BL Series: Available options and what they do: The BL line is pretty much a lower power alternative to a BTL or a higher power alternative to the Q series of woofers. This is more of a street jamming type woofer that “fills the gap” if you will between these two series of subs. Keep in mind this is what we recommend, this is NOT what you have to do. P Chamfer: This is a chamfer on the end of the pole, it helps to bring the air down around inside of the motor and helps cool the coil better. It al