On Sun, 22 Nov 2009, Dan Wilcox wrote:

What do you guys do for your live set? Do you do some sort of EQ/compression on the final stage before going out the the dac~?

A little bit of chaos theory... suppose you apply a filter on sound, and you take into account the net gain of the feedback, and you call all of it as f(x). What can you expect f(f(x)) to be? f(f(f(x))) ? f(f(f(f(x)))) ? and so on. This tells you what happens with feedback.

If you have a compressor that systematically takes whatever there is and divides the dB by any fraction above 1 (e.g. by 1.1 such that -55 dB becomes -50 dB), then in «silence» it will pick up any tiny noise at the smallest noninfinite dB and will divide its dB by 1.1 many times until it becomes extremely loud. That's unstable feedback. (Stable feedback is when the dB of the echo is going down, but this fading out could be at any speed, even if it's slow.)

Therefore you can't add a plain compressor without aggravating any existing feedback, however tiny it is. You need to use something even more nonlinear than that, by adding something like a noisegate component. (nonlinear means anything not made by adding proportional parts).

I found this post about the ears response to certain frequencies at different sound pressure levels http://gabesrocklog.blogspot.com/2009/08/eq-or-how-to-turn-down-suck-knob.ht.... Should I try using these curves on an eq going out?

Those show you what's the gain in the ear. That doesn't tell you about the gain in your speakers, the gain in your amplifier, nor the gain due to reflection (vs absorption) on walls.

_ _ __ ___ _____ ________ _____________ _____________________ ... | Mathieu Bouchard, Montréal, Québec. téléphone: +1.514.383.3801