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Tuesday, September 02, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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Sunday, February 25, 2007

New Rear Speakers

Last year I replaced the front speaker components when the OE midranges began to crackle. Recently I'd noticed the rear speakers distorting a bit more on peaks so I took that as a sign that they needed to be replaced as well. I considered the installation of 8" round subwoofers rather than 6x9 drivers, but simplicity won out and I wound up buying the CDT 6x9 free air subwoofers and some 1" silk dome CDT tweeters. It appears that a lot of people don't recommend installation of tweeters in the rear speaker complement, but I'm used to hearing high frequencies from the rear so I figured I'd try them out and disconnect them later if they didn't work out.

While doing research for this project I read of one case where the owner of a '99 M3 attempted to replace the 6x9s and reported that the CDT units did not fit the OE adapters. This person was a BSW customer so the BSW rep recommended their 6x9 adapters. I took the hint and ordered a pair in advance of the work. They arrived this week. Last night I managed to get a bunch of work done early and had to screw my head onto something else or go crazy so I figured I'd tackle this project.

(Image: CDT 6x9 free air subwoofer mated to BMW mounting adapter)Not far into the process I realized that the OE adapters had one really nice feature applicable to my installation -- a perfect location for an aftermarket tweeter. This and the fact that the BSW adapters had no provision for tweeters (a fact that was not made entirely clear to me when I ordered them, sad to say). encouraged me to modify the OE adapters to fit the CDT 6x9's and put the BSW units back in the box. If you're wondering, the modifications amounted to elongation of the holes in the speaker mounting flanges and sanding down the standoffs on the adapter to compensate for the shallower mounting arrangement. Very simple, really.

I'm extremely happy with the results of the physical installation and I would recommend this solution to anyone who wishes to install tweeters on the rear deck and retain the factory wiring. I should point out, however, that if you don't intend to install tweeters then the BSW adapters will be the best solution. The adapters themselves appear well made and fit the CDT units quite well. The only thing I don't like about the BSW adapters is that they don't come with any adhesive-backed foam insulation as used on the OE adapters to help seal the adapter to the rear deck and prevent rattles -- and for $60 a pair, I think they should.

The end result is sonically promising, if not thoroughly pleasing. After about 15 minutes of listening I can say that the benefit of the CDT drivers, at least when driven by the OE amplifier, is that the low-end is more well defined and composed. They don't really add to the low end as much as they improve its clarity. That's not to say the upgrade doesn't make its presence known. I had to track down some heretofore unheard rattles on the rear deck due to the overall increase in sound pressure level at lower frequencies, so they're definitely doing their job better than the OE units.

The downside to the installation of the 6x9's is that their greater resolution and overall capability has made it very obvious that the OE amplifier is the weak link in the system. The amp lacks the power to drive the speakers effectively, the built-in crossovers are wrong, and the excessive filtering restricts the potential of the extremes of the frequency spectrum. In short, the amp is garbage and should be replaced. I'll likely replace the factory amp with a Zapco DC Reference 360.4 given its amazing featureset and great physical design, but that will have to wait until warmer weather as that's not a simple project. I'll have to take the car out of service for at least a weekend and I can't do that while my backup vehicle is equipped with tires that perform like racing slicks on ice when the weather takes a turn for the worse.

Total time for this project was 4 hours exclusive of a trip to Home Depot for some miscellaneous hardware and a hot-melt glue gun to replace the one that appears to be have been teleported to an alternate dimension. Installation labor at a local stereo shop is $40/hr and assuming they'd done this exact job before they would have likely charged me 2 or 3 hours labor. Was this worth my time to save maybe $120? Probably not, but at least I know the job was done right, and that -- as the commercial says -- is "priceless".

Mileage: 139990, Parts $290, Labor Saved: $120.