Miata Mailing List: January 1993, Message #132
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   From: (none)
Subject: Re: speakers, etc.
   Date: (none)

Well, Since I just got home from getting a new amp installed,
the list traffic called for my humble opinion.

I haven't heard the clearwater setup, but I remember the traffic
regarding the "thunk" upon turning the head unit (radio/tape deck) 
on. This reminded me of an old blaupunkt eq/amp I added to a rabbit
in my college days, and was sorta a turn off. I think this happens
any time you amp the high level (spkr level) outputs from the factory
radio. 

I wanted to keep my factory radio, for a few reasons. It works well
enough (though I had to have the first one replaced after getting caught
in a downpour with top down, where the logic controls all gave out
for about 2 weeks... It still worked fine other than that, but of 
course I couldn't eject the tape -- B52s and They Might Be Giants -- 
definitely not easy on the ears after 2 solid weeks! Finally, the day 
the dealer called to say they had rec'd the new radio, I pressed eject
like I was doing every time I started the car, and wow! out popped the
tape. Of course.) and it is inconspicuous. I live in an urban environment
and am not anxious to appear anything but stock.

So -- Upon first buying the car, I had the factory paper cones in the
doors replaced with Boston Acoustics 767 coaxials. A good speaker, and
a 6.5" speaker that happens to fit in the factory 5.5" spot with only
a cut of the speaker grille. This cut removes the small center ring only,
and there is zero cosmetic evidence of it. Again, subtle and undetectable.
These improved the system from the start. If it weren't for my paranoia, 
I might have gone for the Boston Acoustics separates, which have 
separate bass/midrange spkrs and tweeters. The tweeters are about
2.5" across and can be mounted in the upper door panel.
(BTW - I'm driving a '92 blu pkg B, which came with the headrest spkrs)

I found that I was actually running out of volume on occasion, and bassy
music would make the door panels buzz (indicative of clipping). An amp
was in the plan from the start, just needed to wait for the cash. The
767s are rated conservatively at at least 40W rms. 

So today I went out and had an Alpine 3547 installed (they did it 
as well as I could have in a lot less time, and possibly better). This
amp is rated at 45W per channel at 0.04% THD. The improvement was
as good as I had hoped. It wasn't however cheap.

The project requires a "de-amp" to take the factory spkr outputs and
turn them into "RCA" pre-amp levels. This was available at less than
$30. The system makes no "pop," "thunk" or any noise upon turning on.
Before today, I wasn't aware that these things are available from several
vendors - Alpine even sells one.

The amp was installed under the rear deck. When the carpet is lifted, 
There's a panel over the gas tank, which when unscrewed (it looked like
a LOT of screws!) leaves symmetric nooks over the front of each rear 
wheel well. It appeared that these were empty space. I only hope they 
have some air flow to allow for heat dissipation. Whatever... 
I'm not sure how the unit is turned on and off, there is a remote 
input which they suggest can be hooked to the power antenna, but with 
the miata, the antenna is only energized when the radio is being used 
(I *really* like that, btw) so maybe they just power it on with 
the ignition?

Anyway, my project costs were $150 for the BA 767 spkrs, and $387 
including tax and $80 labor) for the amp system. Not cheap, but the 
system is clean, and there is NO evidence that it's anything but stock.

Now, the place that did the amp for me had a book with shots of at least 
2 other miata projects, and these people had gotten serious. There was
one car with 2 (big) amps in the indent in the trunk floor (with a false
floor built up around them), and at least 8" speakers in the deck. I
also heard of people mounting forward firing tweeters on the rear deck, 
which the top missed perfectly, and which went crossways (left spkr
talking to the passenger, rite to the driver). There were also 2 
different ways I saw 8" speakers put into the door with minimal cutting
and still using the stock grilles. One required removing the entire 
window track for installation, and NO cutting. These guys looked
pretty good. I would speculate that they get expensive, which I consider
$2500 for a miata stereo.

Oh well, sorry for being wordy. Remember - Spring is coming!

-Marc Salit