Nick Batzdorf Interviews David Moulton, Part 2

NB: Why is imaging important?

DRM: The presence of those phantom images is important. But more than that, it's the perceived presence of that alternative space: the recording space. Our ears tell us that we're listening to music in a different room than the one we're sitting in. We sense that we're being enveloped by that music.

That's the big hit I get from surround sound-a reverb wash from behind me; I feel I'm in a really interesting room with the performers.

NB: How did we arrive at the conventional wisdom?

DRM: It's intuitive that we want to hear just what's coming from the loudspeaker, because that's the recording. It's what I believed for years, in fact I had a strong feeling that I'd like to do all my listening and mixing in an anechoic chamber so there would be no confusion whatsoever. That seems like a really good idea.

The second issue is that as we've adopted absorbent material like Sonex and so on, we could immediately hear that the sound had changed. So as we line small rooms with absorbent material, the sound appeared to get drier, so we sense that it must be getting good.

In fact, all we're doing is adding a lowpass filter to the early reflections. We're changing the overall power response of the speaker at the ear in a very undesirable way.

If you look back at the history of recording, we've tended to jazz up the top end just to offset that, to fill in the high frequency content we've taken out because of sloppy monitoring practices. The David Foster vocal reverb with really high-end sizzle so you get all this high end 'verb dying away, really overly bright in-your-face closely recorded vocals, tremendous cymbals, and so on-this has all been done for that reason.

NB: You also believe in having a dead end-an absorbent end-behind the speakers, and then a live end behind the listener.

DRM: Yup. In the hearing mechanism, what happens is that we integrate all the short-term artifacts of a sound. This leads to the psychological meaning of a sound-everything that comes to our ears that's phase-locked to some sound source and that arrives within 50 milliseconds lumps together as one sound.

It seems to me that what we want to do is get all that information and then get no more information from the playback room. My design philosophy for studios is: let's have a perfectly reflective space for 50 milliseconds and then let's have no reflections or reverb after that. So let's have all the early delays with as little frequency response change and as little amplitude loss as possible, and then nothing after that.

I stick in a huge absorber behind the speakers that takes out as much of the broadband stuff as I can manage. The theory is that if you can get everything down 20 dB at that point, there is no reverb time-or, the reverb time is 50 milliseconds (assuming you have a room that's 25 feet deep; if it's a smaller room it'll be even shorter).

NB: You've used windows as bass traps in a room.

DRM: Yes, and they're surrounded by high frequency absorbers. I just designed a piano room for a concert pianist using this philosophy, and it worked out extremely well. We have really nice piano sound in a room about 14 feet wide and 35 feet long, which stunned me.

NB: So if someone has a window in their smaller room, that's where they should put the speakers?

DRM: The window's always troubling for me. Actually, I'd rather have it on the side. Speaking from a designer's standpoint in a sort of low-cost (what I call a Moulton Room) topology, I'd just as soon have that all be absorbent fuzz at the front of the room.

NB: Assuming the room is above a certain size?

DRM: Any room big enough to fit the gear in.

NB: But you don't want to be sitting in the middle of the room?

DRM: You want the median plane going down the long axis of the room, you'd like the narrow sides to be the sides. A shallow room is much harder to make work.

NB: But the conventional wisdom is that you should be sitting in the front third of the room to avoid getting confused by rear wall reflections.

DRM: I just try to lay it out to make the median plane as long as possible so as many people as possible can sit on it and listen. If the rest of the design work's done right, it doesn't matter if you're close to the front walls, close to the speakers, or far back from them. You can hear correctly from all of those perspectives.

You've deadened it so after 50 milliseconds there is nothing in the room.

NB: What a about console splash (sound bouncing off the console)?

DRM: It's a big issue and I don't have a good answer for it. Actually, with our lenses we feel we do have an answer in that our lenses have comparatively little downward radiation, so it minimizes that. But clearly console splash can change the sound quality of the speaker, and that should be accounted for somehow.

NB: In the speaker design?

DRM: Or in how you constitute the meter bridge, how you make that work so you can live with it.

NB: What about angling the speakers?

DRM: That's one strategy that people use; if the meter bridge is high enough, you can get them pointed down.

NB: Since we use small consoles in project studios, how about if the speakers can be at the same level as the console angled up?

DRM: There's something pretty attractive about that. If you get it so the monitors peek over a bridge, the high frequencies won't diffract onto the console surface and back onto your ears. You'll get a nice line of sight with nothing else. In theory it should work well.

NB: Do you believe in the near-field monitoring concept?

DRM: Yes and no. I think it's a perfectly reasonable way to listen to recordings for evaluation. I make sure to check out all projects on near-fields.

It's unreasonable to think that near-field monitors take out all room reflections; they don't. It's just that they give you one particular perspective-and it's one of the ones you should use to mix properly.

I take my cue from Tom Bates and Tom Jung on this: you aren't done mixing until you've made it sound good on a raft of different speakers in a raft of different environments at a whole bunch of different levels. I don't think there is a single speaker set and space that takes care of everything; you have to predict how things are going to sound for a broad range of listeners.