The OEM sub-woof in the TTR is a joke; everybody knows that.
I replaced mine some years ago with a Fosgate Punch 8", driven by a 5-chan amp.
The sub section is a 100W amp.
It sounded pretty good, but the "enclosure" was crap.
The metal frame vibrated, and even with loads of Dynamat, it still buzzed.

<img src="http://mk1tt.montebellopark.com/images/sub2.jpg">

A radical change was due,.
I modeled this after a post on the UK forum some 2 years ago, where someone put in 2 subs behind the seats in a TTR. The posting explained some radical internal cuts to get the results.
I have had my rear panels off so many times, I figured, what the hell.
First step, remove the seats.

<img src="http://mk1tt.montebellopark.com/images/seatsremoved.jpg">

I wanted to clean the interior anyway. What dirt! First time I had both seats out.

<img src="http://mk1tt.montebellopark.com/images/dirty.jpg">

Remove the center frame where the OEM sub is. About 8 bolts,nuts to get it out.
Sorry, no good pic of it, but here's a mod to it.
Cut the back off, so it's just a front frame.
The part on the right of the cut here is the wrap-around back frame the the OEM sub sits in.

<img src="http://mk1tt.montebellopark.com/images/cutframe.jpg">

Remove this bracket, cut off the studs.

<img src="http://mk1tt.montebellopark.com/images/remove1.jpg">

You now have an opening like this.

<img src="http://mk1tt.montebellopark.com/images/initialspace3.jpg">
<img src="http://mk1tt.montebellopark.com/images/initialspace2.jpg">
<img src="http://mk1tt.montebellopark.com/images/initialspace.jpg">

Build a box.

Measure the opening in various places, construct a box. I used 10-ply 3/4" plywood, not MDF, or any pressed board crap. I'm not building a show-winner, I just want good sound.
I don't need any calculus to figure sq. footage either.
This ain't rocket science, and I don't need a heavy box. The plywood box is very strong, tight and more important, it fits the opening. You'd be surprised how much room is back here.
The box is nearly 17" long, 12" deep, and at least 5" high all the way back.
Some "custom" cutting is needed to match the curves of the rear frame under the top area.
It took about an hour to build the box, and fit it well.

<img src="http://mk1tt.montebellopark.com/images/boxplacement.jpg">
<img src="http://mk1tt.montebellopark.com/images/boxplacement1.jpg">


Paint the box, pack the sides and back with fiberglass insulation, install the subs.
These are 6.5" sub-woofs, not expensive-You don't need JBL's or others.
These have big voice coils, and lots of cone movement.
Use the front openings along side the woofs as openings for air movement.
There's your "tuned ports".
Like I said, it ain't rocket science to do this.

<img src="http://mk1tt.montebellopark.com/images/boxfinish.jpg">
<img src="http://mk1tt.montebellopark.com/images/boxfinish2.jpg">


I used a rear side panel from a coupe, cut out the speaker grill, and matched it to the opening in the roadsters rear panel.
It's not a perfect fit, and one corner has a curve to it, but see, it's behind the seat, and it won't really show.
I can bend the upper left curve down when I glue the grill into place.
This shows the initial placement.

<img src="http://mk1tt.montebellopark.com/images/newgrill.jpg">


I've been driving around for 3 days now and the sound is exceptionally good to spectacular.
Much better bass, not boomy, not harsh, smooth, and it has a punch with some good source material.
Sounds better with the iPod-music than FM.

Panels go back on this weekend.

NOTE: I know some of you audio-people will not approve of my methodology.
This is not a true "tuned" system, nor is it designed for show-quality sound.
it's a daily driver, augmented audio system in a daily-driven car.

I have 4 MBQuarts, 2-6.5, with 1" tweets in the doors, and 2-4" coax in the rears.
Overall sound quality is miles above the OEM system.
I like it.
I just wanted to show you what can be done.

 

Great Post - Nice Work!!!!

 

Nice work Jeff. Looks like a hand full to do

 

Looks like alot of work. But looks great!!!!

 

interesting... nice work!

 

What's your experience when driving with the top off? (the car's off course) :-D

 

why didn't you cut a proper face for the box and just make it a sealed enclosure? if you wanted you could have added a port to the little step out to the right. There are calculators available to calculate the port tune and it just takes a piece of pvc pipe for the port. Plywood isn't usually used because it will eventually separate from the vibrations. It looks like you used nails as well, they'll likely come out soon. might want to run some screws in there to keep them from working loose. With the MB Quart front stage you should have very nice sounding mids and highs, I would think you'd want the same quality from the bottom end. But if you like the sounds thats all that matters. just seems like a lot of work when a little bit more would have done it right. I can tell what that would sound like just from looking at it. Seen many projects like that back in the day.

 

Awesome...Nice to see you back!!!

 

will separate.

 

Nice work as always Jeff. Can't imagine what it looks like under my seats!!