In article ,
Chris Berry wrote:
Say I have a cone with a 6" radius back against a wall. How do I
calculate,
roughly at which frequency it starts to radiate sound to the back?

It's only the cabinet resonance that gets radiated to the back so it's a
pretty moot point.
The only other way you'll get sound radiated behind the speaker is using
open back cabs or have something reflect the sound back at the speaker -
Only the open back cab will do this effectively and then you're stumped for
high frequencies...

With a monopole speaker the rear output will essentially match the front once
your wavelengths are 3X baffle width, and there's some effect with wavelengths
as short as 1/3 width.

In free-space you get a 6dB drop in on-axis SPL when this happens.

This is why speakers need baffle step compensation.

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