PANNING FOR GOLD
Part one in a Series on Mixing
(for the do-it-yourself audio geek)ã 1998 by Sir Hound, Eddie Ciletti
updated may 2006NEAPOLITAN SURROUND
For the purpose of this discussion, there are three flavors of surround: Passive, Active (Dolby ProLogic) and Discrete (5.1 fully independent channels). Passive and ProLogic extract "hidden" information from a stereo mix. That’s right, even though multiple speakers are used, there are really only two channels of information. The "center" channel is the sum of Left + Right ("mono") and the "rear" channel is the difference: Left – Right. Dolby ProLogic "steers" the subtracted information — which consists of ambience, widely panned and/or out-of-phase information — into the rear speakers with a form of fuzzy-dumb logic. You can set up a generic Passive or Discrete system without buying any processing equipment.
If you already have a Dolby ProLogic system, listen to a stereo music mix and see what happens. The trick to consumer gear is finding the "plain vanilla" ProLogic setting. Many receivers have DSP effects like "Concert Hall," "Stadium," "Basketball" and "Bathroom." You don’t want any of that. Also, the consumer version of ProLogic has a built-in auto-level-balance detector circuit that can not be bypassed. The system will attempt to correct gross level discrepancies between left and right. This means it may get confused if your mix is in a very raw state.
DYI PASSIVE
The first system is super basic. You don’t need any signal processing gear to get started, just four identical passive speakers connected as shown in Figure One. A subwoofer is recommended, but the choices are numerous so follow the directions provided with that system. Assuming your speakers have three- or four-inch woofers, place them in a four-foot square with you in the middle. The subwoofer should be in a nearby corner, either left or right of the front speakers. (Larger speakers can be spread further apart.)
Figure One
DIY Passive Surround System using standard stereo amplifier and four identical speakers.THAT SPATIAL FEELING
Mono mixing is a similar sort of discipline to live recording. The producer, arranger and mixer are forced to make choices, up front, as to what is important and what can fall between the cracks. Stereo makes it easier to hear "space," but a dense production can still be difficult to balance. Surround — in discrete form — will allow so much more spatial freedom that it might actually "expose" what formerly were seamless transitions.
SURROUND ® STEREO ® MONO: HOW IT WORKS
Anything panned center will appear as normal. Hard-panned (full Left and Right) stereo effects like reverb, a pair of guitars or background vocals will be very prominent in the rear speakers. So will out-of-phase material. One acid test for any mix is to listen in mono. Stuff that’s panned in the middle will seem louder while the hard-panned "pairs" will take a giant step back.
If compatibility is really important, lessen the panning "width." This is true whether "folding" surround into stereo or stereo into mono. I’ve found that a mono-compatible stereo mix translates well to "extracted" surround. The stereo effect may not seem quite as exciting with two speakers, but the mix will come alive with four. This is actually better than using processing to make a stereo mix seem wider on a single pair of speakers.
DYI DISCRETE SURROUND
Not everyone agrees that all the monitors (except the subwoofer) need to be identical, but it’s a safe bet. Self-powered or not, you will ultimately need a source selector and master monitor level control. Two models are available from Studio Technologies (847-676-9177). It’s ok for now to connect the output of an 8-track recorder directly to the power amps. The accepted channel assignment can be found in Table One.
Speaker Tape Left Front 1 Right Front 2 Left Rear 3 Right Rear 4 Center (front) 5 Sub 6 Table One:
Standard channel assignment from mixer-to-tape for 5.1 surround.Next is the connection from the mixer to the deck. If all you have is a Mackie 1604 or equivalent, use buses 1, 2, 3 & 4 as left front, right front, left rear and right rear, respectively. Use two aux sends for the center and subwoofer channels. It will soon become obvious that pan pots need to morph into joysticks for precise sonic positioning. Calling all third-party controllers! In the meantime, have fun and let me know how you make out.
Click here if you want to learn more about 5.1 Surround Sound.
MIXED UP
I have several passive surround systems. It’s great fun and sometimes surprising to hear how your favorite mixes will be reinterpreted. One could argue that an audiophile stereo system would be better than a bunch of speakers, no matter how good. But consider these motivating factors. We mix in the "sweet spot." It’s fun, but it’s also work. The average listener is never precisely positioned between two accurately placed speakers. Surround widens the sweet spot, increases dynamic range and — with the aid of a subwoofer — extends low-frequency response. Many consumers are going to have the really cheap stuff, but even those systems will be better than a single 3-inch speaker mounted in a typical plastic TV cabinet.
Don’t wait for the manufacturers of consumer gear to decide what’s best for us. Start experimenting now! The next time the surround show comes through town you’ll know what questions to ask!
Feel free to e-mail with questions and recipes.