dude, it wont sound the best, but i plan (one day!) to put a woofer where the spare tire spot is. i bought this little alping pdx 5 channel amp/woofer thing to go there.

there are a ton of different versions of these mini amplified subs online and i think they would fit in the spare spot easily and add some punch.

 

I’d already removed the little speaker grill and set it aside. This is what the stock panel looks like without it:



You’ll notice that there are only three little tabs for the speaker grill, and everything else is excess. So that’s where I started:


And from the back side, I cut down the baffle and any other protrusions:



I also cut out those two mounting posts at the back. This didn’t turn out to be necessary, so if I were doing this again I would leave them. All they do is mount to the door insert, so I’m unlikely to miss them.

With those cut out, the next obstacle is the window track mount:



This presented an issue. Obviously I can’t just cut it out, because the window track would flop around. Secondary problem though is that it vastly extended the timeline, which is why this job spiralled way beyond how long I expected it to. But it’s better to do it right than to half-*** it, so I started working on relocating the mount.



This hole up above the existing mount presented an optimal location. The back was flat and it wasn’t in-use already. So I cut some mild-steel I had around and bent a new bracket, test fitting it 100 times:




I spent a long time getting the fitment right. This is not a part that I wanted to screw up, since finding another would be a pain and I wouldn’t have any windows while I waited. I also wasn’t sure how important the precise alignment of this track was, so I erred on the side of caution.



I also took out the window glass before I tack-welded anything, since the spatter might melt the laminate and damage the glass.



After tacking the bracket on the track can come out. With the bottom bolt removed, the trim pulls back and this little clip thing is all that holds the top in. The track just pulls straight down.

To be continued.

 

I needed to remove the original track, but I didn’t want to be needlessly destructive in case I want to go back to stock (lol). So I ended up drilling out the spot welds and keeping the original bracket safe. Then I added some more tacks and painted it up:





Now I was ready to cut the door. It was at this point I realized maintaining the ability to reverse the window track modification didn’t make a lot of sense when I was about to slice a chunk out of the door panel, but hey, no need to cause wanton damage. Taking a saw to my car was bad enough.

Before:



After:



I know why I didn’t do this last time (nobody likes cutting their car), but honestly the amount of space it frees for the driver is just unreal. I absolutely should have done this the first time. I sprayed some black paint on the edge where I cut it for rust prevention. I did actually keep the parts I cut out, again, just in case I want to go back to stock…

While I waited for the paint to dry on the door, I worked on the vinyl of the door cards.

These are the original door cards that came with my car. Well, “original” since I don’t think anything on my car is actually original, but you know what I mean. They were maroon from the factory and had turned this ugly faded colour, which is why I wasn’t afraid to dye them black.

The Duplicolor Plastic & Vinyl dye worked well, but since these were the first part I did over 5 years ago, I had learned a few things about prep in the interim. There were two tiny spots (near the handle and near the vents) where some flaking occurred, so I set out to fix it.

I stripped back any loose dye, and then sanded the entire panels with 600 grit sandpaper. I didn’t want to sand too much or else the texture would be damaged, but then some places (particularly near the vent) were basically smooth already. This is probably part of why the flaking occurred. I also degreased them aggressively.

This is where that left the panels:





Ugly, but the surface is now prepped better. Some of the places I stripped back the dye were pretty shiny, which implies I didn’t degrease or sand them well-enough back in the day. I remember there was a LOT of Armor-All on there.

The vinyl dye sprays really strangely. If you spray a wet coat, the surface dries to a weird hazy look. I’ve discovered the best thing to do is dust the paint on there in many light coats. It takes a long time but provides the best results. After a couple days, I buffed the surface with a blue towel to even it out:



Before:



After:





To be continued

 

I had originally thought I would make the new speaker panels out of wood and varnish it, but the more I thought about it the less sense this made. There had to be better materials for this. The wood was still good for a mock-up though:





The black plastic thing is a prototype water-shield I made and 3D printed. I forgot to take pictures, but basically it acts like a hood on the back of the speaker to prevent any water landing on it from above.

You can see what I meant about clearance. The speaker still doesn’t want to be in the center of the opening. The door card also doesn’t sit as flat as it should, since the wood adds thickness.

