Re: Compression
Cough... microseconds?
The only practical stand-alone live audio rack product using look-ahead was a RANE noise gate, that was able to apply a short delay to the path so a signal that was gated off, could be turned on and the circuit would not smear the leading edge of the sound and click while turning on (circuits can't turn on and off instantly).
With general dynamic processing (like gain reduction) for the look-ahead to be really useful, it needs to be long enough to ramp a gain change slowly so that gain change itself doesn't become an audible distortion. If gain changes are fast in the context of a single waveform period, it just becomes distortion to that cycle of the waveform. Look ahead lets you reduce gain slowly before the transient gets there. Even if you used rapid gain reduction with look ahead, the look-ahead anticipation time would need to be at least a quarter wavelength of the lower frequencies being processed. To not distort the first cycle of a burst. Again more than microseconds.
The RANE noise gate exhibits 1.6 milliseconds of total latency (so look-ahead is less than that). Some were apprehensive about even this much delay in live sound but it's only equivalent to spacing the mic a foot and change further away.
For general dynamics processing useful look-ahead could be full seconds for very slow gain changes, but minimally a fraction of a second to be effective ramping gain changes. It takes time to be slow.
JR
