in the main signal path and the boost cut of the filter is controlled the same way a broadband compressor boosts or cuts broadband gain Relative Threshold
13. e with a medium to slow release and a relatively low threshold Experiment from these initial settings One of the favorite uses of compression by guitarists is to in crease the sustain or duration of a note after it is played Carlos Santana and Gabor Szabo are two musicians who use sustain to great acclaim although they did it the old fashioned way of cre ating feedback by aiming the guitar pick ups at the loudspeaker and then jamming over it A compressor creates a similar effect Set a high ratio and low threshold for long sustain along with fast attack and slow release Again experimentation produces the best results Drums Reducing the leading edge of a drum hit and bringing out more of the body of the drum is another popular use of compressors Try ratios between 2 1 and 5 1 accompanied by fast attack and release times Listen carefully while changing the attack time to find the final setting Cymbals need a fast attack but a slow release to allow the sustain through A low ratio of about 2 1 works well to start Digital Recording For digital recording use the C4 to compress a too wide dynamic range into a signal that does not cause digital overload The Limiter is the primary tool for keeping things under control but a little compression with its threshold set just under the limiter threshold level helps keep the limiting more subtle To control a stereo mix set the mode switches to Slave ORane Corporation 10802 47th A
14. hain goes through the volume control in the hand on a control analogy Side chain The side chain is the hand that controls the volume Side chain circuitry also known as the detector examines the input signal and issues a control message to adjust the gain of the main signal path Full featured compressors like the C4 offer both internal and external side chain options When the internal option is selected the compressor s input signal feeds the detector This arrangement works well for most applications and is especially Manual 2 Output Level dBu 4 lt _ Lf a LIMITER Limiter 00 1 COMPRESSOR 7 4 The Ratio controls 2 7 the amount of gain reduction above the Threshold LIMIT THRESHOLD The Limiter Threshold controls the hinge point of a Ratio set at c0 1 COMP THRESHOLD The Compressor Threshold controls the hinge point 60 50 40 30 20 10 Input Level dBu Figure 1 Compressor and Limiter functions effective with the C4 due to the parametric EQ built into the side chain The external side chain allows any signal source con nected to a dedicated input jack to feed the detector thereby de termining the compressor s response This external signal may be a specially filtered version of the input signal using an outboard EQ for example or it may be another signal altogether It is important that the side chain signal is not heard For instanc
15. he Knights of KNEE KNEE controls the action of the compressor above and below the threshold point Hard knee does nothing until the signal exceeds the threshold point then applies full compression Soft knee begins applying a small amount of compression just before the threshold point is reached continues increasing compres sion through the threshold point and beyond finally applying full compression to the highest level signals Depending on the application and source material soft knee settings can sound more natural On the other hand for maximum loudness before compression for equipment protection for instance use hard knee settings Knee span is adjustable from 0 dB Hard to 10 dB Soft with the Threshold always being at the center of this span The Y pointer at the Hard Knee setting shows the typical setting for De essing Ap cmQqectecO b o u kth kw KH 4 OO amp HLL PULLAA EEE PE 7 46 100 H LHL ELL ULI L 10 9 8 4 5 4 3 2 2 3 4 45 6 7 8 49 10 Input dBu Figure 15 The Hard Knee compression characteristic has a 0 dB span The Soft Knee compression characteristic has a 10 dB span SIDE CHAIN Mode and Listen Comp Listen Dynamic EQ oD SIDE CHAIN Comp selects Compressor mode for the channel Dynamic EQ selects this mode for the channel Tip A sm
