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Multi-Way Conventional loudspeakers with crossovers

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Old 5th March 2007, 10:15 PM   #491
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I must be missing something.

The glue line is telegraphing. This means moisture is leaving and/or entering the substrate, right?

Get the moisture low and keep it that way and you eliminate the problem. Regardless where it occurs or how it manifests visually.

Your thinking is sound about the various surface applications and your wood hardener. But none of the products/methods is of the highest effectiveness at stopping moisture vapor entering your substrate.

Bonda is a polyester resin. Polyester rates comapratively low on a permeabilty scale (it lets moisture vapor pass). Polyesters also are comparatively highly absorbant.

Same for the high build urethane auto primers in general. It depends on the pigment and filler used to some extent. Quartz fillers are the best but the grey pigments are usually hydrophylic and disrupt the continuity of the urethane film.. so.

A thin layer of wood veneer will slow the rate of transfer even more and possibly disguise some of the effects of differential expansion. But I fear not as much as you'd hope for. At least that's been my experience.

Combine all the above and you've slowed the rate of moisture induced movement significantly. But not as much as is needed it seems. Maybe the veneer will be just enough extra, but you're doing a lot of work for what I fear might not be much gain.

I hadn't mentioned this before... It's really an amazing design, Shin. First rate. One of the best I've seen. Kudos!
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Old 6th March 2007, 02:12 AM   #492
KBK is offline KBK  Canada
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Lamiantes (2 sheets bonded) are actually quite a bit stiffer than a single sheet of MDF, but the benefits vs hassles are debateable. IF the machining is easier, that might be seen as a benefit. (single 2" or 4") For ultimate design, I'd go with the laminate, personally. Considerably more hassle to make, yes. Then, proper settling time must be considered, and good bonding is another issue. But, still better than the single 2" or 4" piece. Spraying the glue on is a way to be sure the gluing is correct (layering density of the glue-weldbond thinned with water works incredibly well), and then the issue of imperfect bonds (Air pockets, etc) rears it's head. But..still..properly done, far more stiffness for the mass involved is the end result.

So don't feel to bad about using the laminates, you ended up with a better speaker. Time and effort was certainly not wasted.

BTW, Shin, very nice work, great looking speaker.
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Old 6th March 2007, 02:50 AM   #493
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Default Design

The current vision of your project reminds me of the Sonics Passion.

http://www.sonicsonline.de/produkte.php

I must say that it is a fantastic undertaking.

Congrats,

C
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Old 6th March 2007, 02:55 AM   #494
adason is offline adason  United States
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that looks completely overdone/awfull
one midrange is pointing to the floor, the other to the ceiling
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Old 6th March 2007, 05:23 PM   #495
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looks like a listening distance of about 2 feet.
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Old 6th March 2007, 05:23 PM   #496
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Thanks Bob and KBK. I'm going to stick with the laminated approach with veneer plus the usual products I use because its something I feel comfortable doing and also that it will likely work. If I'm wrong then no doubt I'll be back for your help though!

Applied the veneer to one section and it turned out OK:

Click the image to open in full size.

Also for those interested, some driver pics:

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Old 6th March 2007, 05:25 PM   #497
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What glue did you use in the end?
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Old 6th March 2007, 05:31 PM   #498
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Curious,

What kind of veneer is that and how did you trim it? The trimming part seems particularly complicated because it's on an angle.
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Old 6th March 2007, 05:40 PM   #499
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Quote:
Originally posted by m0tion
Curious,

What kind of veneer is that and how did you trim it? The trimming part seems particularly complicated because it's on an angle.
EDIT: The veneer is a plain Beech which has little figuring or grain pattern - perfect for spraying over.

I used a straight edge and veneer saw to cut roughly to size:

Click the image to open in full size.

Click the image to open in full size.

Then trimmed with straight edge and craft knife once stuck down:

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And finally light sanding to remove the excess.
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Old 6th March 2007, 05:41 PM   #500
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Quote:
Originally posted by pinkmouse
What glue did you use in the end?
Pearl Glue:

Click the image to open in full size.
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