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andy1971 29th September 2009 12:15 PM

density of cabinet material
 
Hi

I am thinking of making my own curved speaker cabinets, what is best?

a) softer materials, such as bendy plywood, that will absorb vibration.

b) harder materials, such as sheet copper or stainless steel?

c) or a combination of the two? bendy ply internal layer (2x 5mm laminated together), with small air gap (3-5mm) to reduce vibration of the sheet metal exterior (0.7mm) the sheet metal is important to the cosmetic appearance as I want to have this Nickel (chrome) plated

Ken Dolph 29th September 2009 01:45 PM

Use Corian
 
Andy1971

You could use Corian. It will bend quite nicely between 325 and 350 Degrees, never higher. You jest put it in an oven for 15 minutes and form it when you remove it.

I hope this helps
Ken

andy1971 29th September 2009 03:39 PM

Thanks for your reply Ken

The use of nickel plated steel or copper sheeting is purely cosmetic, my aim is to have 'chrome' speakers, with a high gloss black baffle.

They will be around 1000mm tall and approximately 300mm in diameter, floor standing speakers, so a little too large for an oven.

0.7 mm steel or copper alone is too thin and fixing mounts internally would be something of a problem.

my final option of laminated bendy ply, air gap and then external steel was my original idea, on the understanding that the ply (being of low density) would absorb negative sound from the rear of the drivers and reduce any vibration of the steel shell, but a look at some high end speakers made from glass etc without the use of any acoustic wadding has left me wondering wether the absorbtion of negative sound and air from the back of the driver is better than the reflection of them back thru the drivers?

which is best, absorbtion or reflection of negative sound waves and air?

mwmkravchenko 2nd October 2009 01:56 PM

Wood plus metal makes for trouble

If you have never laminated metals to wood before you may have to check out some things about expansion ratios between the wood whether composite or veneer. When I have done cabinets for commercial application with metal veneers I almost always use a contact type rubber cement. It only glues to itself and must be applied to both sides of the lamination. This type of laminate system allows for more movement. If you go with a stiff glue you end up cracking the laminate or the wood underneath.

This can be done and look good. You just have to prepare well for the balacing act of the different substrates.

My two cents having done quite a bit of bent work is to sue bendable plywood. Once you laminate two layers at the curves you like it is quite stiff. And it does not have the low midrange ringing of MDF that so many people dislike. The cabinets that I have done with it work well.

My current cabinet that is getting all bent up is using 3mm Russian birch plywood. I think this will be very stiff sending the structural resonances quite high up where they will be able to be dampened by some roofing membrane material that is very sticky on one side and has granular on the other. Here it is called ice and water shield.

Mark

ChrisA 2nd October 2009 05:39 PM

Quote:

Originally Posted by andy1971 (Post 1936965)
Hi

b) harder materials, such as sheet copper or stainless steel?

Metal is never good unlessit is very thick so it it can't vibrate. What you want is "damping", that is a material that is high internal friction can low elsticity. Metal is not like that. MDF is best for home speakers. But you can't bend it

If you need to bend it at home use multiple layers of thin plywood and glue them together by clamping them between two curved pieces of wood.

Another great way to make curved parts is to cast them. Make the part first out of styrofoam, clay, balsa wood or all three hen make a mold. After that you can mass produce as many speaker cabinets as you like.

The best material for casting is concrete. The stuff is cheap as dirt. If you need to be more high tech then epoxy filled with fiber and "micro" makes a very stiff and light but expensive part. Mold making is not hard, plaster of peris can be used for a mold.

But for a one off project just clamp a few layers of plywood over a curved form.

If you like the metal "look" then attach the sheet metal over the wood using contact cement as if the metal were veneer.

MJL21193 2nd October 2009 05:50 PM

1 Attachment(s)
Quote:

Originally Posted by ChrisA (Post 1940198)
MDF is best for home speakers. But you can't bend it

You sure can:

Attachment 142663

Baffle is 2 layers of 5/8" MDF and is bent.

Cabinet material issue is overblown - more important than WHAT your cabinet is made from is HOW it is made. Effective bracing will easily negate any differences between materials.

planet10 2nd October 2009 06:08 PM

Density without stiffness is not beneficial....

Metal can be a suitable material to build speakers with, but you need to execute the box to cater to its properties

This is a lengthy thread that describes one way to approach box building.

http://www.diyaudio.com/forums/construction-tips/98834-discussion-what-materials-build-speakers-out.html

dave

Steve Dunlap 2nd October 2009 06:42 PM

Quote:

You sure can:
You can also powder coat it.

thirdman 2nd January 2010 12:35 AM

Would the use of a heavy hardwood have any negative attributes or drawbacks(other than expense) in the construction of the super v(open baffle design) side panels and baffle? Would it be to resonant as compared to mdf or hdf? What is the maximum thickness the side panels should be? contemplating something like a dense rosewood....or not sure just a brainstorm at the moment. also anyone know of a good source for exotic lumber?

super v pics:

Super V pics...

New Super-V model (that is going to the show) with pics!

thirdman 2nd January 2010 01:43 AM

Would the use of a heavy hardwood have any negative attributes or drawbacks in the construction of the super v(all open baffle) side panels and baffle? Would it be to resonant as compared to mdf or hdf? What is the maximum thickness the side panels should be? contemplating something like a dense rosewood or Lignum vitae(iron wood) not sure just a brainstorm at the moment. Also does anyone know of any good sources for exotic hardwood?


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