Why do I care? Because many of my live sound brethren employing this technique have been doing it in such a terribly inappropriate manner, and with such ineffective tools.
I know, I know – you’re just trying to get the show as “loud” as possible while living within the 98 dB (A-weighed; 105 dB C-weighted) SPL ceiling imposed by the local constable who just loves to hang at the FOH position with his little un-calibrated “Rat Shack” meter.
The harm, at least from my perspective, is that this often does not properly serve the artist, because the dynamics of the music are directly linked to the emotion of the performance.
There are some compression units that excel at allowing the emotion of the performance to creep through the reduction of dynamic range, and there are units that should never be used in this application.
Generally, if a compressor has a low-cut filter prior to the detector circuit (this keeps low-frequency energy from driving the gain reduction), it’s probably a suitable unit.
If there is one set of controls governing both sides of the unit (true stereo versus linked dual mono), then it very well may be an appropriate unit to strap across a mix bus.
It has nothing to do with “toob” versus “squalid state” – there are great 2 Mix compressors that apply to either (and sometimes both) technologies. It has more to do with the internal headroom and overall frequency response of the unit (DC to light is about right), along with the ability of the unit’s gain reduction cell to control the dynamics of the presentation without pumping, wheezing, begging for mercy, or removing the intensity and emotion.
During production rehearsals, simply listen to the mix with the compression engaged, and then disengaged, while making a concerted effort to knock down the dynamics of the presentation as seamlessly as possible.
When the pumping and wheezing ceases, you’re on the right track.
Fletcher heads up Mercenary Audio and also hosts a popular forum here at ProSoundWeb.com.