[Derrick_B]

I have been thinking about replacing the Bose sub since the day I got my 3. At first, it was going to be totally stealthed inside the jack area. After taking the panel off and taking some measurements, I ditched that idea. I would have had to cut my interior up and I really didn't want to do that. I didn't want the sub under the floor and I didn't want a big, heavy MDF box.

The best option seemed to be the passenger side back corner. I took some packing peanuts of the same volume my sub would need and tried to get an idea of the space I would need.

Then I tried to work out how I wanted it to look with a rough Photoshop edit. This still isn't what I want, but it's an idea.

I carefully removed the bag of packing peanuts and traced the face of it. Then I changed the shape to something more like I want. This will be my baffle template.

The template and bag of peanuts gave me good idea of what area to fiberglass, so I taped it off and laid down about 2 layers of mat. No, the tape didn't leak

Before I laid the resin and mat, I sprayed Pam as a mold release. It worked pretty well, as most of the tape came off. There is a little wrinkle in the glass on the bottm, but I'll take care of that.

Here is a pic with the template to show the general shape I want.

This pic shows the depth of the notch I molded and how little floorspace the enclosure will actually occupy.

The enclosure WILL NOT be fleaced. Honestly, I think a lot of fleaced projects look horrible and they're just shortcuts. The contours I want will make it look a lot more OEM. To achieve this, I will be carving some stryofoam to put in the void and spraying gaps with expanding foam. The enclosure will be finished over that. When I'm done, acetone will dissolve the foam and it will wash out.

That's all for now

 

[glennk]

Very cool! Sad to hear that the jack area wouldn't work. I'm going to see what I can do to fit the replacement woofer in the spare housing.

 

[IndyMatt]

Yeah I too want to do something similar! I have no idea how to use fiberglass but I am pretty handy. Where did you get all of the supplies? What size woofer is the box for?

I think I can make the spare tire area work, might need to create a raised portion to fit a sub in that area with the spare still being in there. I will more than likely take it to a shop, with my son I just don't have the time like I used to have.

GOOD WORK!

 

[Derrick_B]

Very cool! Sad to hear that the jack area wouldn't work. I'm going to see what I can do to fit the replacement woofer in the spare housing.

You could make the jack enclosure work, but you'd have to cut out the area underneath the access panel. There just isn't enough room otherwise. If you look at it, you'll probably see what I mean. Another complication is laying the fiberglass in such a way that the box is actually removeable. It the enclosure is even slightly bigger than the hole in the trim panel, you'll have to cut it out if you ever want to remove it.

Yeah I too want to do something similar! I have no idea how to use fiberglass but I am pretty handy. Where did you get all of the supplies? What size woofer is the box for?

I think I can make the spare tire area work, might need to create a raised portion to fit a sub in that area with the spare still being in there. I will more than likely take it to a shop, with my son I just don't have the time like I used to have.

GOOD WORK!

Thanks This is a box for a single 8" sub, but you could easily fit a 10 or 12 by shifting the boundries of the enclosure. Just about everything I will be using is available from Home Depot, Lowe's, or any large lumber yard/hardware store. Some of it is even available at Wal-Mart. The only specialized equipment is a fiberglass roller I used to remove most of the bubbles for added strength. I got that from an auto body supply store. This is my first fiberglass project, so I'm learning as I go. However, I have a instructional DVD and have done many hours of research. I say go for it. The tape and fiberglass work only took a couple of hours. I intentionally used less hardener to give me more time to work the mat and resin, so it took longer to cure. Still, between the time I came home from work and went to bed, it was done. Now that it's out of the car, I can work on it as I have time and you could do the same. You can do it!

I would build the sub into the spare tire, but I don't want the bass muffled under the floor and I don't want to fab a grille into the floor either. I also want to use that area to mount my amp. More on that later. I may build a spare tire enclosure for grins after this anyway. I'm always looking for a project.

 

[BSUBigMac]

Derrick you really are like friggin' MacGyver!!!

Good work, it looks awesome!

 

[ChrisJuede]

Wow dude...again, I am impressed. You keep pushing the boundaries, and you ahve definitely earned your title as resident MacGyver...I am excited to see how this turns out, as I was thinking of putting a sub there too, but all of my stereo mods will take place after the performance and teensy visual mods I am first doing to the car. I am saving up to be able to just throw down for intake, exhaust, and whatever other parts I need for performance all at once....Even though they wont all come out at once....:crybaby 1:

 

[Derrick_B]

Derrick you really are like friggin' MacGyver!!!

