Following on from our recent announcement that we are now carrying JL Audio subwoofers we recently took part in an interesting demonstration in our showrooms regarding the interaction between the subwoofer and the room itself. We, and many others in the industry, have been promoting the fact that any serious Home theatre should include more than one subwoofer.
The bass wave created by a subwoofer is very large and when it is reflected from walls etc. the reflected wave can cancel the primary wave in parts of the room or combine with it, effectively doubling the intensity, in other parts of the room.
If you have a dedicated theatre take a walk around the room and you will notice that the intensity of the bass varies significantly in different parts of the room. Moving the position of the sub will change where these dips and peaks occur, allowing you to achieve close to optimal response in your listening spot.
However this is where the recent demonstration became interesting. Our theatre room has a double seat viewing chair, and at 55Hz there was a difference of 10dB in the two seated positions. This means that one listener was hearing twice the volume of bass at that frequency than the listener sitting next to them.
The use of multiple subwoofers smooth these anomalies, creating a much more uniform bass response throughout the room. We recommend at least two, but even more is appropriate (we are currently building a theatre for a client with eight subs).