Factory Pioneer stereo install help
 

Hi everyone, I just pick up a 91 convertible and it came with a crappy radio poorly installed. The original radio was in the trunk and I have began reinstalling it in the car. The unit appears to work powers up and sound through the head rest speakers.
I have to sort out why the door speakers are not working.

Questions

How many amps are in this system and were are they located?

How many speakers are in the system? I see the headrest speakers and door speakers but behind the seats I have only cut outs for speakers, not Sigurd if these are original or not ?

I found a plug under the glove box that appears to be for the speakers in the doors but it seems to short to go to the head unit so I am wondering if there is or was an amp somewhere under there that is missing or disconnected.

Under the seats the speakers had amps built into the speaker assembly. Doors are just the speakers if I recall correctly.

There is supposed to be an amp behind the glove box, but since it is missing, your door speakers don't work. Your also supposed to have speakers behind the seats. To answer your question about how many, there is supposed to be one behind the glove box and the headrest amp is in the spare tire compartment directly behind the driver seat.

You'll probably never find a functioning factory amplifier. I still have mine in my car, but it is bypassed because I run an alpine 4 channel. Hell, if I could guarantee mine worked I'd sell it to ya.

Really your only option is to install an aftermarket 4 channel amplifier if you want to retain the factory pioneer head unit.

Sorry, but this is incorrect.

Right so what is correct. As it stands I have no amp behind the glove box. I have a cable which appears to be the cable for speakers out of an amp or something but no amp. Rear speakers are also missing.

I would buy an amp and try it if someone had one for sale.

What I said is correct.

You are missing the pioneer amp that belongs behind the glove box.

Did the aftermarket unit you had make sound? If so, then the factory amp is bypassed and you'll also need to undo the amp bypass when you do find a factory amplifier.

Ok, I was partially wrong. The door speakers should work without the amp assuming the factory unit is working properly. The amplifier that goes behind the glove box is for the rear speakers that you are missing. My best guess is that the factory unit no longer works, which there isn't much you can do for that other than getting a new factory head unit.

I Have the FSM and have added a screenshot of the S5 vert diagram to help you out.

I am Getting sound from the headrest speakers so the unit may be good. The wiring has been hacked up so I'm guessing I need to pull it back out and see if I can sort things out a bit.

Not sure what I want to do here I can buy the amp on eBay but would still need the rear speakers also on ebay or I could just scrap the whole idea and through a double din unit in there. It would be cool to keep the headrest speakers working though.
I am guessing this can be done ?

Yes it can.

I guess i should clarify. Yes you can scrap the idea and toss a DDIN in there.

You will need the factory brackets off the factory radio so DO NOT throw it away!

Since you don't have the factory amp or speakers, the fix is easy. You'll need to run new wire to the rear speakers. This is much easier than doing a conventional amp bypass and using factory wires. You can fit 6x8 speakers back there or if you are adventurous, you can cut and wedge 6x9's back there.

Also, I have done this before on a S5 convertible '91 to be specific: where the factory amp is missing under the glove box, the input and output connector that should be hanging there is a male/ female combo. Mazda was nice enough to leave the preamp and post amp left and right feeds from the stock radio as a straight through connection. If you plug the two ends together, you have bypassed the missing amp, and will only have 4 wires now on the ouput side. The unamplified full range +_ for right and left missing rear subs. He can then take that as the inputs for a small amp to power a set of of speakers behind the seats. Also, in ebay, if you are patient, you can get a set of stock rear subs and the missing amp really cheap. There are sellers that are nuts and try and sell the stock amp for $$$, but I picked up a good stock set of the stock subs and amp for $45 shipped. Over the last couple of years I have seen several sets go for under $60.
Another S5 convertible, I worked on had bad woofers in the stock boxs. I took the boxes apart and replaced the drivers with a set of baby midwoofers from parts express. They are tiny.

the factory CD player was terrible, you are going to alot of work for a very inferior setup.
Its really for looks only. I have some S4 amps somewhere and they were working when I removed them but who is to say what has happened to the rest of your wiring after all these years its probably been sliced and diced.

Also, test yor door speakers, if they are still the stock speakers, they may have just failed. When I bought my convertible, one door speaker was dead and the other just murmured. I verified it was defunct stock speakers and not the stock radio, so a new set of infinites fixed me up.
Word of warning, the stock rear subs are babies, and do not seem to do anything. But when you are driving and have the radio turned up, you do get the low frequencys coming through the seat backs from them lightly.

