Bose head unit

[wws944]

Has anyone here played with a Bose head unit from a '90-'93 Riviera? These seem to be fairly rare. However I found one yesterday.

The connectors on the back of it are identical to the normal Reatta radio. Main difference is that the two connectors that normally run to the speakers are used instead for low-level audio outputs. Hooking it up to my bench power supply, (yellow, brown/white, and grey wires on +12v, and importantly, *both* black wires on ground) the panel lights all work and the box seems to power up and function ok. Have not tried the cassette portion, nor hooking up a CD player yet.

For some reason, I thought the Bose units used balanced low-level outputs. However looking at the diagram in the the '90 FSM, page 8A-150-2, it seems like the audio outputs are unbalanced. They also use a separate ground drain for a shield around the three wires. So it seems like it would be trivial to connect it up to a normal amplifier with no balun needed.

I didn't bother buying the amps/speakers. The door systems have a long acoustic chamber that protrudes out and would rely on major mods to a Reattas door panels to incorporate. And that simply isn't going to happen in my car. For now, I just want to use it on the bench to test my junque CD players to see if I can get any of them working, and try out a couple of other ideas.

[KDirk]

Walt,

Your findings are correct. Really, the Bose units are what are now commonly referred to as "dead-heads" (no inboard amplification). Outputs are just line level unbalanced and run to each speaker unit which have integral amplifiers and the tuned enclosure you described. This head unit setup is good if you want to use a real high powered outboard amplifier and good speakers while retaining a factory look control head in the dash.

In the case of Bose systems using a control head and remote radio interface module the RIM module (typically found in Cadillac models) can be used in the 88/89 Reatta to retain CRT control of the radio while using outboard amplifier(s). This does result in the loss of the graphic EQ (not implemented on Bose systems) and balance control (also not implemented as the tuned speaker enclosures supposedly eliminated the need for it).

KDirk

[wws944]

It was actually pleasantly surprising that the unit worked. There is a a small amount of surface rust on the top of it. (There was a *lot* on the top of the HVAC controller.) Since the car had a sunroof, I guess it must have been left open in rainstorms a few times... The front panel of the the unit looks pretty nice though. Only issue is the little cassette door is a little scratched. But I'm sure I can eventually find one of those on other Bose units of that era - not necessarily a Riviera one. No hurry though.

Have now tried a couple of my junque CD player, and of course they still ERR. What kind of cleaning tools/chemicals do you recommend to try on the lasers?

[Corvanti]

Have now tried a couple of my junque CD player, and of course they still ERR. What kind of cleaning tools/chemicals do you recommend to try on the lasers?

i've had "some" success with "Philips - CD & DVD Complete Cleaning Kit". #SAC2550W/27

includes "laser lens cleaner instructions". i think i picked it up at Best Buy...

[KDirk]

The best way to clean is disassemble to the point of exposing the laser pickup block, and using a Q-tip with 91% isopropyl to lightly scrub impurities off the collimator lens. The cleaning discs will remove superficial contaminants, but a really grimy one will usually not get properly cleaned this way. This is because units in cars tend to be dirtier due to outside air contaminants like dust and pollen entering the cabin, and out-gassing of the interior plastics causing a film to form on any clear surface. Look at the inside of a vehicles window glass to see this same effect when not cleaned for a while.

KDirk

[NCReatta]

What does this Bose unit look like? Any different from the stock radio? Could you post a picture?

[wws944]

What does this Bose unit look like? Any different from the stock radio? Could you post a picture?

Sure. Main thing is there are bass and treble controls instead of the equalizer. The Left/Right adjustment is gone too.

[wws944]

i've had "some" success with "Philips - CD & DVD Complete Cleaning Kit". #SAC2550W/27

includes "laser lens cleaner instructions". i think i picked it up at Best Buy...

Looks like Amazon has it for 10 bux. Only one review, but 5 stars. Bunch of other cleaning systems there too.

