Surrounded by Sound

Audio freaks love surround sound! But if you are stuck with a stereo sound card, you will have just two (left front and right front channels). Despair not, for we shall now tell you how you can make your very own surround sound system. You will, of course, need another pair of speakers besides your existing pair.

Let us first look a bit at the concept of ‘channels’ in sound. Channels are discrete sound streams in any audio composition. These discrete streams can either be fed to a single output (speaker) or to different individual speakers. This determines that you hear the piano on your right and the flutes on the left. Our surround sound is not based on this principle, but on the difference in sound between the left and the right channels. We will take this difference component and feed it to two other speakers, which you can use as the rear surround satellites. This is called the Hafler

principle.

Please note that this involves opening your existing amplified speakers and some amount of soldering and desoldering. So if you are uncomfortable fiddling with electronics, we suggest you take the help of your local radio/ TV repair mechanic. The wiring diagram is simple and is given here.

Open the casing of your speakers and look at the circuit board. Trace the left, right and earth terminals from the input stereo socket. Mark them as L, R and E. You will then need to solder wires to the L and R points. After securely soldering them, draw these wires out of the casing through any existing opening.

Take special care that the rear surround speakers are connected in series as shown and not earthed. Otherwise they will simply be in parallel with the main speakers and not produce the difference signal. Also note that the rear signal will be of less amplitude than the main speakers and hence will sound low in volume. Whereas this can be amplified, we will not discuss it because of the amount of electronics involved.

Reconnect your speakers to the sound card and play some music. Check that you get output from your rear surround speakers. If the sound appears ‘out of phase’, the concept is working! Also note that this will work with stereo sound only. If you are playing a mono sound, there will be no difference between the left and right channels and you will not get any output from your surround speakers.