Plywood alternative (aluminum)?

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So, Im waking up in the middle of the night realizing my mind has not shut off, pondered building 2 cabinets from corian but am finding it difficult to source locally.. everyone has gone quarts. Meanwhile I just spoke to a waterjet cutting company and he made a comment that 1/4" 5052 (32 sq ft) is cheaper than the corian! His 1/2" is only slightly more!

So, do you fine folks think 1/4" aluminum is stiffer than 3/4" plywood?

Not to start a war, the next question is for the folks who believe a cabinet should be dead, and not impart any coloring to the sound, Aside from visual warmth, would anyone know of any reasons why it might not sound good?

I have read the threads where some feel strongly about certain woods imparting warmth.. For obvious reasons id prefer not to compair wood against metal as I know its near and dear to what they feel is important to them..

Thanks in advance!
 

PRR

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> 1/4" aluminum is stiffer than 3/4" plywood?

Stiffness goes about as the cube of thickness. So 3X the thickness is 27 times as stiff.

Wood (along grain) 11 *27 = 297
Aluminum 69

So 3/4 wood is 4X as stiff as 1/4 aluminum.

With weasels! MDF is only 4 so only mildly stiffer than Al of 1/3rd the thick. Plywood has half the grain the wrong way so is less stiff than with-the-grain solid wood. Above the thump frequency the stiffness is moot, only mass matters.

For speakers you always worry abut ringing. Wood has high internal damping. Alloys vary, the best make fine bells.
 
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The bending stresses in a rectangular section are inversely proportional to the square of the thickness so the maximum stress due to bending in the 1/4" Aluminum would be 9 times that of the 3/4" plywood.

However, the actual deflections depends on the elasticity (Young's Modulus) of the material ((assuming not overstressing the material) and Aluminum is in the neighbourhood of 9 times stiffer than plywood, so in terms of deflections due to bending, the 1/4" Al would be similar to that of 3/4" plywood.

As for sound, that's another story.
 
...inversely proportional to the square of the thickness so the maximum stress...

Incorrect analysis, PRR is correct.
It's a question of stiffness, not stress.

Aside from visual warmth, would anyone know of any reasons...

Alloy is poorly damped.
But a constrained layer damped laminate of 1/4" ally and 1/2" ply would be pretty nice and balanced combination.
I have started on a similar laminate in my own speakers (3/4" ply + 3 mm ally) well damped and stiff, not impractically heavy.
Metal on the outside for durability.

Best wishes
 
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stress due to bending in the 1/4" Aluminum would be 9 times that of the 3/4" plywood.

However, the actual deflections depends on the elasticity (Young's Modulus) of the material ((assuming not overstressing the material) and Aluminum is in the neighbourhood of 9 times stiffer than plywood, so in terms of deflections due to bending, the 1/4" Al would be similar to that of 3/4" plywood.

As for sound, that's another story.

This is along the lines of what I was thinking but couldn't put it in words,
As 1/4 is as thin as it is, i was considering lining the interior with 1/2 mdf,
And adding a layer of MLV or similar to that..

However, there volume details have to be worked out depending on dampening, and a layered up front panel to simulate the recess on the front panel.. lastly finishes are in the air.. as this is my first build, and spare no expense (within reason) i want to be sure i dont do anything I might regret later..

To anyone who has worked with 1/4" plate aluminum, is there any products you have tried that can glue (and seal) seams that you know of?
 

PRR

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Incorrect analysis, PRR is correct....

Someone better check this. I have been doing badly recently (strong medicine).

Nobody has mentioned several well-loved metal speakers. The little Minimus? However the ones which come to mind have significantly curved corners, which makes it not a flat-plate problem.

_I_ think the question is over-rated. When I have noticed panels it is because they BUZZED.
 
When I've used aluminum before in furniture I simply burnished it with a belt sander, no clear coat or anything, and still looking good after 20 years.

Think aluminum is going to ring, might want to use an acoustic paint or acoustic glue if laminating a damping layer.

Glue:
FMT acoustics - Your partner for acoustic materials and solutions

Other materials in that link, and some might be like Mass Loaded Vinyl (MLV) used in walls and between layers of drywall to soundproof. An underside of a shelf might have this so you can work messy and quick. I think to work that I've read about only 1/3 the surface area needs to be covered.

There are also sticky patches for use in between layers of drywall, maybe just stick a few of those on the unseen surfaces.

Building a Listening Room | The Absolute Sound
Build%20Fig.2.jpg


When I've built Baltic Birch furniture I double layered the edges for stiffness (2 or 3 inches wide, 3/4" + 3/4" deep)
 
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Oh and you can do something like this as well.

Music Tools ISO Square | Audio Reference
Iso-Square-cover.jpg

ISO Square modular designed shelves dedicated to audio equipment. Each shelf is made by welded steel structure and a wood sandwich with special damping compound in between.

The upper wood shelf is “floating” and is not in touch with the bottom one. This system eliminates undesired vibrations and resonances.

Each shelf (sold separately) is available in two different heights (28 and 38 cm) which may be added as your system grows.
 
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great resources kach22i, might come in handy one day!
As far as my project, I am canning the 1/4" aluminum... lol

So to build the Elsinore and keep what I believe are important aspects, true, as much as possible to the original design is requiring additional layers of aluminum. So much so, the sheet count per speaker is now near 1.2-1.4. This pretty much kill's the savings I though I could have over corian. Add to it the MLV, the yet unknown best method of glue up and I understand value engineering this is not going to happen. It looks like old school cool meaning ply or MDF offers way more per dollar than first glance....

If I could build 2 boxes from one 1/2" sheet, I might consider it.. come to think of it.. ohhhh damn.. back to the drawing board lol.....
 
great resources kach22i, might come in handy one day!
As far as my project, I am canning the 1/4" aluminum... lol...
Total brain fart on my part, as I had audio rack shelves on my mind, not speaker enclosures.

However, they share many of the same problems, don't they?

I've been reading about exotic speakers that are lined with natural stone (marble/granite) or have concrete inners fiberglassed over and other weird combinations.

My favorite speakers usually don't use boxes, and I'll leave it at that.
 
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Wood has high internal damping.


Woods vary a lot for damping, some musical instruments rely on dark hardwoods that ring like a bell, xylophones, claves, etc. Generally soft woods are less resonant than hardwoods, and in plywood the glue can be an important source of damping or not, depending on its properties (glass transition temperature, basically). MDF is usually the best damped as it contains a large proportion of glues. I've used OSB before for a speaker cabinet which seems fairly well damped, though not great to work with.


Green wood ought to be well damped, but would warp and crack over time, alas.
 
Woods vary a lot for damping, some musical instruments rely on dark hardwoods that ring like a bell, xylophones, claves, etc. Generally soft woods are less resonant than hardwoods, and in plywood the glue can be an important source of damping or not, depending on its properties (glass transition temperature, basically). MDF is usually the best damped as it contains a large proportion of glues. I've used OSB before for a speaker cabinet which seems fairly well damped, though not great to work with.


Green wood ought to be well damped, but would warp and crack over time, alas.

Good observations.