interesting problem with sealed speaker...

Speaker Asylum

General speaker questions for audio and home theater.

Real problems are always interesting and I thought you'd like to hear one. This modified Dodecahedron loudspeaker is a new design (replacing and older design) for us and is used in acoustic testing of rooms and sound insulation (STC) tests.
In the sound insulation tests the louspeaker is driver by pink or white noise signal at very high SPL's - often exceeding 120dB sound power - for extended lengths of time. One feature of this new design, allowing us to get higher output at lower frequencies relative to the previous design, is the very rigid and tightly sealed, damped, aluminum welded cabinet.
Shortly after release - we started to hear from some customers about decreasing acoustic output after they have run for a while - and we even got one customers unit in with a few smoked drivers.
Anyway, we figured out the problem, you start the signal crank up the volume, the drivers heat up, and this raises the temp in the cabinet - after a while the static pressure in the cabinet is high enough to move the drivers out a bit in their gaps, causing more non-linear operation and the decrease in output. Eventually - when run more the a couple hours straight - and if you keep trying to raise the volume to compensate for the reduced efficiency - you'll smoke the driver.
Solution: replace one of the driver attachment screws with one with a bored through center- the provided a pressure relief. The previous version did not have this problem because the wooden cabinet must have had sufficient leaks to prevent pressure build up.

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Topic - interesting problem with sealed speaker... - gymwear5@hotmail.com 07:21:32 03/16/07 (4)

If you are right - Schu 09:00:02 03/21/07 (0)

Re: interesting problem with sealed speaker... - ontrack2@gmail.com 07:47:14 03/16/07 (2)

Re: interesting problem with sealed speaker... - gymwear5@hotmail.com 21:35:34 03/16/07 (0)

Re: interesting problem with sealed speaker... - STUART 12:45:24 03/16/07 (0)

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