Speaker Boxes Made out of Metal

Hello Everyone,
Me Again will another idea?
Has anyone one the forum experimented with welding up a speaker box out of say 6mm think steel and welding in cross braces to prevent wall flex.
I am sure you could get a very stiff box with this idea?
One thing i hate about my normal boxes is the boxy sound you get at times.
I know it would be heavy, but if it worked it would most likely be worth it.
 
It could sound tinny.

To get the obvious joke out of the way.

If you have the materials on hand, go for it. Otherwise, use adequately spec'd MDF, HDF or plywood. Stay away from chipboard and LDF. Other exotic materials use as required

Anything done right will not resonate in a frequency of concern for the drivers installed.

Metal has one big advantage: you finish it, it's done moving. No swelling with weather (even soaking in water), no shifting joints.
 
Somewhere in here I remember a guy who tried steel about that thickness. He said it rang. I would think something like pickup bed liner sprayed on the inside would help. Or glue something like vinyl floor tile onto the inside. There is special stuff sold for this purpose too.
The HIGHLY regarded Wilson Benesh speakers use a metal framework of some sort.
 
You gotta define strength- the same problem as defining conductivity.
"tensile strength per pound?" Steel wins I'll bet. Its hella strong.

I think Alu's lower weight allows thicker walls which make it "stiffer per pound"

I think alu is inherently better damped (for a metal!) Not too many church bells made from aluminium...

It does seem that Aluminum is more successful. Now steel/sompthin' constrained composite might be pretty good! (I think thatthe Benesh folks combine a steel framework with carbon sandwich panels..tasty!
 
Variac said:
You gotta define strength- the same problem as defining conductivity.
"tensile strength per pound?" Steel wins I'll bet. Its hella strong.

I think Alu's lower weight allows thicker walls which make it "stiffer per pound"

I think alu is inherently better damped (for a metal!) Not too many church bells made from aluminium...

It does seem that Aluminum is more successful. Now steel/sompthin' constrained composite might be pretty good! (I think thatthe Benesh folks combine a steel framework with carbon sandwich panels..tasty!


alum is softer than steel no doubt and therefore has higher dampening properties... but 6mm steel is VERY strong... it would take a lot of pressure to flex that...

1/4" alum would be nearly impossible to bend... but resonance is still a problem

as far as that though you're right steel per thickness is stronger than alum
 
gday!
let's compire material's properties:

Material E, 109 Pa
aluminium 70,0-71,0
beton 14,6-23,2
tungsten 415
granit 49
iron 190,0-210,0
kapron 1,4-2,0
brick 2,7-3,0
ice(about t=-4oC) 10
marble 56,0-73,0
plexiglass 2,9-4,1
spider's web 3
rubber 0,9
lead 16,0-17,0
steel 200,0-220,0
glass 50,0-60,0
cotton 12
grey iron 115,0-160,0
silk 13
wool 6
ebonite 3

do not tell fortunes for it.
 
Unfortunately, because something is stiff, it doesn't necessarily follow that it will be uncoloured, or not resonate. Quite the reverse. Think of tuning forks.

The best anaolgies I can think of, and they have relevance here, are in swords, and battleship armour-plate. Tap a bronze sword, and you'll get a relatively dull 'thud'. A steel one will vibrate and ring quite cheerfully. That's why they tended to combine several metals for these things -to prevent them shattering. Same with armour-plate. Steel, when it was introduced, was harder than the older iron armour, but it shattered easily. So for a number of years they used compound armour -a nice hard steel face supported by a tough iron backing.

All of which sounds as if it's a bit of a downer, but it's not impossible, and superb results can come. Look at how good some metal drivers are, though it's taken quite a while to get them to a really good standard (thank you Acoustic Energy and others). So there's no reason metallic cabinets have to be poor. I still have a pair of the aforementioned Celestion SL600s in the loft (2 blown tweeters). They used a propriatory aerolam technique, mostly swiped from the aircraft industry using aluminium, which is a better bet than steel for this sort of thing. I don't think they can rebuild these cabinets any more though: I believe their supplier went out of business, though I speak under correction here. Unless of course, you can fashon a cab. out of bronze of course... A cabinet constructed from two different types of metal might also be worth trying. Good luck. There are real possibilities from metal cabinets, just like drivers, but it'll need some heavy thinking.
 

soongsc

Member
2005-03-26 2:31 pm
Taiwan
Aluminum alloy plus honycomb is normally used to increase stiffness and keeping damping properties good. Alluminum allow and graphite composite also has good stiffness and damping.

Steel alloys like cro-moly has better stiffness but not so good damping.

Lead has really good damping but less stiffness. The dammping effects absorbes lots of energy before it moves.

Materials in which sound travels faster will have more tendency to ring.

If you solder to copper plates together filling the contacting surfaces with solder, you get somthing that also has pretty good damping.

If you can get a few diffferent materials that have different sound speed properties, then you might be able to find a combination where the modes cancel out themselves.
 

VvvvvV

Member
2003-10-20 1:34 pm
oxfrd
Actually it's worth mentioning, although full of typos, that it would probably be easier to mould speaker cabinets out of aluminium than to make them out of wood given the right tools.
The melting point of aluminium is around 400-500 so you can even melt it using a wood fire stove of some kind. the mould would obviously be plaster. I used to melt aluminium cans in a regular household fires place burning oak, chucked some cans in one-day and was surprised to see a nice ingot of pure silver oozing along the front of the hearth stone .

Aluminium is also easy to machine perhaps with a basic sander and you'd have to make two halves of a shell for each speakers and screw them together.

It would probably be wise to use about 1 kg of aluminium for every 30 W of output.
 
Here's a link to someone who has built identical speakers with wood and aluminum cabinets:
http://www.audio-resolution.com/zhorn/jordan.html

It seems that alu cabs would be most practical for small bookshelf applications, as getting plate that large has got to be kind of pricey. I like the idea of bolted constuction with visible countersunk allen head bolts all over the baffle holding the internal bracing.

Max
 
Aluminium cans are easy to melt, the important thing is having no ashes in it, and then if you are smelting custom shells you wouldn't have to do even a minute of welding, just smelting.

Melting and pouring the metal is really easy with a hot enough stove, the tricky thing is making a nice mould, perhaps using plasterboard or balloon covered in plaster.

I'm sure there's tons of information online, for example you could make your speaker moulds out of papier-mâché, cover them in plaster and then mould the space.
 
I used aluminium die-cast boxes for a pair of portable speakers. They had gaskets (to meet IP** sealed regs). I used some BAF filling, and damped the back with adhesive neoprene strips. Internal volume was about 1litre, suitable for a 3" unit. I took them camping (in the boot of a car), and the rugged but light design served its purpose well. There was no bass due to their size, but I had music!:D
 
re metal enclosures

A very good material for speaker boxes is steel.
If you build a box from 3/4 inch boiler plate instead of mdf the panel resonances are at about the same frequencys but are around 100 times less in amplitude because steel is so much stiffer, the drawback is of course that steel is very heavy, and people are absolutely conviced that such a box must sound "metalic" because steel rings if you hit it with a hammer.