# 1990 Mazda RX7 Convertible...



## johnmasters (Mar 30, 2009)

Greetings DIYMA!

Now that I have mostly finished the first phase of my project, its time to share.

The project vehicle is my beloved 1990 Mazda RX7 Convertible.

I would like to thank everyone that responded to my posts, threads and PMs throughout the process especially Zach, AKA... Boostedrex. As it turns out we both own 2nd generation RX7s so he helped me with insight and info and hopefully this build log will help him in some way when he gets around to the stereo project in his Rex.

Here is a link to all of the pictures of the build...
Image hosting, free photo sharing & video sharing at Photobucket

*1990 Mazda RX7*...










*First, I set about getting the Clarion DXZ785USB installed in the dash. The dash kit required a good bit of modifying in order to fit...*

























*Then I got busy trying to figure out where to install the sub in this tiny interior. The area behind the seats which was meant to hold the spare tire should do, after some cutting...*

















*Well, now we need something to fill that space. After what seemed like unending research the choice came down to the Magv4 or DIYMAr12. The DIYMA won and it sounds GREAT even though this is a convertible with very little cabin gain. Its in .80 Cubes sealed after driver displacement. I tried it both stuffed and unstuffed and I prefer the sound when unstuffed. It is currently being driven by one side of an MB Quart DSC4125 bridged with the gain at more than 85% which should be around 500 watts. If your going sealed with the DIYMA you had better have NO air leaks at all. Since the mounting depth of my box was inadequate for the DIYMA I had to use a 3/4" MDF ring which made it more difficult to get the driver fully sealed to the box. btw... I like the DIYMA so much that I bought another one just because it was available. *









*
Although, I realize that people are hesitant to try the DIYMA out because of its paper thin cone and tendency to tear/warp, you just have to get to know it and respect its limits. So far, I know of only one note in one song that pushes it to its mechanical limit. The first time I heard it, it scared me, but now I know where it is.

There is no wonder people call this thing "Pure Sex"...*
















Later in the build I realized that if I removed the curved red metal bracket and the plastic behind it that it left a totally clear passthrough to the trunk which made life a lot easier when it came time to install the amps...


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## U_got_shafted (Sep 16, 2009)

lovin the 2x4 in the box....


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## johnmasters (Mar 30, 2009)

I knew before I started that I wanted to give a CDT Upstage kit a try because I feel as though I loose some high end frequencies out of the convertible top while on the highway. Originally the RX7 Vert was outfitted with headrest speakers but I think its better to eliminate them as opposed to designing around them.

I removed the little triangle defogger vents from the dash and made some MDF baffles for the upstage tweets to fit in their place. They fit in almost perfectly with no adhesive or anything so its very easy to reinstall the defoggers if necessary... 









*I am not currently using the upstage passives so the upstage tweets are playing the same frequency as the mains and being attenuated with the CDT LPad which is in the trunk. There is also a space for a spare tire in the trunk so I built a platform to install down there to attach the upstage hardware to. This is located beneath a small false floor.*


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## niceguy (Mar 12, 2006)

He's talking about the 2x4 that's part of the enclosure you built....nice job so far and nice car....


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## johnmasters (Mar 30, 2009)

Next, its time to tackle the doors and figure out what kind of midrange drivers will be used.

Firstly, the doors.

These doors drove me completely mad. Its a 2 door so the doors are long and they are just full of rattles and the door cards were worse. Keep in mind that the DIY nature of this project was always present and I attempted to use materials that I already had on hand as much as possible. Thus, what you are about to see. A combination of butyl protect-o-wrap, plastic yard signs, polyfill, laminate floor under-lament, egg crate foam coated in Scotch Guard, several pounds of non hardening modeling clay, and one gallon of elastomeric roof coating... 









































































