Car Stereos: Two 12 300w rms subs and one 300w rms monochannel amp, 1000 watt amplifiers, watts rms

Question
Hello,

I have a Kenwood monochannel 1000w max amp with 300w rms and two 12" Sony Xplod subs rated at 900w max and 300w rms. Will my amp be able to power both subs OK considering the rms of each sub is the same as that of the amp? Do I need to take into account the rms of each sub added together?

Thanks

Answer
Hi Jaymes,

I think you might have overlooked the different power rating of the amplifier with a different load impedance.

I don't know the model of your Kenwood amp, but the current line of Kenwood "1000-watt" amplifiers carries a set of RMS power ratings that look something like this:

300 watts x 1 channel at 4 ohms
500 watts x 1 channel at 2 ohms

If the Sony subwoofers are 4-ohm, then when you wire both of them to the mono amplifier, the load at the amp will be 2 ohms (assuming you wire the subs in parallel, which is what I'd recommend). That means that the amplifier can produce 500 watts RMS, not 300 watts.

When you wire two identical subs to a mono amplifier, the power produced by the amp will be divided evenly between the subs.  If the amp is producing 500 watts, each sub gets 250.  That's a perfectly acceptable power level for a sub rated at 300 watts RMS.

Even if the amp was limited to 300 watts, and each sub was getting 150 watts, it still wouldn't cause any problems.  It's a myth that "under-powering" a subwoofer can cause damage. You might not be able to make the subs quite as loud as they're capable of playing, but that doesn't mean they won't be loud enough for your tastes.  In fact, going from 150 watts to 300 watts only yields another 3 decibels of output.

I hope this helps!

Brian