[MLB]

Ive read about a dozen threads i could find that touch on this option code and i have a few questions left. My car is a 93 cab, (made April 1993, re-VIN'd for sale as a 94) and it has one of the small amps under each seat.


I want to use a new 4x100W class D amp (Zapco ST-4D) to drive the factory speakers for now, since some look like non standard sizes and i dont want to hack up the mountings at this time. (In a previous thread i referred to my new blaupunkt head unit, which is plugged in to factory harnesses)


Does anyone have impedance and crossover specs for the factory speaker system? Otherwise ill see what i can find written on the speakers themselves. My doors have woofer & mid under armrest, rears are the 4x6 version.


Also any info on specs of the underseat amps; class, rms power, etc?


Finally, Im not good at reading wiring diagrams but the ones in the WSM dont seem to show the wiring routes for the 490 option in the cab (?) i can trace wires as needed, but should i even consider re-using the small factory amps, maybe for the high mount door tweeters?


Thanks!

--michael

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[jimham968]

OK, this might take a while. I have a 94 cab that originally came with the M490 option. My year's system is shown on the wiring diagram on a separate page, along with the Club Sport's stereo wiring, from the normal option but I looked at the manual and I think yours is shown on Sheet 9 of the 1993 wiring diagram. My car only had one amp under the passenger seat.

My radio had been changed out by a previous owner so the harness had been cut & spliced and was difficult to figure out. I'm an engineer and it took me quite a while to understand the wiring diagram and the actual stock M490 system configuration. As it turned out the 94 had tiny amps built into each rear speaker which were built into little sealed cabinets, and they were cross connected and actually fed by a line signal from the head unit, and also had power & grounds going to each speaker. My booster amp under the passenger seat fed only the front door speakers.

I looked at the wiring diagram for the 1993 and your system looks more conventional than mine did. I think the amp under the passenger seat ("Booster Right") feeds both rear speakers. The amp under the driver seat ("Booster Left") feeds both front door speaker sets. The crossovers for the door speakers are most llikely inside the door if they're like mine.

After figuring it all out, and a couple of intermediate configurations, I changed out the whole system except for the door speakers (so far). The booster amp under the seat had little power and could barely drive the stock door speakers above the cab's normal background sound.

My recommendation is to replace the head unit and both amps from the start. Run line level leads to both amps. Run good quality speaker leads.

Consider replacing the rear spreakers but yours probably weren't as unconventional as the 94's so maybe you don't need to at the start. I'm not sure there are any really great 4x6 speakers out there but it might be worth checking out. Replacing them is actually quite easy in the cab. Unfortunately you won't get much bass at all from the back speakers because there's not much of a sealed space for the speakers. Other threads on this forum have talked about trying to seal this space better but I'm not sure anyone's real happy with the results - maybe better but still not stellar.

I'm using my stock door speakers for now and they sound OK. I'm sure they could be better - and will be eventually - but for now they sound acceptable given the backlground noise level in the cab.

Good luck!

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[MLB]

Thanks Jim,

I'm looking a that "sheet 9" wiring diagram again and its starting to make more sense now. Looks like the left amp "booster" powers the fronts, and the passenger side right booster powers the rears. My new amp will be mounted in the RR fender where the 'boat anchor' used to be. I built a mount for the amp thats a 8" long wood blade connected to a 1 5/8" wood handrail that actually uses the mount points for the boat anchor weight to hold the compact amp in the space. Powering the rear speakers will be easy, but running wires for the fronts will be a pain, dealing with that carpet.

I

think I'll take the factory amps out, what the heck save the little bit of weight, and avoid cutting any of those wires, just because.

Should be OK to run wires from the new amp up to the new head unit and tap into the front speaker wires from there, right? To avoid running new wire into the doors?

How can I effectively measure the front channel impedance loads, to make sure they are suited to my amp? But the amp is rated down to 2 ohms per channel...

 

Now, Wilcat mentioned that there's access in the cab's trunk to a hot trigger wire for the amp. Where is that? Is it wrapped up in that black fabric tape back by the taillights?

 

Thanks

--Michael

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[jimham968]

I'm not sure your front speaker wires go near your head unit. The wires likely go from the amp below the seat directly to the doors. I'd just run the wires from your new amp in the trunk to the old amp location under the seat and splice them together there. I'm not sure if you can effectively measure the impedance of the door speakers from the wires because there's a lot on the other end of the wires - the crossover plus the three separate speakers that probably have different impedences from each other. I'm confident that your amp can handle the stock speakers. I'm not sure how long the speakers will handle the increased power from a competent amp but that would then give you the motivation to upgrade the speakers!

I'm not aware of a trigger wire in the trunk but you can just run one from the head unit when you run your signal leads.

