Except at resonance, of course, where it has no mechanism for attenuation and the 0.0019 thick cabinet does.
Why obsess about absurd cases? If the norm for cabinet walls is 3/4" or 19-20 mm., if undamped cabinets at 2 or 3 times that still, by accepted measurements show high transmission at voice frequencies, when do you give up? Should we try 2" thick? 3" thick? 6" thick?
Show me some measurements of your 6" thick cabinets. Maybe the resonances will disappear at some extreme thickness. Maybe they will be better than a 5/8" thick wall with heavy damping. What does it prove? We know in the relm of realistic wall thicknesses that damping gives better results than doubling or trebling wall thickness. Isn't that the real answer?
David
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Absurdity is the point of limiting cases. This may have touched on an assumption buried in the discussions. An absurd 190 meter thick cabinet for a 4" driver would be a 380 meter solid wood cube and absolutely not demonstrate the behaviour described. Likewise 4" thick cabinet walls for an LS3/5A interior volume wouldn't have the dimensional proportions of 1/4" thick walls and won't demonstrated the same resonant behaviour.
While the norm for hobbyist construction in 1970's England is an interesting academic discussion the Parts Express forum is littered with examples of layered cabinets of tapered wall thickness using commonly available contemporary tools and materials. Anyone wanting to build a better cabinet - whether it makes a better system is an interesting voicing question - from antiquated KEF drivers has better and completely realistic options today.
We had one special steam mold for these, special order
...huge airride allowed something like +/-1m latteral movement. Scarry thing to test as this is done at double the pressure rating. The "little" ones used in semi's are contained in an explosion proof container. Duds, tho rare, sound like dynamite. The big one is like a small nukeNobletucky plant is where they used to make the abrams tank treds, rubber coated. When Bridgestone bought Firestone they killed off that PITA project.
Main plant entrence is 17th Street S and Division. Can't miss it on google maps, its a million + footage.
My brother still lives in Indy and has a business based out of Cicero, just up the road.
Yes yes yes to the dual tonearm / counter balance / pendulum designs has got to be a direct copy. Heck, why reinvent the wheel. Stepmom remarried an architech who was designing some of these systems in the mid '80's for the Japanese govt. Interesting topic, if I'm not mistaken they employeed Purdue Univ. to assist in the modeling. Their PC AT wasn't up to the task
I am just such a person; wanting to build a pair of small(ish) speakers from antiquated KEF drivers (SP1032 & SP1003) and powered by a Quad 33/303 setup for use in a living room measuring about 4.5m x 3.5m x 2.7m rather than an Outside Broadcast van or a cramped studio.
To return to the original topic of this thread, would you care to describe a couple of these "completely realistic options"?
Depends how much experimenting you want to do. But as a short simple build, I would copy the original Kef Coda, possibly with plywood for the cabinet, with some damping on the walls. The Coda was a well regarded speaker in it's day, and still fetches high prices on eBay though not the manic prices of Ls3s. Whether it is an improvement on the Ls3 is questionable, but I liked it when I heard it a long time ago, particularly with music. It seems to be designed to go against the rear wall of a room, whereas the Ls3 is designed to be away from the walls.
Or you could use Volt drivers.
Interview with designer Derek Hughes about the Graham Audio BBC LS5/9 monitors on Vimeo
Interview with designer Derek Hughes about the Graham Audio BBC LS5/9 monitors on Vimeo
Andrew T,
Your English is fine.
I didn't think you question concerning at what thickness does the panel / wall resonance actually begin to attenuate was absurd. It was still on topic.
This thread drifted to pendulum earthquake building designs. (not a dig at anyone)
Not being an Engineer but a simple Contractor, I've been involved in building sound proof rooms that are almost dead quiet from the exterior.
Take the examples of single pane, double pane and triple pane windows. Because the single pane acts as a diaphragm sound is almost non-attenuated.
Double pane the air between acts as a buffer/ diffuser. Great example someone posted of LCL btw.
Triple panes block almost all the sound, yet on the perimeter they have metal and bitumen between the layers of glass, the frame contacts the interior and exterior pieces of glass which should transmit some energies.
