EQ is meant for fixing a different set problems.
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A distinct inevitability is that someone will be in a “tough room.” They will look at the vast array of equalization functionalities offered by modern, digital, sound-reinforcement tools, and they will say, “Why can’t I fix the space?”
Here’s the deal. A difficult room – that is, one with environmental attributes that make our job harder – is a time problem in the acoustical domain. EQ, on the other hand, is a tool for changing frequency magnitude in the electronic domain.
When it comes right down to it, bad acoustics is just shorthand for “A sound arrived at a listener multiple times, and it was unpleasant.” A noise was made, and part of its energy traveled directly to somebody’s ears. Some other part of its energy splattered off a wall, ceiling, or floor…or a combination of all of those, at least once, and then also arrived at somebody’s ears. Maybe a lot of the high-frequency information was absorbed, causing the combined result to be a muddy garble. Of course, all the transients getting smeared around didn’t help much, either. It gets even more fun when a sound is created, and bounces around, and some of it goes into a monitor system, and gets made again, and bounces around, and some of it goes to the FOH PA, and gets made AGAIN, and bounces around, and all of that gets back into the microphone, and so that sound gets generated again, except at a different level and frequency response, and…
How’s an EQ going to fix that? I mean, really fix it?
You might be able to dig out a hole in the system’s response that compensates for annoying frequency buildup. If the room causes a big, wide bump at 250 Hz, dialing that out of the PA in correct proportion will certainly help a bit. It’s a very reasonable thing to do, and we engage in such an exercise on a regular basis.
But all the EQ did was change the magnitude response of the PA. Sure, equalization uses time to precipitate frequency-dependent gain changes, but it doesn’t do a thing in relation to environmental time issues. The noise from the PA is still bouncing madly off of a myriad of surfaces. It’s still arriving at the listener multiple times. The transients are still smeared. The information in the electronic domain got turned into acoustical information (by necessity), and at that point, the EQ stopped having any direct influence at all.
You can’t use EQ to fix the problem. You can alleviate frequency-related effects of the acoustical nightmare you have on your hands, but an actual solution involves changing the behavior of the room. Your EQ is not inserted across the environment, nor can it be, so recognize what it can and can’t do.