factory amp bypass (my way - lots of pics)

[tim eh?]

Well I'm honestly quite pleased this worked. Originally I tried to rewire the factory amp so my aftermarket head unit could run through the factory speakers unhindered (and also to confirm I had a blown speaker), but I trashed the amp in the process and it became necessary for me to make new crossovers out of the ones from the factory amp. Here's how...

These are the factory crossovers, they consist of coils and capacitors which work as high and low pass filters.


1. Remove the coils and capacitors from the circuit board (which for me was already in pieces).



2. I had to trace the circuits back through the circuitboard to figure out which was what. Once I managed that I drew myself a little diagram.

[tim eh?]

3. Hot-glued all the pieces to a piece of plexiglass and then made the connections...


4. These little motomaster plugs are very handy, you'll see why later. Here are two labled for the front right mid speaker and rear left woofer.


Ready to go- NB there are two separate spliced cables in this photo. I made them with the intent of using the factory wiring for the speaker negatives, which worked but screwed up all the fading. In the end I had to use separate speaker negatives for all 4 corners and wire them straight to the head.

[tim eh?]

5. Next you have to remove all the little plugs from the amp plug, except for power, ground, and remote wires. Shogun posted a great thread about this not too long ago and I finally figured out how to unlock the plug (use a knife!) BTW the B+(power) wire is on all the time so.... you know.

[tim eh?]

6. I used heatshrink around the exposed part of the plugs. The factory mini plug bit fits perfectly into those little motomaster plugs.



7. All plugged in.... hope I got it right!


Sounds much much much better except for the blown rear woofer of course, through the fronts it is #@$%ing amazing!


8. I had already drilled holes... my little board fits right where the amp was and I probably lost a couple of pounds...
when you drive an m20 you have to shave weight wherever you can!


note - jon spencer blues explosion is NOT a good band to eq your stereo to.

[ArnZ!]

mate you've have literally took the concept of 'bypass' to scary new levels!!! lol good work!

[Jeff N.]

help me - what's the theory here?

drop the amp but keep the crossover embedded in the factory amp?

[tim eh?]

help me - what's the theory here?

drop the amp but keep the crossover embedded in the factory amp?

Yes drop the amp, keep the crossovers.

The JVC head unit is supplying *12V as opposed to the stock unit 's *5V(?). Run those high output signals through the factory amp and you get a giant mid range bell curve which reduces the head units efficiency and kills the lows and highs. I (completely) bypassed the amp to the crossovers, which divide the frequencies to the appropriate speakers. So now I'm driving the factory speakers with a nice flat even 40W instead of the factory amp's massive midrange (I'm guessing) 15W or so. Who knows what it is when it's wired to 40W?

Before I did this the tweeters barely worked at all they are great and I am surprised at how much bass the factory woofers can take, they are only rated at 40W. I think they need a tiny bit of help... thinking single 8" nothing massive and just cut the very bottom out, all the speakers sound great I am really pleased!

oh yeah - Thurston Moore's 'Psychic Hearts' is great to eq a car stereo with

[bad_manners_god]

This is a good budget fix. However, what I did was much simplier....Ran new wires from head unit to new speakers individually and didn't have to cross anything over. Given it was tricky running wires into the roof for the touring.

[ladiesman217]

BMG: that is totally bollux... if you had kept the car longer, you would have blown the tweeters. And it sounds like ass. and it is redundant as hell since all the wiring is already laid in in nice twisted pair.

OP:

Nicely done tim eh! That's the way ya do it.

now drop about 80w rms on it instead of 17w and you'll be really happy.

[tim eh?]

Nicely done tim eh! That's the way ya do it.

now drop about 80w rms on it instead of 17w and you'll be really happy.

Thanks - i don't think the factory speakers could take 80w rms, certainly not the woofers!!!! My JVC is old skool and really efficient, the sound is great. I will replace the rear woofers, maybe the fronts too but really all it needs is a (small) subwoofer system and to block the bottom 100 Hz out of the factories and it wil sound like a million bucks.

This is a good budget fix. However, what I did was much simplier....Ran new wires from head unit to new speakers individually and didn't have to cross anything over. Given it was tricky running wires into the roof for the touring.

Cost wasn't the issue here. It was pretty simple too, easier than tearing the car apart to run new wires, although I did have to send new speaker negatives from the trunk to the head which took me a long time. I understand what you are saying but the factory speakers are easily as good as many store bought component assemblies. How did you manage to get your door tweeters to function if you wired it that way anyway?