The reaction to the accelerating mass of cone assembly plus air is a body force within the magnet. The size of the force is mass times acceleration. The acceleration follows from a simple lumped model of the driver. The mass of the air is given by the reactive part of the air impedance which is likely to be fairly constant and modelled fairly well by that of a piston in an infinite baffle though a more sophisticated model should be easy enough. If your software doesn't support body forces within the elements of the magnet then apply an equivalent pressure to the back of the magnet in the way you are doing for the air pressure on the inside of the cabinet. The magnet is going to move effectively as a solid body so it will have the same effect.
Here's a goldmine: https://www.avsforum.com/threads/a-monster-construction-methods-shootout-thread.3154560/page-4
Andy: I will try a coupled acoustic-structural model instead. Thank you for the input!
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Coupling the structural motion and the acoustics is complex and unecessary. The load of the air on the cabinet is weak and pretty well modelled with an impedance. Simulate the cabinet structure with relevant boundary conditions applied for the external forces and then simulate the external acoustic field with an acoustic BEM or FEM software using the calculated motion of the cabinet as velocity boundary conditions. If keen one could recalculate the motion of the structure using the calculated surface air pressure rather than the originally assumed ones but it almost certainly won't make a big enough change to be worthwhile. Might be worth doing once as a check though.
I expected better from this discussion than the same blather we read from deluded audiophiles who favor magic over proven science. So until you someone here posts actual data - as I have done - I having nothing further to add.
Should be obvious.
Air movement — half the energy goes into the box and the other half is radiated out into the air. Furthermore air is not a great conductor of mechanical energy. Not to mention any fibrous damping material.
Direct connection to the box via the baffle: ALL the energy goes into the "box + baket".
dave
I believe i posted this from a study (publihed in the AES Journal) earlier:
Wasnposted here: https://www.diyaudio.com/community/threads/bracing-vs-damping.428225/post-8024367
dave
It's a little more complicated than that because it varies with frequency. At LFs the box is very rigid and is just another mass to the drivers frame, not so at all at frequencies where the box has mechanical resonances. AT LFs the air in the box pressurizes the box with a uniform pressure throughout creating a breathing mode (monopole) which is an extremely efficient radiator. So it's clearly different with frequency.
The fundamental question of this thread was about isolating the driver from the box. That is absolutely the wrong thing to do. An isolated driver has to be on springs. The drivers mass and this spring will resonate. When this happens all the energy will go into the moving the drivers mass and there will be a big hole in the response.
If you are calling the demonstration that you showed as "data" it is seriously flawed in so many ways. i.e. if the displacement of the glass is normal to the water surface then the surface will show nothing. And this is precisely the direction of motion that we are most interested in. Then there is the signal and the "meter" (our eyes!?) In other words, your "data" is not worth considering. There is lots of data that cabinet walls vibrate. Is it significant? I do not and have never considered radiation of the box as a major concern. It is on my list, just pretty far down. Only in a superb loudspeaker would this ever become an audible issue (assuming of course that the speaker is not blatantly poorly designed.)
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Isn't that a dual opposed sub? If so, I think that should be mentioned.
If not, how much does that dang sub weigh not to vibrate ? 🙂
It is. But everything varies with frequency.
Ballooning cn be a probelm with a subWoofer. But SubWoofers can be treated differently. Build light and stiff and take advantage of active push-push reaction force cancellation and once sufficiely braced ballooning becomes quite unlikely.
dave