Good work, it looks awesome!

Thanks

Wow dude...again, I am impressed. You keep pushing the boundaries, and you ahve definitely earned your title as resident MacGyver...I am excited to see how this turns out, as I was thinking of putting a sub there too, but all of my stereo mods will take place after the performance and teensy visual mods I am first doing to the car. I am saving up to be able to just throw down for intake, exhaust, and whatever other parts I need for performance all at once....Even though they wont all come out at once....:crybaby 1:

This is easy stuff and it's been done a million times. I'm confident that just about anyone could do it if they took their time. Money is starting to be an issue for me too, so I feel your pain. Nothing a little self-deprivation can't fix

 

[vcp]

I have been doing a lot of research as well and was really hoping to put a JL 8w3 into the jack compartment like I have seen on so many previous models of the Mazda 3. I have also been concerned with the amount of space available and have been trying to determine if in fact there was enough. So by the sounds of it, there is not.... without cutting the inner lip of the compartment which really sucks. I am really interested to hear and see how your project comes along. This is something I was hoping to to this weekend but I just may have to wait to see how you make out.

 

[Derrick_B]

I have been doing a lot of research as well and was really hoping to put a JL 8w3 into the jack compartment like I have seen on so many previous models of the Mazda 3. I have also been concerned with the amount of space available and have been trying to determine if in fact there was enough. So by the sounds of it, there is not.... without cutting the inner lip of the compartment which really sucks. I am really interested to hear and see how your project comes along. This is something I was hoping to to this weekend but I just may have to wait to see how you make out.

If you can figure out a way to make it work, please go for it an post instructions/pics. I would really like to put my 8 there, but it looks tricky. I'm not really confident that a single screw (jack bolt) would hold it either. Kind of makes me uneasy. There is a safe area back there to drill out and epoxy a nut though. I had that figured out and the baffle too. You should just be able to router the edge of your 3/4" MDF to 1/4" to keep it from sticking out. Lack of available airspace without hacking the panel was my only concern. If I could find a cheap salvaged panel, I'd seriously consider it. The jack WILL fit inside the spare tire rim, btw.

 

[vcp]

If you can figure out a way to make it work, please go for it an post instructions/pics. I would really like to put my 8 there, but it looks tricky. I'm not really confident that a single screw (jack bolt) would hold it either. Kind of makes me uneasy. There is a safe area back there to drill out and epoxy a nut though. I had that figured out and the baffle too. You should just be able to router the edge of your 3/4" MDF to 1/4" to keep it from sticking out. Lack of available airspace without hacking the panel was my only concern. If I could find a cheap salvaged panel, I'd seriously consider it. The jack WILL fit inside the spare tire rim, btw.

Yeah I was thinking the same thing about the single screw, but the weight of the box should be minimal and with say 7 or so layers of fiberglass this thing should be quite strong. Was wast thinking of also rigging something up to take advantage of the slots already in place for the compartment door to help stabilize the enclosure. The airspace is definitely a concern. I have some packing peanuts somewhere, so I just may borrow your idea to see the actual amount of space required. I did test the jack out in the spare already as well as I was not prepared to give it up. I have read that most people just wrap it in towel and they are good to go.

I am curious, how much resin and fiberglass mat have you used so far, and how much do you think you will end up using by the end of your project? I am trying to figure out my material costs.

 

[Derrick_B]

I was only concerned about the jack box mount point because some first gen owners had issues with theirs. Many ended up using another threaded hole in that area to secure the box. Unfortunately, it doesn't appear that we have that option.

So far I have used a quart of resin and about 12 square feet of fiberglass mat. Be advised if you want to fiberglass over foam, you will need to use epoxy resin. Polymer resin will eat the foam. If you aren't using foam, then don't worry about it.

 

[Hybr1d_7h3ory]

This is friggin sweet. I always find something new and interesting on these boards. I agree that fiberglass looks a lot better than the fleece jobs, I might have to give this job a go once I get my amp and install it.

