Discussion of Green Glue/CLD wrt box building

[jquin]

Hi all

I was hoping to start some discussion about green glue as a constrained layer damping (CLD) medium.
From my understanding it is not exactly suited for this.
I have searched this site but still have found some ambiguities.



So we take our green glue and apply it randomly rather than an even coat.
I'd be interested to see it applied as a thin sheet layer for CLD application but I diverge.



So we squish the panel together but this is not an adhesive glue so we need to fasten it destroying the CLD principle right?
So green glue may not be a CLD medium but we still may be able to use it to stop sound transmission.
So I'm guessing screwing the edges or something is required.
I have heard screwing the middle is better but the application guide for green glue on room walls is to screw the edges.
I wonder what the best way to use it for speaker enclosures is?



Now while I have found lots of wonderful discussion about panels using CLD that are magically suspended in mid air,
I haven't found much as to how you might attach a CLD panel to a baffle (green glue or no green glue).
Any suggestions. Is this joint important. Should the front baffle be CLD also if so how does that joint work?



Now bracing how does this work with a CLD panel? Like the picture shown above?



Now in this picture there are smaller floating panels above and below the brace.
I am considering doing this with green glue for my M8ta but goodness only knows if I'm wasting my time.

Any comments?, Well at least you have seen some pretty pictures.

[EdL]

My 2 cents:
I use 1/4" ceramic tile backer board. I factor this material into the volume considerations of the cabinet.
I use a joint sealant as my adhesive. It is chosen because it remains flexible after curing. During this stage is a great time to smear this material into any "suspect-air leak" locations.
The glue pattern is ~1-2" in from the edge, all the way around; inside that is filled with diagonal lines (45 degrees); inside the diagonals are generous dots, so that there is no distance across the surface greater than 3-4" left unsupported.
Once the adhesive has been placed, the backer board is brought against the panel and held there with spring clamps until the adhesive "grabs". I want to get the adhesive layer below ~1/16" thick.

It works for me.

[ThomasW]

My recommendation is to build the M8a-ta the way it was designed and not mess with CLD or green glue.

[rc white]

green glue efficacy

If you do tests of this you will find that this scheme has limited applications in speaker boxes.
From the literature this substance is made as a shear wave dissipation layer for plasterboard and you will probably find that its damping effect on short span, relatively thick mdf, is minimal.
The stiffness of a panel increases as the cube of its thickness, and the resonant frequency as the square of the area, from this there is much more to be gained from increasing panel thickness and reducing panel area by stiff bracing than by attempting to damp resonances.
Apart from the fairly small dissipative factor you will get from applying this to a speaker box, (unlike large unsuported expanses af plaster board), damping resonances only broad bands them, (i.e. the area under the curve remains pretty much the same), this means that a resonance in the range is more likely to be excited than a single high q resonance, this would tend to give a series of lower q resonances that are more audible than a single highr q one.
rcw

[jquin]

If you do tests of this you will find that this scheme has limited applications in speaker boxes.
From the literature this substance is made as a shear wave dissipation layer for plasterboard and you will probably find that its damping effect on short span, relatively thick mdf, is minimal.
The stiffness of a panel increases as the cube of its thickness, and the resonant frequency as the square of the area, from this there is much more to be gained from increasing panel thickness and reducing panel area by stiff bracing than by attempting to damp resonances.
Apart from the fairly small dissipative factor you will get from applying this to a speaker box, (unlike large unsuported expanses af plaster board), damping resonances only broad bands them, (i.e. the area under the curve remains pretty much the same), this means that a resonance in the range is more likely to be excited than a single high q resonance, this would tend to give a series of lower q resonances that are more audible than a single highr q one.
rcw

Thanks very helpful info about green glue.
I have found some local sound deadening material, its not whispermat but
I'm not prepared to pay hundreds of dollars for the "right stuff".

from a purely academic level I'd still be keen to learn how you make CLD boxes rather than panels, unless these designs are all top secret.