Living in a 24-Bit World

Oct 1, 2002 12:00 PM, BY EDDIE CILETTI


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I've made it a tradition to go easy in the AES issue and tone down the geek speak for more tangible concepts. It's always a good idea to zoom out once in a while, so whether you're fried from “the show” or just unable to focus on minutiae, this month, we'll explore “listening space clutter” and other audio obstacles in our organic quest for higher-resolution audio.

No matter where you are in the audio food chain, high-resolution audio has become the affordable rule rather than the expensive exception. To consume mass quantities of bits or not, that is the question, as well as your option. That no 24-bit converter actually delivers 24 bits of resolution is not an issue of quality but rather one of theoretical limitations. It applies to electronics and acoustic spaces, although we tend toward thinking that gear can solve all of our problems.

For example, Prism is but one company that makes premium converters. Check out, and you'll find an incredible array of impressive performance specs, but even they can “only” deliver about 21.5 bits of resolution. To deliver the extra 2.5 bits, the unit would have to be chilled to an icy -273.15° Centigrade, otherwise known as 0° Kelvin or Absolute Zero. That's as geek as this column will get.

No matter how many bits you choose, playing the numbers game is all for naught if the listening space is not up to the task. There are enough sonic obstacles in the typical control room to interfere with your pleasure of actually hearing the resolution we've paid for, even 16 bits' worth! Some of the fixes may be obvious and relatively easy. So, let's shift the focus from gear to space and see what happens.


At each step along the path — from basic tracks to mastering — you'll find a fork in the road, one that can make your life easier or miserable. For music recording, the rhythm tracks should fit together just by throwing up the faders. Reaching for EQ as the first fix is a detour on a bumpy road. Fixing the problem at the source will have a positive ripple effect.

Did you know, for example, that the position at which a cardioid mic delivers flat response is typically 1 meter (3.3 feet)? As the mic is moved closer to the sound source, the inherent proximity effect (bass bump) increases exponentially. (See the response curves for the Sennheiser e609 in the figure above.) This could be good for warmth when needed, but using all-cardioid mics on a session, up close and personal, could result in a massive muck build-up. Rather than boosting treble to compensate, it is much better to try these fixes in the following order: Increase the distance, roll off a little bottom or choose an omni mic (no proximity effect).


In the quest for sonic nuance, two obvious issues are noise floor and early reflections. With their fans and hard drives, workstations are major noise contributors, and worse, their most offensive noises desensitize your ears to some of the most critical frequency ranges. The other obstacle is gear that's stacked too close to the monitors, or poorly placed racks that reflect sound directly to your ears. This doesn't help imaging one bit (he-he!), let alone what it does to your perception of frequency response.


My control room has three computer workstations; the noise from fans and drives was cacophonous until all of the noisemakers were relocated to a nearby closet. Sure, computers can be rackmounted, and applying acoustic treatment to the inside, front and rear panels can be effective, but unless you consider ventilation, the solution is only temporary — the heat will kill your gear. Other gear that is fairly quiet — for example, a Fostex DV-40, an Alesis Masterlink with external drive or a Tascam DA-45 — can live behind the listening position.

With the computers in the closet, I found a clever way to share the same keyboard, mouse and monitor thanks to an Iogear MiniView USB 4-Port KVM Switch ($140 from This box does not have a remote, but for users with geek inclinations, the front panel can be removed and extended to become the remote control. I am running dual monitors on the main workstation, the second monitor being on the Iogear switch. Only two long video cables link the closet with the control room, which is much easier than running expensive, long video cables from each computer. (Long cable runs using cheap cable can blur the image.)


Take a look at Mix's back issues to see if you can pick out the mastering facilities from the front cover. When listening is “job one,” the lack of clutter and obstacles will be immediately obvious. It's not just about visual aesthetics, but also about integrating form with the emphasis on function. A traditional recording console is a sonic obstacle. It should be as unobtrusive as possible, not flanked with racks of gear that can create more reflective space. (See sidebar: “Sonic Obstacles.”) For all of us who have no choice but to work in a room with a low ceiling, try an absorber directly above your head. A panel of Type-703 Fiberglas as small as 2×4 feet, covered with an acoustically transparent material (, can improve the image by eliminating ceiling reflections.


Back in June, I used a nearly finished audio facility to record a jazz trio consisting of Benny Weinbeck (piano), Gordon Johnson (bass) and Phil Hey (drums). (See the sidebar above for session details.) Located in a former carriage house, the control room and studio are integrated (no glass or walls). The second floor (over the control room area) takes up only half of the second story, leaving full height in the studio area.

Notice I said, “nearly finished,” because the space was acoustically untreated. I am neither leakage-paranoid nor intimidated by very live spaces, having worked with sonic cowboys like Eddy Offard, Martin Bisi and Bill Laswell — all of whom chose wide open spaces over an isolated control room for several recording projects. One of the advantages of the open-spaces approach is a constant reference to the original sound. It's too easy to think of the control room as the place to make all fixes. Isolation can become a crutch.

Fearing the worst because the room seemed so out of control, everyone was surprised at how well the recordings sounded — on everything from computer monitors to car stereos. A rock band might have played to the threshold of pain, but the jazz musicians instinctively played to the room, not against it. I won't deny it was a challenge for all of us and the results may not have been perfect, but the ability to burn CDs is an invitation to listen to the unprocessed sound first, rather than reaching for that detour knob, virtual or otherwise.

You would think, for example, that bright monitors would yield a dull mix. Bright monitors alone, at high enough levels, can cause ear fatigue and sometimes have the opposite effect whether in a dead or live room. How does this apply to the carriage house recordings or any other sonic endeavor? First impressions are important, yet in unfamiliar territory, keep “The Force” in mind and listen through the monitors to interpret what is being heard. In this case, the room made the drums seem overly bright during the session and on playback, so I knew it wasn't just the monitors. (It is good to think that all monitors lie — that way, they can't hurt you!) When in doubt, simply balancing the tracks to themselves is better than attempting to compensate with EQ.


In the June issue, I tackled a few acoustic basics, pointing out that the goal of treatment is to evenly tame the reverb time across the frequency spectrum. For example, simply covering all of the walls and ceiling with foam treats mostly high frequencies, leaving the bad stuff and sacrificing any life the space may have had.

Back in the '70s, control rooms were “tuned” using a graphic equalizer in conjunction with a spectrum analyzer. Many sonic tweakers from that era only made things worse by boosting and cutting with wild abandon in third-octave notches. Applying a curve to suit your tastes is one thing. Going beyond that is a 2-D fix masked by the third dimension — reverb time. Near-field monitors were found to diminish the effects of a funky room, and they succeeded to a point, but they do not fix all of the problems.


Of course, I have taken y'all on multiple detours, the purpose of which was to detail just a few of the typical sonic obstacles. It may seem an understatement to say that environment affects our perception of sound; it certainly affects how we judge a room, a recording or a pair of monitors. I hope this article inspires those who need to take a closer look at room acoustics. Like capturing jazz or classical music, ultimately the goal will be to not overtreat the space or the recording. And don't be afraid of leakage. It can be very cool — have fun with it!

Eddie would like to thank Terry Hazelrig at for his help with acoustic fundamentals, and David Ahl for his “Terratex” tip. Additional thanks to Jonathon Grove and Gonzalo Lasheras for the opportunity to record Phil, Gordon and Benny.


Seven microphones were recorded straight to Pro Tools | HD at 88.2kHz/24-bit, as detailed along with their respective preamps in the table. Seven tracks were mixed to stereo via Yamaha DM2000 (some live, some during playback from PT) to a pair of tracks on a Fostex DV-40 4-channel DVD recorder. (The other two channels captured an Audio-Technica stereo shotgun mic from the second-floor “balcony” using a Great River MP-2x transformerless preamp. These tracks were not used for the MP3.) Monitoring was via the Grace 901 D/A converter and headphone amp using Sennheiser HD600 headphones (sweet).

No signal processing was used during recording or mixing. The stereo files were digitally transferred to a modified Alesis MasterLink at 88.2 kHz/24-bit, then normalized, rendered to 44.1 kHz/16-bit and then burned to Red Book CD. Two versions of the same tune are provided, one flat with out compression and the other processed using the TC Dynamizer plug-in for Soundscape via a Mixtreme card. Cool Edit Pro Version 2 was used to convert to MP3.




Kawai grand piano

Josephson C602 stereo pair in omni

D.W. Fearn (stereo)

Neumann U67 on the bottom

API 512

Sonor drum kit with Yamaha snare

Spieden (Royer) stereo ribbon for overhead

Neve 1064

Neumann U67 omni kit mic

API 512


AT815ST or AT835ST in MS mode

Great River MP-2x

Acoustic bass

Soundelux ELAM 251 in the f-hole

Manley Mono Tube

The most obvious acoustic problem posed by a recording console is that short-path reflections off of its face can cause both additive and destructive phase problems. When recombined with the direct signal, the resulting “comb filter” gives a false impression of the loudspeaker's character. This is why you should not place speakers on the console (even though everyone does it). It is possible to limit (but never entirely eliminate) this reflection by tilting the monitors (or console) away from each other or by using ribbon tweeters that have a naturally wide but minimally vertical dispersion. Any of these solutions is a compromise that can be better solved by taking advantage of the smaller footprint of digital consoles.

--Terry Hazelrig,

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