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Surround Sound Simulator

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This surround sound simulator is based on other surround sound wiring I have seen, that turns stereo sound to surround sound. How it works is that it plays different sound in the front and back speakers, sounding very much like real surround sound.

Feel free to comment if you have any questions.
LDW3 years ago
This is a Hafler circuit, and the inventor should be credited. See http://www.instructables.com/id/Surround-sound-for-free-it-could-save-your-marria/
cornflaker4 years ago
 hang on the rear set of speakers are running off two positive connections from the amp... shouldn't it be a positive connection from one side and a negative from the other?
 I'm pretty sure polarity doesn't matter on speakers, speakers use electro magnets and the should fire the solid magnet the same way regardless, there aren't any electromagnets that repel. If you could make speakers so that when one's firing out and the other's going back in they would theoretically cancel

Polarity matters a great deal.  Electromagnets can and do repel.  It all depends on the direction of the current flow in the wire (which is why polarity matters).  Try touching the wires from a speaker to a AA battery.  Hook it up one way and the cone moves out.  Reverse the polarity and the cone will move in.

The polarity doesn't matter as long as all the speakers in the set up are wired up with the same polarity, (so they can be all the right way or inverted). But yeah they do all need to have the same polarity.

What I'm talking about that though is that both the rear speakers are only getting positive connections, you need both a positive and a negative so that the current can flow, otherwise its just sitting there doing nothing... I mean thats how switches work they cut off either the positive or the negative connection so the current has nowhere to go...
When they talk about +/- on speakers, they are talking about phases, not actual voltages like in a dc circuit. They indicate that when a positive voltage is applied, the cones will all move in the same direction (same phase) and the sounds will add up, not cancel. These speakers are wired correctly. What you are thinking is that both speakers on the left and right side have the same signal, so you are correct, nothing would flow. However, in music, the signal is AC and the two sides have different voltages at any moment in time, so current will flow from which ever channel is higher in voltage to the other. This is the out of phase signal that this circuit uses to give the surround sound effect. The two back speakers are also wired - to - so that they add the out of phase signal correctly to the front speakers to create the back sound effect.
I hope this helps.
Ahh I didn't realise that speakers were AC, kinda makes sense seeing as they move both ways...
My dad told me that it does matter about the polarity on the speakers in 5.1 surround sound systems because if they are connected backward, they are out of phase with the other speakers by 180o so you may notice some timing difference and it may sound a little bit weird
Your dad was right.
Actually, using the positive terminal from both sides is correct.  The pseudo-surround sound comes from the "differential" of the left and right channels.  Notice the polarity of the rear speakers.  The left rear speaker gets a "left minus right" (L-R) signal.  The right rear is the opposite (R-L).  The acoustic effect is a greatly expanded sound field. 
frollard4 years ago
Very neat setup...

You want to be sure you can bridge your amplifier's outputs l/r +/- or you might be a sad panda...but very cool.
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