*After many more hours of research I decided that the 6.5" ID OEMs were the way to go for the door speakers. Unfortunately after purchasing a set and trying them out, one of them had a constant buzz so they got scrapped and are sitting on the shelf. What a waste. After that I picked up a pair of Dayton RS180-4s but they wouldn't fit easily and as it turns out their probably not great for a 2-way active up front so they will probably end up in the HT. Then, eureka, I found the PPI 365cs 6.5" component set in the hot deals section of DIYMA and these things are absolutely great...*


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## johnmasters (Mar 30, 2009)

Now its time to decide on some main tweeters and where to put them. I felt it important to get my main tweets as on-axis as possible and you will see that in order to do this I installed the tweets at different locations on each door. I would be interested to hear from the gurus as to whether this seems appropriate or not. It sounds good!

As with the midrange drivers, I went through a few pairs of tweeters before deciding that the ones from the PPI set sounded better. I tried a set of Vifa D26NC55s. They sounded good. I bought a set of Seas 27TFFNCs. One of them had the dreaded broken tinsel lead so I didn't install them but I expect that they would be almost identical to the D26NC55s. 










*I also tried the Passenger door tweeter under the AC vent but I thought it sounded better a bit higher...*












*I tried to deaden the floors a bit with some foam rubber gym floor tiles and laminate floor under-lament. For some reason i didnt want to slather the elastomeric coating all over the floor...*


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## johnmasters (Mar 30, 2009)

I also went through several amps before settling on the MB Quart DSC 4125 to drive the DIYMAr12 and the tweets and the US Acoustics USB4065 bridged to drive the 6.5" PPIs. First, I purchased an Eclipse XA5000 but it showed up with one bad channel so it went back. Then I bought an Infinity Reference 475a from Best Buy which was allowing DC content through to the speakers after power up so it went back. I thought that the Infinity got way to hot anyway. I would have used my trusty old Proton D275 but it has alternator whine. Also, I picked up two of the $30 Cadence amps from the hot deals section but they are still on the shelf. 

The amps were installed onto a board which was carpeted and mounted vertically onto the back of the trunk. The floor of the trunk was also carpeted to match the board and a false floor was made to hide the CDT hardware. Thats the LPad knob between the passives...

















*From inside the car...*









*Next, we have the $25, 31-band, 1/3 octave stereo equalizer to be used with the mids. This was an interesting project, it works and I have actually been able to warm up my midrange a bit...*


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## johnmasters (Mar 30, 2009)

Tuning info here...


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## johnmasters (Mar 30, 2009)

U_got_shafted said:


> lovin the 2x4 in the box....


Look a bit closer and you will see that there is NO 2X4 in that box. What you see is a 3/4" piece of MDF wih a 1/4" piece of plywood glued and screwed to it.


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## lithium (Oct 29, 2008)

where did you snag that eq?

and aren't you worried about the polyfil in the doors getting wet and moldy?


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## johnmasters (Mar 30, 2009)

lithium said:


> where did you snag that eq?
> 
> and aren't you worried about the polyfil in the doors getting wet and moldy?


I was somewhat worried about that but my objective is to always have this car under a waterproof car cover and to NEVER drive it in the rain. I did soak all the egg crate in Scotch Guard at least. It looks funny but the doors are dead as hell.

That eq is the one from the Hot Deals section of the forum that arrives as the circuit board only and you are left to build the case. Its crude but it works good. My favorite part of this eq is the ability to sweep the phase from 0 to 180 on each side. And, of course, the price. Under $30 delivered.

Somehow I'll bet that there are still hundreds of these eqs available.


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## arrivalanche (Jun 27, 2008)

Was that install done the year the car came out? All the equipment looks as old as the car.


