New car stereo questions...
 

I have years of personal car audio experience ( full audio ground up installs) but nothing after 1990 vehicles.

I have a '14 focus st with the upgraded Sony sound system. 10 speaker system which includes an 8" subwoofer. It's horrendously inadequate and i plan to replace the subwoofer with a hidden trunk install.

Apparently i will have to use an LOC (line out converter) to create an RCA output to plug the alpine amplifier into. Question is, where do i splice the stock wire to tap the LOC in to? I think normally you would splice into the two rear speakers ( left and right) to give you the balanced signal.

1. The rear speakers are component, so tapping into just the midrange speaker wouldn't be appropriate, right?
2. It has a factory amplifier. Should I tap into the left and right rear speakers pre-oem amplifier? Assuming the crossovers for the components is done in the amp.

Any tips would help boys. Thanks in advance

We would go right to the factory amp, cut the sub output and take the signal from there. This kills two birds with one fell swoop! You kill the oem woofer which will sound like poo compared to a good aftermarket sub system & 2, you get a sub signal.
I would suggest a digital LOC as it will not melt from the amount of wattage coming out of the amp.
What kind of sub & amp do you have?

Only problem with what you said would be taking the sub "output" as you said from the factory amp. Wouldn't that mean the signal that would go to my new amp be modified by my oem head unit? Such as when i adjust bass and equalizer? The factory amp on the focus is a bit tricky. Seems like they tied everything into it, from speakers, sub, voice control, to even the steering wheel volume controls.

Ill try to track down a wiring diagram tonight, but the only ones i find are the last generation European ST diagram, which is not similar at all

We do this all the time. It's a non-issue

The sub is crossed over at the factory amplifier. So its usually about 30-80 hertz signal coming through to the sub. an electronic line-out converter will make that signal work perfectly for your new set-up. We have done Fusions, F-150's, Explorer's and the like - all of which can come with that optional Sony system.

thats fantastic news. i was actually just out pricing some material for my build. in other news, i found the amplifiers wiring diagram online.

http://www.focusst.org/forum/attachm...ng-diagram.png

as you can see, the oem amplifier has two sets of + and - because the stock sony subwoofer is a dual voice coil. all the LOC's ive seen are usually either four or 5 wire setups (four for speakers, and usually one for grounding the loc) would it make sense to treat each 'voice coil' as its own speaker? and use the LOC's four wires to connect to the subwoofers four wires, then tune it from there.

oh and to answer your earlier question installerz, my girlfriend has a spare 12" alpine type R as well as a mid range alpine amplifier. so i was just going to utilize that for an affordable build. mount the sub in the spare tire well and recess the cone about 1' above its full excursion so i can still utilize the cargo capabilities of a hatchback

Your amp may have built in speaker level inputs as well which will allow you to eliminate the redundant LOC.

Remember, not all LOC's are created equal. In fact, most basic non-powered LOC's cannot handle a high wattage input! You will have to invest in something like an Audiocontrol LC2 or similar to be able to handle the input without catching on fire or melting. This is also the case with an amplifier's high level input. I have seen even higher quality amps suffer and their high level inputs 'blow up' when given a factory subwoofer signal.

That makes sense. orgasm_donor is right though, you will need a better LOC to accommodate the output of the Sony output.
The cargo area will be ideal to incorporate that sub. Would love to see & hear it when it's done.

oh and to answer your earlier question installerz, my girlfriend has a spare 12" alpine type R as well as a mid range alpine amplifier. so i was just going to utilize that for an affordable build. mount the sub in the spare tire well and recess the cone about 1' above its full excursion so i can still utilize the cargo capabilities of a hatchback[/QUOTE]