2 15" subs

2 15" subs

My friend says that he can get me a good deal on 2 15" Rockford Fosgate HE subs. I know crap about systems I just know that I want a good one at a fair price. I know that I need an amp so what kind of watts do I need? I've seen that they say something like 100x2 but I have no idea what they are talking about. Any suggestions? All I want is a good sounding system. I have another friend that just got some 12" subs and he had to get a new de player for some reason but he has a Kia Rio. Do I need to get a new cd player or any other speakers or am I fine with what comes with my 2003 Corolla S? Will the subs even fit in my trunk?

speakers

I'll try to answer one at a time, best I can, one at a time.

When a speaker manufacturer, (especailly for some reason auto speaker makers), say something like "100x2", they're usually stating PEAK wattage the speaker can handle. That means for VERY brief periods the speaker will handle 100 watts. What you've got to look for is the RMS power, that's a FTC mandated standard rating on how much the speaker can handle CONTINUOUSLY. Running any amp at it's maximum power for extended periods of time will overheat it, and depending on the amp design, it'll either go into protection and shut off until it cools off, or reduce it's power output until it cools. Heaven forbid, I've seen cheap amps, that in a very deceptive attempt for a manufacturer to claim a high RMS rating, will keep running after the output devices in it are well above thier rated temperature window. You'll end up frying the amp, and the speaker, due to the distorted waveform the amp is putting out. Also, running any speaker at it's "peak" rating for any amount of time, will cook the voice coil, and probably destroy the magnet to coil alignment (meaning it will never sound good again).

Although in this case, 15 inch JBL subs would definately feel no strain handling 100 watts contiunous.

A 15 inch sub moves a LOT of air, and air is relatively dense. So to move that much air, you'll need a significant amount of power. Again, car amp makers like to quote peak power. That should be ingnored, look at the RMS. My estimate would be at least 150 watts RMS for those subs. There's also a tendancy with car amp makers to quote their power outputs at 14.4 volts. In 99.9% of amp designs, the other .01% being the "high end" manufacturers, output at the real voltage of a automotive system (12.6V) will be less wattage. Not too much, but enough to take into consideration. You need to decide how you plan on running the amp and speaker combination: do you plan on feeding stereo bass to it? If so, you'll need a amp with two high-wattage outputs. Are you going to run mono bass (what most of us do), and wire the subs in parallel inside the box? If so, you need a amp that is bridgable to high power, and you have to make sure the amp is rated to run bridged at 2 ohms (what two 4 ohm drivers in parallel presents as a load). My Kenwood amp for instance will not run bridged at 2 ohms.

Other speakers: You don't HAVE to replace your stock speakers, but if you're planning on having some serious frame-rattleing bass in the car, the bass will easily drown out what the stock speakers can handle. Also, unless you have a HU or DSP that can split the bass out of your stock speakers, and you hook it up to do that, stock speakers will quickly smoke trying to handle loud, deep bass (they will rattle like crazy first). The Corolla speakers are for some reason impedance mis-matched, one pair is 4 ohm, the other 6 ohm. The 4 ohm set will tend to get louder than the 6 at a given power input, so your front to rear balance will be off also.

Fitting in the trunk: Yes, they will, but dual 15 inchers will take a BIG box, especailly if you're planning on running a ported box for a bigger thump. A sealed box is smaller, and will provide tighter, cleaner bass, but because the back of the speaker cone has to fight a sealed volume of air, it takes more power to get the same loudness.

My suggestion would be to get a decent, name brand amp, around the 150 watt bridged rating (run mono bass), replace your stock speakers with something decent (plenty of DIY advice on this excellent board), sell the 15 inchers to somebody who wants to shake the paint off thier car, and pick up a sealed box with two 10 inchers or 12 inchers.

This is all assuming you're dumping the stock HU, and putting in something that will provide either full-range, or low-passed bass line-level outputs.

Hope this helps, and if someone finds a problem with something I wrote, please let me and blkcors know quick, so I don't steer him wrong!