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The ABCs of Subwoofers

Top Mix Engineers Talk Techniques and their Subs of Choice

Between greater emphasis on low frequencies in contemporary popular music and the ubiquity of home theater systems that enhance the delivery of low-frequency sounds, the subwoofer has become an integral part of many an audio professional’s toolkit. Introduced with Dolby Stereo 6-track film prints in the 1970s, today’s abundance of 5.1 and 2.1 systems for movie and music playback on televisions and computers demonstrates the subwoofer’s “arrival” as a critical component in delivering not only LFE but the complete audio-frequency spectrum.

Today, it is common for an audio engineer to use a subwoofer in mixing and monitoring applications. Though not everyone is convinced of a subwoofer’s usefulness in music mixing, many engineers insist that careful application allows greater clarity in the bottom and, thus, better mixes.

Blue Sky’s SUB 12 Nashville-based engineer Jeff Balding (Celine Dion, Brooks and Dunn, John Mellencamp, Faith Hill, Megadeth) has set up a home-based personal studio based around an API 1608 console [see “Geared Up,” PAR Apr ’09]. Balding mixes with a Genelec 2.1 system, comprised of a pair of 1031As and a 7070A subwoofer.

“I’ve been using these for about four years,” Balding explains. “I had Tannoy Golds for years with the Mastering Lab crossovers, and had some live concert projects in surround coming up at the time. I needed something for surround — that’s what got me looking. To go to surround, I wanted to find something consistent for five speakers, and that I could also feel comfortable on. To avoid just buying the latest, greatest thing, I researched what had been proven and around awhile in that format for an amplified, self-contained speaker, and also something that was designed to be used with a subwoofer, so you knew that it went together well.”

As is the case among many engineers, surround projects were limited in number, but the subwoofer remains in use in his “Studio With No Name.”

Genelec’s 7070A “I was looking for something where I could extend the range of the system that I carried with me, that would be consistent,” he recalls. “One thing I didn’t realize is that the subwoofer is extremely sensitive to the room that you have it in. It wasn’t something that I could use a lot in changing rooms a lot. You really have to be careful where you set subwoofers.

“As I begin to develop a place of my own to mix in,” he continues, “and once I settled in and knew this was the direction I wanted to go, all of a sudden the subwoofer became very valuable to me in a monitoring environment, because you spend two or three hours getting it exactly in the spot in the room where all the phasing and everything happens, and it sounds comfortable. Before, it was uncomfortable sometimes, especially to mix on: I’d track using it, but in mixing, sometimes it will mess with your head. By settling into a single mix room that I’m in all the time now, I’ve had a chance to set it where I know what it sounds like. I’m not being fooled; I’m not being hyped. I know exactly what I’m hearing, just by reviewing a lot of different material on it: going back to old records, and to modern records that are more in your face, listening to the differences and hearing things that I never heard on the low end of a record before, even at other rooms with large monitors. And really realizing the difference and taking a little time to study what my mixes were, where they are, where some of the other stuff is, and getting a really good read on how the monitoring relates now.”

Jeff Balding A subwoofer, says Balding, allows him to make more informed choices, and thus be a better mixer. “To be able to hear those low frequencies, way down, is extremely helpful,” Balding confides. “There are some things on some of the stuff I’ve listened to that I was troubled by; if I could have heard that, I would have changed that record. It’s totally expanded what I can catch, especially for radio. Mastering will take care of some of that — they’ll roll stuff off to help you out. But there’s a clarity and an evenness in the sonic picture that I feel I can hear in more detail now by using it. Right now, I’m a big fan of having [a subwoofer] in the system.”

A veteran of New York’s top commercial studios, Bob Power (Erykah Badu, D’Angelo, India.Arie, Ozomatli), like Balding, has created a personal studio in which he uses a 2.1 system, this one consisting of a pair of Genelec S30Cs and a Blue Sky SUB 12 subwoofer. “I never used to [use a subwoofer],” says Power, “but since I started working at my own place, I have. The Blue Sky sub is really great. It’s cost-effective, and is built like a truck.”

Power (engineer/mixer of the appropriately titled album by A Tribe Called Quest, The Low End Theory) added a subwoofer, he explains, “because I was so used to Augspurgers — and certain rooms in New York that I trusted on the low end — that from time to time I would go up top to check it that way. Now, I need to be able to do the same thing, although I’ve become comfortable enough with it that I can leave the sub on most of the time and not make any mistakes. I also got it because I’m mastering now too, and it’s essential to know what’s down there.

Bob Power “I have a bypass footswitch,” he adds, “which completely bypasses it out of the circuit entirely. I had a custom switching box made because normally, if you just disable the woofer, you’re still going through the high-pass filter on the way to your speakers. So I made a footswitch that totally bypasses the sub altogether.

“The room, the subwoofer itself, and the way that the distribution level of the sub is set up so it’s accurate and translates well are key,” Power states. “Even more so, if you’re mixing for broadcast or some other medium than records, because you’ve got to make sure there’s not a lot of ca-ca down there that’s clogging up in the 2-bus. An inappropriate amount of information below 120 Hz can really confuse certain playback systems, as well as rob the level from the presence area that is so important in many playback scenarios. Even for playback on full-range systems, the manner in which the frequencies below 100 Hz are handled is critical in both mixing and mastering.”

Post-production studio, Before Noon Post, headed by multiple Emmy-Award winner Peter Cole, is a home-based facility featuring a 24-fader Digidesign DCommand attached to a Pro Tools|HD6, Video Satellite LE and an additional Pro Tools LE system running Digidesign’s Complete Production Toolkit.

Cole’s monitoring setup is comprised of M&K powered monitors for left/center/ right, Genelec surrounds, and a JL Audio Fathom f112 subwoofer. The system also includes a Meyer Sound Galileo loudspeaker management system and a Bag End E-Trap, a tunable electronic bass trap [see page 22 in this issue of PAR for a full review of the E-Trap — Ed.].

Peter Cole “I originally had an M&K subwoofer,” Cole recalls. “That was replaced with the JL, which seems to have another octave of ‘oomph’ below the M&K — much smoother, much cleaner.”

The E-Trap, Cole explains, “smoothes out the low frequencies electronically. It’s basically a subwoofer that puts the inverse of the problem back out into the room and acoustically cancels the problem. It was a good solution for a small room, to cure a bass problem when you don’t have room for large traps. To fix a problem at 60 or 50 cycles takes a massive bass trap, and this thing really did the trick.”

Working on television and film projects, surround sound is a given in Cole’s day-today work, so the “.1,” channel is always in play. “If you’re mixing in 5.1 for broadcast, and the fold down to Lt/Rt or stereo happens automatically at a network level, most of them use the Dolby method, which would be to throw out the LFE. You have to be careful to make sure that your mix still works fine without the LFE. I usually go through and mix a whole show without adding anything extra in the LFE, to make sure it works real nice, and then add in the LFE — sort of the icing on the cake. The reFuse Software Lowender plugin is great to synthesize a subwoofershredding bottom.

“If I’m the one that’s going to make the Lt/Rt,” he continues, “I have a little formula, a cool little thing that I do to mix the LFE into the Lt/Rt dynamically. It’s not a static thing: I run it through a McDSP ML4000 plug-in, among others, that dynamically alters how much LFE is added. So it keeps the TV speakers from blowing up.”

Christopher Walsh is the recording editor for Pro Sound News and the associate editor of Pro Audio Review.