: Poor man's 3/4 channel surround sound



MachX
11-30-06, 06:39 AM
I was doing some research on Dolby/DTS technologies and I came accross this page on howstuffworks.com. It allows you to wire your rear speakers for a matrixed surround effect, instead of the standard direct fire ambience effect. And it works! I set it up in my car and auditioned it with The Who's Live at Leeds cd and the effect is INCREDIBLE. You really feel as if you are sitting RIGHT THERE. Basically you are setting up your rear deck speakers to simulate a rear wall so you actually get a true 3 dimensional soundstage. Of course, if you have a fancy head unit with built in Dolby, then read no further. First, a little tech. When an instrument is recorded with a mic, the direct sounds are recorded in phase by the mic. If there is a decent accoustical environment, there are echoes off of the back walls. The microphone picks these up out of phase, as in they cause the filament in the microphone to oscillate in a manner opposite to the sound waves coming directly from the instrument. This is especially true of live recordings. So when you wire your rear deck speakers out of phase, you cause the rear speakers to act like the rear surfaces of the recording environment (back wall, crowd noise, bass reverb, etc.). So what you end up having is a true representation of the actual recording environment. Naturally, you need a good strong front stage component system or else you end up with some tinny sound. If you own a 91-up Symphony sound, or any Bose set up, you have a good component setup. Here is the link for a simple 3 channel (front stereo stage, rear ambience) setup. http://kantack.com/surround/surround2.html#tag2diag1
The easiest way to do this is to clip the rear negatives from behind your head unit, and then run a wire between the negative terminals on your rear deck speakers. I believe that the factory setup uses higher impedance rear deck speaks (10 ohms) so you may have fade your system 3db towards the rear to get the proper balance. If you have same impedance speaks all around, you won't need to fade. Further down the page is a diagram for a rear stereo diagram. If you want to go all out, buy the 8 ohm resistor. The diagram makes the wiring look more complicated than it is. All you have to do is clip the rear negative wires behind your head unit then fuse them together at either end of the resistor, and *poof* instant four channel listening environment. There's also a diagram for introducing a speaker to represent centered audiol, but I don't recommend that, it does limit your stereo seperation. Play around with your fader a bit to get the desired effect, but if you're an audiophile like I am, you will appreciate the immersed, three dimensional listening environment present in live and symphonic recordings. I also auditioned Mussorgsky's 'Night on the Bald Mountain' and the orchestra came from the front, while the bass drums rumbled from the front and reverbed from the rear. If there are any quadrophonic or dolby pro logic encoded cd's in existance (I don't know if there are) you will get the full effect, but many stereo cd's will work too.

akimball442
01-31-07, 05:44 PM
that's not actually wiring the speakers out of phase. I use that setup at my house because I only use vintage vacuum tube amplifiers with no rear channels. It's called the hafler arrangment... and it does work well.

By setting up that way, youre removing anything that was recorded in mono.. usually voices. It's also a poor man's karaoke setup. The Who Live at leeds will let through some vocals.. its an extremely stereo recording.

But with stereo, you have Left and Right. This system gives you the difference (L-R). Mono would be L+R.

Hopefully that clarifies. It does sound cool. I like it a lot. It adds tons of dimension to the sound stage. This has been around as long as stereo. Most cheap surround sound receivers utilize this method.

Aaron