newbie question

**moritz1** · 04-30-2007, 07:46 PM

I know very little about car audio so I could use some help installing a sub & a amp in my sons car. Right now he has a kenwood head unit and four so so speakers. A friend gave him a used jbl sub & a targa amp witch is a 2ch 400 watt unit. My question is can the speakers and the sub run off this amp or just the sub. Also how would I wire it? No extra coin to spare right now so I would like to try and do something with these parts if possible.Sorry about the long thread.Thanks for any help.

Tom

**XC-C30** · 04-30-2007, 07:52 PM

I'm afraid you'l have to spend some more money. some speakers and an amp alone won't get you there. You'll need to buy a wiringkit in order to feec the amp its needed power. A kit of some quality will cost you another $100.

In order to be sure amp,sub and speakers will match, you need to supply some more info though. What's the RMS output per channel, what's the RMS wattage of the sub and speaker?

edit: Remember this is not a car-audio forum, but a car-pc forum. So it's about integrating car-pc's in your audio. Though there are some people that know their way around car-audio here (such as myself), you might be better off going over to a dedicated car-audio forum.

**moritz1** · 04-30-2007, 08:10 PM

The sub is 240 watts peak - 120 watts cont., speakers 45 watts each, the amp only has 2 channel 400 watts on it and there is no manual for it.I did get a 500 watt wiring kit from radio shack that has the power wire,ground,remote wire & rca patch cable. Thanks again.

Tom

**XC-C30** · 04-30-2007, 09:10 PM

if it's only a 2-ch amp, you won't be able to power both speakers and sub. I'm guessing that 400watts is max, so I'm assuming it will be 100watts rms per channel. If you bridge it for the sub, you'll get indeed about 400watts, which is overload for the sub.

**lexdiamond20** · 04-30-2007, 09:49 PM

The head unit should be enough for the 4 speakers for now. Your best bet would be to get one more sub to hook up to the amp. In the mean time, you can run the sub off of one channel on the amp. As said previously, don't bridge the amp to that sub.

**XC-C30** · 04-30-2007, 10:09 PM

the second sub should be the same one as the one you already have though.

**WarX** · 04-30-2007, 11:21 PM

why would he not bridge the amp to power the single sub again? elaborate on that for me.

**XC-C30** · 04-30-2007, 11:26 PM

120watt sub 400watts of power? You'll have to be DAmn cotious tuning your amp

**WarX** · 05-01-2007, 08:27 AM

assuming a single 4ohm sub, capable of running 120-150w RMS, nominally at what, 120? okay, so bridging the two channels of a 100w RMS per channel setup @2ohms puts it to 200w RMS @ 4ohms, it's barely overpowering that sub, plus too much power/too little power never kills subs. It's always the signal coming into the sub that kills it. With having too much or too little power w/ a clean signal won't do much to the sub. But you also have to remember, that's at the most it will do continuously is 200w RMS, so put about 2/3 gain will be around 130rms so it would be quite well matched up...

*edit*
Chances are since it's a generic brand amplifier, it's 400w MAX at 2ohms, so assuming that the RMS is 100w RMS x2 @ 2ohms... then again, it most likely, and i'm saying chances are very high that it is likely rated too high and around 70-80w RMS x2 @2

**XC-C30** · 05-01-2007, 08:35 AM

you're wrong at your output ratings.

2x100wrms@4Ohm= approximatly:

2x200wrms@2Ohm
1x400wrms@4Ohm

It COULD work, assuming the output on his deck/soundcard is on the low side (thinking 2Vrms or less.) and he puts the gains WAAAAY down. But it's going to be hard to set the gains right without any knowleadge. Recently I had a guy complaining about crackling speakers. I said "tune your gains right." his answer was "I put the gains about half". But he didn't measure it with RTA or even did it the simple way by turning his HU to 80% and tuning the gains after that..... And the difference in output is too big in this case to just do a sloppy job here, cause it will result in a fried sub.

edit: it's 100wrms @4Ohm, NOT 2Ohm. So even if it is only 70wrms, it would still be about 280watts bridged.