Subwoofers: A Complete Guide

Subwoofers are speakers, just intended for lower frequencies. Many think they're not speakers, but they are and as such I will refer to them as speakers often in this text.

What is impedance and how does it affect me?

Impedance is the resistance that a circuit provides to electrons passing through it. (it's actually the opposite of the conductivity. It's the classic argument that there is no dark just absence of light, no cold but absence of heat...etc. But shut up and just listen). Impedance is measured in ohms, which is represented by the symbol Omega. Google it if you don't know what it looks like, since you'll probably want to know. The less impedance, the more easily electricity can flow through.

What that means in the real world is that power output of a specific amplifier is different at different resistances.

An amp will have a rating of say "75Watts RMS @ 4 ohms, 150W RMS @ 2 ohms". As you can see, with less resistance the amp could flow more electricity. The only problem is, the more electricity it flows the hotter it gets. Don't run your amp at a lower impedance than it was designed for, or you can kiss it goodbye! 

Car audio stuff is generally 2 or 4 ohms. Home audio is usually 8 but sometimes 6.

RMS? What's that?

RMS is the continuous power output of an amp, or continuous power handling of a speaker. In wattage, RMS is the REAL info that you want. Coupled with ohms (your impedance again folks) it tells you pretty much which amp you should buy for which speakers.

Such measurements as MAX will only tell you what it's putting out at a peak. These measurements are pretty worthless to amateurs like you and I. What? Yes, I'm an amateur. The world of audio is very very complicated and I'm only at an understanding of the tip of the iceburg.

RMS isn't the only thing you want to take into effect while purchasing a sub. Sensitivity will also affect it. A sub that takes slightly more power with lower sensitivity might be just as loud as a sub with higher sensitivity and lower RMS wattage.

Crossovers are your friends