16. ications cesses 4 SIDE CHAIN Mode and Listen uu 9 Peak Limiting sssini ariii 5 SIDE CHAIN Parametric EQ sesser 9 Making COnnectiOnS ss sssesssesnsnsnnnununununannnnnnnnnnnnnnenana 6 Limit Threshold and Headroom Meter sses 10 Front Panel Controls ssessssesnuuennuunnnunnnnunnnunnnnunnnnnnnnnnnn 6 Tips and Tricks aioe ecteatscccestictatcteatest nee aeteccensaence 10 WEAR PARTS This product contains no wear parts Manual 1 Dynamics 101 Revisited Introduction Compressors and limiters are in the business of automatically controlling the volume or dynamics of sound just like your hand on the fader or the fat man dancing in front of the mid range cabinet Used wisely often in conjunction with each other or with equalization or filtering dynamics processors improve the intelligibility of voice and the subjective effect of music However in the wrong hands they can sound terrible Heavy compression low threshold and a high ratio often sounds nasty The timbre of the sound changes becoming hard and closed and not nearly as sweet and open as the sounds you envisioned when you got into this business On the other hand attack times optimized for pleasant compression may not track initial transients quick enough In addition pump ing and breathing may accompany heavy compression i e the background noise rises way out of proportion to the foreground sound as the compressor releases Result it just does not sound good Therefore n
17. ignal path The difference in the rms level of the broadband signal and that of the bandpassed side chain signal is compared to the threshold and the Dynamic EQ s gain is automatically adjusted to main tain the proper ratio of sibilant to non sibilant content See the examples in the Dynamci EQ Applications section on page Manual 4 Manual 9 LIMIT THRESHOLD and Headroom Meter LIMIT 3 20 2 o Os 30 19 12 40 122 24 dBu dB In addition to the Compressor De esser each channel of the C4 features an independent brick wall Limiter with an instanta neous attack time fixed 25 ms hold time and a fixed 6 dB sec ond release rate The C4 s limiter uses oversampling in order to ensure high frequency transients are properly detected and acted upon The Headroom meter displays the difference in dB between the LIMIT THRESHOLD and the present signal level For example with LIMIT THRESHOLD set to 10 dBu a peak signal level of 4 dBu results in a display of 6 dB of remain ing headroom 10 dB minus 4 dB equals 6 dB The LIMIT indicator lights when the present signal exceeds the set Limit Threshold When setting the Limiter Threshold keep in mind that music often has peaks which are 12 to 20 dB higher than the average rms value which is displayed on the side chain meter Note The Limiter is active at all times and is not affected by the bypass switch To bypass the limiter simply rotate the Lim iter Threshold control fu
18. itar amplifier Using two channels set up for different tones is very common to switch between a rhythm tone and a lead tone OF ten the musician sets the lead tone brighter than the rhythm tone so it cuts through better The problem comes when the sound system amplifies this all out of proportion resulting in too much energy around 2 kHz 4 kHz a really nasty frequency range due to the ear s maximum sensitivity to this octave Setting the Dynamic EQ for a center frequency of 3 kHz and a bandwidth of about 1 octave cleans this up Set the threshold high enough so that during normal playing nothing is happen ing If the device uses relative threshold once the lead channel is used it will automatically see the change in timbre and apply the Dynamic EQ to reduce the excess energy at 3 kHz relative to the rest of the audio spectrum You can also use this technique to make guitar sounds thick and chunky without being over bearing by using the EQ section set in the 200 Hz range as well Improve Vocals It is common for female singers to have a wide tonality swing when shifting from a quiet breathy passage to a loud crescendo The voice sounds warm and pleasant during the quiet passage but shows a predominance of frequencies in the 1 2 kHz range for the loud crescendo This is exaggerated when the singer moves the microphone away from her mouth thereby removing the warming character of the microphone s proximity effect and adds