It was at this point that I decided to toss out my earlier panels and start from scratch. They were built around the idea of getting something that took minimal door modifications and made it work, so I was fighting my own old designs.

Starting with some cardboard, I cut a new panel that used the same four mounting holes but covered the widest area possible. This left no air gaps and maximum space for the driver. At the same time, I also carefully contoured all of the edges so it sits as flush as possible against the door with minimal added thickness.

Then I offered the door card up to the panel again and traced out the available space:





The triangle is the opening of course, and the round circles are possible driver locations. This was definitely helping, and the next thing I was fighting was the opening in the speaker grille:



From the back, you can see Mazda only actually drilled any openings right over the 5 ¼” driver’s opening. I realized I could widen my options by drilling more holes. I removed the fabric, then popped it on the drill press and went to town:



As you can see, this allows for a much more optimal driver location. It can be pushed further forward while maintaining maximum free surface area. I originally wanted to reuse the factory material to cover the grill, but I found that it was faded and beginning to tear in a few places. I ordered some fresh fabric, and here is the comparison:



The pattern is very slightly different from OEM, but I can find a way to live with that.



I covered the grill with the new fabric. Using spray-adhesive, this was only a 5 minute job per side. I’m quite happy with the results. If you hold it up to the light you can see how much more opening it leaves me with:



But when installed, it looks OEM:



Well, except the pattern being slightly different. It’s not something anyone would normally notice. But I’ll notice…

Looking at the back, you can now see all of the available space we have:



To be continued

 

As far as materials, everyone seems to like MDF. Frankly, I don’t get it. The only thing worse than wood as far as moisture is MDF. They make a lot of sense indoors, but for a car door it seems like a poor choice unless you’re 100% confident in your vapour barrier. And well, you’ve seen my vapour barrier.

I saw some people talking about HDPE. I ordered some, but unfortunately I realized I would need it to be pretty thick before it was rigid enough. Probably around ½”.

As I was getting ready to send the HDPE back I was talking about it with my dad, and he asked why I just didn’t use “the white plastic”. I asked what he was talking about, and it turned out we had a pretty sizeable flat piece of this white plastic stuff:



Neither of us knows what it is. He’s had it for years waiting to find a use for it. It’s got paper on one side (presumably to prevent scratches while working it).

And wouldn’t you know it, this stuff is perfect. It’s very rigid, easy to work with common woodworking tools, it’s waterproof, and the paper even prevented me from scratching it (not that it matters for this application).

It feels sort of like lexan, except that it cracks a bit more easily if you drill too aggressively. It also makes a weird smell when drilled.

I stripped the paper off by leaving the panel in warm water for awhile (I don’t want soggy paper inside my door), and this is what is left:



Neat! You can see what I meant about the contours here. Those let it sit further down in the stamped door panel, increasing clearance for the door.

You may also notice that the mounting holes for the speaker are really large. That’s because this bracket was included in the box:



I wasn’t going to use it initially. I don’t think I’ve ever actually used the mounting hardware included in a set, since they assume you have a wide flat surface to use and I have never found that to be the case.

However, when thinking about the plastic frame for the driver and the plastic panel, I figured the extra rigidity offered with the steel ring would be a good idea.



Installed. I’m quite happy with how it turned out, especially compared to the panel I made last time. We’ll come back to the speakers themselves in a minute.

It was time to reassemble the door cards. This is something I have discussed before, but I thought pictures may be interesting. First, this weather strip pops into the top of the vinyl and then the little tangs fold under to retain it:





Then the insert can go in. It’s held in with these tiny little screws and washers.





I always end up with a few “extras” afterwards, but this time I made sure they all went back where they should. Well, I was two short. I’m going to have to dig around in my bins to try and find some spares (which I definitely have, someplace).

The handles goes on at the same time, and is held in the same way. Except that it also has these little post things, onto which a round washer-looking clip pops:



The best install tool is a small socket. There’s no great way to uninstall, so just get two thin screwdrivers and gently work it upwards if you’re in that position.

Next the vent goes in, but I decided to call it a night at that point. The next day I went out to continue the project, and disaster had struck:



I had been organizing all the hardware and whatnot for each door in a Ziploc bag, and overnight one of the bags fell from the box I had left it on and the vent face had shattered.

