The Use of a Baffle

Author: N.H. Crowhurst

To avoid air escaping round the edges, the diaphragm should be at least one-half a wavelength across. If we want to radiate a frequency of 32 cycles, for which the wavelength is 1100/32 or about 34 feet, the diaphragm would need to be about 17 feet in diameter. One way of avoiding this awkward size is to mount the loudspeaker in a baffle.

Mounting the loudspeaker in a baffle board reduces escape around edges.

The loudspeaker diaphragm is continued by being joined to a solid, fixed board that extends out to the required size. This stops the air from escaping around the edges. Of course the diaphragm will have to move further to get the same amount of air movement than would one the full size of the baffle, because only a fraction of the surface is moving. But preventing the air from escaping around the edges of the diaphragm will also prevent the diaphragm from moving without radiating a wave at all. The situation is thus much better than without the baffle. Of course, a smaller baffle will do the same thing, except that it will not be effective to such a low frequency.