19. l Display In Compressor mode the floating meter displays the side chain level relative to the Threshold dBr making it easy to gauge how close the signal is to the onset of compression The dBr indicators light from left to right as the signal approaches the threshold At threshold the yellow TH indicator is lit Above threshold the TH indicator remains lit and gain reduction occurs Side chain meter ballistics follow the rms detector time constant of 30 ms In Dynamic EQ mode the side chain meter displays the relative difference between the broadband program material and the bandpass signal defined by the PEQ as compared to the set Threshold Example With THRESHOLD set to 15 dB the TH indica tor lights when the sibilant portion of the program material is 15 dB below the broadband program material If the sibilants are 18 dB below the broadband material then the 3 dBr indicator is lit Gain Reduction Display The Gain Reduction meter displays the amount of gain correc tion presently applied to the signal lighting from right to left as the amount of gain reduction increases In Compressor mode this meter display the amount of gain correction being applied to the broadband program material In De ess mode this meter shows the amount of gain correction being applied to the dy namic EQ DEQ in the main signal chain This meter does not reflect any gain reduction occurring due to limiting Gain Reduction meter ballistics follow the
20. lly clockwise 22 dBu setting Manual 10 Tips and Tricks oe O0 10 2 20 4 0 1 5 5 6 6 ACTIVE BYPASS 30 10 i i 40 20 1 10 12 12 D dBu n 1 dB LIMIT COMP THRESHOLD RATIO GAIN 3 100 500 10 x 125 Ts s s 20 0 6 50 250 12 3 7 50 2s 30 Q 25 500 25 Auto 40 hoo 24 ms ms J Hard Soft dBu dB ATTACK RELEASE KNEE LIMIT THRESHOLD Auto Headroom 2 640 0 1 5 125 3 15k Comp Listen Dynamic 0 5 10 20 20k 12 12 D Fa oct Hz dB BANDWIDTH FREQUENCY GAIN SIDE CHAIN PEQ Initial Settings Sometimes it is necessary to start from scratch The drawing above shows where to set the controls for no processing the black knobs have no affect at this point Then you can adjust each section one at a time Suggested Settings There is no magic recipe of compressor settings which work for every audio source in every performance situation There are however a few key ingredients you can add to the ol dynam ics stew to get things going Start with the suggested settings in Table 1 then season to taste by adjusting the Threshold until your ears tell you it s just right Vocals A tough issue with vocals is the extreme dynamic range of some singers Those who can lull you to sleep and then scare you with an unexpected blast The difference between the soft crooning and the loud climax represents too much signal change for many preamps and mixers causing the
21. m to clip and distort badly Compression and limiting comes to the rescue Use the limiter to prevent the extreme levels from causing clipping and distorting the sound With its automatic fast attack and quick release mode all you need to set is the Limit Thresh old Set it as high as the next piece of equipment in the signal path allows The C4 gives you a wide setting range of 40 to 22 dBu that covers all requirements Compression is one of the most effective tricks for bring ing the vocals up in any mix live or recorded This is due to the increase in perceived loudness which results from reducing peaks and increasing the average level Good settings for natural sounding yet compressed vocals are a medium fast 25 50 ms attack and a medium slow 100 ms 1 sec release Releas ing too quickly sounds unnatural while attacking too slowly misses the problem surges Soft knee compression generally best matches vocal dynamics Adjust the ratio to match the dynamics of the singer with 2 1 being a good starting point ATTACK RELEASE RATIO KNEE Vocals Medium to Fast Medium to Slow 2 1 to 4 1 Soft Clicky Bass Fast Fast 4 1 or higher Hard Mushy Bass Medium to Slow Medium to Slow 4 1 Hard Raging Electric Guitar Fast Slow 4 1 or higher Hard more sustain Acoustic Guitar Medium to Slow Medium to Slow 4 1 Medium Brassy Horns Fast Fast 5 1 or higher Hard Drums kick snare Fast Fast 4 1 Hard D
22. o matter how you slice it compressors and limit ers are just fancy electronic volume controls Think of them as an extra hand on a control turning the volume down and turning it back up again Luckily this electronic hand is quick and ac curate but it is just adjusting a volume control Compression A compressor when the input signal reaches the level set by the threshold control begins turning down the signal by an amount set by the ratio control Modern compressors make the loud sig nals quieter but do not make the quiet parts louder However by keeping the loud signals under control you can turn up the output level which will make the quiet parts louder along with the rest of the signal Primary uses are 1 reduce dynamic range of vocalists and other musical instruments that exceed the recording or repro duction capability 2 prevent clipping and distortion in live sound systems or recording chains 3 smooth and balance an instrument such as a bass guitar with wide dynamic range and string to string level variations 4 reduce vocal sibilance de esser 5 produce louder recordings for broadcast and 6 even out paging variations due to different speakers in large systems Signal Path A compressor has two internal paths the signal and the side chain The signal path is the route the main signal takes through the unit from the input circuits to the gain control section and exits through the output circuits The signal c