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## lithium (Oct 29, 2008)

johnmasters said:


> I was somewhat worried about that but my objective is to always have this car under a waterproof car cover and to NEVER drive it in the rain. I did soak all the egg crate in Scotch Guard at least. It looks funny but the doors are dead as hell.
> 
> That eq is the one from the Hot Deals section of the forum that arrives as the circuit board only and you are left to build the case. Its crude but it works good. My favorite part of this eq is the ability to sweep the phase from 0 to 180 on each side. And, of course, the price. Under $30 delivered.
> 
> Somehow I'll bet that there are still hundreds of these eqs available.


oic, very nice job. ill have to look into that eq... price is alittle to nice to pass if its still available.


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## KMelt (Jan 19, 2009)

Like your ride. Ex 1st. gen. owner and missing it. Is the dual tweeter set-up necessary, just asking not knocking. I would wonder if a compromise of pillar mounted and angled properly, if one pair would suffice. Like the diyma 12.


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## johnmasters (Mar 30, 2009)

KMelt said:


> Like your ride. Ex 1st. gen. owner and missing it. Is the dual tweeter set-up necessary, just asking not knocking. I would wonder if a compromise of pillar mounted and angled properly, if one pair would suffice. Like the diyma 12.


I'm sure the upstage kit is not necessary but I've always wanted to try it and my defogger vents were broken.  I'll try it for a few days with the CDTs turned all the way down and see what I think and then I'll hook up the passives and see what I think.


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## veleno (Sep 16, 2006)

Interesting build.

I also had an '88 vert with a 3-way setup up front plus 4-8" subs all running active. It sounded awesome for being an open top car and hit a decent 140db with minimal tuning.

Your sub box is interesting. Do you have a speaker grill/cover so the top doesn't touch the speaker face when the top is down?

I'm also curious how that 2 tweeter setup sounds. I didn't have any height issues with my setup but different strokes I guess.

It was great to see what others have done to their cars, especially when you've gone through the process yourself! Keep us posted on your future progress.


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## johnmasters (Mar 30, 2009)

veleno said:


> Interesting build.
> 
> I also had an '88 vert with a 3-way setup up front plus 4-8" subs all running active. It sounded awesome for being an open top car and hit a decent 140db with minimal tuning.
> 
> ...


I actually had a 3-way setup in my last RX7 but it was passive and it was before I discovered DIYMA. 

You'll notice that I have a speaker grill ring attached to the top of the DIYMA which allows enough clearance for the top to sit almost on the ring. The mounting depth of the DIYMA was a big problem for me but I really wanted to try it out, and I'm glad i did. I have actually bought another DIYMA and built another box to house both but I think I have decided that that is overkill. My plan is to either stretch a piece of black speaker cloth over the DIYMA to hide it and/or to modify the spare tire cover a bit so it will fit back on. I DO miss the wind deflector.

As I said before I will spend some time without the CDTs to see what I think.

Do you have any pictures or your RX7 build. I have a line on 4 JL 8s and wouldn't mind trying that out as well.


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## MachRc (Sep 29, 2009)

pretty sweet little rx-7! Nice lil project!


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## veleno (Sep 16, 2006)

Attached are some pictures taken when the system was about finished. Minor cosmetics to take care of but for the most part it was complete and ready to go. Ahh the good old days.


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## johnmasters (Mar 30, 2009)

Wow! That spare tire area looks awesome.

So, where did you get the speaker pods?

Do you have a picture of the entire door panel so I can see what you have done and can you explain it a bit... what material was used and so forth?

Also, can you explain a bit about how you went about upholstering the spare tire area?

Is your roll bar made for an RX7 or Miata?

Do you still have this car?

Very nice!


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## veleno (Sep 16, 2006)

Thanks.

I'll have to check to see if I have pictures of the whole door. These pictures were taken back in the 90's when digital cameras were not so common (I think I scanned these pictures back then). Basically I removed the bottom portion (different than on your '90 model) of the door panel and replaced it with a solid mdf piece that housed a single 6-1/2" mid bass speaker. The pods were made for another car and I got lucky that it fitted really well to the contours of the kick panel area which made it look like it was made for the car. The speaker angle and position really worked out great that when I was tuning it the stage height was right in my face, which is how I had hoped it would be.

