I owned a pair of Jim Rogers' JR149 speakers, cabinets of medium gauge aluminum sheets rolled into a cylinder and lined with a thick bituminous sheets. Excited by a 4" KEF B110 they still rang like bells. Damped bells for sure, but for vibration those cabinets were second only to my adolescent experiments with cardboard boxes.
Since the start of this thread I have been envisioning such a material.
I watched a show a few weeks back on the scraping of the Russian Akula class submarine. The rubber skin they were removing inspired me.
I wonder if you could get away with just using it in the corners, isolating the panels from each other. Or use it all over, it looks heavy.
From Wikipedia:
"After the war the technology was not utilized again until the 1970s when the Soviet Union began coating its submarines in rubber tiles. These were initially prone to falling off, but as the technology matured it was apparent that the tiles were having a dramatic effect in reducing the submarines' acoustic signatures. Modern Russian tiles are about 100 mm thick, and apparently reduced the acoustic signature of Akula-class submarines by between 10 and 20 decibels, (i.e. 10% to 1% of its original strength)."
Anechoic tile - Wikipedia, the free encyclopedia
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anechoic tile
Thanks Alvis
what if?
several layers of rubber roof membrane (or shower underlayment) glued together with silicone caulk? green glue if you got the $$$
the caulk would serve as the adhesive. it would be applied in "bead" form, not spread into a thin layer. generally follow the perimeter of each wall "panel"
within the panel edges, the glue pattern would be random, forming many random sized and shaped chambers.
what if?
Thanks Alvis
what if?
several layers of rubber roof membrane (or shower underlayment) glued together with silicone caulk? green glue if you got the $$$
the caulk would serve as the adhesive. it would be applied in "bead" form, not spread into a thin layer. generally follow the perimeter of each wall "panel"
within the panel edges, the glue pattern would be random, forming many random sized and shaped chambers.
what if?
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Aston Martin used to use a sandwich of layers of rubber and lead to soundproof the DBS, I don't think it did much for the acceleration or gas mileage though.
Can't. Because you are misleading people. What I said, had been proven on practice.
So it's 2012.
Do we really not know how to make an ideal enclosure by now?
Please dont tell me to use "1-inch MDF with bracing" ...
id try and contribute some more of my opinion, but...this subject has been beaten to within an inch of its life on numerous occasions, no1 ever agrees, someone always thinks theyve found the magic elixir. I dont know why folks think there has to be a consensus of opinion, there are 2 camps. End of. Both reasonable theories. Bit like quantum vs string theory. The debate kills the whole thing. Its settled that rigidity is key, mass is relevant depending on your viewpoint. Material wise a composite offers advantage over a single material generally. Pick your poison. I suppose we are all going to advocate graphene cabinets 'grown' in a lab...no?
I'm not sure which part you think is misleading people but the proof of well damped cabinet walls reducing resonances, and conversely of higher mass, higher stiffness walls being more difficult to damp is well proven science. See the papers and measurements of Sowter and Harwood.
Also read the published reports on room wall construction. Architectural acousticians no a lot about preventing sound from getting through a barrier. Look up coincidence effect.
This booklet answers some of the basic questions asked by the newcomer to building acoustic measurements
What is misleading is the often repeated audiophile notion that all we need is to make our cabinet walls thicker and stiffer and all will be well.
As to non parallel walls and variable thickness, lets take a look at the shape and thickness profile of the typical bell.
David S.
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Nice easy to read booklet, covers what most would require for reference, including myself. Thank you. I may be able to calc a ballpark figure for my granite placemats prior to cutting them up now!!!
Seriously though, Im in neither camp. I am of the opinion that EVERYTHING is a compromise. Stiff and light, versus heavy and damped; the ideal i believe is somewhere in the middle, in practice and in the realistic scope of what is possible to the DIYer.
Bang on. If you haven't ever built and listened to a concrete cabinet you might be a little surprised. It is the deadest cabinet imaginable. No ringing, no nothing, just dead.
...and heavy, really really heavy.
Bang on. If you haven't ever built and listened to a concrete cabinet you might be a little surprised. It is the deadest cabinet imaginable. No ringing, no nothing, just dead.
...and heavy, really really heavy.
Exactly. No ringing, silent like in grave. When after concert of Alexander Gorodnitsky I put record of Garry Kaar playing Amati contrabass with organ accompaniment we heard as if cold air breezing in that temple where Sony recorded it. Alexander said, "I never heard such acoustics before".
