newbie question

moritz1 · 04-30-2007, 06:46 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, 06:52 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, 07:10 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, 08:10 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, 08:49 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, 09:09 PM

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

WarX · 04-30-2007, 10:21 PM

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

XC-C30 · 04-30-2007, 10:26 PM

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

WarX · 05-01-2007, 07:27 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, 07:35 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.

WarX · 05-01-2007, 11:59 AM

meh, you could be right, but again, it's a generic off brand that i've never heard of, we have very little information on it, and of course it could be like dual and rated for 1200w MAX and have 200w RMS or somethin ridiculous like that

UV7 · 05-02-2007, 12:07 PM

If you can post up model numbers, I might be able to help you out a little more. Most woofers list their thermal power handling in watts, which in most cases, can be exceeded considerably provided that the gains are kept below the point of distortion. The amplifier possibly can be bridged and you may still be able to run the woofer. The big deal is impedance. Not all woofers are 4 ohm. Also, not all woofers are a single voice coil design, which means that they can be wired differently in order to optimize their own impedance. With a little more information, I will do my best to help.

moritz1 · 05-02-2007, 01:26 PM

The sub is a jbl mt100. It is 4 ohm & a single voice coil. The amp is a targa hx 2ch 4 watts. On the back of the amp there are 4 screws for the left & right speakers.Also under where the speaker wires go there are 2 lines that say mono. So I wanted to know if the 2 front speakers can be powered by the amp & can I run 2 wires from where it says mono to the sub?That would be 6 wires going to 4 connection screws. Also ther is a switch that says x-over. what would that be set at hi,full or low?Also a turning knob that goes from min to max. Thanks for any help

Tom

UV7 · 05-02-2007, 02:15 PM

Wow. That is some difficult equipment to get any information on! We'll try to work with what you've got.
First, that amplifier probably will not support a mixed-mono setup, meaning that it is an "either... or..." scenario. It obviously can bridge to mono, but exactly how much wattage it is going to put out is unclear. More than likely, the Targa amp is rated at 400w peak, @4Ohm mono, which means it shouldn't have any problems shoving that JBL. At 400w peak, which I highly doubt the amplifier will ever put out, you could expect 150-200w RMS or so. The JBL should handle this wattage fine without problems, provided that the gain is set below the point of distortion. Pushing the woofer to the point of distortion will dramatically reduce the woofer's life.
As for the X-Over, if you intend on running this to the JBL sub, use the low-pass setting. It will cut off the frequencies passing to the woofer to < 100Hz or so.
I hope this helps.