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[MCL968]

If you do run wires to the trunk, run a couple extra for a remote trunk release and flashers for an alarm. Getting wires to the trunk is a pain, might as well do it once and do it right. Assuming you don't already have an alarm with flashers and a remote trunk release.  

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[bombfactory]

At 100 watts x 4, you're likely to shred the stock 20 year old woofers! Good luck though - it's really difficult to get good sound out of a 968 at decent volume levels. I've replaced everything and I'm still not entirely happy - more work to do!

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[MLB]

Bomb - yeah the amp will have a bit of unused overhead, but its really compact and a competitive price through a local guy. I dont like to crank it too loud, but i want a little more volume than the new head unit provides.

Then i can upgrade speakers as they get destroyed...i mean as time and budget allow. ;0)

By the way, did u have to modify the speaker mounts or are there modern replacements that just fit? For example isnt the door woofer a 5" and not a 5.25?

I just dont wank to dink around with modifying things to fit unless or until necessary

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[MLB]

OK so I unplugged and removed both of the small factory amps that were under the seats, then last night I turned on the head unit just for grins and I still have sound coming out of the front door speakers and the rear speakers!

Now im confused about who's been running the show?

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[bombfactory]

MLB - Yeah I did a LOT of dinking around with the stereo install. My car has the hi-fi option, so originally the stock door speakers were three-way (tweeters up high, mids lower and forward, 'bass' unit inside armrest) and powered by an amp under the passenger seat. The rears were 2-way separates, powered by their own little internal amps. What a crazy setup!

 

Anyway, I couldn't find a modern 3-way speaker setup for the fronts that wasn't ridiculously expensive, so I went with a 5.25" 2-way (the mid speaker location isn't being used). Unfortunately this isn't ideal for front imaging, as Flash has mentioned many times, the main door speakers are shooting right at your hip. I had to do quite a bit of dremeling to get the new speakers (and crossovers) in the door panels, as their magnets are larger, but eventually it all worked out fine and is completely invisible.

 

For the rear I went with 6.5" 2-way separates in the stock location, which required drilling some new mounting holes, but other than that, no sweat. I have a 5 channel amp sitting in the spare tire well, and a KLA sub box with an 8" sub in the passenger side cubby (my car is a coupe). My head unit is an Alpine unit with the internal amps bypassed via 3 sets of pre-outs.

 

So after all this, how does it sound? At lower volume levels and when the car is not running, very good actually! On the road, the bass gets swallowed up by all the engine, drivetrain and road noise (I've done Dynamat in the doors and some in the hatch area - need to do more). So to compensate I turn up the volume (I have 50w x 4 and 250 for the sub available) and then the less-than ideal speaker placement and enclosures come into play. The lack of midrange up near the tweeters really hampers the sound stage, while the rear speakers turn boomy at higher volume levels due to the large metal chambers (the rear fender wells) behind them.

 

If I ever get my car running again - it's been dead from an electrical meltdown for a long time - I'm going to add more dynamat, try to source a proper 3-way front speaker setup, do Flash's rear speaker foam-fill mod, and perhaps flirt with a 10" sub. That should do it!

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[MLB]

Thanks for these details bombfactory, very helpful. I'm a nervous Nellie when it comes to cutting up stuff on the carthat I can't put back.do you have any advice on where/how to route my eight gauge hot lead from the battery through the firewall?


Also, here's hoping you find a great new job soon! i was laid off for a time and it wasnt fun, but a number of good things came through that experience, not the least of which was getting to spend a lot of time with my then three-year-old daughter. She is a real daddy's girl which probably stems from that time

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[bombfactory]

Yeah no action on the job front lately, but I have been super busy doing freelance design work from home (don't tell the EDD). The trick is to keep the jobs coming in fast enough to pay the bills. So far I haven't been able to figure that out! I do get to see my daughter more tho, so that's a plus. She's 17, heading to college in a couple of weeks.

 

For the power cable running to the amp, I got a bit creative. I did not want to run the power wire alongside the RCA cables under the passenger side door trim, and unfortunately, the drivers side is used for the wiring harness to the rear of the car. I could have gone down the center of the car, which would involve a lot of center console disassembly and carpet peeling, but I decided to go underneath the car.

 

From the battery, the wire goes into the front passenger wheel well (behind the big plastic liner of course) along the brake lines to the ABS unit. Then I threaded it down under the passenger side of the car, through all the brackets that hold on the plastic side panel (hockey stick). It turns inward along the rear suspension arm, then back to the spare tire well, where I drilled a hole and used a rubber grommet to seal out any water (not that I ever drive the car in the rain!). Oh, and I forgot to mention I enclosed the whole length of the cable in that ribbed plastic protective tubing. All was working fine until my car went DOA.

 

Hey I'm closing in on post 968!

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[MLB]

Post #968 coming up, that's cool bombfactory! make it a good one.

