Custom car audio

[danf]

Well. I've had enough and want to take out my subs. I'm tired of them taking 2/3+ of my hatch space. 

More seriously, I have two 10" MMats Pro subs, bought waaaay back in 2002. The problem with these subs is twofold: they're old and the surround is falling apart (no refoam kits ), and they take up soooo much space.

Nowadays though you don't need multiple subs to have decent bass. They also make some decent powered shallow mount subwoofers. Shallow mount enough/low enough cubic feet that a single 10 can fit in our spare tire wheel well and retain the factory wood floor.

So, the 10" sub I found only needs 3.25" of mounting depth. It also only need .5 cu ft of space for a sealed box. The sub is a dual coil sub with RMS handling of 400-500W and decent excursion of 1.2". Is it cheap? Definitely no, especially when compared to Walmart value subs. I can buy 8 Pyle subwoofers for the cost of one of these. 

I can probably even fit the two small amps I have under there with a sealed box. It will require some custom work... haven't done that in ages.

I figure the easiest way is to get something round like the tire and use that as a sidewall. I can do this a couple ways: first way would be to get a shop to router me out 5 pieces of 1" MDF that will be perfectly round and have a minimum of 3/4" all the way around. This will be perfectly round and I can laminate them together... although getting a shop to make the circle will likely not be cheap.

I think the second way is probably easier and I can probably do it with tools I have lying around. I was thinking a 12 sided circle  which would probably have length about 6" apiece. Each piece would have an angle of 7.5 degrees. I can manage that with my chop and table saw.

Once they're together it's a matter of fibreglass-to-fit.

Well, I rambled on for a while. I can't think of any other ways to get something round that can be used as a starter point for fibreglass, anyone else have any ideas?

[ozzie]

Well. I've had enough and want to take out my subs. I'm tired of them taking 2/3+ of my hatch space. 

LOL! I used to have a pair of 10s in a ported box in the back of my EG hatch! I had them for maybe 2 years before I got tired of them taking up over half the trunk.

For cutting circles in plywood, pick up a jigsaw - you can get a cheap one for under $30 at lowes, home depot, or harbor freight, or else I find better quality ones at yard sales/pawn shops all the time.

[sirdan]

I think you can also buy wooden rings for the speakers, but id rather spend money on the jigsaw and have another tool. I want to one day make a speaker box that fits in my quarter panel so the speaker face is flush with the cargo area and doesn't really take up additional room. Probably wouldn't be the best sounding box possible but I doubt id notice that anyway.

Here is an example someone did very professionally.

[danf]

Well, the problem with laminating circles is the massive MDF waste. I still am scratching my head a bit.

I have time to try multiple things. I've been meaning to do this since I discovered the missing sub surround a couple of years ago. I still like some bass though, but I really don't want it taking up all the space in the hatch.

[danf]

I found this calculator which will make life easier. A multiple side speaker box sounds interesting, lol. Then I don't have to deal with so much waste of 3/4" MDF (which is pricey here.)

[danf]

So after using the calculator and doing some maths, I've got a rough idea what it'll look like. Dodecagon box, here I go!

[danf]

Finally the rain broke and I was able to drag out the table saw.

Hopefully I didn't make the thing too big...

Edit: I ripped 3/4 MDF to 5.25" wide. This means with the top plate it should be close to flush with the floor. Our hatches are a bit uneven though, the passenger side of the spare tire well is lower than the driver's side. Each piece is 155 mm long, and each end is a 15 degree angle (15 * 2 * 12 = 360 degrees.) It was just easier to work in millimetres, dealing with 1/64" was going to be a pain in the arse and I didn't have any measuring tape that went that small. I did find my metric measuring tape though. 

Edit 2: So I did some calculations, that box's internal volume as it sits is at 1.11 cu ft. So I actually only need a little less than half for the subwoofer (0.5 cu ft, including the displacement of the woofer), maybe I can step it down some to make the amps fit.

Making progress!

[corax]

Jigsaws are awesome and cheap.  I use one for a lot of my small wood projects, as well as cutting steel up to 1/4" thick (4-5" diameter is about the smallest I can get with steel).
To reduce MDF waste, if the surround is multiple laminated layers, can you cut several half circles and stagger the ends when you glue it all together?

[danf]

I actually have a jigsaw. My OCD was more how to get a perfect circle which is really hard with a jigsaw. Back when I had access to a CNC I would've just made them there.

What I tried with the dodecagon box used very little material actually - about 16" x 26". I still can try doing some half-rounds later if this way doesn't work out.

[ozzie]

I actually have a jigsaw. My OCD was more how to get a perfect circle which is really hard with a jigsaw. Back when I had access to a CNC I would've just made them there.

What I tried with the dodecagon box used very little material actually - about 16" x 26". I still can try doing some half-rounds later if this way doesn't work out.

Just an idea I had, use a scrap piece to make an arm, call it 2" wide by the radius + 2" long. Mount the saw at one end, and drill a hole in the other end, so the distance from the blade to the center of the hole is the radius. Drill another hole in the center of your circle, bolt the arm to the plywood, and you've got a perfect hole cutter.

[danf]

Hey that's a great idea. I've done something similar to mark a circle, why didn't I think of that. 

If this method doesn't turn out I'll try that method. When all else fails, there's always the belt sander. 

I should be able to see if my dodecagon box will fit today...

[danf]

Well, the dodecagon box fits OK.

After doing some more math I think I'll need a tad less than 1/2 the space though. I did funky math while averaging to try to figure out how much area the little bump in the middle of the wheel well is. After I 'glass it up I can do a more accurate measurement and reduce the internal volume accordingly. This may leave me with enough space to mount the amps, so that's a bonus.

[danf]

More success! I should be really close to the half a cubic foot required.

Unfortunately for me I don't have any fibreglass supplies that isn't really old. Resin has a shelf life, I found that out last time. Most of the stuff I have is 2+ years old, not going to try it.

I will be able to use the lower platform to bolt the whole thing down so it won't move. 

[twotone_ra64]

Looking good so far! I was going to suggest doing something like this but reading that you wanted to build something proper, I restrained myself.

[danf]

Sooooo I just spent 11 minutes 5 seconds watching that video. Was kind of funny. I've seen quite a few MCM videos but not that one. 

I finally picked up some resin, etc. Maybe this weekend I'll 'glass up the car some.

I haven't actually bought the sub yet. But at least when I do I'll be ready for it.