My stereo system consists of a basic CD head unit, two 6.5" door speakers, four 3.5" headrest speakers, two 8" subwoofers, and two amplifiers. It sounds decent but I still have some work to do over time. One of the amps is to drive the headrest speakers at a 2 ohm load (I could have wired them to the head unit but I was concerned of over powering the head unit's built in amp). The other amp drives the two subwoofers. The subs aren't monster thumpers, but it certainly helps with the overall sound quality. Since most of my system is pretty ordinary, except for the subs, I'm using this page as a primary point for the subwoofers.
The subs I currently have are made by Pyle and are designed for a sealed enclosure. Since my install is not a sealed enclosure, the speakers sound quality is a bit limited. I may someday swap them for some 8" free air units but these are working out ok so far. I got them very cheap on www.ubid.com ($10 each + about $15 each... for shipping - what a rip off - but overall $50 for a pair of subs isn't too bad).
The subs mount on the metal package tray behind the seats. I chose these spots after seeing what my friend Gary Madison did to his miata. 8" subs is definitely the biggest size you can go back there. There is just barely enough room for the speaker magnets and housing.
To install the subs, I first pulled up the carpet behind the seats, removed the metal tray and positioned the speakers in each corner to get an idea where they would go and have sufficient clearance. I marked the centerlines of the speaker on the painted portion of the body so that I could remove the subs, put the metal tray back on, invert the speakers and put into position so that I could scribe a circle where they would go. I drew another circle about a half inch inside the outer circle and cut along this circle.
The speakers are mounted directly to the metal tray.
There is a rubber sound deadening mat that was trimmed to make room for the speakers. Above the mat is another layer made of the insulating carpet which also needed trimming. I left the carpet over the speakers to keep them from being invisible, but I'm thinking of now trimming the carpet and installing grills to prevent the vibration I get sometimes of the speaker cone hitting the back of the carpet.
Wiring is run on the passenger side of the trunk to an amp positioned on the back side of the trunk. A remote wire from the head unit to the amp turns the amp on when the head unit comes on.
Another note about these speakers and roll bars. I have the Hard Dog Sport bar and there are no interferences with these speakers. The rear supports of the bar go through the painted metal portion behind the subs so there is no problem with clearances in this area.
3/28/01 Update: After putting the roll bar in, I noticed the speakers tend to vibrate more against the back of the carpet. So, I finally decided to get speaker grills and cut the carpet. It turned out pretty good (so far). No buzzing and the bass is a little clearer.
10/17/02 Update: I changed the subs from the Pyle units to Kicker Competition Free Air's. Much better sub. A true enclosure would still help a lot. Note: whenever I put the hardtop on, the sound improves significantly.
Head unit, mounting kit, etc... I installed
my stereo head unit with a standard mounting kit for a miata from a company
called Metra. For the most part, I used the kit as-is. Well... I did initially back in '91 (then replaced the stereo a few times, etc...) It fastened to the center dash bezel, not the dash itself. I have a base model so it never had a factory stereo, but from what I understand, the factory stereos mount to the cage within the dash and then the center dash bezel then goes on.
What I did to modify this kit had to do with the gauges I mounted below the head unit. I wanted a flat, textured surface to cut holes into for the gauges. The lower section of this kit had a rectangular cut out (I think they call it a half-DIN size) that can be used for equalizers, etc... The kit came with a snap-in cover to go over that hole but of course that area was a raised portion. I have an alarm and the LED/indicator light was mounted in the center of this snap-in cover. You can see what I'm talking about if you look closely at this picture:
Since I needed a flat, hole-free surface to mount the gauges, I came across a flat piece of textured plastic (got it from a friend cleaning out his garage) and "epoxied" it to the existing lower section of the mounting kit. I had to pop out that hole cover and relocate the LED to the new plastic. The overlaid plastic fit perfect. I even had a little gap behind the stereo bezel (actually, it was behind that metal cage/sleeve that most aftermarket stereos use today) and the original lower section of the mounting kit that this plastic overlay slide up in and filled in nicely. The adhesive has worked fine. I think it was a special plastic bonding epoxy.
If you notice in the pictures, the gauges are tilted toward the driver. I did this to be able to see the gauges better. The gauges are tilted with angled trim rings sold by Autometer. They came three in a pack. I cut the holes for the gauges in the plastic overlay (and thus through the existing lower portion of the Metra kit) with a door hole saw bit in my drill. I don't recall the size of the bit but I think it was 1 3/4" (whatever was recommended in the gauge mounting instructions). Note that I drilled the holes in the same axial direction of the gauge... so the holes were somewhat oval if you looked at the plastic straight on. I used the same epoxy to mount the rings in the orientation I wanted them, then mounted the gauges.
It is possible to fit three of the 2 1/16" size gauges underneath the radio instead of the two that I did. However, there is not enough room to tilt the gauges or to use the trim rings. Here is a picture of my friend's miata (the "twin") with three gauges mounted flat to the surface: