The Process of Surround Mastering

Audio mastering is the process of taking audio mixes and preparing them for their best presentation to the world. It is a process that involves tremendous technical knowledge of the audio path and all its possibilities and liabilities. It also is a process that requires an emotional commitment to the audio being serviced. The past twenty years has seen this profession grow tremendously as two-channel audio has been dominated by the CD. As we move toward other formats and surround audio growth, new challenges are facing the mastering houses. The issues concerning surround audio mastering have barely been identified let alone standardized. Gateway Mastering (www.GatewayMastering.com) in Portland Maine and Peerless Mastering (www.PeerlessMastering.com) in Boston are leading the charge into surround mastering technologies and services. They have carefully created surround monitoring environments that permit accurate/discerning sculpting decisions. When you consider the tremendous variables in your own residential surround environment, and then think of the needs of a critical audio facility you will see this is no easy task. I hope your curiosity is now duly peaked to learn more about the process of surround mastering.

The question still remains (I’m sure) “What is Mastering?” Beyond the quick answer in the opening sentence and short of a technical course study, a mastering engineer receives the final approved mixes from the artist/producer/engineer of a project. The task is to polish or finish the mixes so it will sound the best possible for the intended listeners. An analogy to the building industry would be similar to what a premier finish carpenter adds to a luxury house. The tools of the mastering engineer are always esoteric and specialized. They include compressors, limiters, EQ’s, reverbs, phase correctors, and devices that establish the stereo/surround field. These devices are both hardware and software and each mastering engineer is very likely to have a personal “bag-o-tricks” that varies slightly from his/her fellow mastering engineer. In mastering, the “legbone” is connected to the “hipbone”. Every decision made can affect all areas of the audio. Once completed, the artist/producer/engineer takes delivery of a mastered final version that is in the correct format for their duplication needs.

So how would a surround mastering room be configured? There are more than a dozen “authorized” surround speaker configurations for residential purposes all of which can be considered “good practices”. There are at least two primary stereo control room design theories, both of which have almost infinite mutations in existence. It has been said that surround control room environments are currently at the development stage that stereo control rooms were in the mid-60’s.

The compatibility from mastering room to listening room is at best a challenge. Consider: a central phantom image is produced by two separated loudspeakers (left channel and right channel). These two sources will also produce comb-filtered reflections by sound reflecting off surfaces and “stuff” in the room. Surround only increases the degree of difficulty. A five-channel surround environment can produce at least 26 different phantom sound stages and an exponentially complex set of reflection issues.

To help answer these questions and gain a ton if insight into the nuts and bolts of the surround listening experience, I contacted Bob Ludwig of Gateway Mastering and Jeff Lipton of Peerless Mastering. What is particularly interesting about these two flag bearers are there niches. Bob is by every account the top of the craft and has been for…well decades. It is worth your time browsing his credentials and your own catalog…you will be surprised how prevalently placed Bob’s fingerprints are on our listening culture. Jeff Lipton is tremendously regarded as well. He services the Indie record market primarily. One of Jeff’s customers told me firsthand how Jeff offered him a degree of service and care for his project he could not find anywhere else. Although Bob certainly does Indie type records and Jeff absolutely works on major releases, I think it is safe to say that by gaining the insights of Bob and Jeff we are getting both the Uptown and Downtown perspective on surround mastering!

Interviews

I asked Bob to highlight the exciting new aspects of surround audio mastering?

“If one considers the accurate reproduction of a live acoustical concert in one’s listening room as the benchmark for great sound, there is no question in my mind that properly recorded surround sound can yield a closer approximation to “being there in person” than stereo ever can. We only have two ears, but the constant movement of our head gives the ears lots of auditory cues as to what the concert hall is like. In addition to greater sonic accuracy, surround sound in the non-classical genres opens up exciting opportunities to involve the listener in hearing the artists’ music in a new way; it could be in the middle of the band instead of being a listener out in the audience. So many possibilities!”

Jeff Lipton was asked to comment on why he built his surround mastering room, what were his hopes and what were the market opportunities at the time?

“When I was building my facility in 1999, surround was being pushed in the industry as the wave of the future. I had always enjoyed listening to music in surround and I really wanted to work on surround projects. Since the room was being designed from the ground up, I thought it would be great to be on the forefront of technology. Surround also has the advantage of having different sonic requirements. Clients are much more comfortable with surround projects being more dynamic and musical than stereo tracks mastered for CD, on which the clients often want it to sound competitive in volume on their iPods with other recordings they’re listening to, and that’s not necessarily going to produce the best results for the project. When I’m working on surround projects, I usually have more leeway to do what's best for the music without having to compare it to anything else. It’s very liberating and wonderful. Most surround mixes are also much less compressed coming into mastering, so I believe they give the listener more texture and sonic beauty.”

The Peerless A-Room was designed for unparalleled sonic accuracy so both the mastering engineer and the clients can hear the material flawlessly. The A-room was designed by one of the world's foremost acousticians, Bob Alach of Alactronics. It is exceptionally sonically accurate with a frequency response of below 10Hz to above 35000Hz. Prior to construction, the room was acoustically computer-simulated in order to ensure that every feature of the room, including furniture, accessories and the minutest of details, would be optimally suited for acoustic purposes. This process involved making the computer model of the room and tweaking the design until Alach was able to create an optimal listening environment. His model included all construction materials, furniture, and even the listener, to perfectly simulate how the room would sound. The design concept of the room included concealing much of the acoustical equipment behind sonically transparent cloth walls, so this remarkable room is actually almost twice the size it appears.

