i'm looking to build a sub box for my bike. every dB of efficiency is essential. right now, i'm not getting much volume out of my 15 WPC sonic impact amp.
i know that you can increase a system's output by 3dB when you add a second speaker, so 2 X 8" will be louder than a single 10" with the same efficiency (though they might not move as much lowest octave air), but what about wiring configurations?
would 2 woofers at 25w each be the same as if they shared a mono 50w? i had a 12" (2 X 8 ohm) sub and heard no increase in volume between one coil powered and both with seperate amplified channels. why is that? the extra power didn't seem to control the woofer any better either.
that experience makes me think a pair of 8s with the biggest (up to say 50w) class D module i can find. efficiency will be critical as the setup will be powered by D cell NiMHs. i'm not keen on lugging a 50 pound 12 volt or 15 minute run times.
i'm not planning on porting or folding a horn either. i prefer the tight punchy sound of acoustic suspension. bandpass is TOTALLY out of the question. i just want to move a bit more air than my 89dB 5 1/4" 2 ways i'm using with my current bike.
i'll keep the 15 WPC sonic impact to drive a 500Hz on up 94dB efficient planar/ribbon 2 way. i could squeeze 95dB out of a pair of 92dB dayton 8"s and have tighter transients than a 10". i'm not looking to boom, just thump with a little bit of authority.
BTW does adding more drivers to a box raise the resonant frequency or change the tuning some other way? i'd even consider adding a second pair of 8s for an extra 3dB if it could add LF extension. i'm guessing it would only raise the volume above the resonant frequency.
the box will be approximately 10"D X 18"L X 12"H minus stuffing, batteries & enclosures for the mids.
is my understanding of "bang for the watt" correct? am i missing something? thanks in advance for any correction of my limited DIY knowledge.