+1:
MDF or ply will be fine, if braced well. Things like concrete and ceramic/stone, are good for experiments....IF thats your thing.
I would expect some difference between the concrete and the original cabinets. Even if they were entirely identical. Since they cannot be, they should sound different anyway....
If you brace well, and paint the inside surface with resin, you can stiffen the walls. Sand filled walls are great, do settle, BUT can be 'pre-settled'. Still a LOAD of work for some gain.
If you wanted to go nuts you could just go and buy some cast Nylon66 with 30% ground glass, in sheet form of the same thickness, and build a copy of the originals. Itll cost a bomb though.
MDF or ply will be fine, if braced well. Things like concrete and ceramic/stone, are good for experiments....IF thats your thing.
I would expect some difference between the concrete and the original cabinets. Even if they were entirely identical. Since they cannot be, they should sound different anyway....
If you brace well, and paint the inside surface with resin, you can stiffen the walls. Sand filled walls are great, do settle, BUT can be 'pre-settled'. Still a LOAD of work for some gain.
If you wanted to go nuts you could just go and buy some cast Nylon66 with 30% ground glass, in sheet form of the same thickness, and build a copy of the originals. Itll cost a bomb though.
Here is my know-how: glue boxes from Pergo by epoxy, then mold inside uneven walls. I used sand and liquid nails. Nasty stuff: sticks to rubber gloves better than to inner walls of the box. 
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mond,
Nylon 66 over Delrin? At least there are some glues that will stick to Delrin. Maybe I like it because it is so easy to machine. About 15 years ago the company I was with experimented with chopped carbon fiber in molded Nylon6. Almost worked to replace a beryllium part. Almost. A slab of it could have great possibilities.
Does anyone know what the various "magic" materials Wilson has made for them actually are?
Wave, now that has some real possibilities for a small club PA. Cool. Your vertical dispersion must be "no".
Nylon 66 over Delrin? At least there are some glues that will stick to Delrin. Maybe I like it because it is so easy to machine. About 15 years ago the company I was with experimented with chopped carbon fiber in molded Nylon6. Almost worked to replace a beryllium part. Almost. A slab of it could have great possibilities.
Does anyone know what the various "magic" materials Wilson has made for them actually are?
Wave, now that has some real possibilities for a small club PA. Cool. Your vertical dispersion must be "no".
They sound awesome in one surgeon's living room in Berkeley. Compared to Magnepans they have huge sensitivity.
Here's a company that makes "concrete" speakers.
Loudspeakers - Terrazzo Art Fidelity - Outstanding in Sound and Design - TAF Oss
I have no idea how they sound though.
Loudspeakers - Terrazzo Art Fidelity - Outstanding in Sound and Design - TAF Oss
I have no idea how they sound though.
Your analogy is like saying polyethylene and carbon fiber reinforced polyethylene are the same because they are both made from polyethylene.
I will say it again. There is a very big difference between Cement and Concrete.
You obviously have not done mechanical testing on these materials or you would not be arguing with me.
By the way you can even make steel into an acoustically dead material if you know what you are doing. I am not suggesting anyone do that though.
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Concrete is often reinforced with steel, because it tends to crack. If it rings it is most likely due to the steel reinforcing.
Or if it is mounted to a steel frame then what you might be hearing is the resonance of the frame.
re nylon
i hadnt considered delrin, from my fractured recall i didnt think it was as rigid, could easily have missed it however. The point you make about bonding is true, nylon requires phenol i think, in order to glue weld with chips and solvent. And its not a nice solvent and difficult to buy. This is why i havent tried it yet, aside from the cost of 20mm cast nylon sheet itself.
i hadnt considered delrin, from my fractured recall i didnt think it was as rigid, could easily have missed it however. The point you make about bonding is true, nylon requires phenol i think, in order to glue weld with chips and solvent. And its not a nice solvent and difficult to buy. This is why i havent tried it yet, aside from the cost of 20mm cast nylon sheet itself.
I think the key would be to attenuate the back wave from the driver, to keep it from bouncing back out through the woofer. Concrete would be/is very reflective to sound.
You need something dense, as opposed to just a thin layer of poly.
This will help control the negative aspects of a concrete cabinet.
As far as cabinet resonances, if you are concerned, or think your power level would excite these resonances, then structural bracing could easily be added.
One way would be to cast "ribs" inside the cabinet, or have pieces of re-bar embedded from sidewall to opposite sidewall, preferably close to a corner. "Gussets" could also cast into the corners.
Be creative, there is lot's of options if you are open minded.
You need something dense, as opposed to just a thin layer of poly.
This will help control the negative aspects of a concrete cabinet.
As far as cabinet resonances, if you are concerned, or think your power level would excite these resonances, then structural bracing could easily be added.
One way would be to cast "ribs" inside the cabinet, or have pieces of re-bar embedded from sidewall to opposite sidewall, preferably close to a corner. "Gussets" could also cast into the corners.
Be creative, there is lot's of options if you are open minded.
There is a company in the UK dedicated to it!
Home page for Sound Dead Steel sound deadened steel sheets and adhesive dampers for noise and vibration control. Sonphonon, Alidamp and Aludamp
Sorry, totally wrong.
I recommend a few folks here actually do a little reading on materials science or do a little research for yourselves. I also recommend many here read the background work on desirable material properties. You might start with the AES speaker anthologies. Intuition will serve you far better after you get some fundamentals.
When you put energy into a system, you need a way to get energy out. In this case, we are talking about transforming motion to heat. ( actually just a frequency shift) I doubt the rockwool has enough friction to do the job well. One property you will take advantage of is that transferring energy from one medium to another is lossy, so any time you have disparate materials, you will reduce transmission. Another thing to consider is that any system, such as described, attenuated differently with different frequencies. You may get a nice 50dB at one frequency, but find it is almost transparent to others.
When you are talking about perf board over a cavity, even if stuffed, you are talking about a Helmholtz resonator trap. Please go read up on them.
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