R-e/p: Did you know before you went in there, or at least before you started designing control room B what transducers you would be using?

GA: No. Actually, the two were done sort of concurrently, but the room design came first. They had not decided, at the time that we started on the room; Rob, and the rest of the people there, hadn’t yet made up their minds.

R-e/p: Between JBL or the Altec 604’s they already had?

GA: Well, let’s say between picking a stock monitor or going to custom design monitors or whatever, they still weren’t sure. And the only situation I can think of where you might really worry about designing a room around a particular monitor is if you knew you had to work with one that had a particular problem, maybe a heavy resonance somewhere in the low frequency range that you wanted to take out. Most of the time it’s just the opposite.

If people want to work with, a distinctive monitor, it’s that sound that they want. You don’t want to try to compensate for it in the room.

R-e/p: So here you just said, “We want a certain type of sound and we’ll do what we have to get it.”

GA: Right. And, as it turned out about halfway through, they decided to go ahead and do custom monitors for the room. Clients go to custom monitors for a number of reasons. One of the most important ones is space.

You’re always working in little, funny, weird trapezoid and triangular-shaped spaces that are left over. To get the volume that you need, standard monitors just won’t fit.

R-e/p: Would you describe the speakers you used?

GA: There are two versions, the right and left hand ones. The whole cabinet is slanted to fit into the corners.

One of the fronts and one of the rears are identical, and then the other front and rear are made with just the opposite slant.

R-e/p: Why use two fifteen inchers per cabinet?

GA: You use two fifteen inch woofers in high-power monitors simply because you have to, to be able to get the power levels that are required without blowing out woofers.

It would be nice in some respects if you could do it with a single fifteen, but if you really want to give them assurance that they’re not going to blow woofers out, the dual fifteen seems to be absolutely necessary.

The woofers are mounted on an inverse “V” which is really not deep enough to be called a horn.

It is an attempt to do two things. Number one, to push the woofers back a little bit to get a more desirable relationship between the woofers and the high frequency driver. I know that about six to eight inches is what we want there to make the crossover network come out right.

Number two, the woofer angle gives more horizontal dispersion up in the mid range where they start becoming directional.

In this case, it happened to work out just right, because one woofer is turned toward the mixer and the other is pointed toward the producer and we get a pretty good balance across the console.

R-e/p: Where do you cross over out of the fifteen inch units?

GA: In most of these high power systems, again, for purely practical reasons, somewhere around 8001 Iz.

R-e/p: And at what point does a fifteen inch unit start becoming directional? GA: Well, if it were a perfect piston, it would start becoming directional at about 400Hz.

What really happens is the cone starts to break up in various modes, and most Fifteen inch units are reasonably non-directional up to between 600 and 1500, somewhere up in that region. We pushed the woofers out quite a ways so there’s quite a big overlaping region in this system.

R-e/p: You’re saying a gentle crossover slope?

GA: Yes, the high frequency unit is protected but the woofers overlap effectively up to something like, 1500 probably 2000Hz, before they’re really out of the picture.

R-e/p: What about the midrange and tweeter?

GA: The big midrange assembly here is standard. This particular system happens to be all JBL. The mid range unit is the big JBL 2440 and the horn lens is the old Hartsfield horn (JBL 2395) and lens, which I have used in other custom monitors.

I happen to like it for a number of reasons: it’s very well behaved, it’s predictable, it has a nice broad distribution pattern and so it was used in this particular system. (JBL specs: 140°II x 45°V).

There are two super tweeters, that arc then mounted in front of the woofers.

R-e/p: Are they positioned for a specific phase relationship?

GA: Well, with the super tweeters it would be nice if you could, hut up in those frequencies, it really isn’t critical. What you try to do is to position them where you’ll maintain the center of the image where it should be.

In this case, we used two to make sure that nobody was ever going to blow them out. And then we oriented them to get maximum uniformity between the standing and sitting positions.

R-e/p: That’s interesting, because that room does have a pretty low ceiling, or at least a pretty low apparent ceiling.

GA: Yes, the false ceiling is low, right over the console location. That’s part of the basic approach.

R-e/p: Docs the ceiling focus those highs?

GA: No, not the extreme highs. The units used are directional enough vertically that it’s just a question of orienting them individually. Then there was another thing we did which helped give a very tight image.

When they were installing the speakers, we worried a lot, not only about getting them angled so they were focusing at the same point, but getting them at exactly the same distance from the mixer, because with the usual amount of slop that’s built into carpentry, it’s very easy from the center of the board to be two or three inches farther away from one monitor than the other.

If this happens, then your image shifts again. So we managed to keep it right where we wanted it, right in the middle of the board.

R-e/p: Is all of the tuning done after monitor installation? Or can some tuning be pre-planned?

GA: One thing we do on these custom monitors is run the enclosure design through analog circuit simulation. Computer analysis, if you want to call it that, to determine the optimum size, and if it’s going to be ported, the optimum port frequency.

In this case, we decided as an experiment to go back and use one of the older models of JBL woofers. I felt and Rob felt that we might get a little more of that sort of tight bass, that extra sock, with the 2220B rather than what we think of as neutral consumer loudspeaker sound. And, in any case, the enclosures would allow substituting any other kind of woofer, if we later decided to change. But it turned out to be very successful, I think. It’s a neutral sound, and yet at the same time, it has a little bit of that up front effect that the mixers like.