The amp area is made of 3 pieces. 2 side pieces that are contoured and attached to each plastic side panel, then a single 3/4 mdf down the middle to hold the amps and processor. I didn't cut the center brace like you because I used it for support, but I did remove the metal tire separator that kept the spare in place. Each piece was then carpeted.

There is also a 1 farad cap RF cap beneath the amps that I didn't care to display. I had the EPX lettering redone in gold foil as well as the RF name plate on the end caps of the amplifiers. All speakers were RF Power Series (probably the best they made of that era) that had neodymium magnets and ferro-fluid in the surrounds to keep things cool and accurate. Then there was the EPX2 with 28 band EQ and the 4v Alpine player (which was again the top Alpine deck of that time).

The roll bar was custom fitted to work on my car. It was made for the Miata.

I don't have the car anymore. I sold it back in '98 to a good friend but later the car was broken into and they took the stereo. Sad day for him and me as that car was my baby!

The car was originally white, then painted black, then lambo blue. I wish I had digital pictures of the black as I loved that color on the car. I'll see what I can dig up and scan.

You can see some pictures on the Bay Area Rx-7 Club Home Page page under featured cars. I'm in there somewhere 

I'll check for more pictures and post them if I find any. I just completed my new project so I think I'll post some pictures. Be sure to check it out and let me know what you think.


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## johnmasters (Mar 30, 2009)

As much as I searched before starting this project I just couldn't find much in the way of photos of 2nd generation RX7 stereo builds so seeing yours is very nice. I would sure like to know what car those pods came from and if it would still be possible to find a pair. I expect when zack does his RX7 he will probably build a pair. Also, a guy at auto zone just put a set of those wheels on his 350z and they sure look good on your car and his.

I wouldn't mind installing a miata roll bar as well but I expect that interferes to some degree with the top operation and that you can no longer use you convertible boot. Is that correct?

Not having to have a sub box sure frees up a lot of room.

i wonder if we could find anymore RX7 builds for this thread?


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## SSSnake (Mar 8, 2007)

Great looking install so far.

If you need more airspace or mounting depth for the sub fiberglass is your friend. Back in the day we had 4 tens mounted in a fiberglass tub where the spare was. Great sound and with the grilles in place we were able to replace the carpet above the tens so no one noticed (much).


On a different subject... Do you still have the Vifa D26NC55s? I am one short for an install and I really don't want to swith to the XT25s.


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## veleno (Sep 16, 2006)

Back then there weren't many, if any, builds that were showing up on the internet. I also searched many times and talked to many of the rx7 guys but there just wasn't anything more than a simple HU/speaker replacement being done. I guess someone has to start it! I'm sure there are more builds now but not everyone would be posting them up (like I didn't).

I had no problems with the operation of the top or of the boot. Everything worked just like factory. The only issue I had was with the wind deflector. When I put the center piece back into the car, I had to chose between the down or up position. I did not have the option of putting it up/down at will as it hit the roll bar, but it was still functional so that was a plus.

I believe the pods came from a Honda Accord around the time of the build, so maybe between '94-'97, somewhere around those years.

The roll bar was one of the best additions to the car. I had an rx7 specialty shop make me custom brackets for the roll bar, modify the bar as needed, and they did all the R&D to make it fit on a car they had in their shop. So when I received it there weren't any issues. The bar was solid when it was on! Back then there were maybe 2 other companies making bars, but they were raw aluminum looking and used for racing that they didn't have any visual appeal to them at all. 

Like mentioned above, I do know of one other car that glassed that bottom portion area using a single 10" so that's another option. I did consider that route using 8" subs instead but did not want to cut out that center bar.


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## johnmasters (Mar 30, 2009)

SSSnake said:


> Great looking install so far.
> 
> On a different subject... Do you still have the Vifa D26NC55s? I am one short for an install and I really don't want to swith to the XT25s.


