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9.5. USING THE COMPRESSOR/LIMITER

The dynamic range (how loud we can hear to how quiet a sound we can detect) of the human ear is far
greater than the capacity of sound systems to reproduce.  Although some of this equipment limitation
is at the upper extreme of the dynamic range (where too loud a signal will produce distortion), much of
the restriction occurs at the low level end, where the signal disappears below the “noise floor” of the
circuitry.

A compressor (or in its most powerful form, a limiter) is the most widely used tool for controlling dynamic
range.  In the simplest terms, a compressor is designed to restrict the dynamic range of an audio
program; i.e., to make quiet signals louder, and loud signals quieter.  A compressor becomes a limiter
when the compression ratio (the ratio of the input gain change to the output gain change) is so high that
the output level won’t rise above a “brick wall” ceiling regardless of how loud the input gets.

A compressor acts like an “automatic mix engineer” with a hand on the fader, and an inhumanly fast
reaction time.  When the input level increases, the engineer drops the fader; when the level decreases,
the fader is raised.  If the amount of fader compensation equals the variation in signal level, the output
level of the audio program will sound consistent.

The practical benefits of compression include:

1.

Speaker protection.  A compressor will control sudden level peaks and prevent your speakers from
damage.

2.

Perceived increase in loudness.  Because peak levels are kept from rising as high as uncompressed
signals, you gain headroom for your audio program and can raise its overall average gain.
Compression is often added to the entire audio mix, both in live sound and recording, to increase
its perceived loudness.

3.

Mix consistency.  For expressive instruments or vocals, which may have a large dynamic range,
compression can help maintain consistent mix levels.  So a vocal that varies from a whisper to a
scream will not disappear or stand out in the mix, relative to other less dynamic instruments.

Like any signal processing, compression can be misused, and cause undesirable problems in the audio
signal.  Some of these problems include:

1.

Noise.  If the threshold for compression is set too low, and the output gain is raised substantially
to make up for the gain loss of compression, the resulting output signal can be noisy.  This is because
the input signal must be raised significantly to produce the same output level, and the noise floor
of your equipment will be amplified unnecessarily.  This problem will be exaggerated if the input
signal level to the compressor is very low (which will already degrade the signal-to-noise ratio).

2.

Breathing.  In situations where the compression ratio is high, the threshold is low, and the release
time of the compressor is short, the noise floor will modulate up and down as the audio signal stops
and starts.

3.

Pumping.  When the compressor release time is set too long, low level signals that follow a peak
closely will disappear or fade back up as the compression releases.  Experiment with the release
time to obtain the ideal setting; this will be a function of the program content.

4.

Over-compression.  Applying too much compression to a mix can sometimes result in such evened-
out dynamics that the “life” of the music has been removed or curtailed.  Dynamic variation in music
is a major component of its excitement and interest; don’t remove them, just control them.  This may
be particularly true for percussive sounds such as drums.  While compressing drums can “fatten”
up the sound, setting the attack time to be longer may allow the initial strike of the drum to have more
impact.

Section Nine:  Suggestions for Optimal Use of the GRAPHI-Q

Summary of Contents for GRAPHI-Q

Page 1: ...7 This manual written for Sabine GRAPHI Qs with GRQFirmwareVersion3 10 GRQ Remote Software Version 3 10 Visit Sabine s website for the latest information and FREE software firmwareandoperatingguideup...

Page 2: ...that the equipment specified above conforms to the above Directive and Standard Place Alachua Florida USA Signature Date February 20 2000 Full Name Doran Oster Sabine President Declaration of Conform...

Page 3: ...ease and knee adjustable with remote Digital Delay with up to 1 second delay adjustable in 20 microsecond increments Bypass dedicated switches for FBX EQ and Delay with built in LED indicators LED Seg...

Page 4: ...Feature Front Panel Models only 15 6 2 HIGH CUT LOW CUT FILTERS 15 6 2 1 Front Panel Control 15 6 3 FEEDBACK CONTROL AND PARAMETRIC EQUALIZATION 15 6 3 1 Glossary of Terms 15 6 3 2 Front Panel Control...

Page 5: ...ord 38 8 8 4 Removing Password Protection 38 8 8 5 Passwords For Multiple Units 38 8 9 NAVIGATINGWITH MULTIPLE UNITS 39 8 10 UPGRADING GRAPHI Q FIRMWARE AND SOFTWARE 39 8 10 1 How to Upgrade Your Firm...

Page 6: ...expanded range of adjustment and ease of storage and recall that are much more difficult to achieve with analog technology And with the Sabine FBX algorithm one of the most serious problems of audio...

Page 7: ...sed on mathematical formulas and will remain constant over time and changing temperatures 4 LESSNOISE Asanalogpartswear getdirty orcorrode readjustingthemcanintroducenoiseinto thesignalpath Allaudioen...

Page 8: ...Power connector fuse GRQ 3101S FRONT PANEL Additional RS 232 Serial In Power On LED GRQ 3101S BACK PANEL GRQ 3101 FRONT PANEL FBX Section 12 filter indicators Reset Width Set Lock Fixed Filter Contro...

