Leibson's Law

My last visit before leaving the CES 2008 show was with a British company named airSOUND. (You’ve gotta love these silly corporate-centric capitalizations.) Founder Ted Fletcher has invented a way for two co-located speakers in one enclosure to produce a stereo-effect sound field. The secret is the way the speakers are fed and the way they’re positioned in the box. A forward-firing speaker emits left-plus-right sound. A second speaker, trapped in a sealed port in the box, emits left-minus-right sound from a port in the left side of the box.

Thus the composite signal emitted to the listener’s left is simply “left” (L+R+L-R) = 2L (effectively L). The acoustic signal emitted out of the right-hand enclosure port is 180 degrees out of phase with the left-port signal (as generated by the back of the (L-R) speaker), so it is –(L-R) or R-L. Thus the composite signal heard on the right side of the enclosure is (L+R) + (R-L) = 2R. Ingenious.

It sounds good as well. The need for only one enclosure to produce a stereo sound field simplifies many product designs, so if you need something like that, look into airSOUND.