Disgression 3: Quadraphonic

Quadraphonic

Typical Quadraphonic Setup -- 4.2 Channels

Ah, the glorious days of Quad!A time of breakthroughs in audio, enveloping sound all around you, a bandperforming right in your own living room, audio that has not been matchedsince! That's not quite the way it was. Unfortunately there were two majordilutions which quickly dissuaded most listeners from taking thatexpensive step of doubling up on speakers and amplifiers. The advertisingpromised what the reality wasn't able to deliver. One of the problems wasthat most of the recordings released in albums marked "Quadraphonic" wereactually only stereo. They relied on one of a handful of "Matrix Quad"bootstraps to turn the actual stereo two track recordings into fourseparate signals for your quad amps and speakers. In truth, they were outto get something for nothing.

 But for most music applications the truth is not far from what your brain is tellingyou: it won't work. Well, it still can create some nice, pleasant musicaleffects. And with certain kinds of music the very best "logic decoders"can do somewhat better than that. Let's ignore the question since therenow are several fine systems available to present excellent multichannelsurround to the home listener.

 The second major dilution that crippled the early quadsystems is the faulty plan of distributing this doubled information in away we can readily hear and appreciate. The folly of "Obvious Quad" hasalready been covered up above, in Digression I. That provided the second of  the "one-two punches" that spelled the end of quad. Until now. Thistime we've started by basing the music surround systems on the well-provenfilm surround designs. We're not as likely to fall into either trap, as wewill have truly discrete channels of very high fidelity indeed, and willdistribute these channels around the room in an extension of good film track practice. For musical purposes there's still a lot to be saidfor four track versions, or Quad. Most home systems don't haveparticularly good center speakers, often making do with the "phantom center" that any ordinary stereo can do. And many musicians seem less interested in plopping the vocalist automatically in a center channel, anddon't even have much need for that channel.

Minimum Basic Quadraphonic Setup-- 4.0 Channels 

There are two changes in the next plan. Many homes andstudios don't have subwoofers, so we've left them out. Won't change thedirectionality one whit, a matter of wide fidelity rather thanstereophony. Also we've placed the side speakers back to the theoreticaloptimum, directly opposite one another on both sides. For music this iscertainly the preferred choice, and the original quad was nearly always amusic, not film sound, method of reproduction. Since we've covered theLCRS four channel systems like Dolby Stereo above, now we're looking athome music systems, and the studio setups for making and monitoring suchrecordings. The other change you may consider to favor music reproductionis to restore an equal 60 degrees between each pair of channels, back towhere we started aboveThere are two changes in the next plan. Many homes andstudios don't have subwoofers, so we've left them out. Won't change thedirectionality one whit, a matter of wide fidelity rather thanstereophony. Also we've placed the side speakers back to the theoreticaloptimum, directly opposite one another on both sides. For music this iscertainly the preferred choice, and the original quad was nearly always amusic, not film sound, method of reproduction. Since we've covered theLCRS four channel systems like Dolby Stereo above, now we're looking athome music systems, and the studio setups for making and monitoring suchrecordings. The other change you may consider to favor music reproductionis to restore an equal 60 degrees between each pair of channels, back towhere we started above.

The Worst Quadraphonic Setup – 4 Channels

Sometimes the eye can fool theear into thinking things are fine and jolly, when they ain't. We can allcount the four corners of a typical room (har-dee-har, my studio is semi-trapezoidal, and has SIX corners!) or studio. When the first quadraphonicsound was being introduced in the early 70's guess where they put thespeakers (you've had enough hints)? Yup, just like the image above, onefor one. It also seemed like a nice, democratically evenhanded approach,we have 360 degrees to split up, let's see now, 4 goes into 360... And weget this "classic" setup in name only. It's a complete blunder of the job,about as bad an arrangement for surround sound with four channels as onecould devise. If there is but one lesson to be learned via thisintroduction, it's the graphic one visualized above.

 Take a look with your foolish eyes once again. 90 degrees is a pretty wide angle totry to fill with two speakers. Even from the equidistant "sweet spot" asthe seat above is located, you will find images tend to vanish when theyare midway between the speakers. You have another classic going on here,stereophonically speaking, a "hole in the middle." Add the two otherchannels and what you get is FOUR holes in the middle. You end up withsound that can only be precisely heard from but four spots. Everywhereelse is an omniphonic spread of hard-to-point-to vagueness. It gets worse.Try listening to a normal stereo system (about 45 to 60 degree speakerseparation) with your back to the speakers. Hmm... the stereo sort ofcollapses inwards, doesn't it? I'm not trying to lay any dogma on you.These are simple matters to try out with your own ears, as is all thestuff on this page. We all were surprised to learn how things are not soobvious as we first think they'll be.

 And it gets worse again.When you face forward, you can hear any speaker located in front of you,and follow it as it moves to the exact side, either side, whereupon itwill sound like it's moving back in towards the middle again, but withoutthe same precision when the speaker moves behind your head. Again it workson both sides the same way. All stereo relies on the fact that our earswill hear "ghosted" virtual images of sounds located between any no toowidely separated loudspeakers, if the distances, phases, and sound levelsare correctly adjusted. But aside from some very clever tricks heard fromexacting positions and setups, you normally won't hear sounds come fromoutside of a pair of speakers.

 The result is that you canimage sounds rather well in central locations, with speakers moved to eachside a bit, but those speakers set the maximum width you'll be able toreproduce well. Think about those two speakers behind you in the viewabove. Their sounds are towards the center, just like the front pair. Sothere's nothing that sounds like it's coming from the sides. The only wayto fill in the side "hole" is by locating a speaker there, one on eachside works splendidly. After you have normal stereo there is no betterplace to locate the next two channels than exactly to either side of you.That also works when you add a 5th channel, as the latest surround soundsystems do. Like this: