alpine swr1242d

i wouldnt recommend using a bandpass enclosure.  The SQ from it is going to be very poor.  Ideally an alpine type r will sound its best in a sealed or ported enclosure..  It all depends on whether or not you want loud boomy bass, or nice tight bass

I recommend a vented box for that sub, built a bit larger than the manual indicates.  Instead of net internal volume at 1.3, make it 1.8 cu ft.  Port, slotted, with 14 sq in of opening area and no less than 1.5" wide (2 X 7 is good).  Usually these slot ports are built the length of the internal box height, but the 1.25" the manual indicates is too narrow, IMO.  (I also dropped the port sq in opening down from the indicated 15" to 14 sq in.)  Port length 21 3/4".  Of course, the port structure takes up airspace so you have to calculate how much it is going to displace.  Tuning freq and F3 is at 29 Hz.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

actypes wrote: i wouldnt recommend using a bandpass enclosure. The SQ from it is going to be very poor. Ideally an alpine type r will sound its best in a sealed or ported enclosure.. It all depends on whether or not you want loud boomy bass, or nice tight bass

You are probably thinking prefab bandpass boxes...if that is the case than yes sound quality will be crap and the bass will be boomy and sound like crap. But a properly designed and built bandpass enclosure can have excellent sound quality and a flat response...I think you are misunderstanding the bandpass box.