Strangest Box Material You used or Have Seen?

[stephenmarklay]

I think I should caveat this by adding: That sound great too

I suppose you could by a truck load of shoe goo and make that into a speaker with patience but it may not sound great

I have seen some corian, concrete, granite, plastic and even cardboard.

Since boxes resonate and we have to deal with that it occurred to me why not start with something that does not resonate much. Or in a frequency that is not a concern.

Rubber? Has anyone made a rubber speaker? I have, In my home gym 4’x6’ rubber horse stall mats. I keep looking at them thinking one day I will cut one of them up and make a box. They would to resonate for sure.

I also have a box of unused cork flooring. Cork inside and out with pressboard In between. I could easily make a box out of that, but use a Baltic Birch Baffle to mount the drivers to, and use a lot of roofing paper or similar to mass load it. This may happen.

How about you guys?

 

[JMFahey]

Any material will do, (even cheesy plastic) , as long as you make it thick enough so it can reasonable stand speaker sound pressure without flexing too much and resonating wildly.

 

[planet10]

In our speaker boxes we aim at pushing up potential panel resonances up in frequency because they become less likely to get excited — if they aren’t excited it is as if they are not there. This requires stiffness, strategic bracing, and distributing driver reactive energy across as much material as practical. Easy to use panel materials that lend themself to this approach are quality plywood and stranded bamboo plywood.

dave

 

[scottjoplin]

I also have a box of unused cork flooring. Cork inside and out with pressboard In between. I could easily make a box out of that, but use a Baltic Birch Baffle to mount the drivers to

I like cork, I have a cork floor. Why don't you give it a go and let us know. I wouldn't bother with the pressboard (whatever that is) just use as many layers of cork as it takes

 

[phase]

HDPE has a very nice resonance, have only used .5” thick.

 

[nigelwright7557]

I am pretty boring, used 18mm chipboard in my early days (1980's) and 18mm plywood now a days.

 

[stephenmarklay]

I like cork, I have a cork floor. Why don't you give it a go and let us know. I wouldn’t bother with the pressboard (whatever that is) just use as many layers of cork as it takes

I probably will. Take one for the team This stuff is multi layer. I get the wood/paper composite for free The inside cork looks like 1/16” the outside looks like about 1/8” with and about that much more thickness of the inside material. So it is probably 3/8” total.

I could layer them and use some green glue in the middle.

The outside finish has a nice clear and if I am carful it may look nice. I bet cutting could be done with large razor knife of sorts. Score and break.

 

[stephenmarklay]

In our speaker boxes we aim at pushing up potential panel resonances up in frequency because they become less likely to get excited — if they aren’t excited it is as if they are not there. This requires stiffness, strategic bracing, and distributing driver reactive energy across as much material as practical. Easy to use panel materials that lend themself to this approach are quality plywood and stranded bamboo plywood.

dave

Thanks Dave for your thoughtful comment. A bit like drinking from a fire hose

Your tatic of driving the resonant frequency up is a different take on this. The BBC and UK company’s try to push it lower, out of the ears most sensitive, and critical range for speech and much of the vocal range from 2-5k. How high do you push it and what level of attenuation do you see?

Now excitation is a different matter and I cannot comment with any authority.

I am trying to grasp your thoughts on spreading the load and want to know more

 

[Sonce]

Glass, done it long time ago. Had beaten Waterfall Audio, but they do it better:
Enceintes en verre - Page Selection | Waterfall Audio
Sounds good, too.

 

[scottjoplin]

if they aren’t excited it is as if they are not there. This requires stiffness,

That's the opposite of my experience, fnar fnar

 

[stephenmarklay]

I had an idea for my next box and this cork may be a good thing to try;.. I want to build a free-standing Front and Rear Baffle. They will be bolted with a long enough bolt to give me the depth I need. That Baffle combo would have feet forming the part that sits on the stand.

The sides, top and bottom will “wrap around this frame but only between a visco-elastic seal like sorbathane.

The idea is that very little mechanical energy is allowed to transfer from the front and rear.

