YG Acoustic speakers, meaning the boxes and the cones, are make of aluminum -
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I think it would depend on the size of the cabinet, or more accurately, the size of open expanses - sides most likely.
It is important that the cabinet does not vibrate, if it can vibrate, it can resonate, and that can effect the sound of the speaker.
Regardless of the cabinet material, the inside of the cabinet needs to be damped, or insulated. It has to have sound absorbing material. In the past, most used Fiberglas house insulation, today many people are using egg-crate acoustical foam. The Foam could be easily glued to the inside panels of the aluminum.
A good test of a speaker cabinet is to simply rap (knock) on the side; if it sounds hollow, then there is too much vibration in the cabinet. If it sounds solid, then the cabinet has sufficient bracing and thickness to suppress cabinet vibration. I suspect the same would hold true for aluminum.
Just a few thoughts.
Steve/bluewizard
I'm pretty sure somewhere in the last 90 odd pages I've seen formulas for working out panel resonance frequencies, and what it takes to excite them at that frequency, but daft me didn't bookmark the page. Does anyone have that info handy? I'm happy to chug through the math myself, just don't have any formulas or a clue where to find them.
Pretty much since the main objective is to keep it from 'breathing', so all six sides tied together to a 'fare-thee-well' along with mass loading [coupling] the driver to the cab to provide a stable work 'platform' while still allowing its mounting gasket to damp out any HF coupling vibrations, i.e. don't over tighten it, a too common problem in general and a no-no with thin metal, especially steel, cabs.
As already noted, damping is required to quell any eigenmodes, so either damp at least the top, one, back and any intervening 'holey' braces along with a small pad opposite the driver on the other wall since it's made out of metal or make all panels non-parallel with at least a >12 deg included angle to allow these 'slap echoes' to rapidly decay away same as in an amphitheater, etc.. For this, light stuffing or a diagonally hanging acoustic 'blanket' was what me and a few others that either used prefabbed boxes and/or welded our own preferred.
Foam back then sucked big time, just turned to a nasty goo in our high heat/humidity, but today's is pretty impressive and relatively cheap, so just make sure it's open cell if you choose to use it. FWIW, I recently scored a 'like new' 2" thick king size bed pad already neatly rolled up at the curb that from just blowing through it would be ideal for lining larger cabs like my dual 15" ~30" x 24" x 49" [o.d.], so a crude 'frame of reference' of sorts.
GM
Another approach to "internal lining" would be the following:
A moquette carpet with gummed base, and it is mounted inverse as usual:
the carped side is held/glued in place onto the cabinet and the gum side
watches the rear of the loudspeaker, so it could easily deform as it is interlayered
A moquette carpet with gummed base, and it is mounted inverse as usual:
the carped side is held/glued in place onto the cabinet and the gum side
watches the rear of the loudspeaker, so it could easily deform as it is interlayered
Hmmm, angles aren't a problem, I have access to a brake press, I can bend it any which way I want, could have every panel an interlocking zig-zag if I wanted.
I guess my next question is, is it worth the work to use aluminium plate as apposed to BB ply (my poor wood working skills aside), can I expected an audible difference in a good way using something with such a high natural resonance?
I guess my next question is, is it worth the work to use aluminium plate as apposed to BB ply (my poor wood working skills aside), can I expected an audible difference in a good way using something with such a high natural resonance?
A very basic rule of thumb for speaker enclosure construction is that it doesn't take a heck of a lot of cross bracing to greatly reduce resonances.
If given the choice between exotic materials or construction in an unbraced box and a well-braced box made of conventional materials and otherwise conventional construction, experience and science says take the bracing.
Simply glueing braces that cross the box and are centered on the panels can turn a resonant mess into a concrete-like coffin.
In that context, it might be possible to create a well-braced box out of cardboard that would be high performer.
Bracing is cheap from a materials standpoint, but can be very costly in terms of labor, which makes it an ideal feature for home constructors.
Ok I now discover that constrained layer damping usually involves two layers with a viscolastic layer between them. That's maybe fine, but involves the sort of damping that MDF would probably provide, and that some here dislike.
I first thought constrained layer damping involved rigidly glueing two layers with different resonant frequencies together, say steel and plywood, with a rigid glue such as thin epoxy, so that they just have a hard time resonating, not that they damp out resonances as much. So what happens when you laminate a very stiff layer with a less stiff layer with very rigid adhesive? It resonates at a frequency in between the two? Seems unlikely...?
I first thought constrained layer damping involved rigidly glueing two layers with different resonant frequencies together, say steel and plywood, with a rigid glue such as thin epoxy, so that they just have a hard time resonating, not that they damp out resonances as much. So what happens when you laminate a very stiff layer with a less stiff layer with very rigid adhesive? It resonates at a frequency in between the two? Seems unlikely...?