I DO still have the Vifas but I will have to consider whether i want to sell one as i just bought another vehicle and was thinking about giving them a try there. Its to bad you dont need one of the Seas since one was bad.


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## nightdream (Apr 29, 2008)

Great instal


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## johnmasters (Mar 30, 2009)

Update...

OK, after someones advise above and reading the fiberglassforum.com website for the last week, it has become obvious that fiberglass is going to be the answer to some of the problems that i have in my install.

I will spend the next several weeks learning how to fiberglass and hopefully accomplish the following...

1)build a set of door pods to attach to my door panels that house the PPI 6.5"s thus playing the music directly into the cabin instead of through the awful grill.

2)Build a set of tweeter pods into my A pillars thus getting the tweeters up higher where i like them and allowing me to get rid of the CDT upstage kit.

3)Build a sub box under the spare tire cover that will actually house BOTH of my DIYMAs and still allow the spare tire cover to be reinstalled.

4)If all of that goes well, maybe something artsy in the trunk for the amps.


I will post pics along the way.

Any advise and/or suggestions appreciated.


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## johnmasters (Mar 30, 2009)

Alright, a little update...

After spending a few weeks learning how to fiberglass I have finally finished my passenger side door pod.

I actually ended up making two. The first pod had the tweeter incorporated into it but it ended up be a bit funny shaped and a bit heavy.


After some practice, I have ended up with the following...









So, after I am finished with the drivers side and some tweeter pods its time to build a fiberglass sub enclosure in order to add my 2nd DIYMAr12.


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## SSSnake (Mar 8, 2007)

Wow! Great job, especially for your first attempt.


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## johnmasters (Mar 30, 2009)

Thanks! 

Here is the build thread at www.fiberglassforums.com

http://www.fiberglassforums.com/showthread.php?t=10762

I believe that you will actually have to register in order to take a look at the pictures. If, in fact, you do register for this forum, you'll thank me later.


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## JAX (Jun 2, 2006)

just ran across this.....I myself am a former 7 owner...7 of them to be exact...I had a blue 90 vert like your red one....liked the targa top effect...

I actually had to drive to Atlanta once to take back a 90 that I got from a guy in Atlanta off ebay that delivered the car to me but couldnt produce the title....had to make him give me a 91 that was nicer...nightmare that was....

dream car would be a fd with a LS6 v8.....


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## johnmasters (Mar 30, 2009)

JAX said:


> just ran across this.....I myself am a former 7 owner...7 of them to be exact...I had a blue 90 vert like your red one....liked the targa top effect...
> 
> I actually had to drive to Atlanta once to take back a 90 that I got from a guy in Atlanta off ebay that delivered the car to me but couldnt produce the title....had to make him give me a 91 that was nicer...nightmare that was....
> 
> dream car would be a fd with a LS6 v8.....


This is my 2nd 2nd gen convertible. My first one was stolen a few years back and I found this one in Virginia a few months later. I just dont feel rite without an RX7 to drive.

Somehow I'll bet I know whoever you bought that RX7 from. There are several self employed guys around town that work on rotaries specifically. A 2nd gen on ebay sounds like a guy named Bryn from RX7 restorations.


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## JAX (Jun 2, 2006)

johnmasters said:


> This is my 2nd 2nd gen convertible. My first one was stolen a few years back and I found this one in Virginia a few months later. I just dont feel rite without an RX7 to drive.
> 
> Somehow I'll bet I know whoever you bought that RX7 from. There are several self employed guys around town that work on rotaries specifically. A 2nd gen on ebay sounds like a guy named Bryn from RX7 restorations.



I knew you would know the jerk....yes it was from them "RX7 Restorations..." ..he must have had some issues as he couldnt refund my money and he lied about the title the entire time...I was pissed having to drive to Atlanta but the run home was nice in the 91 he swapped me for...I rode there and back non-stop round trip from North Louisiana to Atlanta...not too fun since I had no real papers on me.....got stopped in Mississippi by state trooper but he understood and let me go....