If a speaker cabinet (box inside a box) has a more flexible inner box, ie: 1/2" MDF with an adhesive (green goo or silicone) on the perimeter only, and 1/4" dead air space in the middle, glued to a exterior plywood 3/4" box, would that be viable for our purposes?
Would dampening still be beneficial inside the 1/2" MDF box?
Just thinking out loud.
Ron
Your English is fine.
I didn't think you question concerning at what thickness does the panel / wall resonance actually begin to attenuate was absurd. It was still on topic.
This thread drifted to pendulum earthquake building designs. (not a dig at anyone)
Not being an Engineer but a simple Contractor, I've been involved in building sound proof rooms that are almost dead quiet from the exterior.
Take the examples of single pane, double pane and triple pane windows. Because the single pane acts as a diaphragm sound is almost non-attenuated.
Double pane the air between acts as a buffer/ diffuser. Great example someone posted of LCL btw.
Triple panes block almost all the sound, yet on the perimeter they have metal and bitumen between the layers of glass, the frame contacts the interior and exterior pieces of glass which should transmit some energies.
If a speaker cabinet (box inside a box) has a more flexible inner box, ie: 1/2" MDF with an adhesive (green goo or silicone) on the perimeter only, and 1/4" dead air space in the middle, glued to a exterior plywood 3/4" box, would that be viable for our purposes?
Would dampening still be beneficial inside the 1/2" MDF box?
Just thinking out loud.
Ron
I don't think this is an attenuation example.
The air between the two panes will transfer the sound wave from source to receiver panel quite effectively.
I think the attenuation comes from the interface from solid to gas and again from gas to solid. It's the very inefficient interface that gives the attenuation.
It's the same for a moving coil loudspeaker.
The coil moves the coil former = efficient.
The former moves the cone = efficient.
The cone moves the air = inefficient.
The air moves the inner face of the cabinet wall = inefficient.
The inner face of the wall moves the outer face of the wall = efficient.
The outer face of the wall moves the air = inefficient
We hear a attenuated version of the wall emitted sound compared to the input power applied to the moving coil.
The big inefficiencies come at the solid to gas and gas to solid interfaces.
This is very much influenced by the effective impedances at the interfaces.
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All wrong.
It is an LCL equivalent network, as I stated before.
The glass layers have mass and the air has compliance. If you increase the air gap you will see issolation improve from the greater compliance. The physics of this is well known and there are some calculators on line for predicting performance.
This also works for issolated walls and would work with a double cabinet, although you would have to have some contact somewhere. Also, between walls they recommend damping anyhow, since there will be some coincidence frequencies that might make it through both walls.
David
It is an LCL equivalent network, as I stated before.
The glass layers have mass and the air has compliance. If you increase the air gap you will see issolation improve from the greater compliance. The physics of this is well known and there are some calculators on line for predicting performance.
This also works for issolated walls and would work with a double cabinet, although you would have to have some contact somewhere. Also, between walls they recommend damping anyhow, since there will be some coincidence frequencies that might make it through both walls.
David
I find this conversation fascinating.
Speaker Dave, Please explain where you believe Andrew T. went wrong in the above speaker scenario.
I'm not picking sides..............
I'm not smart enough to know theory, I DO know what works though.
In a double pane window, the sound is attenuated from one pane the other. Either the transference of energy from glass to air is inefficient or from air to glass is. Right?
Can this model be transferred to a speaker cabinet for example only.
Actually unless the seal has failed there is no Air in between the panes, usually it's Argon.
Ron
Speaker Dave, Please explain where you believe Andrew T. went wrong in the above speaker scenario.
I'm not picking sides..............
I'm not smart enough to know theory, I DO know what works though.
In a double pane window, the sound is attenuated from one pane the other. Either the transference of energy from glass to air is inefficient or from air to glass is. Right?
Can this model be transferred to a speaker cabinet for example only.
Actually unless the seal has failed there is no Air in between the panes, usually it's Argon.
Ron
Its not really possible to speak of efficient transfers and inefficient transfers of energies at these various boundaries. I suppose if you were looking at a long transmission line you could consider transmission and reflection at transitions but that is not a very useful model here.
