Vents on speakers in the Boom?

[Andy8421]

My son is designing a PC desktop speaker system for his DT project at school. The speakers will be active, based upon the excellent miniDSP and miniAMP system. The system topology matches the Boom (4 dacs, 4amps, active DSP crossover and EQ), using speakers sourced from a Boom (bought off eBay with a blown network interface).

We have already connected the miniDSP and miniAMP to the Boom's speakers (still in the Boom enclosure as a test mule), and using a 2KHz crossover point and some limited bass boost, the system sounds remarkably good.

Using REW to run a frequency sweep and a behringer measurement mike, the frequency response looks over the place, but I think we can get that dialed in with some tweaking of the EQ. However when running the sweep at LF and large speaker excursions, the system chuffs like a steam train. Having investigated further, the chuff seems to come from rear vents on the speakers themselves which in turn are vented to the enclosure via a molding in the rear case. I think we may be overdriving the speakers given the bass boost we are using (Caleb had a volume dependent bass boost in the Boom), but we still want to understand more about the vents and the chuff.

Can anyone help with:

1. Why do the LF speakers have rear vents, and why is this vented to the enclosure via a plastic molding?

2. Why do both LF drivers share the same enlosure - wouldn't it have been better to have separated the two drivers?

Thanks in advance for any help.

Andy.

[superbonham]

Unfortunately I can't help you with these question, but there is a whitepaper on the audio design of the Squeezebox Boom that might be helpful; you can download it here:

http://wiki.slimdevices.com/uploads/...dio_Design.pdf

Cheers

superbonham