Page 9: ...Section Three Front and Back Panel Views GRQ 3102 FRONT PANEL GRQ 3102 BACK PANEL GRQ 3102S BACK PANEL GRQ 3102S FRONT PANEL...

Page 10: ...Section Four Block Diagram Internal Signal Path Section Four Block Diagram Internal Signal Path...

Page 11: ...ill look like this This configuration represents the simplest installation using a single channel one input using only one output GRAPHI Q You may also follow a similar connection diagram for a two ch...

Page 12: ...power of the GRAPHI Q to one or two single channels on your mixer or to a subgroup of inputs for example all the drums in your mix The patching will look like this 5 5 SINGLE CHANNEL GRAPHI Q ONE INPU...

Page 13: ...RAPHI Q in an auxiliary or effects loop such as would be used to add reverb to different channels in your mixer Effects loops are designed to split signal paths and then mix wet processedsignalswithth...

Page 14: ...itersettings can be applied to one or both outputs using software control but the GRQ 3101 will not permit unique output settings for any processing except delay and for the output levels 6 1 1 Front...

Page 15: ...eremotesoftwaretocontrol the EQ faders the resolution is always dB regardless of range 6 2 HIGH CUT LOW CUT FILTERS 6 2 1 Front Panel Control These controls are located immediately to the right of the...

Page 16: ...encies may change due to microphone repositioning and represent the second layer of feedback protection Note that both Fixed and Dynamic filters can be set while music is playing as one of the disting...

Page 17: ...ynamic filters However you may follow the instructions in STEP 5 below to reconfigure the setup to be any combination of Fixed and Dynamic filters 6 3 2 2 Eliminating Feedback with the GRAPHI Q FBX Fi...

Page 18: ...to mix filter widths between one tenth and one fifth octaves You may set all filters to one width or some filters to tenth octave and some to fifth octave Width selection is controlled by the button...

Page 19: ...hout reducing the volume of the feedback before it is filtered out You ll know if TURBO is on by the LED indicator on the GRAPHI Q front panel Whether or not TURBO MODE is used the end result of setti...

Page 20: ...burst of no longer filtered feedback It ain t pretty when this happens so proceed cautiously 6 7 CHANGING FRONT PANEL DEFAULT SETTINGS ADJUSTABLE ONLY BY SOFTWARE GRAPHI QmodelsGRQ 3101andGRQ 3102all...

Page 21: ...are and software necessary to run the units via remotecontrolfromaWindows equippedcomputer YourunitshouldincludeoneCDROMthatincludes theGRQ RemoteSoftwareandtheSabineUpgradeWizardforfutureupgradesofyo...

Page 22: ...ensive Also commands from the computer controller may sometimes be executed faster than the update of thescreenthatdisplaystheparameters inotherwords thereportoftheexecutionofthecommandmay lag behind...

Page 23: ...in cannot communicate directly to another only within its own chain Double click your GRQ icon and you are presented with the Welcome Screen You can connect to your GRAPHI Qs or run the software off l...

Page 24: ...h and Low Cut Filter Controls on the Remote Control are located just below the slider controls Changing high and low cut filters can be accomplished by two methods 1 Click and drag on the left horizon...

Page 25: ...offers powerful options for setting and controlling FBX filters that are not available using front panel controls In addition the software allows programming of parametric EQ filters which is not pos...

Page 26: ...in the bar for quick editing Level Indicators Input output compressor gain reduction and limiter indicator for both channels High Cut Slider Low Cut Slider Click to toggle EQ boost cut range between 6...

Page 27: ...th Turbo Mode operation click Turbo Help The following screen will appear USINGAUTOTURBO BeforeselectingAUTOmode makesureallyourmicrophonesarepositioned and turneduptotheapproximatecorrectgainsettingf...

Page 28: ...APERFORMANCE Itisasetuptoolonly Ifyouplayaudiothrough the GRAPHI Q while it is in Turbo Mode Manual or Auto the audio may sound distorted and FBX filters will set inappropriately 2 TURBO WORKS BEST IN...

Page 29: ...esets with large differences in delay settings onlywhenaudioisNOTplaying through your system Pitch shifting may temporarily occur as delay is adjusted You may bypass the delay section with out pitch c...

Page 30: ...the value of a parameter for an unlinked cell will not affect any other cell default condition ABSOLUTELINK ValuesofparametersforABSOLUTELYLINKEDcellswillbecopiedtotheidentical setting The first cell...

Page 31: ...eSection5 5 Thisisaveryusefulfeaturethatenablesasingle inputunittoemulatetwo channeloperation withadditionalcontroloverthetwooutputsaccessiblewiththe Sabine GRQ Remote Software Two parameters output l...

Page 32: ...ess when a peak level exceeds a certain threshold and the sound engineer intentionally designs his audio program to have more soundintheleftchannel thatchannel ssoundwillbecompressedmorereadilythanthe...

Page 33: ...ilter 6 for example and be set to Parametric in order to be reset via linking Resettingparametervaluesforlinkedunits orloadingpresetstolinkedunits cancreatesomecomplicated scenarios When in doubt remo...