 

[E.Tinker]

Great work! Looking forward to seeing the final results! :yes:

 

[Zlog]

if you havn't set the speaker just yet, i was going to make a suggestion to have the sub angled a little bit. despite the fact that the opposite wall of the car is not flat and paralell with the sub speaker, having it tilt at an angle towards either the back seats or the the trunk (i'd go towards the seats and maybe upward a bit) would help make SURE that you didn't have any phasing at any frequencies.

 

[Derrick_B]

if you havn't set the speaker just yet, i was going to make a suggestion to have the sub angled a little bit. despite the fact that the opposite wall of the car is not flat and paralell with the sub speaker, having it tilt at an angle towards either the back seats or the the trunk (i'd go towards the seats and maybe upward a bit) would help make SURE that you didn't have any phasing at any frequencies.

Thanks for the suggestion. I haven't fiberglassed the baffle in yet. I will probably angle it slightly toward the back seats.

 

[Zlog]

no problem. Honestly you could probably do whatever looks the nicest and most natural since the opposite side isn't flat, but you can completely avoid it altogether with like a 20 degree tilt upwards and inwards so that it is essentially projecting the sound into a corner which should make it radiate nicely.

Since you're building a sealed sub you can suffer from phasing a bit more then you would on a ported sub. Sealed subs, imo, always sound better though when they aren't fighting themselves. You'll have some real clean notes coming out at all frequencies!

Best way to fight phasing if you really want to be picky is buy a crappy box from cartoys, and just use it temporarily to mount your speaker in. doesn't need to be perfectly sealed and mounted, just something that will let you find the right angle. Run that with a LFE rolling scale and adjust until the note is smooth all the way through.

Would you mind giving me an idea what you spent in materials for the enclosure? I've always wanted to do my own, and i've finally got my OWN car to do it in, not a car i have to share with the wife

 

[Derrick_B]

Update.

I laid a lot more fiberglass. I think I have about 28 square feet in it and 3 quarts of resin (yeah, too much. I know). In this pic is the outline for cutting as well. A lot of "eyeballing" here.

Shell is cut and baffle is complete. It's made of 1/2" MDF and the sub is recessed 1/2". More on that in the next picture.

Here you can see how I chose to do the recess. The sub mounts with 8-32 stainless hex screws to tee-nuts. The tee-nuts do stick out into the speaker cutout a little, but they do not hit the basket. The two layers of MDF are glued together and also secured with screws. The two braces are unnecessary and just for mockup purposes.

Test fitting in the car. Hard to tell in this pic, but the weight of the sub is compressing the carpet cargo mat toward the front of the enclosure. This is causing the enclosure to tilt slightly. I will address this by building-up the surface about 1/8" with bondo. That, plus the enclosure carpet, should take care of it.

The hatch DOES close and there is actually plenty of clearance. I was a little worried about it, but no big deal.

Next on the agenda is stuffing the enclosure with foam, shaping it, and attaching the baffle. I should have no problem getting that done before the epoxy resin arrives on Thursday. I love U.S. Composites, but their shipping is SLOW.

 

[Derrick_B]

...Would you mind giving me an idea what you spent in materials for the enclosure? I've always wanted to do my own, and i've finally got my OWN car to do it in, not a car i have to share with the wife

Man, I don't really know. Off the top of my head, I can tell you this...

I have used:
A little over 3 packages of 8 square foot fiberglass mat
3 quarts of polymer resin
1 2x4 sheet of 1/2" MDF

I will be using:
1 quart of epoxy resin
Probably another quart of polymer resin
At least one more package of 8 square foot mat
Some bondo (I had a gallon of it already)
Part of a 4x8 sheet of 1/2" pink foam insulation
Self-expanding foam
Package of Poly-Fill
Automotive carpet

Then there are the little things, like hardware, disposable gloves, dusk masks, brushes, glue, and tape. I didn't keep my receipts, so I couldn't tell ya. I'm having a good time, so it's worth the cost to me. I'm not doing it the cheap way, that's for sure, but it's going to look the way I want. That is more important to me.

 

[twowings]

Nice work ! That's going to look factory.....

Next project: Hood Scoop ????

 

[Derrick_B]

Nice work ! That's going to look factory.....

Next project: Hood Scoop ????

Thanks. That's the whole point

Lol. No, I don't think so. It wouldn't be functional and that's not my style anyway. However, I may think about making a lip/splitter. I think making my own would be pretty hardcore, but that will be way down the road. Hopefully some good lips come out before then.