Re: 2 12's vs 2 15's
the real question is how much space do you have to sacrifice? how good subs sound is not based on their size, is a full blown myth dont ever spread that around @_@. How good a subwoofer sounds is dependent on the enclosure you put it in. if your 2 15s only get 2 cubic feet each, then its going to sound like crap compared to 2 12s with 2 cubic feet each. The design of the box also plays a big role too. Everything from sanding down the edges, making 45 degree angles in corners to bracing to proper baffling to port size and tuning. All those factors along with adequate power and electricals with proper EQ will determine how efficient and how good your system actually sounds.
To end this off, go big or go home if you have the space for it. 2 15s is going to need 3.5(minimum) - to 4.5 cubic feet of airspace to breath and thats a NET number that means thats the space left after subtracting the thickness of the wood, bracing, port area and sub displacement.
09 Sienna Subs : Four Team Ascendant 18s......Sub amp: Two Taramps 15k
Headunit: Pioneer 80PRS................................Mids/Highs amp: CT 500.2 and Alphard 200.4
Front stage: Two PWX 10s per door midbass only....... PRV 6MR500 midrange....... Massive CT 2 german tweeters.
320 amp Singer alt....... 1 group 34 under the hood 6 group31 agms in the back 560 amp hours total.