How do I hook up a subwoofer when the HU doesn't have RCA outs? The amp has speaker level inputs; do I just tap into one of the rear speakers to get the signal? I'm putting a sub in the trunk of my son's 1991 Toyota Camry, the rear deck speakers are right there.
KKmike, You can buy a high/low convertor at any audio shop. The convertor will convert high level audio signals (Speaker Wire) into low Level Audio Signals (RCA level). However, you will most likely lose the ability to juice the 6x9's. Or, you could unhook the 6x9s and wire the speakers leads directly into the amp, and go from there. If your amp if of higher quality, it may be able to run in three-way mode, in which you power the 8 ohm stock speakers with each channel of the amp, and then bridge the two channels onto a four ohms sub woofer for a third channel. What kind of amp is it?
In that case, look for High/Low convertor that allows you still run the 6x9's from the HU's power while converting the signal to low level (RCA's). That should do the trick.
I don't need a converter, the amp accepts high speaker level input, I don't need an RCA. My question though is can I just run another set of wires from one of the rear speakers to the amp, or am I missing something with regards to what speaker level input means?
That is what speaker level inputs mean, I was just trying to offer a way to run the 6x9's and the amp. If you run the amp off of the speaker level inputs, you will need the amp to recieve all of the available signal for the input. That is why I suggested a High/Low convertor with flow thru inputs, that way you could run the 6x9's and the amplifier. You could try springing off of one of the speaker wires, since the amp in mono, but it would then drain the power away from that speaker, which would have a balance problem between the rear speakers.
Thanks TBone for helping me out, even though I don't know why I'm having such a hard time understanding this. I just realized the HU does have front & rear pre-outs - not a sub pre out though. It's a Sony CDX-MP40. So does this mean I can leave the 4 speakers hooked up the way they are (factory wire harness adapter) and then use the rear pre-outs for the sub? Or can't you use both a pre-out and the speakers hooked up with the wire harness at the same time?
Nope, leave the factory wire harness alone, which will power all of the front and rear speakers with the headunits power. Now run a remote wire from the headuntit (the Blue Wire) and run a set of RCA cables to the sub amplifier off of the rear RCA outputs of the Headunit. Once you have that done, turn the gain down on the amp (input level adjustment) and turn the radio up slowly until the factory speakers distort. Next slowly adjust the gain on the amp until it distorts at the same level as the other speakers. You do not want to use the speaker level inputs if possible, always use the low level RCA inputs.