Constraint layer damping is the most effective. Possibly aluminum/flexible layer/aluminum.
Layers of different materials also works, such as aluminum/MDF/aluminum.
From damping factor values : damping factor values
Material...................Damping Factor
Aluminum......................... 0.004
MDF................................. 0.017
Aluminum/MDF/Aluminum... 0.218
Layers of different materials also works, such as aluminum/MDF/aluminum.
From damping factor values : damping factor values
Material...................Damping Factor
Aluminum......................... 0.004
MDF................................. 0.017
Aluminum/MDF/Aluminum... 0.218
Well one thing that i know 
is that for instance the armored glasses when hit they are quite dead sonically
And they have layers of glass (stiff material) alternate with layers of plastic materials (damping materials).
they are also quite good at isolating from outside noise like in the banks
But my new discovery is this Panzerholz
Nobody knows if it is used in some commercial units like a sub or what ?
Thanks again, gino
is that for instance the armored glasses when hit they are quite dead sonically And they have layers of glass (stiff material) alternate with layers of plastic materials (damping materials).
An externally hosted image should be here but it was not working when we last tested it.
they are also quite good at isolating from outside noise like in the banks
But my new discovery is this Panzerholz
Nobody knows if it is used in some commercial units like a sub or what ?
Thanks again, gino
Well one thing that i know
And they have layers of glass (stiff material) alternate with layers of plastic materials (damping materials).
Laminated glass is essential a constrained layer damped (CLD) system.
Glass.....................0.03 damping factor
Glass, Laminated.....0.35 damping factor
Permali and Panzerholz are similar materials, compressed beech with resin.
Jabroc is compressed plywood, though not sure about the resin content.
So they are right at PERFECT8 Technologies
ok glass is clearly not an option
But if there is a wood based material that is both stiff and damping ... well this should be a godsend and quite common around
Why it is the first time i hear of this Panzerholz ?
at least for high end sub-woofer seems to be the material of choice for the cabinets ... am i wrong ? is so damned expensive ?
thanks again, gino
Thanks ! i see some prices now ... it is really a special material ...
http://audioqualia.prophpbb.com/topic6.html
Kind regards, gino
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Hey how about Phon N by Wisa, UK based company.
Imho a great way to dampen resonance in cabinets.
No need to attache (with heat or glue) bitumen (tar/asphalt) to the walls and adding another layer of wood / aluminum (shear forces - energy passing from wood / AL to bitumen to Wood greatly reduce the vibrations / sound waves exiting the cabinet walls).
Anyone tried the Phone N?
Regards
Imho a great way to dampen resonance in cabinets.
No need to attache (with heat or glue) bitumen (tar/asphalt) to the walls and adding another layer of wood / aluminum (shear forces - energy passing from wood / AL to bitumen to Wood greatly reduce the vibrations / sound waves exiting the cabinet walls).
Anyone tried the Phone N?
Regards
Yes, and you can tell by the price that they are plenty "proud" of their material.
Another wood, Ipe, also known as Brazilian walnut, has a modulus of 3.2 Mpsi / 22.1 Gpa and a damping factor of 0.50. Well damped, 3 times stiffer than Baltic Birch and 7 times stiffer than MDF. Being a solid wood, you have the typical drying/humidity issues with expansion/contraction and warping. Ipe is heavy, stiff, hard, and well damped. It's imported from South America and used for outdoor decks.
Ipe | The Wood Database - Lumber Identification (Hardwoods)
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Sadly I haven't found a reference yet for the material other than the quote: "viscous damping material" sandwiched between two layers of aluminium.
Hi of course no discussion about that. Reading some notes about the manufacturing process is indeed complex.
I understand now because is used mainly for high quality turntable plints ...
It could be competitive with other proprietary materials developed by some audio brand like Rockport Technologies, that are even much more complex and expensive.
I guess that the laminated concept is the right one then.
I have seen somewhere some metal honeycomb panel but i cannot remember where. That material could also be useful to realized the stiff layer i guess.
Thanks a lot again, gino
Hi and sorry but i am too interested ...
i was thinking about the damping effect resulting from assembling a cabinet with two different materials, one stiff and one damping
Then the solution of a metal front baffle connected to a normal mdf cabinet should work perfectly.
Am i wrong ?
Even a thick aluminum front baffle with holes for the drivers should not cost that much
And its natural tendency to ring would be stopped by the rest of the cabinet made from normal mdf or better a wood with good damping properties ... even a cheap one properly sized.
Cost for me is an object after all.
This is the solution used for the Magico Mini of which i re-attach a picture
And at least for the Mini the concept seems to work very very nicely.
P.S. an interesting video ....
https://www.youtube.com/watch?x-yt-ts=1421828030&x-yt-cl=84411374&v=sMOf9KNkhnw
i was thinking about the damping effect resulting from assembling a cabinet with two different materials, one stiff and one damping
Then the solution of a metal front baffle connected to a normal mdf cabinet should work perfectly.
Am i wrong ?
Even a thick aluminum front baffle with holes for the drivers should not cost that much
And its natural tendency to ring would be stopped by the rest of the cabinet made from normal mdf or better a wood with good damping properties ... even a cheap one properly sized.
Cost for me is an object after all.
This is the solution used for the Magico Mini of which i re-attach a picture
And at least for the Mini the concept seems to work very very nicely.
P.S. an interesting video ....
https://www.youtube.com/watch?x-yt-ts=1421828030&x-yt-cl=84411374&v=sMOf9KNkhnw
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Laminated bamboo lumber, LBL, is also another alternate.
