I have 2 12' Alpine sr12 powered by a PPI 300x amp with a 1.5 cf box with a pioneer head unit. My question is when I turn my subs setting up to 0 or above it gets louder but the bass doesn't get clean and it seems like all you hear is the sub moving just not the nice clean bass. I have my sub setting to -9 now and it's fine and the subs are still loud but i wish i could figure out whats up. My friend has the same setup only difference is he as diamond audio subs instead and his sounds perfect. I wonder if I need a bigger box say a 2 cf 12' box or do I need a bigger amp. Any ideas would help

 

How did you connect the amp to the head unit? Did you use an RCA converter or the line level inputs on your amp?

 

1.5 CF is a little on the small side for 2 12's, but it should work for most.

Don't know much about Alpine subs, but are they recommended for sealed or ported boxes?

If you think you need a bigger box, just line it with plain old fiberglass house insulation. Don't stuff it full, but put a good layer or two of it in there. That makes the speaker think it's in a bigger box.

You also say your friend has the same setup... but is it in an HHR? Speakers will react alot different in a trunk, rear fired, front fired, in a SUV cargo area, etc.

One more... where's your crossover set at and what kind of music do you listen to? 60-80 hz is probably where you want to be, but it all depends on a bunch of other stuff. Just play around with it some, you'll get it in tune.