Subs and amp.

Hey guys I know this isn't an audio forum but I thought lots of you guys would be knowledgeable in this area anyways. I recently got 2 subs and a box given to me and I want to find an amp and hook them up. They are both 10" and 4 ohm. They are different brands. One has 250 Watt RMS and 500 peak and the other has 200 watt rms and 400 peak. I already know that these subs are kinda trash but hey I got them for free.

Where I'm stuck is what amp I should buy. I have lines to a cheap 600watt Rockford fosgate t600-4. It's a four channel amp but it puts out 300watts RMS @ 4 ohms when bridged to 2 channel. From what I hear it's a decent amp. Also, does anybody know if you can adjust the channels settings seperately or does a two channel amp put out the same power through each channel? I don't really want to run a 2 amp setup because it's expensive.

Also I have heard that it's a bad idea to run 2 different subs in the same box. Anybody know something about that?

A two channel will only have a single gain control, so both channels are adjusted together and always produce the same power. A 4 channel will have two gain controls, one for each pair of channels, which can be adjusted independently, normally for adjusting the fade from front to rear.

The RF is a good amp, better than most. It will power your subs fine.

If the box is sealed and has a partition in the middle dividing the subs, it might sound alright. Empirical testing always beats theorizing, try it and find out. If it's ported there's a good chance they will not sound good together.

look up the specs (thiele-small parameters) of the subs. pay attention to the FS (free air resonance) of them. IT should be somewhere in the range of 26-35hz. if they are both pretty close to one another, they could work together. if they are too far apart you will run into cancellation issues and sometimes one sub would be actually louder than both of them put together.

Also look at the power/efficiency of them to make sure they are close. if one sub is rated at 500 watts RMS with a 90dB efficiency, and the other sub is rated at 300 watts RMS with a 90dB efficiency, it's going to take a lot more power to run the 500 watt one. Also if you have both subs rated at 300 watts RMS and one has a 85dB efficiency while the other is rated at 93dB efficiency, it's going to take a considerable amount more power to run the 85dB efficiency sub. If both subs (assuming the FS is close) aren't moving the same amount because one takes more power, again you can run into cancellation issues. You could overcome this with a 4 channel amp because bridging them down you could lower the gains on the more efficient sub so it's getting less power, but it will take some tweaking.

And enclosure volume will also make a huge difference as well, as the enclosure volume will DRASTICALLY alter the sound charactaristics and resonant frequencies of the subwoofer. they both need to be in recommended enclosure volumes, which may be very different between the two. You can also alter enclosure to compensate for different FS. you can't just drop a sub into any old box and expect it to perform correctly.

This is also keeping in mind only the output of the speakers, not taking musical performance of the sub which to me is the most important part! Who cares how loud it is if it is sloppy and sounds like garbage...


While they can be made to work together with some trial and error, i typically wouldn't recommend running 2 different subs together. You would likely have better results picking the better of the 2 subs and putting it into a well designed enclosure to maximize the performance of that 1 sub. Not only would it perform better musically, but many times overall SPL output can be better with a single well executed sub/enclosure. plus it won't need as much power and won't cause as much strain on our car's puny electrical systems where pressing the door lock switch causes the headlights to dim lol. these little cars are pretty efficient at making subs plenty loud. in my p5, I just have a little boston acoustics 10" sub that i've had for years, running off about 200 watts on a very very old MTX amplifier and it's more than loud enough for me. I wouldn't want/need anything that's any louder.

pb4ugotobed said:

... plus it won't need as much power and won't cause as much strain on our car's puny electrical systems where pressing the door lock switch causes the headlights to dim lol....

Click to expand...

^^^ What he said...

Keep in mind that our alternator only puts out 80 Amps and the 600 Watts delivered by your amp will be using 50 amps alone (at full output,.. plus waste... no amp is 100% efficient)

That only allows less than 30 amps to run your car... Turn on your headlights and your blower, and you start pulling huge amps out of your battery....

You'll start going through batteries and alternators regularly as well as other components as the ECU tries to keep up with the pulsing demands of your high power amp.

You are way better off with a very efficient sub that needs less power to be loud.

A sub with an SPL (sound pressure level) of 80 db needs 100 times more power to be as loud as a sub with an SPL of 100 db.