Lightweight Foam Core Sub Enclosure Project
 

I figure this has at best a 50% chance of success (defined as - functions and sounds good enough that I choose to use it instead of trashing it), but I am going to try and make a lightweight sub box.. Think it will work? Vote in the poll!

Tentative Enclosure specs:
Zenclosure-style with an Alpine Type R 8"
3" Round Port (Oversized for Alpine Type R 8, to reduce port velocity since I will need to put a sharp bend in it)
Port tuned to 37 Hz (Recommended for Alpine Type R 8)
Net volume ~0.7 ft^3 (Recommended for Alpine Type R 8)

Tentative construction:
Inner layer: FRP tub with plywood mounting ring
Core: 1" rigid foam insulation (pink foam from home depot)
Outter layer: Polyurethane Elastomer (aka polyurea aka 2-part truck bedliner)

I begun yesterday and started construction of a hot-wire foam cutting station. I probably could get away with just using a knife, but I this will make my life easier and will be useful down the road as well! I am using the general design shown in this youtube video:

(as an aside, this guy's videos are awesome)

My version is a little different in terms of size, shape, electronic components, and stand/base design but I ripped 90% of the design from him.

So far I have the base done and the stand roughed out... I'll get some pics up this evening. Hope to finish the cutter sometime in the next week.

This project is going to move at a snails pace.

What do you guys think? Discussion, criticism, and suggestions are all welcome.

Here's a pic of the hot-wire cutting station in progress...

I am not super happy with this prototype and am considering scrapping and starting over, even though this one would be fine for this particular project. Haven't decided yet. As I said before, this thread will move at a snails pace.

http://www.the370z.com/attachment.ph...1&d=1488905993

Thats funny...we had one of those in Poland back in 80s in high school, here is the thing, unless you're a robot you will not be able to cut out perfect shapes, there will be some manual sanding/shaping and if you cut out too much which is really easy because that thing cuts like butter, you will have to start over. For what you're doing if i understand it correctly, you're making a square box? so you can cut it with a razor just as well.

Yup -- I am prepared for more sanding and shaping outside of just using the hot wire =)

will it work? depends. I believe box dimensions/bracing will dictate whether or not this beast vibrates like a lonely chick on a Saturday night. Mounting will also come into play, here as well.

These are my biggest concerns - good point on the bracing. With the inner airspace being done in FRP - any ideas on how I might do the bracing? I could glass in some wooden dowels between the larger surfaces... that would be relatively light.

I am also not sure about the mounting. I've arranged to buy a second hand Zenclosure to see how it fits, since it is advertised as fitting tightly enough to not need to be mounted mechanically. It does have quite a bit more mass though, so I am not sure how helpful it will be. I'd like to avoid screwing it down because that will make accessing the spare a pain. Right now I am leaning towards blowing it off for now and then trying to address it if it becomes a problem.

I am open to suggestions and ideas =)

My diy fiberglass box w/MDF bottom is too light imo. Idea of a lightweight box is great but she slides around. I had to tie it down to keep it from moving. Plus I think dense enclosure material produce better sound. My box is 5 layers of glass iirc. 12" type r shallow.

YzGyz

The wood dowels sounds like a good plan... As far as mounting goes....tough one. Im thinking removeable straps of some sort would hold it fairly well, if possible.
Not mounting a light enclosure loses a little of your oomph... Not to mention is quite dangerous.

I thought about it some more today. The fore-most plastic panel has a bit of a concave shape in it. If I made the box in the 'zenclosure style' to fit reasonably tightly, I could mask that area off, fit the box, and pour some expanding foam down there to fill that gap and stick to the box.. then just carpet/vinyl over the urethane foam with the idea that the box will now fit very snugly and can be squeezed into place. Seem crazy?

and removal, if and when necessary?????

That's the idea... just squeeze it back out.

Finally finished up the foam cutter. It works OK... I am pretty sure there will be a new version sometime in the future if I get bored, but it works well enough for now.

Here is my fiance testing it out.... aside from having no interest in cars, she'd fit right in around here.
http://www.the370z.com/attachment.ph...1&d=1492031336

And I rough-cut a couple of pieces to help me lock in the inner tub dimensions... these are just to help in figuring dimensions, won't be used on the final piece.
http://www.the370z.com/attachment.ph...1&d=1492031336

I cut out the pieces of FRP to make the inner tub as well.. I decided to go with a cuboid design to simplify construction as I didn't want to spend a year making something only to find out it doesn't work. Next step is to learn how to use my jasper jig to make the necessary plywood pieces... Then I'll be able to start glassing the inner tub together.

We're moving forward....slowly.

Is that a cocknballs shes cutting out of your foam???? LMAO

Indeed. Just one of those moments that tell me I made the right choice with her :tup:

Cut out some plywood for a baffle and a couple of mounting rings for the port and terminal cup so that the screws have something to bite into... though some of the rings will need to be re-cut due to my inexperience with a router and jasper jig. As promised, this build is going to take forever.