The low frequency response of a system and room is a particularly intriguing area to explore. Bob offered this in regard to the surround environment:

“For the majority of music, this LFE part of the “bass management” system has little value. Indeed, even for pop music one must be careful not to put anything important in this channel as a stereo fold-down (or mix) of the 6 channels derived from a high definition TV broadcast is simply thrown out. Of course one can put a little something in there if it truly helps to fill out the lowest octave of the music. The sub woofer is an important speaker. Many audiophile enthusiasts look to see how low in frequency their speaker goes, but that is not as important as to the quality of the sound. Many subs go down low, few stop their excursions as fast as the music requires! A bass managed system requires careful placement of the sub woofer. Employing two of them in mono can be an excellent idea to create more of a sense of low frequency envelopment in the room which has been found to increase the realism if the experience.”

I picked up the topic of phantom sound stage and comb-filtering with Jeff who replied:

“I often physically stand up and move out of the sweet spot while mastering to explore how the surround speakers work together. Most listeners are not going to be in an ideal environment and I try to take that into account within the context of the artist’s vision. I also take all my surround work into as many residential situations as possible.”

When asked how similar of an experience an Audioholic could expect to have compared to his finished masters, Bob replied:

“If the surround sound is being heard from an audiophile quality SACD (Super Audio CD) such as the Meitner Labs CDSD Disc Transport (http://www.emmlabs.com/html/audio/cdsd/cdsd.html), the sound coming from the converters is really indistinguishable from our masters. The same can be said for an audiophile quality DVD-Audio player. DTS surround playback used in DVD-Video will be somewhat compromised. Dolby Digital playback is also compromised plus its complexity sometimes turns on compressors and other gain-ranging amplifiers that the listener does not realize is in the circuit!

There is a marriage between the room’s loudspeakers and the acoustics of the room where no divorce is possible. We use fantastic speakers from Eggleston Works (http://www.egglestonworks.com/ivy.htm) and we have, I feel, one of the world’s greatest sounding rooms. The closer you can get to this combination, the more similar experience you will have auditioning our surround mastering.”

That brought up the following description of Bob Ludwig’s audio system:

“The console in my studio is made by Sound Performance Laboratories in Germany. It is ultra state-of-the-art analog electronics with 124 volt DC rails. I use the custom designed Eggleston Works “Ivy” speaker. (www.egglestonworks.com/ivy.htm)

I have serial #’s 1 & 2. The speaker’s designer William Eggleston III and I hand-tweaked the crossovers in my room. To my knowledge, there is no other pair of these speakers in the world exactly like mine as William Eggleston left his company (he has since started another speaker company (www.wegg3.com). The 790 lb. speaker is unique in that it is designed with the isobaric theory of creating equal pressure on the speaker whether going in or outwards. There are 23 drivers in the speaker. 3 woofers face the listener with 2 interior woofers behind each of them. They are simply extraordinary. They are powered by a bridged pair of Cello Performance Mark II high current amplifiers capable of putting out >4,000 Watt RMS signals into 2 ohms. The interconnects and of course the speaker cables are the incomparable Transparent Cable Opus MM. In my opinion, Transparent achieved such a technological breakthrough with this design that we re-wired my entire studio a few summers ago with brand new Transparent cable after starting out with their cables 14 years ago when we built the studio. The system is an utter joy to hear, and I look forward to it every day!

The all important question on every surround enthusiasts mind is about formats and where surround audio is headed. Jeff Lipton has a great pulse on this topic that today rests square on the potter’s wheel:

“Surround has a bright future. Video games and HDTV markets are the major supporters of surround in the current market. With more people wanting to watch TV and play video games in surround, they will want music in surround to play on their new surround systems. Right now it seems like major labels have all but abandoned surround sound, but I believe this will be temporary as other media pushes the format. I've found that indie artists are intrigued by the surround possibilities but are not willing to spend toward that goal on limited budgets.”

Bob Ludwig added to the topic:

“The format war and the invention of the iPod greatly hurt the DVD-Audio and somewhat the SACD format’s growth. Both of these discs are superior to the Compact disc in so many ways. Never seeming to learn from its past mistakes, the industry again has a new format war between the HD-DVD and the Blu-ray. Both of these formats have concentrated on movie-only content, be it Hollywood or live music concerts, but there is no reason why it can not continue on as the DVD-Audio disc attempted.”

This effort would be totally remiss if we did not ask Bob to bring the history of past formats and their mastering challenges into perspective:

“When mastering for vinyl and cassettes we always had to take into consideration the limitations of those formats. Cassettes could not reproduce high frequencies at full level; vinyl could reproduce high frequencies at full level, but not for sustained tones without heating up the cutterhead to dangerous levels. Also, with vinyl, the phase relationships of the low frequencies could result in the groove thinning out and causing the playback stylus to skip the grooves. The problems with tape hiss on cassette and with noisy vinyl manufacturing with disks made extremely low level sounds less satisfactory than with any digital system, let alone a high definition audio system like an SACD disc.”

Summary

The field of surround mastering is uncharted territory and I personally have a great appreciation for Bob Ludwig, Jeff Lipton and others who have taken the risk to help create this new discipline. Surround audio is the place where the creative artist can push the limits in both a “music-phile” and audiophile manner. Bob alluded to the artistic possibilities of being in the middle of the band. Surround audio currently makes perfect sense for classical recordings, live concerts of popular music and retakes on classic records. However, as Jeff pointed out, it may in fact be the market drive from the gaming industry (or some similarly indirect path) that establishes surround audio as an economically defined and viable listening format. The commitment and eternal optimism toward surround audio by Bob and Jeff points toward some exciting content coming our way…the sooner the better!

Jeff Hedback is Chief Designer at Hedback Designed Acoustics which offers acoustical design and consultation services specializing in small room acoustics.

See www.HedbackDesignedAcoustics.com