Poor Man's Surround Sound, A.K.A., the Hafler Circuit

Why use analog surround?

With all of the digital processing available to us, why use an old-style hack to create a surround effect? These days, you may not need to. Just hook up speakers to your multi-channel receiver, and you’re good to go! However, there may be cases where you still want to be aware of this analog solution. In my case, it’s because I have an old 2-channel amplifier (without any surround or center channels), and I often like to customize my car stereo. You can get a convincing stereo effect just by changing the speaker wiring.

How to setup

All of the needed information is already online, however you need to be aware that different circuit designs depend upon the amplifier design. Also, such wiring schemes may put a hard load on an amplifier, so do not attempt if you have any concerns about burning up or damaging your amplifier. Wiring incorrectly, especially using the wrong diagram for your type of amplifier, could damage your amplifier.

First, check to see if your amplifier has a common-ground; the answer here will determine which circuit diagram you can use. Then, do an online search for “Hafler Circuit”. I have to emphasize – the circuit is different depending upon if you have a common-ground amplifier or not. Most car amps are probably not going to be common-ground.

Rear Surround or Three-channel (center)?

Another consideration is if you’re going for a 3-channel stereo, or a rear surround sound. This link shows wiring for 3-channel matrix audio, if your amplifier has a common-ground. While I like this wiring scheme, the center channel seems a bit too strong; I’ve tried adding a resistor (not shown in the linked diagram) to bridge around the center speaker, which dampens it down some. The resistor needs to be able to handle enough wattage; more internet searches can find more information on this. A simple bridged center doesn’t sound as convincing.

For car audio, I have used the rear portion of the Hafler circuit. This is very similar to the old “Dolby Surround”, except that that implementation also included a short delay, to give it a big-hall ambiance. While that helps the effect, if your rear speakers are far enough back, it can still sound good.