It’s my own fault for being careless with it. Now it needed to be fixed. I don’t have a spare black vent, and new ones aren’t cheap. I may still purchase one in the future, but for now I had a spare maroon vent face:




Well, it used to be maroon. This is what happens to maroon Rx7 interior parts with enough time and sun.

To be continued.

 

We’ll come back to the vent situation shortly.

One minor thing I wanted to fix was the door wiring. Keep in mind, everything worked fine. It just wasn’t very neat. The first and easiest thing to address was the connector for the power lock. I’m sure most of you are familiar with the Deutsch DT connector. If you aren’t, it’s a really easy to use and relatively affordable solution for waterproof connections:



You only need to crimp the terminals onto the wires, pop them into the back of the housing, and then insert the wedge-lock. Then you have a waterproof connection:



With that sorted out, the next thing to do was to replace the existing power-window relays with waterproof ones. These ones were pretty affordable on Amazon, and Amazon relays are just fine for a non-critical application. I had originally used two-position .250’ connectors to make the whole power-window relay setup plug and play, and those connectors were fine. So I ended up splicing downstream of those wires and using solder with adhesive-lined marine heat shrink tubing:



Apparently solder in automotive wiring is controversial, but I think it’s fine for this application. It’s a straight run of wiring with no bends, which will be well secured under the door panel for the rest of its life. I probably wouldn’t want to solder a joint in the middle of an engine harness that will flex around during install, but for terminals or straight runs it doesn’t worry me at all.

I wanted to mount them with a nut and bolt, but that put them in an awkward position uncomfortably near the window. Alternatively, they would fit on the interior side of the door, but then the door card wouldn’t sit right. So I settled for liberal zip-tie use in multiple locations:



I also can’t leave those gaping holes in the door seal, now can I? I hadn’t noticed any water ingress into the car, but water had definitely leaked into the door past the ancient window seals, so it might shorten the lifespan of the door card or cause mold.

The old seal was held on with bitumen. While I don’t like working with bitumen, it is still easier to deal with than double-sided tape. So I ordered a new bitumen roll:



Removing the old bitumen took a few hours and quite a bit of enamel thinner, but it ultimately came out clean.

There’s no great way to apply the new plastic sheet, because the moment it touches the bitumen it will not want to come off. So you really need to be sure before you press the sheet down. I saved myself some time by using the old sheet as a template, pre-cutting the holes for the power window connector and door latch rods, then installing the sheet onto it and shoving it into the hole in the door frame.

Then I rolled the new bitumen on. I followed the existing track, except for a detour around the new speaker panel. The panel seals to the door with foam, so I don’t need to worry about water leaking past. It looked like this:



And then I started from the corner near the speaker and worked my way around:



And there we go. After a bit of trimming it was ready for the door card. Speaking of which, where did the speaker placement end up?


Please forgive the obvious water spots on the lens.

Still not perfect, but about as close as I can get without visibly altering the door card. I might be able to go up ½” further and forward a little bit as well, but then there’s almost no frame behind the speaker panel for the foam to seal against. So this will have to be enough.

To be continued

 

Detouring back to the door card, it was time to inspect the door vent a bit further. There’s a small crack along the top, but it’s better than the other one. So I prepped and painted it with the same Duplicolor dye as I used on the door cards. Then I installed the black vent parts onto it.

The little vanes pop into these pivot point things:



Then the back housing clips on (nerve-wracking when the part is ~37 years old):



Then the little dial goes on, and it engages with the post for the innermost vanes:



And the vent is complete:



It’s not a 100% match to the OEM vent, but it’s fairly close:



And with that, I put the vents back into the door cards and reassembled. I tried to be gentle on install, but tightening the screws down into the vent plastic I did hear some splintering sounds. I’m thinking a new set of OEM vents should be on the short list…

Thinking about it, the door vent opening is actually a good location for a speaker. I think I remember Styx doing that on one of his FCs at some point. The only downside is that you lose the vent functionality.

Also, I feel like someone has mentioned this in the past, but it’s weird that FCs have the vent in the door. Most cars have the vent in the dash itself and then the door has a depression near the dash, but in our cars the door wraps around to the dash and the vent flows through. Neat.

I also zip-tied the crossovers inside the doorframe. No picture because I can’t take a picture inside a doorframe. I put them in locations where moisture wouldn’t reach them (I checked after it rained and they were dry) but I also put them in Ziploc bags and zip-tied them shut with the open end downwards. That should be acceptable as far as preventing water ingress.