+1 Cal. there just is not enough energy to excit them. When I first recieved my 350hz Edgarhorns, I had every intention of using one of them to make a mold then pour a set for outdoor use. Never got a round to it, and don't need outside speakers any more.
Bang on. If you haven't ever built and listened to a concrete cabinet you might be a little surprised. It is the deadest cabinet imaginable. No ringing, no nothing, just dead.
...and heavy, really really heavy.
So those who have already commented on their experience that concrete rings like a bell?
I find there is a similar laziness in those that won't try to digest the theory that previous engineers have worked out. Read (and understand) Harwood and we'll talk.
I have made and tested many cabinets over the years. Thicker and denser makes for a particular cabinet resonance sound, solid and high pitched. That is the sound of high Q.
The first cabinet I experienced that sounded different was a BBC LS5/1ac cabinet. It was relatively thin plywood with a heavy amount of felt damping. After that I went on to make rubber sandwich baffle cabinets (internal layer of neoprene) at Snell and then layered damping glue cabinets. They were much deader with well damped resonances and a quiet "nuckle rap" sound.
Harwood explains why this is preferable.
I find there is a similar laziness in those that won't try to digest the theory that previous engineers have worked out. Read (and understand) Harwood and we'll talk.
I have made and tested many cabinets over the years. Thicker and denser makes for a particular cabinet resonance sound, solid and high pitched. That is the sound of high Q.
The first cabinet I experienced that sounded different was a BBC LS5/1ac cabinet. It was relatively thin plywood with a heavy amount of felt damping. After that I went on to make rubber sandwich baffle cabinets (internal layer of neoprene) at Snell and then layered damping glue cabinets. They were much deader with well damped resonances and a quiet "nuckle rap" sound.
Harwood explains why this is preferable.
I believe that there are those who made ringing concrete enclosures. But they had to try hard to make it ringing.
I myself did that once. I used rectangular plastic box as a form, took uniform mix made of cement and sand only, and made less than 1 inch thick flat walls. Yes, it was ringing. But it was an experiment that demonstrated results of wrong approach.
Contrary, this cabinets were absolutely dead, though ugly looking:
An externally hosted image should be here but it was not working when we last tested it.
For a sustainable resonance few conditions have to be met. 1. an overall steady flow of energy which is proportional or bigger than damping, 2. mass in motion 3.a spring (stiffness could be interpreted as (non)linear compliance after the proportional limit). So, if our loudspeaker is creating the energy flow which is agitating the structure of a box at a point of least stiffness, and the duration of resonance is related to the amount of damping. The damping is proportional to all included mass/material in the resonating structure, so it is not the same if the mass vibrates only partially or as a whole. The shape (then) defines natural and critical freq's because it is directly tied to stiffness and damping (as I pointed out in graphs)(flat membrane breakup vs cone breakup, anyone).
The bell is in a way the same and totally different. It is excited using a pulse (quasi Dirac) and resonates at all possible frequencies for which is designed to resonate. There is a difference because bronze, a high modulus metal, is chosen to sustain resonances, not to suppress them.
Layered composites (or constrained layer damping) are used when special conditions apply. They are not panacea for vibration, more like a scalpel. You have to know what you are cutting.
The last thing to point out is that the amount of resonance is tied to driving force in relation to the mass/stiffness ratio. So, if the walls are thick and stiff enough there will not be a vibration. Dave is thinking about a transmission loss through critical frequency in the coincidence region. Then don't excite those frequencies, simple as that.
The bell is in a way the same and totally different. It is excited using a pulse (quasi Dirac) and resonates at all possible frequencies for which is designed to resonate. There is a difference because bronze, a high modulus metal, is chosen to sustain resonances, not to suppress them.
Layered composites (or constrained layer damping) are used when special conditions apply. They are not panacea for vibration, more like a scalpel. You have to know what you are cutting.
The last thing to point out is that the amount of resonance is tied to driving force in relation to the mass/stiffness ratio. So, if the walls are thick and stiff enough there will not be a vibration. Dave is thinking about a transmission loss through critical frequency in the coincidence region. Then don't excite those frequencies, simple as that.
Wavebourn, no offense, but those are the ugliest loudspeakers I've seen in a long time. And I've seen a lot of them
I myself have not sen uglier loudspeakers, But I did not hear better results obtained from dynamic drivers in closed enclosures.
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