Thanks guys. I have found an amp on eBay and verified that the head unit works by bypassing the amp. All I need now are the rear woofers. Anyone have a set ?
I realize the old head unit is not the beast but it keeps that classic 90s feel of the car in place.

Yes the stock cd player sucks, and that was from the factory. That is why I bypassed it internally and added an aux jack for my iphone. The cd player connects internally to the radio through standard computer cd audio cables. I ordered a special 3.5mm jack and installed it in the face plate on the right hand side of the stock AE processing unit that mounts under the radio. I wired the output from the cd to the jack and then from the jack i went to the cd input on the radio. When no cable is plugged in, the cd player works normally. when a cable is inserted, the audio from my phone plays. You have to leave a cd in the player, so the radio will accept input on the audio channel. It works fine on the bench, I have not gotten around to putting it back in the car. I have a spare stock radio in there at the moment.

Hopefully the amp you found on ebay has its mounting bracket. the stock amp actually uses the bracket as its ground path. If I remember There are four machine screws that hold the amp to the bracket and the bracket to the mounting point under the glove box. All 4 screws are the same size, so you can get the size for the 2 that you will need from the ones on the amp. You will need to plug in the two cables before you mount the amp. Also mount the amp, before you turn on the key/ radio, or you will get some arching from the amp, trying to ground.

They changed / modified the audio system several times between the S4 and S5 cars and there is a lot of misinformation out there. '88 was the largest number of verts made, then they changed many things for '89. Then '90 came and they tried out more stuff.
From '88 to '91 they moved the door speakers from up high to down low. They added the rear sub boxes, but took away the under dash speakers. The base models did not get the headrest speakers, etc.... Many think a vert is a vert. Or a s4 is a s4 and a s5 is a s5, but that thinking will get you in trouble on the verts.
I dare you to use the '89 wiring diagram on a '91 with airbags.

only verts I have seen without headrest speakers are the super rare S4 cloth seats

still think you are going to a lot of trouble for little return, the money you are spending could be used towards an upgrade. Basic headunits that accept USB or iphone/android control are under $150, 4 channel amps are dirt cheap. You can get a digital only receiver for under $100

Mainly, I like having functional volume control on the headrest speakers from the center console, and the 100% stock look of the dash. Also, no one is going to slit your top, or in a parking lot with the top down, smash your surround, to steal the stock radio.
Back when I had my first gen, I had the window smashed twice for the shiny aftermarket receiver out of the dash, but that was back a while ago. I ended up putting in a cart unit that I pulled out and carried with me in a back pack. Good old days.

I've been working on my S4 vert stereo and I found one of the amps (the one for the door speakers) behind the drivers side dash speaker under the steering column. There is a second amp for the headrest speakers as well. Door speakers are component (door woofer) and dash speakers are full range. I ordered new head rest speakers as well - and I am keeping the factory CD player in mine as it fits with the way I'm restoring the car.

s4 you can remove a single component and install an aftermarket receiver. It fits in the factory chassis and is pretty stealth with the remainder of the factory stereo in place. If they steal $100 radios in your neck of the woods most still have removable face.

The factory headrest speakers are just about useless. You can have them off and not even realize it, all they do is add a minimal amount of "fill", turning them all the way up has almost no effect at all.
The headrest amp is in the spare tire area its clearly marked Pioneer its easy to spot.

I have a pioneer premier deck sitting in the attic from my old car stereo days - we'll see after I finish everything. Nothing I'm doing is going to go to waste. I also have a pioneer 12" sub and a phoenix gold amp I could do an enclosure for - I know if I take out the bracket for the spare tire I could stuff it in there....

even though all my new cars dont come with a spare I like keeping one in the vert. After my big brake project I was delighted that an RX8 spare fits the brakes and in the stock location under the tray.
But yes removing it does give you a place for a sub. I have one in the trunk- I find the rotary exhaust tends to drown bass out- like they are almost on the same octave. Sounds great with the car off, but once im driving its lost. One of those things I never bothered to try to improve.

My first step is to get the project car running - which I'm working on now. I can improve the rest of the stereo later - just getting a few basic speaker replacements in place for now. :)

You can install an amplifier without removing the spare tire. Please see dire warning message below...

Dire warning: If you install an amplifier to the right of the spare tire be aware fuel lines run there and you can easily put a screw through one if you aren't careful.