The size of the box will be determined by what the woofer requires. Generally a 10 will require from .75 cu. ft. to 1.0 cu. ft. and a 12 will require form 1. to 1.5 cu. ft.
I have a spectra 18 and I put in 4 6x9s ( two on rear seat base and two on side panels by front seats) I put my woofers up under the bow in boxes mounted to the forward facing side of the bulkhead. my woofers point up (so I can throw stuff under the bow still. I also ran 12" woofers. I put the amps on the rear facing side of the bulkhead with fans blowing directly on the circuit boards.
As far as equipment goes I used eclipse 6x9s,Orion xtr 12s wrong woofer for a marine application (paper cone and foam surround but they were free so I cant complain) Eclipse Premium series amps (I wold recommend Rockford or JL (but again they were free so I cant complain) A pioneer dehp640mp w/ xm radio.
I am going to be redoing my boat real soon and will be changing the deck to the new MB Quart marine radio with the wired remote, the amps will be going to the new rockford power series, Speakers will be going to mb quart reference 6x9s and the new marine rockford woofers. And I will also be building a set of our removable 6x9 pods for when I am parked or floating.
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