In Our Last Episode . . .
In my last column, I described an experimental concert recording I did in Faneuil Hall, Boston, with the Boston Classical Orchestra, using three different surround microphone arrays simultaneously. A good orchestra and soloists, playing decent repertoire, in a decent hall. Opportunities like this don't come along very often! Naturally, I couldn't resist leaving you hanging in suspense, so I put off telling you how it all sounded until this month. Too many Saturdays at the movies as a kid, I guess.

Well, I've had a good listen to the tracks by now, and all three recorded versions sound decent, if a little too dry (God bless digital reverb!). And, they all sounded quite different from each other. There is a fair amount of insight to be gleaned from this little exercise.

First, to review the setups, we had four Earthworks omnidirectional microphones spaced in a quad array, suspended above the audience, plus a cardioid microphone pointed at the ceiling from the above the rear balcony rail. Second, we had an experimental coincident microphone built by local acoustician Richard Campbell that utilizes four Audio-Technica cardioid capsules oriented at 90° from each other, forming what might be reasonably described as "Double XY," (with full apologies to Curt Wittig and Neil Muncy, inventors of the "Double MS" microphone configuration). Third, we had a preproduction prototype 6.1 microphone built by Mike Godfrey of Toronto (with help from George Wong of the National Research Council of Canada). This was a "dummy head" type mic with seven Sennheiser capsules mounted on/in it to cover Left, Center, Right, Left Surround, Right Surround, Overhead, and Low Frequencies. Seven wireless transmitters sent audio from this battery-powered remote mic to the console. The microphone is designed for location film, FX and Foley recording work. See last month's article for a detailed description of this setup.

We recorded all of this directly to 16 tracks, with no processing of anysort. Music included some Alfred Schnittke music for string orchestra and soloists, plus Haydn's Trumpet Concerto and London Symphony. The playing was very good, professionally secure, in tune and time, with generally excellent ensemble quality.

The Sound of the Spaced Array
At first listening, the spaced array was the most spacious and entertaining version. The surround channels were rich and gave a strong sense of hall. The orchestral timbres were true to life, and the general orchestral ensemble sounded both life-like and spacious. There was decent envelopment (the term reverb designer David Griesinger has coined to describe our sense of being "in" the soundfield created by the recorded ensemble, as opposed to perceiving that soundfield as being "in front of us"), and a generally satisfying sense of spaciousness and involvement with the recorded event. It's not perfect, however, and over time, a number of annoying flaws made themselves known. First, the lack of precise localization began to get a little obvious, and the entertaining wash of spaciousness began to be supplanted by a sense of a non-orchestral vagueness, which is to say that the "solidity" of the orchestral image wasn't all that solid. Further, the highly directional characteristic of the trumpet soloist made the level of the trumpet sound a little louder in the rear mics than it was in the front mics. To make it worse, the off-axis sound quality of the trumpet in the front mics made them sound camparatively reverberant. This resulted in a sense of "trumpet everywhere," rather than as a point source. On the plus side, the string soloists sounded quite decent in the front mics, with their strong upward HF radiation.

Solutions for these problems lie with the inclusion of a center mic (we just ran out of omnis, plain and simple - wouldn't ever happen on a real gig!), plus placing the Left and Right mics closer together, and possibly moving the rear mics significantly farther back in the hall.

And The Double XY
When I switched from listening to the spaced omni array to the coincident Double XY, the sound immediately moved toward the front of the playback room. The sense of hall became a lot less obvious, although a similar sense of soundfield collapse occurred when the surround channels were muted. The general orchestral timbre and presence was quite good. The trumpet soloist was obviously a phantom image. The hall sound (too dry in fact) sounded in fact too dry, and cried out for reverb in a way that the spaced omnis didn't. (In fact, when I sent a quick stereo rough mix to the orchestra, I added a fair amount of reverb, just for this reason.) In short, the Double XY was adequate, but underwhelming in this application. In other chamber music recordings I have heard that use it, it works quite well, and has the virtue of simplicity and straightforwardness. The biggest technical problem with it is that it doesn't solve the center channel problem.

Mike Godfrey's 7-Channel Prototype Microphone
Switching to Mike Godfrey's 7-Channel microphone, the difference was (and remains so, with repeated listening) quite striking. The Left-Center-Right spread was really excellent, and the Sennheiser capsules did a really nice job of resolving the soundfield. The result was a sense of engagement that grew stronger over time, an almost "itchy" sense of awareness of the orchestra and hall. The rear channels were too dry, as expected (can't blame the mic for this!). The soloists (especially the trumpet) had a wonderful crackling sense of presence and solidity, and the sense of solid placement of instruments in the orchestra was superb. A really enjoyable and effective listening experience.

Fun And Profit Time
All of these configurations work, and all have both virtues and vices. The Godfrey mic yielded the best raw results in this case, but that wouldn't necessarily always be so. Further, some of the virtues of the Godfrey mic lie in the musical quality of its capsules, not in its configuration.

When I began to fool around with the playback mix, I found the recording got a whole lot better when I added the spaced omni rear channels to the Godfrey mic. And things got better yet when I put slightly less than 40ms. delay on the Godfrey rear channels and 60 ms. on the omnis. The hall opened up with considerable richness and sense of place. Some additional reverb wouldn't be bad, mind you, but the sound wasn't uncomfortably dry anymore, and little sonic incidents (a cough in the right hand balcony, a dropped pencil or something on stage that rolled a couple of inches, stuff like that) were palpable in their sense of realism.

Another point worth noting is that the overhead channel continues to impress. In all of the playback arrays, I included an overhead channel. It rewarded me with added richness of sound and integration of spaciousness. Maybe you can live without it, but now that I've got it, I'll never go back. The point of all this is, it seems to me, that there is no single right
way to do this stuff. Depending on your needs, various different qualities can be extracted using different techniques, and fortunately those techniques aren't mutually exclusive. And while much of this is way too picky-picky for much video production work, awareness of what will really give a kick to the production quality when you really want to hammer home a strong "sense-of-place" in a video production context will be really valuable. These approaches have a lot to offer. Me? I want Mike's mic, plus a coupla omnis anywhere for additional spaciousness. Good place to start, anyway.

Thanks for listening. See you next month!
Dave Moulton is a recording engineer and audio researcher in Groton, MA. You can complain to him about anything at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .