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Old 15th January 2006, 12:04 AM   #11
soongsc is offline soongsc  Taiwan
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Quote:
Originally posted by BassAwdyO
MDF should be fine and probably holds the advantage for full range cabinets.

I'm also working on a curved loudpseaker which will use laminated mdf. I'm not the most critical, and I'm not using any jigs or precision cutting devices. Just my bandsaw and beltsander. It looks very promising

If you use MDF, it's best to coat the inner side or it might crack. This is due to the way MDF is pressed together. Cutting it to cabin wall thicknesses allows mosture change more freely, causing expansion or shrinkage. The Banda Wood Hardener rout might work also. I wish we could get that here.
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Old 15th January 2006, 01:58 AM   #12
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Default Kevlar and Fiberglass

You can do a lot with composites.
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Old 15th January 2006, 01:58 AM   #13
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More of the same.
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Old 15th January 2006, 04:49 AM   #14
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I built (am still building :-)) 45" (1,115 mm) tall speakers that are similar in shape to the SF Cremonas. I used the translam approach as per Andy's site.

Be careful with your alignment of the slices.

I used 25mm (1") MDF so I had ~45 slices for each speaker. I had the CNC factory drill six holes in each slice and I used wood dowels for alignment. Sounds simple, eh?

No, it isn't.

Even with dowelled alignment you can still go off track easier than you might think.

I did.

And I spent many hours with a planer and sander and straight edge correcting my wayward alignment. Then, because I've decided to lacquer them instead of veneering, I couldn't trust the translam layers to hold fast and not show up as hairline cracks. So I laminated a piece of 3mm (1/8") MDF over each side...

...and man, that's a whole story on it's own!

So, at this stage I'm working on the baffles. 2 x 18mm MDF laminated to give 36mm thickness for each baffle. I'll be glad when that's done and I can get around to the hard part of measuring and XO design :-)

Conclusions:

I think the translam technique makes perfect sense for complicated or non-flowing shapes (like simple curves). But I'm not so sure, with hindsight, that I'd do it that way again. I think I'd have internal ribs CNC'd then laminate multiple thin sheets onto those until I had my sidewall thickness.

Either way, these damn things are HEAVY (I use a furniture barrow to move them, and that's without the baffles or drivers attached) and will be impressive in black gloss lacquer.

[drivers: 2 x Vifa M22 8", 1 x Peerless HDS 134 (850488) & Vifa XT25 tweeter]

Hey, it's not a hobby, it's an adventure!!

Ross
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Old 15th January 2006, 06:42 AM   #15
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CNC shaped cabinet??? i'm finding my way around....

http://fullrangedriver.com/forum/viewtopic.php?id=303

http://fullrangedriver.com/gallery/d...pn&cat=0&pos=0

http://fullrangedriver.com/gallery/d...album=4&pos=32

Thanks
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Old 15th January 2006, 11:24 PM   #16
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"If you use MDF, it's best to coat the inner side or it might crack."

I used Gripset which is a thick, water-based bitumen rubber sealant which I brushed on every surface inside my cabs. As well as a sealant it's rated for sound deadening.
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Old 16th January 2006, 12:51 PM   #17
Audist is offline Audist  United States
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Thank you guys,
I'm think that I have idea about the shape.
Thanks for advice how coat the inner side, the bitumen is the good sealant.

The CNC Horn cabinet is very impressive even that I not looking for Horn.

Mos Fetish, good luck with your design. You have a pictures?
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Old 19th January 2006, 03:06 PM   #18
scotts is offline scotts  United States
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Default CNC shape cabinet

I have been building a pr. of speakers and can echo many of the comments made by Ross. My design and approach has been a little different though. My design is similar to the Kharma Midi Exquisite or the Marten Coltrane. I had an internal rectangular bass unit made out of multi-ply birch with one additional layer of MDF on top of that. For the top section (which holds the mid and tweeter), the shop I used, made multiple elipitical side shaped CNC layers out of MDF. They used the dowell alignment technique also. This is a tricky part as it is difficult to perfectly align. I had originally wanted to paint the surface directly and also realized that you would see the lines in between so I covered the whole cabinet with a thin paintable material. This covered the laminations, but after painting you can still somewhat see the lines between each layer. I may still go back and try to sand down the sides better and cover it with carbon fiber or leave it. The front and back baffle were CNC cut and look great. If I were to do it again, I would probably make the frame in the desired shape I want and then cover that with multiple thin layers of either MDF, wood, fiberglass/carbon fiber or a combination of these materials. I am at the point where I am working on the crossover and balancing things out. I am using an Accuton C12, C88 and a Lambda SBP10. The top and mid sould great, but the bass is much less efficient and I'm at a quandry as to what to do. I really hadn't planned on bi-amping, but my amp (Berning ZH270) simply will not drive the bass and so padding isn't the answer. I don't want to get off the topic, but will add that the speakers are heavy as all. As a matter of fact, I hurt my back lifting them. Anyway, just a few thoughts.
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Old 19th January 2006, 03:15 PM   #19
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Quote:
CNC shaped cabinet??? i'm finding my way around....
That is just plain sick!!!!! Gawd..I wish I could do that kind of stuff!!!
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Old 19th January 2006, 08:40 PM   #20
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Scott

You said you covered your speakers with a thin material. And the slice lines still show through? What was it?

I used 3mm (1/8") MDF and it was laminated using yellow PVA. I never even considered that anything would show through that thickness.

Ross
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