Instead of bolting the “wrap” I would figure out some form of strap system. I could just use some tie downs I have to prototype it.

I don’t even drink so this is a runners high

 

[scottjoplin]

Sorbothane is great stuff. I used sorbothane insoles cut up as feet for my U-frame subs, they were the only thing that cured the cabinet twisting at very low frequencies and high driver excursions

 

[stephenmarklay]

Some neat thoughts here.

 

[Pano]

I've covered speakers in shaggy faux fur, but that's not really a box material. Also done plaster with fiber, AKA "Staff". Nothing too exotic. I suppose we've all used a cardboard box.

 

[planet10]

The BBC and UK company’s try to push it lower, out of the ears most sensitive, and critical range for speech and much of the vocal range from 2-5k. How high do you push it and what level of attenuation do you see?

I have a friend with Spendor BC-1 and a pair of LS3/5A. I can here them both resonanting down low. The BC1 makes them sound kind of romantic, the LS3/5A are downrightboxy sounding.

Since energy to excite resonances decreases as frequencies rise (above a certain point), if you can push them up above 500-1k they are unlikely to get excited. As well damping is related to the thickness of the material is much greater proportion of the wavelength, and with each transition from ply-to-ply acts as a damping mechanism, even if it does get going it is highly damped. Further we push for any potential resonances to have a highish Q. That means to get them going you have to have a lot of a tight (highish) frequency range pounding the panel for a long time… something rare in music. I get a lot of kickback on that last one, but it wors in practise.

dave

 

[Sonce]

That's the opposite of my experience, fnar fnar

LOL

 

[planet10]

The idea is that very little mechanical energy is allowed to transfer from the front and rear.

Opposite of what we do. The baffle is the weakest panel and the one you least want excited. If the back panel moves it is a lot less audible. We purposly transfer energy from the moving driver basket to the rear panel. As well as removing energy to a less critical panel, you also end up sharing the energy across much more panel meaning each one gets less energy (that same brace also sens energy to the top/bottom or sides as well). That points out one of the issues i have with KEFs tactic of gromment mounting the driver — it may remove energy from the cabinet, but it leaves it all in the basket decreasing the speakers DDR (Downward Dynamic Range — ability to reproduce small details).

dave

 

[stephenmarklay]

I've covered speakers in shaggy faux fur, but that's not really a box material. Also done plaster with fiber, AKA "Staff". Nothing too exotic. I suppose we've all used a cardboard box.

Ok that shaggy faux fur is not a box but it makes me want to do this

 

[stephenmarklay]

Opposite of what we do. The baffle is the weakest panel and the one you least want excited. If the back panel moves it is a lot less audible. We purposly transfer energy from the moving driver basket to the rear panel. As well as removing energy to a less critical panel, you also end up sharing the energy across much more panel meaning each one gets less energy (that same brace also sens energy to the top/bottom or sides as well). That points out one of the issues i have with KEFs tactic of gromment mounting the driver — it may remove energy from the cabinet, but it leaves it all in the basket decreasing the speakers DDR (Downward Dynamic Range — ability to reproduce small details).

dave

Interesting stuff here Dave. I like your thinking about moving to the rear. Never thought about that. The thing about the entire enclosure sharing makes sense too. However, one gotch (for the less experienced than you) is the vibration amplitude only needs to be small due to the relative larger area compared to the driver.

BTW I think Kef stopped grommeting drivers. They using a lot of constrained layer concepts etc.

 

[planet10]

one gotch (for the less experienced than you) is the vibration amplitude only needs to be small due to the relative larger area compared to the driver.

If one is careful with the bracing, and one gets into a situation wher ethe panel resonantes (rare with music on my boxes) as long as the 2 subpanels are out of phase there is little output.

Constained damping works. But costs time & money. And if my cabinets don’t resonant then i see little point in guilding the lily.

Another trick is to load woofers in tightly coupled push-push so as to take advantage of active vibration cancelation… one gets dramatically lower box load. KEF does this in their Blades. As do a number of other makers.

dave