Room boundaries work a similar sort of magic, but uniformly over a fairly wide frequency range. Move dual subwoofers from the middle of a room to up against a wall, and they will play 12-dB louder than a single sub (Fig. 1). Slide the two subs inot a corner fo another 6-dB, yields +18dB (Fig. 2). What does that mean? A 1-dB (decibel) volume change is about the smallest we can rec- ognize as a level change. To hear a really obvious difference, you need about a 3-dB change. And to get a subjective doubling you need about a 10- dB level boost. So the gain achieved by moving a subwoofer into a corner is a pretty big deal.
Which brings us to the glory of multiple sub- woofers. Put a second subwoofer right next to your first one, operating at the same level, and you get about a 6-dB increase in total acoustic output. That’s equivalent to increasing the amplifier power by four times! Double the number of subwoofers again, and you get another 6-dB increase (Fig. 3). That’s equivalent to another quadrupling of amplifi- er power, or sixteen times the original. And so on. It’s the ultimate scalable system.
Combining all these tricks can yield quite formida- ble bass from very compact subwoofers, right down to the very lowest audible frequencies. Over time, you can build the sonic equivalent of a much larger subwoofer just by daisy-chaining additional SWS subs into your system (Fig. 4). Not quite a free lunch, but certainly a very economical one.
Warning
Do not vertically stack more than three SWS units!
