Yeah I bought this sub (Cerwin Vega VMAX 122) a couple months back had it in an IB setup, not very impressed....moved it to a ported prefab box tuned to around 45 or so hz...Vastly improved got really really loud for a single 12 but lows weren't great....SOOOO I went to lowe's, bought a 24" length of 4" pvc, a 41/2" hole saw, and drilled a hole right through the side of the box and through the internal baffle (port wall), and I plugged the slot port with a piece of mdf I cut from an old carpeted box.
Man, let me tell you the very lowest bass songs I played shake my entire car now (08 civic sedan), and tickle my ears to the point of discomfort...All off a Memphis PR 500.1.
Very impressed with the lows on this sub. Although the range is not great (may try to bump up the bass boost which is probly around 50HZ), I will experiment with the crossover and maybe cut a bit off the end of the port.
Overall, for the $140 OTD I paid for this sub, I am extremely pleased with the output and low frequency extension.
If you are looking for a good sub around $150 dollars, you can't go wrong with this one