Modulus of Elasticity 1.5 Mpsi / 10.3 GPa
Damping Factor 0.2
There is some concern with warpage, though some have figured it out.
Sierra - The Cabinet
http://www.htguide.com/forum/showthread.php?41409-Wavecor-Ardent-Design-and-Build/page10
See JonMarsh posts #340 & #349
Best bamboo we have seen is the stranded plywood. An interior layer of blocks with skin made of an engineered material based on strands of bamboo. It also has a VERY tough surface to resist dings.
dave
Dave, people appear to use different types of LBL. I'm open for all information. I plan to use some LBL in the future. My primary concern is warpage after setting, after cutting, and after assembly.
As best as I can tell:
Ascend Speakers uses vertical edge grain, single ply bamboo sheets
Jon Marsh uses 3 ply cross laminated bamboo sheets
You and others have recommended stranded 3 ply laminated bamboo sheets
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Early on we had warpage issues with the 3-ply with vertical outer layers after machining it. The issues were recoverable. After assembly no issues.
With more recent builds we have not have any issues. Don't know whether that is because the material is better now (vertical & stranded), the boxes we built were smaller, or experience meant carrying out steps in such a way that warpage was avoided,
Plyboo has measured mechanical data on their horizontal, vertical, and stranded 3 layer plywood. Stiffness of the stranded is significantly higher. It is also denser (not necessarily an asset) and has a much tougher surface (definitely an asset)
People have succesfully made cabinets with single layer bamboo, i wouldn't bother.
Another possibility is making your own plywood from the available stranded "veneer". Would require a serious many ton press.
dave
Hi and thanks and i am sure of the goodness of the solution
Even throught Youtube i hear great sound from the speakers you mention
But this construction seems very tricky to me
The use of an extremely rigid one material baffle coupled with a cabinet in mdf could do the trick i guess
The problem is the material for the front baffle .. that must be an expensive one like solid alluminum of this panzerholz ... or like i have seen corian ... a very expensive material used for kitchen.
Extremely hard and stiff ... another very good candidate for one piece baffles.
Like in this speaker here ( i guess a good one also )
The Boulder studio monitor
this is the updated version with Seas aluminum 8" woofers ...
An externally hosted image should be here but it was not working when we last tested it.
Quite impressive i think
But the real discover for me is to have understood that the cabinet can indeed have a big impact on sound
I have not yet understood how much ... but i feel a lot.
I have seen speakers with exceptional cabinet and just good drivers to get the high praise of famous audio magazines and reviewers ...
for what this can count of course.
But i want to trust them ... so cabinets are a real challenge.
Thanks again for the very valuable advice, gino
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Corian is stiff as laminated bamboo, and 1/3rd more stiff than Baltic Birch. Corian is not well damped. I'm not aware of how the Corian front baffle would interact with MDF or Baltic Birch enclosure walls.
Corian
Modulus of Elasticity..... 1.4 Mpsi / 9.7 GPa
Damping Factor............0.04
Understanding loudspeaker enclosure wall vibrations and sound emission involves more than just simple stiffness, mass and damping. If one looks at the cumulative spectral decay (waterfall plots) of MDF and Baltic Birch enclosures, the two are very similar. Similar both frequency and decay wise, yet the stiffness of Baltic Birch is 2.4 times greater than MDF. General vibration principle is natural frequency = Square Root(stiffness/mass). So the vibration of Baltic Birch should be about 50% higher frequency than MDF, and its not.
I posted this on another thread concerning enclosure wall vibrations:
The link below is from the Netherlands. One can figure out some of the information. Once on the site, go to the "Projecten" area,
then select "Kast Materialenonderzoek". Translator software does work on the site.
http://www.hsi-luidsprekers.nl/Kastmaterialenonderzoek.htm
You think about enclosure wall vibrations too much and you start to suffer "paralysis by analysis".
Structural borne sound, transmissibility, coincidence frequency, stiffness controlled, mass controlled, damping controlled...... Ah!
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Hi and thanks again for the very valuable advice.
I admit i have a very trivial approach but i am observing some common traits of some very high quality speakers.
One above all ... a very stiff front baffle ... they have all something like this. All of them. Materials can be different but if a more "flexible" material is used then the thickness is very high to get the necessary stiffness.
I have become obsessed more of the frontal baffle more than any other face of the cabinet. For other sides just a decent mdf can work ok.
If you look at this picture taken from the article you kindly mention
An externally hosted image should be here but it was not working when we last tested it.
you can see clearly the flection of the front baffle ... this is the most detrimental effect that can happen ... not so the flection of the other panels.
I would ask to the open baffle sepakers designers how they realize their only panel ... the baffle
I am sure that all and i stress all of them design the baffle to be extremely stiff to be still during the most stressing passages ...
just look at this mighty example ... and look at the impressive support behind it whose only task is to avoid any flection of the baffle.
I would even think to laminated bullet proof glass just for the front baffle.
And again i would not be the first and the only
An externally hosted image should be here but it was not working when we last tested it.
Once you get an extremely stiff and still front baffle the rest is much much less critical. Any resonance/ringing possibly generated by the front baffle could be absorbed by the rest of the cabinet.
The emission from the side panels is so low in level compared to main frontal emission to be neglected
There is an easy way to assess this
To mount a stiff panel/adapter above the original and fix the woofer to it
I would decoupled the tweeter instead ... very easily done with a rubber mat under the flange.
Thanks again, gino
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