While Bose may have a reputation for innovation in the audio world, they also have a reputation for failure in the automotive world. I will be documenting my experiences in restoring a Bose system in a 1990 Nissan 300zx 2+2. Much of this information will be applicable to other Bose automotive systems in Nissans, Infiniti’s, and other makes. I have gleaned information from sources relating to Corvettes and Infiniti Q’s. This has provided me a start in the restoration.
Background:
This website provides a good detail of Bose systems found in the 300zx family of cars.
Z Max Stystems Bose Page
Here are the high points:
- Bose automotive systems use individual amplifiers for each speaker.
- The amplfier/driver/enclosure are all tuned to each other (as they should be) http://en.wikipedia.org/wiki/Thiele/Small
- The amplifier gain, equalization and compression are all changed based on what car the speaker is located in, where the speaker is located in the car, and it is rumored that even cloth/leather trims are considered.
Root of the problem:
That being said, it is common for these complex systems to fail. The most common problem is capacitor failure. Much of the blame can be put on Bose for attempting to save a couple cents, opting for capacitors with a 16v tolerance. Now, a typical car circuit works on 12v (12v battery up front, right?). However, when the car is on, the alternator typically brings the voltage up into the 14-15v range. Getting awful close to that 16v break down voltage, huh? There are additional stresses that can be caused by jump-starting as well. While a higher break down tolerance may have helped most problems, the truth about electrolytic capacitors is that they can deteriorate in time, lowering the breakdown voltage. Let’s not forget the stress that all the bumping around can cause. Also moisture in the air, hot and cold… It’s really a miracle that more car stereos aren’t broken.
Solutions to the problem :
Its still possible to purchase speaker/amp modules from Bose. They charge $140 a pop for a new unit. For a lot of people, this may be a solid option if convenience outweighs cost. You know for sure you’ll get a working unit that is up to factory spec. There are also amps that come up on ebay that have been used or are refurbished. One must be careful they are getting the EXACT replacement for their make/model/year/trim/speaker position. Other amps may work, but they won’t be matched as they were from the factory.
For those who want to spend the least amount of money, this is the option. 20 bucks, one can purchase replacement capacitors for all of the amps in their car. However, some mechanical know-how, soldering skills, and time are the trade off. Some sources also claim that the performance will not be as good as new amps, however, I contest that IC’s, inductors, and ceramic capacitors don’t deteriorate like electrolytic caps, so upon replacement, the unit should work like new.
This option has the advantage that sound quality can be improved (ie louder), modern equipment can be used (cd/dvd/nav systems) and other personal touches can be added. However, this means a non-stock headunit, which leads to two things: thieves like stereos and new headunits won’t match your interior. Also, all speakers must be replaced. Bose uses speakers whose DCR is <2 ohms. Most amps (and no head units I’ve ever seen) cannot run these speakers.
Personally, repair is what avenue I have chosen. For an heirloom car like a 1990 300zx in great condition, having the stock system is a definite plus. I’ve had a loud bumping system before, but the cleanness of a stock system is nice, especially in a small car like a 300zx. Not to mention, there are some weight savings to be had over a large system! The notes below should help anyone trying to restore their 300zx or any early 90′s car equipped with a Bose system.
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