I have searched through the threads but haven't seen this particular subject. I'm looking at fabricating a complete composite subwoofer enclosure within the spare tire well of a 98 Saab. There will be a dividing wall in the center creating two seperate chambers. Considering that aspect I believe that I'm going to make 2 different foam plugs and wrap them individually with resin infusion. Then I will cut out the holes for the subs and extract all of the plug material. Then glue them together with polyurethane adhesive to install them into the well. I would like to use a combination of carbon(exterior), glass fiber(center filler), and aramid(interior shell). This will be my first use of this resin infusion. 1: What thickness would you recommend making the walls and what layers of the above materials would be best? I would rather it be too thick than be subject to cracking considering the amount of pressure and vibration from the subwoofers. 2: Can you see any problem areas with this process?

Wrapping the foam core with fabric via resin infusion won't be simple as its a 360 degree part so youve got to get the resin all round.  You might find it easier to wet lay and vacuum bag.  You need to make sure your foam is suitable to take vacuum.

If you want it nice and chunky then I'd go for around 1.5mm thickness which based on a rough 200gsm/0.25mm thick layers i would go for a couple of layers of kevlar on the inside, 3 layers of woven glass and then 1 layer of carbon for the cosmetic effet.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I had the same idea. Please post pix of it when you are done. MDF boxes are so heavy

What kind of upper frequency cut-off are you looking at on the Sub?   A CF/Glassfibre composite "box" will have rather high frequency "ring" to the walls because of the stiffness of the composite materials.

If you are going for a low (below 80 Hz) cutoff (which I would, considering the placement of the sub) then it will probably not be a problem for the sound, but ALL the "home-built" composite Sub-enclosures, bar a few, that I have heard were "buzzy" as heck...

I once made an enclosure for a spare-wheel well for an Audi, I made it as a two part construction, one "bucket" with a dividing wall and perforated extra walls to add stiffness to the "bucket", this was made from hand layup glassfibre and laminating resin, i covered the inside of the wheel-well with a 15 mm layer of selv-adhesive foam "sound-mat" and put a plastic bag (Bin-liner) on top using a little bit of spray adhesive.
The I built the "bucket directly in the "well" I used pieces of flat laminate, already finished and cured to support the dividing wall and the supports.

I made a "lid" for the bucket as a CF/ glass sandwich construction. Since I I already had the Sub-speaker, I made a "ring" from solid CF tape to fit the flange of the speaker,with laminated in M6 aluminium studs.
This ring was made directly on the speaker (a bit risky -- i know ... but judicious use of vac-bag film and wax made sure that nothing got stuck to the speaker.. )

The ring was laminated into the "lid" which was made as a vac bagged hand layup.. two layers of 200 g twill on the top ... layup was done on a glass plate ... I made up a thick "paste" of heavy Zircon-sand (the stuff used for sandblasting) and put down a thick layer of that on the back of the lid, to make a "dead" material, the same stuff was added to the inside of the "bucket"  (all after the layup had fully cured and the peel-ply was removed.

The sound was very good, no "buzzing" and the guy who now owns the car, is very happy with it :-)



 

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)