23. passing the Master channel does not automatically bypass the Slave channel Channel ACTIVE BYPASS switches are the only controls which do not follow the Master channel making it possible to bypass each channel individually e Selecting Listen on the Master channel automatically puts both channels into Listen mode Side chain function switch indicators are turned off on the Slave channel e Meters for Master and Slave channels remain active indicat ing both channels are being processed ACTIVE BYPASS ACTIVE BYPASS Selecting BYPASS disables all Compressor Dynamic EQ processing including the GAIN control The side chain dBr meter threshold indicator and gain reduction meter continue to operate when a channel is bypassed Similarly the side chain Listen function is also available Channels can be individually bypassed even in Linked mode Note The Limiter is active at all times and is not affected by the BYPASS switch To bypass the Limiter simply rotate the Limiter Threshold control fully clockwise 22 dBu setting Manual 7 COMPressor THRESHOLD RATIO and GAIN 10 20 4 0 2 0 i 1 5 5 6 D 6 30 10 o 7 J 40 20 1 10 12 12 dBu n 1 dB COMP THRESHOLD RATIO GAIN The threshold like crossing through a doorway is the beginning point of gain adjustment When the input signal is below the threshold a compressor acts like a straight wire Above threh sold the side chain asserts itself and turns the vol
24. rums cymbals Fast Slow 2 1 to 10 1 Hard Table 1 Suggested Compressor Settings Bass It is common for the sound mixer to reduce the bass signal because it overwhelms the total system Use a compressor to smooth a bass sound by lessening the variations between the strings or strongly resonant notes and increasing sustain Typical settings for a bass guitar are a ratio of 4 1 with a fast attack of 25 ms and a slow release of around 500 ms These settings should produce a strong smooth bass line to start with but feel free to adjust further as necessary A hard knee setting is often preferred since all that is desired is to tame the excessive peaks and leave everything else alone Where does a compressor belong in a bass player s signal chain Well that depends on how you want it to function As a compressor limiter for the input signal it goes after the bass if the bass has a line level output and before the preamp If it were to function as a limiter to protect the speakers in the bass rig it would go after the preamp and before the power amp Another method is to insert the unit in the effect loop of the preamp This allows the bass signal to be affected by the pre amp first then the compressor limiter and then sent to the power amp This can be desirable with tube pre amps Guitar Here is a suggestion on how to achieve a lower volume without sounding as if you are playing out of a transistor radio set a slow attack tim
25. ternal side chain mode is automatically selected whenever a connector is plugged into the rear panel SIDE CHAIN jack Selecting LISTEN mode routes the side chain audio to the channel output allow ing you to hear the effect of PEQ adjustments when doing frequency sensitive compression or de essing If you d prefer to not use the side chain PEQ simply set the PEQ GAIN to 0 dB Setting up the C4 is a breeze thanks to the fast accurate side chain and Gain Reduction combination meter For users unfamiliar with de essing the W pointer on each control indicates a recommended setting for this specialized application The Auto attack and release mode speeds up sound check and the Tips and Tricks on page Manual 8 serve as a handy reference guide for getting started with compression Thank you for taking the time to read this Quick Start We now return you to your regularly scheduled sound check or recording session Contents Quick Start ince seccecinscciseccnsssncssceantctcssceseccetactstencetesncncecase 1 Side chain and Gain Reduction MeterS s000 6 Dynamics 101 Revisited s s sssnsnsnsnununununununnnnnnnnnnnnanana 2 MASTER SLAVE Stereo Link 7 COMPrESSION siisii iniiis iniaiaiai 2 ACTIVE BYPASS pieseccscsssccssscessccsssccsserssessscnsesestnacsecersees 7 Dynamic EQ essensen 3 COMPressor THRESHOLD RATIO and GAIN 8 DO OSSING siescessciscssceescts sxatsessesndpesaccactavednasatsnsecsscraraszesnn 3 ATTACK RELEASE and KNEE 8 Dynamic EQ Appl
