omg, need help with Z3 speaker

[Mr. Walnuts]

I'll apologize up front... I'm admittedly NOT a bimmer guy specifically... (as seen in my photo album;more of an NSX and Audi guy)

However, my brother's Z3 convertible is having some serious sound issues.. As an audiophile myself... I'm baffled...

It sounds as though it has a blown woofer in it, distorting at any tone below 250Hz... but everything I've researched says the car doesnt even have a damned woofer... just kick components and tweets in the doors...

Does ANYONE know whether or not for CERTAIN if the 1996 Z3 convertible (with CD Changer in trunk) has a woofer hidden somewhere?

If not... I may add an eD flat 10" sub free-air bhind one of the seats and splice in bass-blockers into the components.

thanks a ton for any help btw...

and feel free to check out the project cars I posted in my album. cheers