Subwoofer Terms

RMS Measured in watts, root-mean-square power tells us the average power output over a long period.  It is a good measure to determine an appropriate amplifier.

Peak Power  Don't get fooled by a high number here.  Operating regularly at peak power will certainly blow your woofer.  This tells you how well the woofer will handle "spikes" in frequency.  Look for 400 watts or better.

Crossover Subwoofers deal with very low frequencies, usually under 200hz.  A crossover is a circuit that filters out higher frequencies, typically anything over 100hz.  Some come with crossover dials so you can decide what goes to your subwoofer.

Cone material Paper and paper pulp are the lightest materials and move easily, unfortunately paper cones distort the most.  Stronger materials like aluminum and polypropylene coated paper are most common.  If you're going all out, get Kevlar. 

Wire Gauge As signals pass through speaker wires, impedance will reduce the quality of the signal.  A lower gauge means a larger wire and less impedance.  Use as little wire as possible.

Frequency Response Human hearing picks up frequencies between 20hz and 20,000hz. Subwoofers cover frequencies at the lowest end, from 20hz to about 400hz.  A wide frequency response isn't all that important, as your other speakers can handle the rest. 

Excursion Your sub's cone is going to move a lot, about an inch in either direction.  If you push too many watts through a sub, you'll end up with a little too much movement and a ripped voice-coil.

Passive or Powered Passive subwoofers rely on an external amp for power.  Powered units are self-contained speaker/amp combinations that don't drain your external amplifier as much, leaving more power for the woofers and tweeters.

Capacitor The capacitor powers the amp.  It is not necessary but recommended in car audio systems that push the limit.  You risk burning out your alternator without one. 

Enclosure Also known as a subwoofer box.  Sealed enclosures give off a tighter sound than bandpass boxes or a ported enclosure.  In a sealed box, the air pushes back on the woofer and prevents over-excursion.  Bass gets deeper with more air space in the box.  A smaller box gives tight, percussive sound.

More information on subwoofers