5.1 Ways to Lose a Lover

Panning for Gold: Part Two

5.1 Surround Sound on a budget

ã 1998 by Sir Hound, Eddie Ciletti

Edison first recorded sound 122 years ago (as of 29 novemberí98). In the seventies, Paul Simon recorded a song describing "fifty ways to leave a lover." Now itís 1999. There are fewer steps and a twist ó you get to stay and, assuming an aversion to "extra furniture," the lover goes.

Most people who have "visited" my shop for a tape machine repair havenít even considered Surround Sound. For audio people, they are surprisingly uninformed and barely curious. No one expects much from the nickel tour but all are impressed by the "deep impact" of the subwoofer and "space" (the final frontier) created by spreading out a 24-track mix amongst six monitors. One of the greatest benefits of surround is that the combined power of six channels minimizes the need for dynamics compression. (A whole Ďnother discussion, after youíre hooked!)

You may still be uncertain about the necessity of Surround Sound. My goal here is to arouse curiosity ó to encourage all of you to experiment. While meeting this DIY challenge head-on, keep in mind Thom Edisonís theory of "one-percent inspiration, ninety-nine percent perspiration." Itís not just about genius anymore. Surround is almost a no-brainer but there is a surprising amount of wiring involved.

1.) SET UP THE STACK, MACK

Most consumer systems have "dedicated" monitors: full-range for the front pair, limited bass response for the center-channel and surround speakers. The center channel is designed from dialogue localization at the video monitor (it should have a tweeter). Rear monitors do not usually match the front stereo pair. A subwoofer, placed in the corner, takes care of biz.

As professionals, we take our control room environment much more seriously. Most of us have one pair of really great speakers. My front monitors are Dynaudio BM15As. It makes sense to have five identical monitors. But at a list price of $3,559 per pair you can easily see that five monitors, a subwoofer, monitor control and wiring could tip the scales at or near $10,000! (And that doesnít include a DVD player!)

So, in the interest of science and a severe DIY mentality, hereís what I didÖ

For the center, I placed a modified pair of (magnetically shielded) Auratones left and right of a TV monitor. To bring up the rear, I chose my old main monitors ó EV MS-802s ó similar in size to the Dynaudio BM-15A. A Tannoy PS115 adds the rumble factor.


 
 Dynaudio has a "package price" for various surround systems. 
You can download the Adobe Acrobat files for PASSIVE and ACTIVE surround systems.

 
 
2.) MAKE A NEW (wiring) PLAN, STAN

I already had a passive surround system (Click here to read, Panning for Gold: Part One) so the rear-channel wiring was in place. It was only necessary to add the center and sub cables. Surround is mixed to a digital eight track ó either an Alesis Adat or a Tascam DTRS. How you get there depends on whether the "source" is an analog or digital mixer. The latter in my case is a Soundscape workstation.

Monitor control is the real challenge. If this is "just an experiment" you can wire directly from the eight-track to the power amps, using the tape machineís INPUT control to monitor "source" or "tape." For flexibility and control I chose (and bought) the Studio Comm 68/69 controller/console. It has two surround and two stereo inputs, a level control and mute/solo switches.

3.) GO TO THE SHACK, JACK

Once the wires are all connected, itís time to calibrate the monitor level. Bob Katz wrote an article about establishing a reference level for stereo monitoring back in the Septemberí98 issue. Surround level calibration is even more important especially in my case. You donít want to make EQ decisions when the monitors donít all sound the same. Itís also not possible to equalize / tune out the differences. My way around the problem was to not use the rear speakers to evaluate EQ. (I spend much more time on balances anyway.)

To balance all of the monitors you need a Sound Pressure Level (SPL) meter. Radio Shack has two ó cat 33-2050 ($35) and 33-2055 ($60) ó nearly identical except for the analog and digital displays, respectively. For a noise source, I used SOUND CHECK, a CD by Alan Parsons and Stephen Court. It not only has full frequency "pink" noise, but also filtered bands of noise, tones, sweeps, audio samples of music and voice, time code and a tuning reference.

4.) LETíS MAKE SOME NOISE, BOYZ

Lest you think I am a renegade, there is actually an established procedure for calibrating the monitors. The Dolby website is rich with details, theory, practical applications and of course, their product line. You donít need any Dolby products to create a discrete surround mix.  However, to create a Dolby Digital (AC-3) version you must use their DP 569 encoder. The professional DP-562 decoder does provide some extremely useful tools; such as the ability to hear how your 5.1 mix will sound in stereo or Pro-Logic Surround.  (There are also TDM software plug-ins for both the encoder and the decoder for use with ProTools.)
 


 
 
 
Please Note:

This article is about creating a mix using 5.1 discrete surround channels.  Dolby Pro Logic Surround is a method of "embedding" surround information within a traditional stereo pair of tracks. 

If you intend to "down-mix" the 5.1 channels into two channels, you absolutely need a Dolby Pro Logic encoder to do a Dolby Pro Logic Surround mix.  Even if you are not using a Dolby Surround encoder, it is a good idea to monitor the stereo bus through a Pro Logic decoder in order to minimize the potential for the unpredictable. 

Either the analog SDU-4 or the digital DP-562 decoders will work well, and have no auto-steering (the balancing function found in many consumer decoders that could cause inaccurate decoding in a mix situation). 

