Sharoma Out Of Phase Stereo

Out Of Phase Stereo

(OOPS)... is destructive interference. It is anti-sound. If you are confronted with a sound, and manage to produce the exact opposite waveform, the sound ceases to exist... this is the essence of...(OOPS)

Out Of Phase Stereo is a new way of listening to your music. It is usually referred to as "OOPS", so please try and refrain from thinking about tinned spaghetti. Basically, if you do not know a single thing about how sound waves work, it involves hooking up at least one speaker incorrectly to achieve a surround sound effect (or to hear previously hidden sounds) from stereo music. I myself read about the technique at the following pages. Visit these, and do your own research, before attempting to comprehend my own crude 'Paint' drawings.

»»» Video: My stereo system, wired for OOPS.

Microsoft Paint helps illustrate my point

Here is how my system is set up:

OOPS stereo system

At the front of the room is the amplifier, which has two sets of speaker outputs (A and B). The two front speakers, as you can see, are wired conventionally to set A and are in phase. This is a normal hook up. For the rear speakers, their own negative terminals are linked by one wire, the left rear positive is connected to the amp's set B left positive, and the right rear positive is connected to the amp's set B right positive. This means that the two rear speakers, situated behind the listening position, are going to operate out of phase with the front speakers. This is interesting for at least two reasons:

Hidden sounds

If a mono source is played, then the rear speakers will output nothing (actually they mirror the set A speakers, but at exceedingly low volume). With any stereo source, they will reproduce what is different in each of the two channels. Confused? Well, stereo isn't all that complicated. The left and right speakers each produce different music, right? That's how the stereo image is created. So, the rear speakers will then only reproduce, since they are out of phase, the sounds unique to each channel, and not the sounds that are present in both channels. Still confused? Okay, imagine this: the left and right speakers both have a guy singing, and the stereo mix has his vocals placed at identical levels in both channels. Then, the engineer has mixed a drum in the left speaker and a guitar in the right. Well, the out of phase speakers will reproduce everything but the vocal. Now, I have connected two rear speakers out of phase. You can of course go with a single one, and the effect will be the same (although it sounds, obviously, slightly different). Using the amplifier's switch, I can remove altogether the set A speakers and listen only to that which is out of phase. Sometimes, depending on the source, you get distant sounding music and vocals, or just vocals, or just instruments (The Beatles stereo recordings are a case in point and an ideal starting point for experimentation).

Poor man's surround?

Rather than just connect one rear speaker (which would have both its positive terminals connected to the amp's set B left positive and right positive), I went with two. Since they are connected by their negative terminals, I am not sure if this puts them in series, and thus raises the impedance to 16ohms (since all are rated at 8ohms each). The level seems to compliment my front speakers, and since they are reproducing music out of phase, it creates a very pleasant surround sound experience, not unlike any modern surround sound receiver. It is not a poor man's surround system, because all a fancy modern receiver can do to stereo music to make it sound "surround" is to invert the phase in the rear channels, and I have done it literally rather than running it all through software or some fancy DSP. The result is a crystal clear sound, and when the listening position is between the front and rear speakers, the phasing is ideal (the speakers behind you go in as the fronts go out, and vice versa). I wonder how many producers engineer the sound for an OOPS setup? Probably none, even though it would be quite simple.

Risk

I have had my amp and speakers wired up like this for a year, and it hasn't caused any problems. Always power off your amp, or at least disable the corresponding speaker terminals, when conencting wires. If you short them together, you may trip your amp's protective circuits, or, in the worst case scenario, blow them completely.

So go on, try it...

Anyway, I love the way it sounds. It brings much more life and presence to all stereo recordings, regardless of source. Every record is mixed differently, so you never know what extra sounds you will hear in the mix (and they will be very prominent!), or how the overall listening experience will be affected. Sometimes just the rhythm section is out of phase, so you effectively have two rear speakers dedicated to bass and drum.