Modeling is the key. In engineering we search for a model that fits a situation well enough that it can explain the current system's performance and predict the performance of other similar cases. For a double walled barrier we can use the simple equivalent circuit of LCL or mass compliance mass, the first layer of the wall has a mass and so a rising mechanical impedance with frequency. The greater the mass the greater the inertia or impedance. It is coupled via a compliance (the springy air gap) to the next wall with its inertia. This gives a third order low-pass system with an 18dB per Octave loss in high frequency energy. Increasing wall mass or widening the air gap both lead to greater attenuation.
People in the building trade know that they get better issolation from non coupled walls and that wall mass increase or air gap increase both help. The same model applies to dual or triple pane windows. Argon is inert but it is still a coupling compliance, not a vacuum.
The whole notion of efficient boundaries and inefficient boundaries is not really the way to look at it and can't result in a useful model.
Regards,
David
Modeling is the key. In engineering we search for a model that fits a situation well enough that it can explain the current system's performance and predict the performance of other similar cases. For a double walled barrier we can use the simple equivalent circuit of LCL or mass compliance mass, the first layer of the wall has a mass and so a rising mechanical impedance with frequency. The greater the mass the greater the inertia or impedance. It is coupled via a compliance (the springy air gap) to the next wall with its inertia. This gives a third order low-pass system with an 18dB per Octave loss in high frequency energy. Increasing wall mass or widening the air gap both lead to greater attenuation.
People in the building trade know that they get better issolation from non coupled walls and that wall mass increase or air gap increase both help. The same model applies to dual or triple pane windows. Argon is inert but it is still a coupling compliance, not a vacuum.
The whole notion of efficient boundaries and inefficient boundaries is not really the way to look at it and can't result in a useful model.
Regards,
David
Speaker Dave,
Thanks for that concise explanation, even a simple Contractor could understand.
"The greater the mass the greater the inertia or impedance." This is the statement which Andrew T. was questioning. Not the validity, but the application, i think.
At what point does the wall mass surpass the LCL model? His example was stone walls.
Perhaps this conversation got off track somewhere when we left the realm of realistic speaker cabinet building. I'm not going to put a double pane window in my speaker. LOL. No one is going to build an 18" thick concrete walled speaker, and ever move it again.
Back to real world construction. Thinking about a woofer cabinet here, as MDF is more compliant, would that be best on the interior wall? Then Bitumen, then BB plywood? or would a second layer of MDF / Bitumen then BB plywood be worth the added cost and weight. Where's the handtruck?
Thanks for that concise explanation, even a simple Contractor could understand.
"The greater the mass the greater the inertia or impedance." This is the statement which Andrew T. was questioning. Not the validity, but the application, i think.
At what point does the wall mass surpass the LCL model? His example was stone walls.
Perhaps this conversation got off track somewhere when we left the realm of realistic speaker cabinet building. I'm not going to put a double pane window in my speaker. LOL. No one is going to build an 18" thick concrete walled speaker, and ever move it again.
Back to real world construction. Thinking about a woofer cabinet here, as MDF is more compliant, would that be best on the interior wall? Then Bitumen, then BB plywood? or would a second layer of MDF / Bitumen then BB plywood be worth the added cost and weight. Where's the handtruck?
I'm leaning toward asymetrical dual wall construction with cld bracing. Light/Stiff panels raises resonance but if we exchange argon (or air for that matter) with sodium hexafloride the speed of sound is reduced by roughly 5x! Now those resonances are frequency shifted downward where another braced cld outer panel mechanically attenuates these lowered resonances. I would be hard pressed to believe the amplitude of a raised panel resonance would pass through this medium without a great degree of attenuation passed onto the outer panel.
This air gap so to speak would most likely require a mylar bag to contain the gas and minimize leakage.
This air gap so to speak would most likely require a mylar bag to contain the gas and minimize leakage.
If you can't stay on topic,why don't you muppets go and find a room to discuss how many angels can perch on the head of a pin?
Your tedious ill-mannered drivel has absolutely Sweet FA to do with whether or not one can build a better (non) LS3/5A speaker based on T27s & B110s?
ps - many thanks for your helpful advice Jerry & Colin
Your tedious ill-mannered drivel has absolutely Sweet FA to do with whether or not one can build a better (non) LS3/5A speaker based on T27s & B110s?
ps - many thanks for your helpful advice Jerry & Colin
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