Car Stereos: subwoofer and amplifier matching, watts rms, ohm load

Question
Hi Brian
I want to match 2 Pioneer Premier subwoofers TS-SW1201S2 which are rated at 2 ohms, 400 watts rms, and are single voice coiled to a Power Bass ASA 1500.1Dx mono block amplifier which is rated at 325 watts rms at 4 ohms, 750 watts rms at 2 ohms, and 1500 watts rms at 1 ohm. I want to set the amplifier to 750 watts rms at 2 ohms. At this setting would both subwoofers split the 750 watts rms and receive 375 watts rms each. And since both subwoofers are rated at 2 ohms each would they be wired by just matching up the positive and negative wire leads of the subwoofers to the positive and negative terminals of the amplifier.

                          Thanks.

Answer
Hi George,

The problem is that there's no way to combine two 2-ohm, single voice coil subwoofers in a way that results in a 2-ohm load at the amplifier.  There's no 2-ohm "setting" on the amplifier; the load impedance is determined solely by the impedance of your subs, and your wiring method.

You have two options for wiring your subs:  you can wire them in series to make a 4-ohm load, or you can wire them in parallel for a 1-ohm load.  In general, series wiring is not recommended for separate subwoofers, because the coils can interact in a way that's not necessarily good for sound quality.  On the other hand, parallel wiring would result in some pretty severe over-powering, unless you were extremely cautious when setting your amplifier's gain control and playing your system.

If you had the 4-ohm version of the Premier subwoofer, instead of the 2-ohm version, then the amp/sub match would be just about perfect.  You could then combine the two subs for a 2-ohm load.  You are correct that the power output would then be evenly divided between the two subs.  However, there's no possibility of wiring the amp for a 2-ohm load with your current pair of subwoofers.

Hope this helps!

Brian