As presented, yes and no. Yes, you'll hear a difference and no, not in a good way until you add some damping to quell its natural 'ringing' when excited due to its greater rigidity, then it will be superior, i.e. it has a 'faster' [higher frequency] wave speed than wood in general and BB in particular.
BB OTOH is already somewhat damped due to its material properties, so bracing primarily just increases its rigidity, which in turn moves the panel's wave speed [resonances] higher where the BB's damping can more easily damp them since sound power falls with increasing frequency [1/f].
GM
No, not really, i.e. MDF has a low resonant BW with the slow decay this implies relative to BB ply or similar whereas constrained layer damping 'rings down' any panel resonances like when using your hand to damp a ringing bell.
The best overall construction is laminating two or more panels with very different properties such as MDF outer wall and a thin alum or steel panel on the inside, held together with a non-hardening bonding agent such as used to install 'floating' floors to keep them from creaking.
If a hard bonding agent is used, then you can get away with using the same material for both panels, which must be very lossy.
When braced, then best to bond ceramic tiles or similar or if it's already quite rigid, then using self stick floor tiles work well; though if not the thick, rubbery commercial ones, then you may need to add an extra layer or two of the cheap vinyl ones on larger cabs.
In short, it's all about creating a high, mismatching impedance between each, so plenty of design/materials flexibility to one's 'fancy' or budget. Of course the inner panel has to be free 'floating' for this to work, so can't be mechanically anchored in any way.
GM
Probably not so much.
The problem with that line of reasoning is that when you glue two things together with rigid glue, they become one thing that tends to have one set of resonances.
Probably very likely. They stiffen each other, which is something that constrained layer damping tries not to do.
A constrained layer damping system is composed of 3 or more layers. Every other layer is composed of something hard but flexible like sheet steel, and the layer in-between is composed of something that is flexible and has lots of internal losses when it changes shape, such as certain kinds of rubber or adhesive.
The idea is that when the hard sheets try to resonate, they deform the flexible layer and it absorbs energy by gently resisting the deformation.
A classic product for assembling constrained layer dampers is called Green Glue. NOISEPROOF YOUR LIFE® | Green Glue
Add two layers of ordinary somewhat rigid construction materials, and you will have a pretty good vibration damper.
Searching the internet, I stumbled across this MATLAB package that contains sheets for vibration analysis of rectangular plates, both classical and finite element. I thought it might be of use to some, with regards to working out ideal panel sizes for placing the natural resonance where you want it?
OK, I think I have an insight for my use, if one thinks that damping might affect the sound in a negative way then the only other option is to have the panel resonate above or below and frequency reproduced by a driver in a cabinet with said panels. So an option is to make the panels very stiff so they resonate at a frequency above the frequencies being reproduced, which of course is what bracing does. Or a stiff laminated structure can do
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Correct for the lower frequencies, but once above ~250-300 Hz it's easier to push them lower, so a mid-range on up alignment such as a horn is where particleboard, etc., is preferred; ditto if the driver has a high Qt, so above a ~0.5 we ideally want a decreasing cab stiffness with increasing system Qt [sysQ] as proven by the some of the foam core builds.
GM
GM
Has anyone tried, or tested , or is aware of any information, on the use of the latest stone veneers on the exterior of loudspeaker cabinets? How does this material affect the resonance of a conventional ply or MDF cabinet? Being of a very different resonance character intuition says it should prevent and suppress, but intuition can often be wrong.
stone veneers
Your intuition is good regarding the potential of stone veneers as a means of controlling panel resonance. I'm not entirely sure what thickness of stone you mean when you write of stone veneer though. I have tried using slate due to its incredible stiffness. It is a foliated metamorphic stone adding to its structural stiffness. Pavers are available in a thickness of 0.4 inch and have stiffness probably great than 2 inch MDF. These would certainly help suppress the panel resonances of any loudspeaker panel that they are applied. Ryobi makes a great little hand/wet saw cutting stone easily. However, it should be mentioned that natural slate doesn't have regular foliation structures and breaks easily resulting in a significant amount of waste. Use something like styrofoam to backup the material when cutting to help control breakage.
Your intuition is good regarding the potential of stone veneers as a means of controlling panel resonance. I'm not entirely sure what thickness of stone you mean when you write of stone veneer though. I have tried using slate due to its incredible stiffness. It is a foliated metamorphic stone adding to its structural stiffness. Pavers are available in a thickness of 0.4 inch and have stiffness probably great than 2 inch MDF. These would certainly help suppress the panel resonances of any loudspeaker panel that they are applied. Ryobi makes a great little hand/wet saw cutting stone easily. However, it should be mentioned that natural slate doesn't have regular foliation structures and breaks easily resulting in a significant amount of waste. Use something like styrofoam to backup the material when cutting to help control breakage.
I haven't tried, so I'm just theorizing out loud. My concern with stone veneer is actually vibration between the stone and substraight panel if the veneer is not really well secured, and even if it is, will it stay that way over time? It's entirely possible you could add noise to the equation with stone.
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