26. to the naturally occurring peak in this frequency range To fix this simply set the EQ section to the problem frequency typically 1 2 kHz and set the threshold so that the compres sor only kicks in when she sings the loud passages Use the ratio control to determine exactly how much of the original tone change remains low ratios leave more change while high ratios clamp down hard and allow very little change Create Radical Sounds Dynamic EQ lets the user create sounds that change tone with level or at extreme settings which allows the creation of radical sounds based on the threshold attack amp release times Experiment the results will amaze you Peak Limiting A limiter is just a compressor with a really high ratio right Well not exactly Although the two devices use similar termi nology Threshold Attack Release and so on they serve two completely different purposes and therefore operate in different manners Fundamentally a compressor uses an rms detector to keep the average level of a signal under control while a limiter uses a peak detector to act on the instantaneous level of the sig nal Compare Figure 2 to Figure 7 Primary uses of limiters 1 preventing clipping and distor tion in power amplifiers 2 protection of loudspeakers from damage resulting from destructive transients like the proverbial dropped microphone 3 preventing overs clipping during digital recording 4 preventing overmodulation
27. tput jacks permitting connection to virtually any mixing console Side chain inputs are also auto balanced unbal anced on 4 TRS only Dynamics processors typically connect using a mixing console s insert points send return although they can be used in line such as when compressing or limiting an overall mix for example MIC INPUT gt CH 1 SIDE CHAIN INSERT SEND I gt CH 1 INPUT INSERT RETURN CH 1 OUTPUT INSTRUMENT IN gt CH 2 SIDE CHAIN I gt CH 2 INPUT INSERT SEND INSERT RETURN CH 2 OUTPUT SUB GROUP 1 gt CH 3 SIDE CHAIN gt CH 3 INPUT INSERT SEND CH 3 OUTPUT INSERT RETURN MASTER STEREO LINK SUB GROUP 2 gt CH 4 SIDE CHAIN INSERT SEND I gt CH 4 INPUT INSERT RETURN CH 4 OUTPUT MIXER C4 Figure 11 Connection to a mixing console MIC INPUT CH 1 SIDE CHAIN INSERT SEND gt CH 1 INPUT INSERT RETURN lt MIXER C4 CH 1 OUTPUT Figure 12 Using an external equalizer in the side chain Manual 6 Front Panel Controls Each channel of the C4 features the following meters and con trols Side chain and Gain Reduction Meters 12 6 3 1 TH 18 12 8 4 2 1 0000000000 dBr Reduction dB This triple function meter displays the side chain level threshold indication and amount of gain reduction being applied It allows you to see at a glance exactly what the compressor is doing at all times Side chain Leve
28. ume down In Compressor mode COMP THRESHOLD defines the absolute level adjustable from 40 dBu to 20 dBu above which compression begins If soft knee settings are used the threshold is defined as the point at the center of the knee See the KNEE description for more details In Dynamic EQ mode this control defines the relative difference between the broadband program material and the bandpass signal defined by the PEQ The V pointer between 10 dBu and 20 dBu shows the typical setting for De essing RATIO defines the ratio of Input change to Output change and is adjustable from 1 1 straight wire no change to 10 1 heavy compression as shown in Figure 14 For example a Ratio of 4 1 means that a 4 dB change at the input causes only a 1 dB change at the output The V pointer at 10 1 shows the typical setting for De essing 205 1 1 15 10 5 E OOF u F 1 5 E gt E 10 1 ioe Ratio t 15E d 20 u25 Threshold 30 35 F ao fuu an ad a fa 40 35 30 235 20 15 10 5 o 5 10 15 20 Input dBu Figure 14 Input versus Output for various Ratio settings hard knee Once you reduce the dynamic range using compression you can increase or decrease the overall loudness by adjusting the GAIN This control features a center detent marking the unity gain point with a range of 12 dB or 12 dB on either side Manual 8
29. ve W Mukilteo WA 98275 5098 USA TEL 425 355 6000 FAX 425 347 7757 WEB www rane com All features amp specifications subject to change without notice DOC 107487 Manual 11
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