Amp - Sub Combo

I feel kind of dumb asking this, but I've never learned before.  If I were to get a sub that had an RMS range of 50-150 watts, how much of an amp should I get?  I'm looking for an 8" sub to go behind the seat of my pickup, otherwise I'd get a 12" (not enough room behind there).  I found a Fosgate 8" sub for decent money ($60), and it has that RMS wattage.  This will be going with a clarion proaudio HU, and 4 4" two way pioneers (that's all that will fit in my Chevy).  I'm guessing since it's pretty much a stock setup, I wouldn't want to get an amp that's too powerful, so as to overpower the rest of the system, but I could be way wrong.  I really have no idea.  Thanks!

You could take advantage of the proliferation of dual voice coil subs on the market...and choose a DVC 4 ohm model.  It can be wired in series to 8 ohms, and a lot of mono amps would provide the right power to it.  You would look for a RMS rating on the amp at (double your sub's RMS) @ 4 ohms.  So if you want 150 watts to the sub, and it is wired at an 8 ohm impedance, then the amp rating would be 300 watts X 1 @ 4 ohms.

This would solve the problem for this install, and still give you equipment you can work with in the future.

Here is an example ot a sub available in both 4 ohm or 8 ohm, and both are single voice coil.  Here is another sub that is available in three different configurations, one being dual 4 ohm. 

This is a diagram showing the wiring of a DVC 4 ohm sub to 8 ohms.  Prices of dual coil subs are usually just a little higher than SVC.

Yes, that's called series wiring.  A DVC sub has two voice coils, a SVC has one.  Each voice coil has a pos and neg terminals.  The diagram shows one coil wired with the other coil to make the overall impedance of the sub 8 ohms.

The reason I suggested the DVC 4 ohm is that, right now you are using minimal sound in your truck, but in the future you may want to increase it for your next vehicle (or even this one).  It is difficult to find an assortment of amplifiers that will output only 150 watts at a 4 ohm load.  But that can be done, too. 

Some ways you can go: 

Use a two channel amplifier that outputs 1 X 200 watts RMS @ 4 ohms bridged.  Buy a single voice coil 4 ohm sub rated at 200 watts RMS.

Use a mono amp rated at 250 watts RMS @ 4 ohms.  Buy a dual voice coil sub (DVC 4 ohm) with a RMS rating of 125 watts.  Wire the coils in series.

Use a mono amp rated at 200 watts RMS @ 4 ohms.  Buy a single voice coil sub with a RMS of 200 watts.

There is not a huge increase in sound after 150 watts, at least that you can tell.  If you find something, an amp and sub combination, that works with each other but seems to be too powerful for your vehicle...it just may not be all that too powerful. (?)  The gain on the amp can always be turned down a bit to lessen the impact of the bass.  Some mono amps also include a remote wire to control the bass level.  So you can set it up to be loud when you want to bump, and softer for the right mix with the music.  You really have a lot of possibilities here.  Just take your time and put it together.  Good luck.

Doh! I thought that was the original poster responding there...

I would not worry about "overpowering" the rest of your system with an 8.  You are probably right were you should be with your setup.  The quality of the sub will have a huge impact on the outcome of you system.  Either of those choices from JL that Stevdart mentioned are good candidates. 

Personally, I prefer to stick closer to the maximum RMS then the minimum.  Depending on the box, you will need more power to reach the same SPL (loudness) with the same woofer.  Sealed boxes generally take more power, ported less.  Box size is another factor.   Also, it is easy to adjust the gain if you find you are getting to much bass, but impossible to make an amp produce more watts if your not getting enough.

Are you sure you cannot fit a 10" in it?  You said a 12 would not fit, tens are often 1-2 inches shorter when top mounted.  You do not have to mount a sub in the middle of the box, you can mount it low (if your going with a behind the seat sub)  you have more space down low.