R-e/p: In your treatment of control room B, did you go for trapping a particular frequency or just attenuating a broad band?

GA: Well, everything in there, in that particular room, is broad band and the reason was, we did not change the existing side wall treatment.

And as nearly as we could figure out, from some measurements made in there, and also from talking with Geordie about how those walls were built, we figured the walls were going to be doing most of their absorption somewhere in the 100 to 200 cycle range.

That’s usually a problem area in control rooms. So we thought, all right, that is probably being pretty well attenuated now, so we don’t have to worry about putting extra absorption in there. Then the thought was to go ahead and do it and if we have to change some thing in the side walls later, we will.

Well, it turns out the only slightly negative aspect has to do with the side walls; there is a side to side mode in that room which does result in a little dip right around 60Hz in the center at the console.

If we wanted to fix that acoustically, we could tear out the side walls and redo them and take care of that too. But since the systems were going to be equalized anyway, it frankly just did not seem serious enough to warrant rebuilding the rest of the room. We could just take care of it with equalization, if necessary.

R-e/p: It’s interesting because, on the one hand, you started out realizing that you were going to have certain resonant modes and reflections that you had to take care of, just on an absolute basis, “We know we’re going to have to do this,” and treated the room that way. On the other hand, you bring in the aspect of equalization.

Now, obviously, you were going for some sort of an overall room sound, a sound which you started out looking for.

What is that sound, and to get it, where does the room treatment leave off and equalization begin?

GA: All right, we always try to do as much as possible with the room itself, for a couple of reasons.

One is it just makes sense. You don’t use equalization as a band-aid type of thing. The other, of course, is that, especially in the low frequency end, these peaks and dips in the room are very space dependent.

What you get at the mixer’s location may be completely different from what you get at the producer’s location, and if this is true, there is no way you can equalize it out.

R-e/p: So you try to make the whole console area smooth?

GA: You try to get the console area as uniform as you can. And, as I say, sooner or later you simply run out of ability to predict; theoretically, you just can’t do it. Just the uncertainties in the construction process make it impossible even if you could feed everything else about the room into a computer, you still couldn’t do it.

And sooner or later you run into the problem; “Well, it’s pretty smooth across the console, but we still have this little peak and this little dip.

Now, do we want to work for another two weeks, or do we just want to lake it out electrically?” And sooner or later you get to the point where the trade-off makes a lot more sense to do it electrically.

But, from my standpoint, the advantages of the equalizing process are not at all to take care of bad rooms. Once in a while you have to do it, simply because it’s the least undesirable thing to do. But if you’re starting from scratch as we did in this case, there was no thought of that and no reason to do it that way.

R-e/p: When you spoke to the AES a few months back, you were talking about giving a particular room a fairly even curve, without a lot of dips and bumps. You cautioned not to use equalization to make one room sound like the next.

GA: Right. And you can’t, because your interpretation of what one room sounds like is a three dimensional thing. You have a three dimensional aural picture of this room which involves what it is doing from all the reflecting surfaces and one thing and another.

The only way you could do this electrically would be with the approach that some of the consulting firms take: simulating an auditorium. You start out by building an anechoic chamber and creating all of the acoustics electrically, which is possible, but it’s incredibly expensive.

And in most cases you simply wouldn’t have the space to do it if you wanted to. So you do the best you can in a small room, which is always a problem in the low frequency range. Then you use the equalization to give the subtle trim that the particular client wants, and, what’s more important, to get the most exact balance possible between the two speakers.

Because speakers will drift very slightly. There’ll be subtle differences. But for the clients who like equalized speakers, this is the one thing that they like to work with the most. They can literally trim these things up until they get an absolute, perfectly defined mono image. The two channels sound, for all practical purposes, identical, or almost identical. And when they drift a little, you can bring them back again.

R-e/p: Is the image adjusted primarily with program or with noise?

GA: Well, the measuring process is done with noise, with individual third-octave bands. But you notice it on program material, of course. And this is the way you can tell if your monitor speakers are drifting, or have changed, when you can simply punch a track alternately between the two and begin to hear a difference between them.

This aspect is not as important to some mixers, and they don’t feel at all unhappy about working with two speakers that sound very much alike but not identical. They figure, “fine, this is the way the guy’s going to listen to it, why should it bother me?”

R-e/p: Generally speaking, how frequently does monitor equalization need trimming?

GA: It depends on the particular speakers used and typically the kind of abuse they get in a given studio.

R-e/p: You’re saying that it’s wear rather than atmosphere?

GA: What it is primarily is changes that occur in the loudspeaker units themselves. Changes that occur primarily because the things are driven very hard, or momentarily overdriven from time to time, this type of thing.

R-e/p: Do the normal atmospheric changes, humidity and temperature cycling, also fatigue them?

GA: They might have some affect on low frequency cones. The things are not water proof, and they will vary over a period of time just by themselves.

But I know that, in my experience, the studios that are tight with control, where they never let anybody else operate the console except their own mixers, and where they are careful about accidental overloads and things like this, and don’t run at horrendous levels, you can come back a year later and you may have to tweak something a dB, 2 dB, and that’s it.

The studios that are into very heavy rock, and allow groups to bring in their own mixers to do their own mixing on these 24, 48, 72 hour sessions, where the levels keep going up and up and up and up, those are the ones where you will find things shift dramatically over a period of two or three months.