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In the Forum: Playback Listening
In the Thread: Attention Sound Engineers (compression and loudness)
Post Subject: Compression, not just amplitudePosted by Andy Simpson on: 4/22/2009
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 Romy the Cat wrote:

Let do not forget that acoustic space also have own compression… not to mention that the performing intend itself has own “compression”.



The question of 'self-compression', where the performer moderates their performance, is the only form which does not introduce harmonic & non-harmonic artifacts.

All other forms of compression comprise a nonlinear system, which introduces both harmonic & non-harmonic distortion.



Anyhow, I kind of view noondays the whole subject of compression slightly different then I use to do it before. I agree that various type of compressions rule playback but my interest is what type of compressions they are and HOW the compression applied. To a degree a properly made compressions might be in fact a beneficial tool. Someone before proposed it but I discarded it – now I feel that the idea of full-of-sense compressions had own merit.


An interesting aspect to the idea of nonlinear systems (compressors/microphones/speakers/etc) is that the resulting distortion is cumulative, propagative & non removeable/correctable.


The most interesting aspect to me in whole idea of compression is not the compression itself – we people who sit in the end sound chain have very little control over it. What interests me is hot to organize playback DIFFERENTLY in order to make the playback to sound the most properly with this or that type of compression. The compression itself is like an input parameter of some kind of function and the playback shall react to compression and to be able to deal with it…


Regarding harmonic distortion, the general response is to roll-off the HF, but this is a poor compromise.

Regarding the non-harmonic distortion, there is no way to remove this after the fact. If the nonlinear system responds to 2k + 3k tones by introducing a 1k difference tone, there is nothing you can do about it without causing other problems.

For a demonstration of this, take your favourite digital compressor and set it up for some 'reasonable' amount of compression.

Next introduce a pair of sinewave tones (say 2k + 3k) and observe the introduction of harmonic tones (above) and non-harmonic tones (below).

Andy

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