Just starting to design a new 'cd free' incar system for
my mk2. I have it running into an older cd head now, and
the stock system has an odd "T" tapped rear channel for
a minimalistic under-seat sub.

For all intents and purposes are the front and rear channel
outputs the same if the eq is zeroed? In terms of output
data? I found a couple threads about making them output
different data all together, I just want to know if there is
a difference without EQ adjustment. FAQ doesn't seem to
mention this either. I'm assuming the answer is yes.
Otherwise I figure it would have been mentioned somewhere.
both 4v but with the same range?

I'm a touch worried about draw on the rear channel (where
Subaru tapped the factory sub) making everything sound
a little funny now from the old head-unit I have in. Turns out
the speaker-level stock outputs were a volt higher on the
stock head. Trying to figure out a way around that and
how to keep the cost low. 4 channel with higher wattage rears maybe.

Man I need some sleep. RMS numbers running around
my brain at 5am. ugh.

Ed

For all intents and purposes are the front and rear channel
outputs the same if the eq is zeroed?

Yes. The mp3 contains 2 channels of data, each is split into 2 (front and rear) and then fed through eq and fader.

So if there's no difference in equalizing front/back and no fading, then
front/rear should be identical (disregarding stuff like variance in components like caps, op-amps etc...)

Can't say I can visualize your set-up... Where's the amplification?

/Michael

Correct. If you don't EQ the fronts and rears separately, then they are the same audio signal pair, with their relative volume controlled by the fader.

I never used my fader and it was always set to the center position. I used my gain adjustments on my amplifier to balance the difference between front and rear speakers. I found that even with passengers in the car, I never changed the front/rear balance.

So what I chose to do was to run both the fronts and the rears off of the front pair of outputs, and run the subwoofer off of just the rear pair of outputs. This now allows my fader to work as a "subwoofer level control".

Dunno if this will help but here goes. (does this belong in ICE now?)

Stock its like this: 6disc indash player full DIN HU (damn hu)
to "iso T header", to ISO header, to speakers. The T is a tap
of the rears to an underseat slimline self-amped sub. Not
a very good one, but audible none the less.

Now I've only changed this to an aftermarket 5 yr old cd deck
with an aux 1.2 din with my mk2 above it. No real changes.

What I'd like to do is mk2 to amp, amp to 'T' to speakers.
The T is identical to the factory iso header with the addition
of the tap for the sub. (then use the empty 1/2 din for
more gauges)

However unlike many cars, the WRX has 4 5"+ front and
rear in the doors, no dash, no rear-deck. Plus a pair of
mini-tweeters crossed over off the fronts later in the wiring.
So the sound is fairly "square" and does its own crossing over. There doesn't seem to be the high/front low/rear that
most vehicles seem to have. This doesn't deafen rear-seat
riders, but seems to lack some punch and range.

I was planning on using a 4 channel amp mounted in the trunk
under the rear-deck as its blank save for seatbelt tensioners.
use the amps built ins for a tiny bit higher front and lower
rear with the factory sub still attached. Then I could
perhaps boost the bass, but that leaves me wondering how
to protect the rear speaker without adding another crossover.

I don't tend to muck about with the fader either so I may play
at using the rear line as a seperate sub feed. Maybe a
box in the trunk is in order. The factory sub is rather lame.

But how to wire out 4 speakers off one line in? I need to
go do some serious amp research I guess. Didn't think
if you used 2 line ins you could split the outs like that.

Perhaps one of these nice 4channel+1s that are out,
drop the T-tap and run the sub directly off the amp. that
would fix a lot of problems.

Ed

I don't see your dilema at all. Your 4 speaker system sounds like any modern car. Simple. The small sub is obviously running with high-voltage to its dedicated sub - you can easily keep this or get rid of it.

Car audio is stereo. That's 2 channels. So any tuning beyond balance is accomplished by splitting those two channels. Splitting a signal from 1 to 2 leaves you with two idenical signals. It is not like a water tap where you get half the water to each. So I don't know why you'd be concerned about splitting out to 4 speakers.

A quality amp will allow you adjustments to tune without an additional crossover or dsp. To a degree of course. You can go with 2 2-channel amps or a 4 channel. There are numerous ways to connect either setup. You can do 2 paris of interconnects to the amps or 1 pair. With 2 pairs you retain fader control. With 1 you have to make all your front/rear adjustments at the amplifiers.

Don't know how much you want to spend, but the king of adjustments in the amp market right now seems to be JL Audio. Check out their amp section: www.jlaudio.com

If you want to start a dedicated thread in the ICE section, go for it.

Bruno

No real dilemna. Question was asked/answered. Just need to do my homework on amps now. They seem to have come a long way since I last rigged up my S2 ;)

Normally I worry more about sump guards and remote shock
resoviors.

Ed