One other point, if a program producer wishes to use Dolby trademarks 
on their products (i.e. Dolby Digital, Dolby Surround, etc...), they must 
obtain a royalty free license from Dolby (a very simple procedure, described on the website).


 
 
To calibrate the system, pink noise is applied to each monitor. I recorded the noise @ -20dBFS to six tracks of tape. The SPL meter ó placed equidistant from all monitors ó should be set to SLOW and "C" weighting. Playing back the noise tape, I adjusted the MASTER level control of the Studio Comm for 85 dB SPL from the Left Front monitor. (Adjust as necessary using one monitor at a time.) Mark the "reference level position" on the control room monitor pot. If going straight from tape-to-monitors, try to not kill yourself! (Start with the power amp gain trims way down.)

When matching the level of the subwoofer to the full range monitors, Dolby more than recommends a spectrum analyzer. In fact, they are emphatic about it. When you are ready to compete with the big boys, you will need to get on the serious good foot. In the meantime, using the band-limited noise from the CD worked out OK for me. The bass band on the test CD is limited to 200 Hz. Using this instead of full-frequency noise keeps the tweeters from tricking the SPL meter. I used the same technique to balance the center channel speakers using the 200Hz~1kHz band. (Dolby specifies that the subwoofer response should not go above 120 Hz.)

5.) LETíS WHIP UP A MIX, CHICKS

Unlike the setup procedure, there are no rules for mixing but there are "conventions." Film mixers place dialog in the center channel. This is OK when watching a movie in a theater. L-C-R speakers are directly behind the screen which is elevated enough to avoid "obstructions," a.k.a. human heads.

At the time I was preparing to create a 5.1 mix, a DVD produced by A&M records served as a practical reference. The sampler disc featured 10 music videos with 5.1 surround mixes by engineer Ted Hall. I especially liked Sounds of Blackness, Jonny Lang, Suzanne Vega and Soundgarden. Sheryl Crowís massive compressed sound (which I assumed is on the multitrack and could not be "undone") didnít transfer to the surround environment.

On all mixes, Ted used the lead-vocal-in-the-center convention. This is cool for karaoke purposes (if the center channel is muted, then you can be the star) but it is not my preference. My first musical surround experience was at the MPGA demo last May. I was sitting behind someone and the lead vocals were unintelligible coming from a single center channel monitor.

For this reason, I chose to route the lead vocal to both front and rear pairs so that it would "appear" in the virtual center above my head. This also served as a reference for front-to-rear balance. I played the finished multitrack tape on several systems, from San Fransisco to New York. It sounded great at the JBL demo room (tweaked by John Eargle) at the AES convention. It also played well in Dolbyís private theater located in their Midtown Manhattan offices.

In one room my mix did not play ó the front-to-rear balance was completely out of whack. I suspect that particular control room had been calibrated to accommodate a dozen visitors and that the mix had been specifically tweaked for that demo. (No one has come clean as to the specifics, yet.)

.1) JUST TURN UP THE BASS, GRACE

Of all the steps, this one will ensure that your lover will leave (either your life or head to the bathroom) and that your neighbors will complain (after realizing that you are the earthquake). Nothing makes bass easier than a subwoofer; nothing is missed more when it goes away.

There are "low-frequency management" issues. You can not rely on the subwoofer exclusively for low-frequency instruments. On the cheapest consumer systems, the "sub" is barely a six-inch woofer supporting five satellites, which in the Bose system are three-inch diameter drivers. In the big picture, six discrete channels are encoded into a digital bitstream, as is the case with Dolby Digital (AC3). On the decode side, the six channels emerge as discrete as the original. However, if the destination is only a stereo pair of speakers, the decoder is smart enough to mix the rear-channel and center info to the front pair but it will ignore the "sixth" channel (subwoofer) information.

I treated the center and sub channels as one "monitor system" with an electronic crossover. Routing bass and kick to Auratones gave the expected mid-range sans boom. Adding the subwoofer made Ďem large, alive and natural. (Remember, Dolbyís upper limit for the subwoofer is 120 Hz.) If, however, sub-sonic muck appears in the low-frequency channel (from a bass guitar, for example), judicious use of a high pass filter should clean things up. You could also go the traditional route, sending kick and bass to the front pair. Your mixes will maintain compatibility on a wider range of systems so long as the subwoofer isnít exclusively used for bass.

ASSIGNMENT

The track assignment I am about to give differs from the one detailed in the September issue. The reason for the re-assignment is for "compatibility." (Video decks have four channels and it was felt that the most important information should be a no brainer to patch: L, R & C to tracks 1, 2 & 3.) In the big zoom-out, this is no big deal, but you should regularly check the Dolby site for procedural updates.
 


 
Speaker
Tape
   
Front Left
1
Front Right
2
Center
3
Subwoofer
4
Surround Left
5
Surround Right
6

One final note. dts is also in the surround business. While their web site provides no technical information, there are many albums that have been remixed for 5.1 surround. Dolby Digital decoders are built-in to all DVD players but to decode dts an external converter is required.
 

Feel free to e-mail edaudio@tangible-technology.com with questions and recipes.

Check out Panning for Gold: Part One?  ( for a passive DIY surround project )

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