 

I found a good solution to getting amp power through the firewall near the battery. There's a rubber grommet already in place to let the antenna (small black wire) from the windshield pass through at the back of the battery tray. The rubber had already failed with a tear in it, so I decided to open it wider to pass the amp hot lead (big blue wire) through. had to remove glovebox to get under there inside the car, but might as well add to the pile of screws laying all over (organized) for everything thats been taken apart to get this cussing stereo update done. (Id rather be working on the engine than doing this kind of electrical stuff, and Ive still got to deal with that carpet. hooey boy :0)

 

   

this is the before picture

 

   

and after pushing the grommet back in place, nice!

Took me a while to get "step 1" done, but oh well I'm happy with it.

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[MLB]

Now i have the power lead neatly threaded through the cabin, under the incredible hulk glued carpet along the bottom of the passenger side of the torque tube. Whew. I chose no to go along the passenger door side to avoid risk of breaking the NLA black plastic scuff plate channel that i otherwise would have removed.

So now if I run front speaker wires from the amp, which will be (if it ever arrives off backorder) in the place of that ballast weight in the right side of the trunk, back up the driver side of the torque tube is that enough distance from the power lead to avoid sonic interference that ive read about?

By the way I'm hoping to set a record for the slowest stereo update in 968 history, but I am learning a ton and fixing lots of little annoyances along the way as usual, and now I know where all the wires go :0)

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[bombfactory]

I think Flash's 'stereo update' took him about ten years so you have a ways to go :-) and I agree, removing those scuff plates is a PITA. I always think it's going to break because it takes so much force to get it to pop off. So those things are NLA now too - great! - add another thing to the growing list...

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[apex]

Guys so good to see others struggling like I did ? as MLB says what a great way to learn.


Seriously these forums were a tremendous help to me when I tore everything sound related and reinstalled good up to date stuff.


I kept both sets of wires inside the car and ran them opposite sides through the rocker panels, Billy have zero alternator whine. There's a thread about my saga here if you want to look for it.


Good luck!

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[williamoss]

What brand and Model of radio did you use as the built in unit? and which brand and model numbers of amps did you use that would fit under the seats? I have the 8 way electric seats in my 1995 coupe. I also have the 8 or 10 speaker system, which currently is messed up. two of the mid range speakers on each door do not work at all, and the combo unit under the arm rest has some sort of crazy electrical connector on them. I do not know what to call it. I have never been satisfied with the sound. When I got the 968 from RS barn it had a blaupundt radio in it, that unfortunately I could not see the digital screen from the drivers seat. One had to put your face directly in the front of the radio in order to see the digital screen, since if you were sitting at an angle you could not read it. I plan on replacing the radio I currently have and all the speakers, and adding a amp to drive all the speakers

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[MLB]

I intstalled the Blaupunkt Brisbane "mechless" head unit (loving it!), and just last nite got the Zapco ST-4D 4x100W digital amplifier. This amp is small enuf to fit under passnger seat! I had hoped to avoid speaker replacement at this time, by just tapping into the red/yellow/white/black leads at the head unit and hoping for the best. Amp isr rated down to 2 ohms/channel. But the protection circuitry is tripping even at low volume, with minimal amp gain and head unit volume settings.

So i primarily suspect an impedance mismatch since the speakers put out good volume when driven by new head unit. But my driver side high mount tweeter is not working and the witing diagram doesnt say how all those crazy separates are wired together or what the door crossover is doing. How can i measure impedance of each channel? Other troubleshooting tips?

Thanks everyone

--michael

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[apex]

williamoss

 

Becker/JL Audio 400w/JL Audio C5 speakers/... the Becker has a modified LCD face so it's readable with 968 angles.

 

At risk of too much detail you can read all about it here. Very happy with the install.

 

Also there's a great iPhone app called "Equalizer" providing seven-band parametric control. Truth be told, as fun as that is to play with, I'm pretty happy with out a lot of sonic tweaking.

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[williamoss]

thanks for the speaker and radio information model numbers and the link to read about it. IN my responses 2 above I was searching in my brain for "crossover" as I said "the combo unit under the arm rest has some sort of crazy electrical connector on them"

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[MLB]

Can I put screws into the floor under the passenger seat to secure the amp, or is there something that could get damaged underneath there?

It seems like a hollow space between the inner and underneath surfaces of the floor of the Cabriolet


Regarding speaker channel impedances, I just bought a digital multimeter, and I don't know if this is a meaningful reading but I disconnected the speaker wires from the amp and reading the resistance for each channel I get about 4.1 ohms for each rear channel and about 2.5 ohms for each front channel. Does that sound about right?

The manual for the new amp says "stable into 4 ohms bridged or two ohms stereo load" I don't really understand what that means, but I suspect the front speakers are lower than the amp wants. Maybe I need to insert a resistor for the fronts?

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