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Old 1st September 2005, 07:50 AM   #21
Collo is offline Collo  Australia
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For gluing steel to wood, epoxy would be much stronger than polyurethane glue. I guess it depends on surface area, but then we are talking overkill here!

The "footplates" are basically to spread the support onto the panel, and could be cut from 1/4" plate steel. I would be surprised if a wander around the hardware store didn't yield something suitable. If not, you can always brag to your mates that your subwoofer required an oxy-acetylene torch to build...

The cross connection would be best in tubular steel or angle, rather than threaded rod, which is not as strong in compression.

PVC pipe would not be all that great as a brace except for one word - "concrete" .... fill 'er up!
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Old 1st September 2005, 05:53 PM   #22
hooha is offline hooha  Canada
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Quote:
Originally posted by Collo

PVC pipe would not be all that great as a brace except for one word - "concrete" .... fill 'er up!

And why even stop there? Use your wood scraps to build a form in the shape of your speaker box and fill it with concrete. ReadyMix isn't all that expensive.

Provided you don't make the walls too thick you won't have to start saving your money to buy a forklift.

Mark
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Old 1st September 2005, 05:55 PM   #23
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Quote:
Originally posted by morbo
I suppose I could just glue some of them to the internal walls in the center of any unbraced panels.
Never right in the middle of the panel.... you will likely have some scraps left from your ply. strips about 1.5" wide, mounted edge-on, off-centre and at a slight angle (to divide panels into trapezoids) goes a long way. (your metal braces should do an even better job)

Perhaps even easier than the steel rods with the flanges would be to get some ready-rod and run it all the way thru and use them to add compression to the panels (ie try to bend the walls into a dish shape).

My favorite bracing technique is push-push woofers. Then the majority of the box load comes from the air and not transmitted directly into the box by the chassis.

dave
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Old 1st September 2005, 07:06 PM   #24
morbo is offline morbo  Canada
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Well I think I've settled on my design. I wanted to use mostly 'off the shelf' hardware, and I wasnt able to fine easy/cheap ways to implement some of the other (very good) ideas on this thread.

I used some cut sheet layout software to figure out that 3 24x48" sheets of 3/4" BB ply will give me enough material for a box with double thickness baffle and back, a single front-back shelf brace, and 2 8" high front-back panels. The 24x48" sheets run 19.20 at my local building centre, and 3 of them comes out to $5 more than a single 5x5 sheet. So far, cost = ~ $ 60.

To this I will add:

- 4 steel 'L' braces screwed and epoxied as close to the driver itself as possible, hopefully coupling the baffle (which IIRC with the big hole cutout and direct coupling to the driver, is most prone to vibration) to the side and top panels extremely rigidly. Cost = $ 1.50 each, so $6.

- .75" wood corner blocks along the corners, leaving a 12" span on the bottom panel where a 12" x 12" ceramic tile will be. Already have these. Cost = $1 for tile.

- The shelf brace will be installed about 2/3" of the way up the cabinet, leaving 12" high panels below it which will also have 12x12 ceramic tiles. Cost = 2 tiles x $1 = $2

- above the shelf brace, the 7.75" or so panel left will be double thickness using the leftover ply mentioned above. Cost = $0.

- 2 aluminum 'rib' braces, running diagonally on the largest remaining panels (probably top) , epoxied and screwed in. Cost = $ 2 each so $4.

- any remaining 3/4" panels will have scrap pieces glued on diagonally to break them into triangles

So my net cost will be ~ $73 CDN in materials per sub box. Not including paints, glues, etc which I would need anyway. Yeah, I'm a cheap SOB Am I overanlayzing this? Probably. Am I overbulding it? Possibly. BUT - hopefully this will meet my goal of the stiffest box possible within my budget. I really want these to be my reference for 10+ years, so I want to do all I can now to avoid the 'wish I'd done x, y, or z' syndrome I'm sure many of you are familiar with. Plus, I will get some first hand experience with how well these techniques work.

Please continue this discussion though - I am laying this out just in case anyone is curious what I decided on - but this thread is full of very useful information on a topic that is not often discussed.
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Old 2nd September 2005, 12:09 PM   #25
hooha is offline hooha  Canada
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Not bad. Cheap and good - just the way I like it. Now, on to the driver....

Have you decided on one yet?

Mark
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Old 2nd September 2005, 03:57 PM   #26
morbo is offline morbo  Canada
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Yup, should have mentioned that. In fact, it just showed up in the mail this AM, and is sitting here in front of me. Its this one:

Click the image to open in full size.

TC Sounds built 12" from Rythmikaudio. The picture doesnt' do it justice, this this is built like a tank! I got the 380w servo plate amp as well, so I guess I'll find out pretty soon how a servo system sounds. I'm starting to get pretty excited
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Old 2nd September 2005, 09:21 PM   #27
hooha is offline hooha  Canada
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The TC Sounds drivers are pretty mean units. I was about to get a pair myself when Ascendant Audio decided to tank the pricing on their product.


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