Speaker Theory

Speakers are the final components of the audio chain—the interface between electrical signals and sound. With few exceptions, a typical speaker enclosure contains several transducers that disperse sound into your living room. The sound seemingly spreads every which way and may bounce off the walls, carpet, or furniture several times and to various degrees before it arrives at your ears. The more I think about this the harder I find it to understand why this does not result in total sonic chaos.

To make it easier to understand, I could ignore the living room for now and look at speakers in an anechoic chamber. But since I don't own a speaker lab, I'd have to drag the speakers out into my back yard, put them on a high pole, and have them speak towards the sky. This has a similar benefit as the anechoic chamber in that hardly any sound bounces off my lawn and none off the sky. If I looked at the speakers from above, with a microphone attached to an even higher pole, this should give me almost anechoic results. Unfortunately, living in the Pacific Northwets [sic], this is not an option either, at least most of the time.

Enter the computer. My speaker design software (LspCAD) lets me simulate many of these things. Understanding that simulations likely simplify reality, I still find them very educational. For instance, to simulate the behaviour of speakers in a room, the software lets me specify width, length, and height of my living room, along with the size of the speakers, the transducer positions on the enclosure, the rates at which my walls, floor, and ceiling absorb or reflect sound, and the position of my ear. Granted, my living room is L-shaped, and I have two ears, but it's a start, and it is way easier to change the speaker position in a dialog box than constantly moving around large pieces of furniture.

I still remember the first time I saw the simulated in-room frequency response curve after entering all the numbers, particularly my haphazard speaker positioning choices. These choices can ruin the best speakers, and my speakers were nowhere nearly the best. I played around with the numbers for a while and settled for a new set of speaker positions that made the frequency response look somewhat decent. Luck had it that this required to move my 32" TV which in turn displaced the stereo rack and then dominoed on to the guitar amplifier. But after some exhaustion I finally got to tune back into my local jazz station and simply could not believe my ears. All of a sudden my stereo began to convey the illusion of width and depth, or sound stage, to use some gear jargon.

Now I was hooked and wanted more...