Page 34: ...eset set tings for individual channels For single channelGRAPHI Qs youmayresetOUT PUT LEVEL and DIGITAL DELAY set tingsforthetwodifferentoutputspossible with these units all other parameter set tingsa...

Page 35: ...ONT PANEL will apply only to GRAPHI Q models GRQ 3101 and 3102 and not to the S blank front panel slave models In this setting the front panelcontrolsoftheGRAPHI Qwillprovidetheonlymeansofcontrollings...

Page 36: ...the lower right of the main Remote Control screen at all times 8 SeeSection6 7forinformationaboutchangingdefaultvaluesforfrontpaneloperationforparameters that are not accessible without Remote Control...

Page 37: ...cluding downstream amplifier connections andthatyourGRAPHI Qsareplacedinthesameequipmentrackandderivepowerfromthesame circuit 8 7 ASSIGNING NAMES TO THE GRAPHI QS Youcanassignany8 characternametoallof...

Page 38: ...word will follow the GRAPHI Q 8 8 3 Gaining Access With Your Password Oncepasswordshavebeenentered oneofthethreecodesmustbegiventoallowaccesstothesecurity levelallowed Ifnomatchingpasswordisprovided t...

Page 39: ...ollowing power up of your unit 2 For all models the current firmware version will be stated in the About screen of the Remote Control software unit connected and powered up NOTE If you have a slave un...

Page 40: ...especially DOS programs 1 OnthefirstUpgradeWizardscreen selectthesecondoption UpgradeGRAPHI Qfirmwareandclick Next 2 The screen will tell you that you must be connected to at single GRAPHI Q Make sure...

Page 41: ...you re working in the more the bass problem you ll have You might consider building a bass trap to selectively absorb bass frequencies Many of the current trade publications offer advice on easy inexp...

Page 42: ...Q slider Is the industry standard choice offilterwidthagoodorabaddesign Itdependsentirelyontheintendeduseoftheequalizerinquestion There are at least two basic design intentions of equalizers both of w...

Page 43: ...stic process There are many well documentedmethodsofoptimizingyoursystem andusefulmeasurementtoolsandtechniques but ultimately the skill of the operator is the determining factor of sound quality So y...

Page 44: ...ency ranges attenuated or boosted by your system or acoustics that are not first compensated for by graphic EQ your FBX filters may cluster together using several narrow filters to address a problem b...

Page 45: ...to be quite expensive Fortunately simpler tools are sufficient for most applications Inthe1930s engineerssynchronizedthelowandhighfrequencyspeakersinmovietheatersbyfeeding a sharp click through the s...

Page 46: ...larger wave In other places the crests are out of phase so the crest of one wave source is canceled by the trough of the other Ripple tank experiments show the interference patterns are strongest whe...

Page 47: ...plitude by 6 dB while the out of phase frequencies cancel completely to 4 dB Combfilterscausealotofproblems Thefrequenciesthatarereinforcedarepronetoexcitefeedback while the out of phase cancellations...

Page 48: ...was played through both speakers simultaneously the listenerperceivedtheacousticimage thedirectionfromwhichthesoundseemedtobecoming centered between the speakers WhenHaasdelayedthesignalgoingtooneoft...

Page 49: ...ee Comb Filter Distortion p 45 You can use the GRAPHI Q to preciselysynchronizethespeakersalongthisaxistoeliminatethemostseverecombfilters Combfilters off the equal level axis are much less of a probl...

Page 50: ...in the mixer s channel insert point and adding a 25 msec delay Certainly taking advantage of the Precedence Effect is not as obvious to the audience as eliminating feedback but it is nice to know you...

Page 51: ...ncrease its perceived loudness 3 Mix consistency For expressive instruments or vocals which may have a large dynamic range compression can help maintain consistent mix levels So a vocal that varies fr...

Page 52: ...in makeup boosted slightly soft knee BASS GUITAR Bass players use a variety of tech niques often in the same song that can benefit from compression Compressingbassevensoutpeaksand keeps the bass level...

Page 53: ...REQUENCIES CLUSTERED TOGETHER TURBO SETUP DOESN T WORK CORRECTLY DISTORTED AUDIO Check GRAPHI Q compressor settings See Section 9 5 Check filter availability Make sure unit is not in BYPASS See Sectio...

Page 54: ...the extreme left right pins of the back panel contact connector Parametric filter linking obeys a set of rules that will make it difficult for you to accidentally defeat an FBX filter already in place...

Page 55: ...3101S GRQ Remote RS 232 Remote switching SAVE RECALL CONFIGURATIONS 68 user defined 1 factory default 1 most recent configuration power down save 1 front panel INPUT OUTPUT Input impedance Balanced 10...

Page 56: ...apparatusdoesnotexceedtheClassBlimitsforradionoise emissionsfromdigitalapparatussetoutintheRadioInterferenceRegulationsof theCanadianDepartmentofCommunications Lepresentappareilnumeriquen emetpasdebru...

Page 57: ...ly related to the cause of action Such purchase price will be that in effect for the specific product when the cause of action arose This limitation of liability will not apply to claims for personal...

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