I partially disassembled a CD player a while back, and think I did try some isopropyl alcohol on it. Didn't change things. But I will try again on a different one. Maybe take some photos along the way. Probably won't get to it for a couple of weeks though.

[wws944]

I found a booklet titled "Sound Service - Audio Systems Diagnostic Guide" on ebay. It was published in 1992 by Delco and covers our cars. In it, there is some additional interesting info on Bose systems of the era.

There were three Bose setups: Delco/Bose, Delco/Bose Gold, and Delco/Bose Silver. In the regular Delco/Bose system, each amplifier is rated at 25 watts - giving 100 watts total. In the Delco/Bose Gold system each is rated at 50 watts - 200 total. And finally Delco/Bose Silver - which is configured a bit differently. In the Delco/Bose Silver system, there is a trunk-mounted unit containing three amplifiers. Two are rated at 35 watts for the front speakers. The third is rated at 80 watts and provides a single rear channel for the two rear speakers. The book does not specify if the power rating is RMS or peak.

There is also a comment that each of the Bose amplifiers has a 32 band equalization capability. This is what allows them to tune the speaker to the enclosure and the rest of the car. Thinking out loud, I wonder how easy it is to modify a Bose amp to change the equalization curve?

Also, on the CD player, there is also additional information on the infamous "ERR" condition. They document two things that can cause the ERR: Fogging of the lens - which they tend to blame on moisture/dew point. The other has to do with high temperature. Given this, I suspect many "broken" CD players can be fixed with just a good cleaning. I haven't bought a cleaning kit yet, but will soon.

[gkhashem]

If you would like to learn more about a Delco Bose Gold CD system I have one in my 1991 Cadillac Eldorado. It has been quite a ordeal getting it back to working but I did.

Hit this link to read about my trials with my system.

1991 Eldorado Biarrtz Bose Gold System

The CD players can fail often and the speakers have their own amps (the head unit does not) which almost all by now have failed even if you find new OEM ones that have never been used. The amp circuit boards need to be rebuilt and there are a few places that repair them I have had good luck with a place in Longwood Florida. They guarantee there amp repairs for life.

Once you get a Bose working there is nothing like it. I remember reading that they are actually designed to fit the actual car they are installed in. So if your looking for optimum performance you would use a system with the speakers and amps for that car.

[wws944]

If you would like to learn more about a Delco Bose Gold CD system I have one in my 1991 Cadillac Eldorado. It has been quite a ordeal getting it back to working but I did...

Thanks for the link, and good work! Do you have the CD version or the cassette version of the head unit?

I had an audiophile uncle who bought his 1985 Deville back in the day specifically because he was so impressed with the sound. He also had at least one of their Wave radios at home and really enjoyed it too.

The Bose sound system was never offered as an option in the Reatta, however it was offered in the Riviera. Since the instrument panels are the shared between the two, the Riviera Bose head unit matches the Reatta perfectly. However the tuned chambers for the door speakers and amps are another story. I have no idea how practical it would be to fit these, or Bose chambers from some other car, behind Reatta door panels. Not something I expect I will be doing.

About 15 years ago, I replaced all the audio gear in my 944. At the time, I bought a sound meter and a CD with some test tones and such so that I could try to equalize the system to the cars interior. It is really hard to do well. Given the small interior and wave interactions, one can move the sound meter just a few inches and wind up with entirely different measurements. In the end, I tuned things "by ear" as much as by measurement.

I guess what Bose really did was use the 32-band (!) equalization in the amps and tune it to their enclosed chambers first. Kinda like a Wave radio, only bigger. This would get rid of most of the issues of door leaks and resonances. Then they would tweak the EQ to match the interior of the car from there. Not sure how easy it is to change the EQ settings. Will have to take a look at a Bose amp one of these days.

[gkhashem]

I have the CD version and it is nice sounding. Your right that Bose tweaked these systems to work with the car cabin.

I am not sure how you would get one into a Reatta, but its kind of surprising it was not offered in a Reatta considering its hefty price tag.