The 5 ¼” speakers I was running before were a component design, and I had mounted the tweeters on the door triangles in these 3D printed pods. They were pretty good, but the silver ring on the tweeters bothered me. Conveniently the new tweeters seem to be identical, except that they’re all black.

I modified the 3D design and printed two new pods:



The barrels are an exact fit for the tweeters, so they just pop in, Then the entire thing mounts to the door triangle with two screws, and it pops onto the door:



Meanwhile the door card itself looks completely unmodified from the exterior:





And there we go. It’s all installed. It’s a bit underwhelming since I can’t actually demonstrate it for you, and the car looks almost no different from before. Except the black door inserts.

So, did it work? Well, sort of. The sound is definitely a vast improvement over my previous setup, but I still don’t find the vocals as clear as they should be. Cymbals and the higher range of the vocals are clear from the tweeters, but the real body of the human vocal range isn’t as present as I want. It’s not bad at idle, but when driving it lacks something. The subs can now be tuned with the crossover at a reasonable level though, and there is a good amount of punch coming from the doors that just wasn't there with the 5 1/4" drivers.

The next step would be a DSP and maybe some 4” speakers under the dash, but that’s a lot of expense to go to. I think before I make any further changes to the audio system, I’m going to replace the diff and subframe bushings (which are definitely bad) and minimize cabin noise while driving. I might find that I don’t actually need the extra speakers at all.

The door card inserts no longer match my maroon seats, but at some point I want to reupholster my spare GTU seats anyways and have an all black interior.

Until next time

 

That's a decent plan, and I was thinking of something similar in the past. Apparently you only need a small opening for a subwoofer, so you could easily cut the carpet to add a vent or something. Or if you're running a big sub really low (like 40Hz and under) it would probably even sound fine with the carpet. You might still need 8" subs in the towers to fill the 40-80HZ area with that setup.

For me, the 8" subs in the towers are the easy button. I mostly like music with clear vocals and instrumentals (Fleetwood Mac, Red Hot Chili Peppers) and don't need the area below about 60HZ to be super loud. The 15" sub in my Celica is better, but it eats up a ton of space and weighs a lot. I do have another identical 15" sub around though...

 

did you put foam in FRONT of the driver between the speaker and the door card? it helps "funnel" the sound. we used to sell these kits. the big center goes on the door for waves, one went between the speaker and the mounting surface, and the biggest went on the front of the speaker to seal it to the door card.


that looks like white acrylic for making things like signs. another great option is expanded pvc. you can buy it in 4x8 sheets at the hardware store. cuts drills and routs exacly like MDF with no dust(just chips) and its 100% waterproof.

 

I actually tried two such solutions; a silicone baffle, and a foam ring setup like you linked. Neither one fit properly under the door and they were too firm to compress properly.

That being said, worst-case scenario I can just shave the foam down in the bottom half of the opening to fit. It's a good thing for me to try before spending any more money on audio equipment.

 

the one i linked goes from a couple of inches to nearly flat with little pressure. its a very open cell and squishy . try a different foam.

 

cool project! you mention the diff/subframe and on my car the new exhaust is a such a different frequency than the old one that noises in the car are actually more audible, despite the new exhaust being louder (probably)
when i put the silencer in the new exhaust, its like someone has an EQ and just takes away all the noise under, i'll say 6k, which sounds better, and makes things even more audible. (my diff is really loud, and its getting worse i think)

and then B Grill Cloth, the guitar players in either trying to get Eric Claptons Beano tone, or Eddie Van Halens first album sound have played with grille cloth, as Marshall had a bunch of different ones. its a total rabbit hole, but here is a peek
i kind of wonder if it would be better if instead of a bunch of holes the grill cover was open?

 

I went out this morning and installed the foam rings I had purchased back in the summer. I had to cut a lot of the height down and I'm still not 100% sure how good a seal it is, but it definitely made a difference.

I was able to play with the EQ settings to get it to sound pretty good with the car off. In fact, if I could get it to sound that good all the time I would be quite happy with it.