I had to finally stop buyinf them after 7 and then bought my first 300zx ....mush more user friendly stock motor...

rotaries are still in my blood...even though I dont currently own one


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## johnmasters (Mar 30, 2009)

Man, its a small world. I've bought a good bit off stuff from him over the years but its always been in person and I have not had any issues such as that with him. 

I was actually looking at a 300z Vert while I was trying to decide whether to buy another RX7. I liked them a lot but in the end I decided that I would stick with something I already understand. And, an RX7 vert can be found for a good bit less than a 300Z vert.


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## 94VG30DE (Nov 28, 2007)

Not to mention a FD (or even an FC I would assume) is a heck of a lot lighter than a 300zx. Maybe the TT Z32 guys don't notice this as much, but I definitely feel all of that 3500lbs. I would second the desire for a LSx FD. If I had the money I'd be looking for one right now. They are cheap right now. This economy is awesome for buying fast cars.


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## johnmasters (Mar 30, 2009)

I must admit that when I first got into the RX7s I was interested in doing an LS1 type thing but i have really become a rotor head. 

Although, there is a guy in town that owns a place called Mazcare that has built some very impressive V8 verts. My mind may get changed if I ever drove one.


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## JayinMI (Oct 18, 2008)

94VG30DE said:


> Not to mention a FD (or even an FC I would assume) is a heck of a lot lighter than a 300zx. Maybe the TT Z32 guys don't notice this as much, but I definitely feel all of that 3500lbs. I would second the desire for a LSx FD. If I had the money I'd be looking for one right now. They are cheap right now. This economy is awesome for buying fast cars.


All this talk of V8-swapped FD's....tsk tsk, how about a VH45DE swap into your Z32? I found this, and it peaked my interest:

Quote:
Thanks Lost for clearing this up. Fact of the matter is the VH45DE is the same width as the VG30DETT engine and only 3 1/2" longer, but 100lbs lighter than a VG30 engine. It fit in my engine compartment with ease and being I'm using a automatic, the TT automatic bolted right up to the VH45 bellhousing. 



Do it! 

After the stereo, of course 

Jay


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## 94VG30DE (Nov 28, 2007)

JayinMI said:


> All this talk of V8-swapped FD's....tsk tsk, how about a VH45DE swap into your Z32? I found this, and it peaked my interest:
> 
> Quote:
> Thanks Lost for clearing this up. Fact of the matter is the VH45DE is the same width as the VG30DETT engine and only 3 1/2" longer, but 100lbs lighter than a VG30 engine. It fit in my engine compartment with ease and being I'm using a automatic, the TT automatic bolted right up to the VH45 bellhousing.
> ...


haha if my chassis was still in tip-top shape, I would consider a swap for my car. But 170k+ miles in MI (much of which was on a stiffened suspension) has not been nice to the unibody, and there are dents in almost every panel. If I want 300HP in a Z32 I'm buying a different one


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## pionkej (Feb 29, 2008)

Install looks great so far. I signed up over at fiberglass forums as well. You build looks good and I certainly appreciate the link, lots of good info.


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## JAX (Jun 2, 2006)

My uncle has a Grand National turbo six in his FD but it never gets driven....

RX7s can be really sexy but the rotary is a wild thing...


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## johnmasters (Mar 30, 2009)

pionkej said:


> Install looks great so far. I signed up over at fiberglass forums as well. You build looks good and I certainly appreciate the link, lots of good info.


I was very grateful to the person that turned me on to fiberglassforums.com - (lilmsprelude) 

Knowing how to fiberglass can help solve such a multitude of problems.


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## johnmasters (Mar 30, 2009)

Here is the fiberglass box that I built recently to house the two 10" Phoenix Golds that i picked up from the hot Deals section. I spent just under two weeks working on it and it sounds great.


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