The Mastering Plan.A look at the challenges facing surround and high resolution mastering engineers today.

This site offers surround professionals an opportunity to exchange information, voice their opinions, and get their production questions answered by their peers. This was created for you to discuss issues pertaining to the surround sound revolution.

by gary eshew

The rapid rise of DVD-Video has many observers counting the days until tape goes the way of the Model T. The difference between the analog and digital formats is obvious, making the shift from tape to discs played on low-cost machines simple. DVD-Audio presents a different set of issues, however, not the least being the fact that consumers resent being told that the Red Book CD standard yields inferior sound, since they were induced to repurchase their LP catalog because of the supposed “perfect” sound of this medium.

Convincing a skeptical public that DVD-Audio is worth the investment is critical to the success of this platform. Fortunately, more and more recordings — both classic hits from the past and current fare — are getting the full, advanced resolution 5.1 mix treatment from some of the best engineers in the business. A new understanding of the way that multi-dimensional mixes can be used to enhance the listening experience is being developed. Mastering technologies for 5.1 recordings are also evolving. Surround Professional spoke with three of the leading mastering engineers in the recording industry — Ric Wilson, Bob Ludwig, and Denny Purcell — to find out where we are now, and how things are shaping up in the world of DVD-Audio.

With over 500 Gold and Platinum albums under his belt, you’d expect Denny Purcell, president of Georgetown Masters in Nashville, to have a few ideas about how surround sound mixes affect the listening experience. He does.

“The most important aspect of surround sound mastering is mechanical: you must stretch the canvas properly if you expect to paint a beautiful picture. The artist and producer — whoever has the artistic and creative control over each song in an album — has a philosophical take on exactly what the picture they’re painting should look like. It may be that each song changes perspective, or that the whole album fills one perspective. Some people like to put the listener in the front row, others like the listener to hear from the same perspective the artist was in when the work was being performed. There is no right or wrong way.”

For Purcell, stretching the canvas means setting up the six speakers precisely. “We use a 2×2 sheet of wood with a protractor and a nail in the center of it. Using these tools, we find the center of the listening area we’re working in. Then we suspend a crystal to mark the center area. In front of you you’ve got an equilateral triangle formed by the left and right speakers — the traditional “sweet spot.” You place the center speaker in-between. The sub can go left or right of the center speaker, or left or right of one of the front speakers.

“Turn your chair around 180 degrees and plot out another equilateral triangle for the rears. Or you can splay them out somewhat to mirror the typical listening environment. We also use a level to make sure each speaker is perfectly level.”

If you’ve properly defined your surround space, the art comes for both the mix and mastering engineers. Purcell spoke about his work on Mark Knofler’s last recording, Sailing to Philadelphia. The original surround mixes, executed by Chuck Ainley, came to Purcell in 48 kHz/24-bit form. “We could get off on a long discussion of sampling rates. I’ll tell you this: I’ve worked all the way up to 192 kHz/24 bits, and there is definitely a difference between 96 kHz and 192 kHz. The higher the sampling rate and bit resolution, the closer to the original sound you stay. Your A/D conversion is also critical. We use the Pacific Microsonics MDCD Model 2, I think it’s the best A/D converter in the business.”

Purcell says that surround work helps further the art of a natural storyteller like Mark Knopfler. “Mark uses language so well. You can close your eyes and listen as he sings about a guy out on the race car circuit. Chuck took the sound of tires squealing and the sound of sand swirling out on a Nevada desert and placed them beautifully in the surround field. I have to make sure that none of this placement is lost.”

Georgetown Masters recently took delivery of a Sony DMX-R100 console, and Purcell says the board found an immediate home. “The R100 meets my criteria. Sony has been kind enough through their design program to help me get some things I need, including an intricate Q and extremely fine EQ resolution.

“I had a Muse console for a long time. There were only about five of these digital boards in the world. Best console I ever used in my life. Unfortunately, they went out of business, and I’d have to have a guy on staff just to maintain the old, one-of-a-kind technology.

“Overall I really love the sound of this R100 console. My other criteria — besides simply having a high-quality digital signal path that sounds neutral and a good sounding compressor, was that the board I work on must be able to easily handle 96, 88.2, 48, and 44.1 kHz, with 24-bit resolution and surround sound capability. The R100 meets all these requirements.”

