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Trapezoid build guide?

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To Dave/Chris/anyone who has built a trapezoid enclosure.

I've had a go at an dmar-ken7 trapezoid test build out of mdf. I built myself a table saw and sliced up all the panels then cut them accurately down to size and cut all the appropriate angles.

This is where I became unstuck. Well, I had trouble clamping the panels for gluing because of the obvious angles. Being mdf I cheated by marking each panels postition on the bottom panel, gluing/screwing them to that and then to eachother. The result was accurate and turned out well.

Thats all very well and good with mdf that could be veneered/painted etc but for a proper build for 10.3's I would prefer to use bb ply. I would love to then leave it bare but waxed as I'm not too keen on veneering and I like the ply layers to be visible so I wouldn't be able to use the screw technique as this would leave screw holes all over them.

I'm also building up the courage to buy a sheet of bamboo ply from a supplier not too far from me and using that but again, leaving it bare as it looks lovely.

So, my question is has anyone had any success assembling such an enclosure without using screw/nails etc?
 
Once I started thinking it through it was too easy to get very long winded. Dave is now in possession of today's treatise on the subject, and between the two of us, something that makes sense should be possible.

Or we could just take some pictures of the next build - but as I rarely have time to slow down when building, and Dave is more proficient behind the lens that I, that's a matter of scheduling that's easier said than done.

If you have some specific questions, PM me your personal e-mail to avoid wasting forum bandwidth until something more official and polished can be contrived.
 
Yes it perfectly possible.

I have built a pair of JBL tki10 's which are a Trapezoid but the sides are curved from front baffle to centre of the back & also curved from the base to the top. it wasn't easy at all but its wood so you can do almost anything with it.
Just get the right wood for your particular application.

I used thin Flexible ply & lots of straps !

Jay
 
Jay - Harmolodics beat me to it, but note that the "trapezoid" design in question here is actually an irregular octagonal prism, all flat panels, with the three layer side walls requiring multiple bevels.

There are no doubt a couple of approaches that could be taken - as I don't have Bernie's skills with solids, I work exclusively with plywood for which the planer / jointer isn't as practical
 
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frugal-phile™
Joined 2001
Paid Member
I found these pictures helpful ufonkenset-solid-cedar-flat-pak-prototypes. Though this method requires a jointer. Apparently the builder didn't like them, but I found it to work alright. It just took a lot of clamps, and a strap around the middle.

Those use the same set sof pieces as any of the other trapezoids, they are just small which makes them easier to play with designing a flat-pak.

No jointer was used in their manufacture. No clamps were used in the assembly, just masking tape. Clamps likely needed for larger ones.

The builder -- me -- likes them just fine (we are not happy enuff with the flat-pak yet), and the fellow who ended up with this set just loves them.

dave
 
Ah I see your Trapezoid is a straight forward design for an actual design, rather than the conceptual design that JBL made. Or rather the box makers in Holland did. Who I believe used a 100 tonne press to make the sides for the JBL tKi10.
I used a workmate & straps !
 

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Dave, do you have plans for a taller floor standing version of this enclosure and if so, are there any sonic benefits?

The reason I ask is I've just discovered a company a few miles from me that manufactures bamboo ply. They make 3 ply 18mm sheets and will make the outer plys in a few different wood species including my favourite Zebrano.

I'm now absolutely ready to explode with excitement at the the thought of a speaker box made in this material but I obviously want to make the most of the material and build the best version possible but also the most striking.
 
frugal-phile™
Joined 2001
Paid Member
Dave, do you have plans for a taller floor standing version of this enclosure and if so, are there any sonic benefits?

There is a Compact floorstander version of these. Same tuning,same volume. They don't need a stand, can have a bit more bass impact (due to floor/wallloading if the vent), are an easier build, but don't have as low a diffraction signature are the trapezoids so they don't have the same potential to dissapear and to throw as wide and deep a soundstage.

dave
 
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