Then I went for a drive and it was basically impossible to hear. I always knew the car was loud, but only after not driving it for a few weeks do I realize just how loud it truly is. I definitely need to do something about the bad bushings, and then find a way to quiet the exhaust down too. At least I know the stereo isn't the issue

I know for a fact my differential bushings (the rear two) are original to the diff. I replaced the front mount so it no longer flops around, but the rear two are definitely causing a lot of vibrations when driving. I also have original sub-frame bushings (rapidly closing on 400k km), and poly bushings on all the control arms.

The exhaust presents a bit of an issue too. I don't really want to spend on it since I'll be replacing the forward section when I swap engines anyways. The turbocharger itself will also probably help with a lot of the noise, especially since I'm running the Racing Beat REV TII exhaust. Without a turbocharger in the exhaust stream it's a lot louder than designed. I like the sound from the outside, but I spend 100% of my time on the inside where the drone is really loud and quite annoying at highway speeds.

 

Going off what jd said above, you can cut the entire center area of the metal grille frame out and just have the edges. The stretch cloth doesn't care.

 

Oh and look what I got today

 

I could cut the triangular grilles into just frames, but then the cloth would stretch flat across it and not convex like the OEM part. I like the convex shape.

Everything looks brand new!

Also, those are really long lower arms. I know wishbone suspensions do that to gain negative camber during compression, but boy is it noticeable in this picture.

 

If you’re on the stock radio your next step might be an amp or another radio. Mine came with a 55 watt unit and I installed some 65 watt speakers in the doors and they are very easy to hear. Granted I have basically a stock exhaust but I also still haven’t done anything about the fact I’m missing all my sound deadening because it smelled like mouse. I’ve got some new 4 inches for behind the seats and 2 8inch subs but I don’t have an amp for the sub yet.

 

I'm running a 90s Nakamichi head unit, and two amps. A ~300W for the subs (set at low gain) and a smaller one for the front speakers.

Thinking about it, I'm only using a 55W sub for the fronts and they probably would benefit from some more oomph. But the biggest problem is the road / exhaust noise right now, so I think I'm going to have to address that before I throw more amplification at the problem.

Where are you putting the 4 inch speakers behind the seats? They will go in the shock towers if you use the stock adapter pieces, but they're not very useful back there due to the location.

EDIT: Wait, I forgot you have a vert. So those 4" speakers will go in the headrest I assume?

 

The car didn’t come with the factory seats but there are 4 inch speakers right behind the seats in boxes that aren’t rated for 55w so I figured I’d replace them. I’m constantly looking for a somewhat affordable pair of vert seats in my area but have yet to find anything.

 

Gotcha. I ran some boxed 6x9s in the hatch for awhile, and they worked pretty well. The position isn't exactly optimal, but they're at least pointed towards the occupants.

Seats are tough because you can't ship them, and because lots of them weren't stored right. Either they have holes in them, or mice got to them, or mold from moisture. You have to find a good set within driving distance, and nowadays they also cost an arm and a leg. Especially TII seats, which I really like.

My current seats are basically mint, except a bit of wear on the driver's bolster. And they're GXL seats and in the wrong colour. So I will eventually be swapping them out, but I intend to keep them as perfect as possible until then.

 

I was told mine are Toyota tundra sport seats, they’re alright and the headrests look kind of cool.

 

mine were like two round rocks, totally transformed the car. they came out really easily too, there is a lip, and you can hit it with a chisel (screwdriver), and usually you need to work it around the edge, but if they are really bad, they will just fall out, like mine.

with the exhaust mine is kind of easy, its a huge diameter single, so i can play with the diameter of the tailpipe using a silencer, i bought an adjustable one from Amazon, and it wasn't obvious what the adjustment was, but it has some extra cutouts i could open up, doubt it will make any difference. the tip is really hard, none of my drill bits will do more than scratch it, so i made this goofball adaptor


its harder to do something like that with the RB setup, you might just try the turbo

 

Removing it isn't too big a deal for me, but installing is. I don't have a press, and I can't hold my differential in a vise.

I do, however, have a hydraulic log splitter... That might work with some careful planning and a helper to press the power button while I hold the differential up.

 

I’ve seen people set them up and then hold a torch to the outside and melt them out, would that work with these or are they different?

 

They do work with that method for removal. I've done that on the control arms in the past.

Installation really requires a press, or at least a really big vise and a long tube to put on the handle.