Bob Ludwig, owner of Gateway Mastering Studios, is also a member of the most elite group of mastering engineers in the industry. Ludwig says that mastering in 5.1 is extremely rigorous, and far more detailed than working in stereo. “With stereo, you can listen to the 2-channel mix over headphones to detect glitches and drop outs. That’s relatively simple. However, with 5.1 there’s a problem: your ear doesn’t have the acuity to hear what’s happening in the rear speakers as finely as the fronts. You have to use headphones and make two passes to really pick out problems. Let’s say you’re mastering a DVD movie that’s 1.5 hours long. It will take you 3 hours to hear it through once! If you have sample-rate conversion, or are using Meridian Lossless Compression (MLP), or watermarking, you have to listen yet another time to make sure nothing went wrong with the transfers.”

The expense involved in retooling a mastering facility for 5.1 work is immense, says Ludwig. “It’s like building a whole new studio from scratch, in a way. You have to buy at least three more main speakers, two subwoofers, bass management systems, and special equalizers and compressors that work on all six channels at once. Sample-rate converters and AES distribution boxes are also expensive, as is the technology that lets you make a one-off 96 kHz/24-bit DVD audio disc for reference. Because it is so much less expensive, many clients request DTS 5.1 surround CDs as a reference, even though it’s lossy — not the quality the DVD-A might have, but it’s in the ballpark. The DTS box only works at 44.1 kHz though. You can not gang together three stereo sample-rate converters. To my knowledge, only dCS has a multitrack mode that lets you lock all three devices together.”

You can ask Bob Ludwig which sounds better: AC-3 or DTS encoding, but don’t expect an answer! He works with both formats, and is distinctly nonjudgemental. “Remember, you’ve also got the SACD (Super Audio CD) format that Sony and Philips developed. There’s no lossy compression at all with this format or possibly compromised down-mixes. A fully loaded SACD has dual layers with Red-Book play-on-any-CD-player material on one layer and eight DSD channels on the high-density layer (6.0 channels for surround and 2 channels for stereo). DTS uses less data-compression than the Dolby process, but the two use completely different algorithms. You have to listen for yourself to decide which you prefer.”

Ric Wilson is a freelance engineer who operates under the aegis of his West Coast-based company, Digisonics. He has been mastering for 12 years, with the last three of those involving surround sound. Some of his music surround projects include Pacific Coast Highway and Studio Voodoo. In addition to his musical work, he has been a music editor on several major feature films, and is currently mastering a pair of DVD-A discs in the DTS format.

To Wilson, when mastering, a great deal of importance is placed on the quality of the original tracks. “At the mastering level you’re extremely limited if the 5.1 image is compromised; a big part of the job is stabilizing the image throughout an album. The mastering engineer takes a group of songs that were recorded and mixed, quite possibly at different studios and times by different engineers, and creates a single product — the album — out of this collection. If the image shifts, the listener will be disturbed.

“We use both DTS and AC-3 encoders in our facility, so I can listen in real time to how the mastered product will sound with both compression schemes added. To my ears, DTS changes the original master very little, and retains the sharpness, definition, and punch of the original. With AC-3, we’ve had to make adjustments in how the low end is handled and how the center speaker is processed in order to accommodate the changes that this process brings to a record.”

Wilson says having the room to place instruments and voices in their own individual places in a surround mix has been ear opening. “When you mix and master in stereo you’re trying to cram a lot of information into one spread between two speakers and you tend to use a lot of EQ and compression to distinguish the elements. With 5.1, all of a sudden you aren’t limited to that one narrow arc. We tend to use less compression and EQ with 5.1 because instruments can be assigned their own space. That also has the benefit of retaining the dynamic level of the recording.”

Wilson has recently completed work on two DVD-A albums for Studio Voodoo and Larisa Stow. He is currently working on projects for Esteban and The Les Brown Big Band.

It seems clear that we are in a transition period, and that audio at opposite extremes of the quality spectrum is drawing consumer interest. MP3 downloads played over personal computers are not diminishing, despite the travails of Napster. And yet audiophiles are being joined by a growing portion of the buying public in an enthusiastic embrace of DVD-A. How all of this technology shakes out in the marketplace is, however, still an open question. We’ll let Denny Purcell have the last word on the subject: “Consumers need to be educated. Question: Given the chance to have the best audio ever in history, will the consumer attach value to it and want it? Can DVD-A co-exist with MP3? Most labels have told me they plan on eliminating replication entirely. I happen to think this is our last shot at proving that quality and artistic integrity has value to people. I don’t think we’re doing enough to educate the consumer about how cheap it really is for them to get into this technology.”

Surround Professional Magazine