Originally Posted by rnixon

No HU recommendations, but I would check that all your speaker sets are 4 Ohm for that amplifier:

Originally Posted by killav

I am using the same Fosgate PBR300X4 amp in my 87 S4. It does fit with no problems underneath the factory passenger cover by the seat.

The only thing I don't like about it, is that the floor level HISS is rather annoying. When the volume is all the way down, the hiss is noticeable. Even with the amp gains at a reasonable setting (not all the way up). But the amp is great other than that. Still no bass however without a subwoofer. But it plays loud and clean. Also, it does get VERY HOT when cranked up.

I would run RCA jacks to the new amp from your JVC, even though this amp will take high level inputs.

The factory wires to the speakers are fine in my opinion. Audiophiles will spend thousands on cables and wires, but absolutely not necessary in most applications.

For the sub amp input wiring, you could get a sub amp that will take high level inputs and do as you mentioned and run one of your rear speaker wires to the input. Just make sure the sub amp has a built in crossover to kill the high frequency's to the sub.

Or, you could get a LOC (Line Output Converter) from anywhere (sonic electronics for example) and run your speaker wires to this, and it converts the high watt signal to a low voltage RCA output for any amplifier.

HTH.

Originally Posted by bureau13

If his head unit switches off the internal amp when line-outs are connected, he still won't be getting a signal to his sub amp. Personally I think I'd spring for a new head unit. You can get some decent, modern gear for not a lot of money these days.

Originally Posted by rnixon

If you're going to fit a sub and amplifier, I'd get a larger amplifier in a non-stock position. It doesn't have to be huge - I use this one, which I find very good and is still quite compact. I have it in the passenger footwell - here's a thread discussing install locations.

The designs that were compact enough to fit the stock amplifier position didn't have specs that looked that good to me. I already have aftermarket speakers (6 DynAudio, with the two in each rear panel unused) and a sub inside the spare tyre's rim (this one). It has quite a small driver, but produces a reasonable amount of bass. If you ditch the spare, then something like a sharkwoofer provides a lot more bass and space for an amplifier or two.

I'd probably start by getting a better head unit, especially as they're not that expensive. Having the sub level controllable from the head unit is necessary IMO.

Originally Posted by Alan

You should not connect a sub-woofer input to existing speaker outputs - since those will likely already have some high-pass filtering by the crossovers or amps to eliminate low frequencies that they cannot reproduce.

You should feed the line-level/pre-amp RCAs to the new amp (for best quality) and also feed these to the subwoofer - most will accept at least 2 sources (e.g. to combine sub input across at least L/R on a single channel).

I do agree that the stock speakers are likely the biggest limiting factor here - due to both original quality and age and probably deserve the most attention.

Alan

Originally Posted by Bmw635

The newer Eclipse speakers the PO installed is 4ohm, 40W RMS, 80 W peak so it's a good match for amp.Thx.

Originally Posted by Andre The Giant

Thank you Alan. I will have to confirm if that head unit which I have can use both connections at the same time and if so, then great, otherwise I might have to purchase a new one. As far as the speakers go, I am in discussion with Hans to see about his suggested design.

Originally Posted by bureau13

I think he's saying not to use the speaker connections at all, just use the line outs, and get a splitter to give you an effective (but not separately controllable) sub out.

I still think the benefits of a not-very-expensive new head unit would be well worth it, but that's up to you :-)

Originally Posted by Alan

Yes a splitter would work for this if needed - the head unit doesn't care either way there is no loading on the pre-amp outputs to worry about here.

Alan

Originally Posted by Jetdriver69

In front, Kenwood Excelon 5 inch woofer 2 inch tweeter component set.