Signal Processing Fundamentals: Equalization

The best way to deal with budget loudspeakers—although it costs more—is to commit one equalizer channel for each cabinet. This becomes a marriage. The equalizer is set, a security cover is bolted-on, and forever more they are inseparable. (Use additional equalizers to assist with the room problems.)

And now for the hard part, but the most important part: If you do your measurements outside (no reflections off walls or ceiling) and up in the air (no reflections off the ground) you can get a very accurate picture of just the loudspeaker’s response, free from room effects. This gives you the room-independent response. This is really important, because no matter where this box is used, it has these problems.

Of course, you must make sure the cost of the budget speaker plus the equalizer adds up to substantially less than buying a really flat speaker system to begin with. Luckily (or should this be sadly) this is usually the case.

Again, the truth is that most loudspeakers are not flat. It is only the very expensive loudspeakers that have world-class responses. (Hmmm … maybe that’s why they cost so much!)

The next thing you can do with equalizers is to improve the way each venue sounds. Every room sounds different—fact of life—fact of physics. Using exactly the same equipment, playing exactly the same music in exactly the same way, different rooms sound different—guaranteed. Each enclosed space treats your sound differently.

Reflected sound causes the problems. What the audience hears is made up of the direct sound (what comes straight out of the loudspeaker directly to the listener) and reflected sound (it bounces off everything before getting to the listener).

And if the room is big enough, then reverberation comes into play, which is all the reflected sound that has traveled so far, and for such a (relatively) long time that it arrives and re-arrives at the listener delayed enough to sound like a second and third source, or even an echo if the room is really big.

It’s basically a geometry problem. Each room differs in its dimensions; not only in its basic length-by-width size, but in its ceiling height, the distance from you and your equipment to the audience, what’s hung (or not hung), on the walls, how many windows and doors there are, and where. Every detail about the space affects your sound.

And regretfully, there is very little you can do about any of it. Most of the factors affecting your sound you cannot change. You certainly can’t change the dimensions, or alter the window and door locations.

But there are a few things you can do, and equalization is one of them. But before you equalize you want to optimize how and where you place your speakers. This is probably the number one item to attend to. Keep your loudspeakers out of corners whenever possible.

Remove all restrictions between your loudspeakers and your audience, including banners, stage equipment, and performers. What you want is for most of the sound your audience hears to come directly from the speakers. You want to minimize all reflected sound.

If you’ve done a good job in selecting and equalizing your loudspeakers, then you already know your direct sound is good. So what’s left is to minimize the reflected sound.