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#1
Posted to rec.audio.pro
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What does compression really do?
I've seen compression/compressors described as an "automatic volume/
gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. What do you consider to be an accurate description of what's happening with compression? |
#2
Posted to rec.audio.pro
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What does compression really do?
muzician21 wrote:
I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. What do you consider to be an accurate description of what's happening with compression? It depends on the settings. As used in most pop music, the channel gain is increased to the maximum, so that the quietest parts of the track give full output, and the compressor is used to keep the dynamic range as close to zero as possible. Then they do the same with the final stereo output. Or one can be used to subtly decrease the dynamic range of a symphony orchestra so that the quiet bits can be heard over a car engine or room air conditioner without deafening the neighbours with the loud bits. Or, preferably in this case, the mastering engineer could either automate the gain or ride it by hand. If the channel gain is increased, it will bring the lower levels up closer to the high level, while keeping the high levels down to the maximum desired. If channel gain is low, then it can bring peaks down to a sensible level, and depending on the settings, can work as a limiter. Then, there is the effect of attack and release times..... -- Tciao for Now! John. |
#3
Posted to rec.audio.pro
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What does compression really do?
muzician21 wrote:
I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. What do you consider to be an accurate description of what's happening with compression? "automated fader-operation" is called Automated Gain Control, AGC. To properly describe it takes also rate of gain change and attack and release. What describes a compressor is attack time, release time, ratio, strictly speaking also input gain and output gain. Some designs use the expression "threshold", but the same effects are possibly with suitable combination of input gain and fixed threshold, so while actual electronics circuit implementation may be different it is conceptually different wordings for the same effect. Simplified: "ratio" is an expression of how it redraws the entire signal curve so that the excursion around the center-line gets smaller, mathematically it is an expression of the steepness of the transfer characteristic. I often used multi-curved transfer characteristics when I draw my own compressor in A3, in virtual hardware they are real easy to implement, whether they were so in the software source-code is not my problem. The example "saturator" is a simple version of such a curve, basically it is just a "soft knee" at the top of the transfer-characteristic. For well isolated studio-recorded vox (pop, but not only) a soft-knee characterstic with the knee starting around -20 dB can be quite useful, it is just not the type of recording I'm currently into doing. kind regards Peter Larsen |
#4
Posted to rec.audio.pro
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What does compression really do?
Its suppose to be a simple volume control. But many analog compressors had
great side effects of introducing subtle harmonics as a side effect to the volume compression. A 'good' compressor is one that does these side effects well. FYI an Exciter is a device that adds such effects without compression. "muzician21" wrote in message ... I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. What do you consider to be an accurate description of what's happening with compression? |
#5
Posted to rec.audio.pro
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What does compression really do?
On 5/20/2011 4:09 AM, muzician21 wrote:
I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. A compressor has one primary function - to reduce dynamic range. It has a lot of secondary mis-uses including adding a tube or transformer (for those compressors that have them) in the signal path, adding some distortion, or modifying the waveform envelope to exaggerate or suppress the attack of a sound. If there's one thing that a compressor isn't, it's an automatic volume control. There's another device that does that, sort of, that works on a similar principle as a compressor, but with very different time response. There's an article on my web page entitled Compression Exposed that has a good overview of what a compressor does and how it's used and abused. -- "Today's production equipment is IT based and cannot be operated without a passing knowledge of computing, although it seems that it can be operated without a passing knowledge of audio" - John Watkinson Drop by http://mikeriversaudio.wordpress.com now and then |
#6
Posted to rec.audio.pro
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What does compression really do?
muzician21 wrote:
I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. That's just because you can't work the fader fast enough. The compressor can be set to smooth out peaks much faster than a human being, and this causes a somewhat different effect (almost like the removal of tremolo). What do you consider to be an accurate description of what's happening with compression? It's like amphetamine-crazed chihuahuas on the faders. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#7
Posted to rec.audio.pro
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What does compression really do?
muzician21 wrote:
I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. AGC is a specialization of gain reduction. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. SFAIK, you cannot emulate a real human riding a fader in real time. What do you consider to be an accurate description of what's happening with compression? It's dynamic gain reduction. -- Les Cargill |
#8
Posted to rec.audio.pro
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What does compression really do?
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#9
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What does compression really do?
yrret wrote:
Its suppose to be a simple volume control. No, it's a tool for reducing dynamic range, something quite different from a typical volume control. But many analog compressors had great side effects of introducing subtle harmonics as a side effect to the volume compression. A 'good' compressor is one that does these side effects well. Some consider a good compressor to be one that reduces dynamic range without introducing artifacts. FYI an Exciter is a device that adds such effects without compression. Artifacts of compression and effects of excitation are generally different. "muzician21" wrote in message ... I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. What do you consider to be an accurate description of what's happening with compression? -- shut up and play your guitar * http://hankalrich.com/ http://www.youtube.com/watch?v=NpqXcV9DYAc http://www.sonicbids.com/HankandShaidri |
#10
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What does compression really do?
In article , "yrret"
wrote: Its suppose to be a simple volume control. But many analog compressors had great side effects of introducing subtle harmonics as a side effect to the volume compression. A 'good' compressor is one that does these side effects well. FYI an Exciter is a device that adds such effects without compression. "muzician21" wrote in message ... I've seen compression/compressors described as an "automatic volume/ gain control" but it seems that's not really accurate. That characteristic compressed sound indicates there's more going on than simply reducing the volume as if you were working a fader in real time. What do you consider to be an accurate description of what's happening with compression? I wouldn't compare an exciter with a compressor, but I def concur that pros use compressors for more than just taming dynamic range. We use really good compressors to **** with sound. It's why LA2's & 3's and 1176's are still being manufactured. They are indispensable for shaping sounds. When you get it right, them boys can hump your ear. David Correia www.Celebrationsound.com |
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