Damping metal baffles

[454Casull]

I have some 1/8" (don't worry about rigidity issues) mild steel baffles for my next speaker project. Problem is, they ring when I flick them. I was thinking of applying a constrained layer of damping to the back, but there are 3 things that I don't know:

1) What material to use as the backing
2) What material to use as the damping layer
3) The thicknesses of each layer

I have access to aluminum and steel sheet. As for 2), I was thinking of either Green Glue or GE Silicone II for metal.

[ScottG]

"Constrained layer":

1. Steel
2. Complaint material
3. Heavy material

Perhaps:

1. Steel
2. 1/8" to 1/4" pure silicone caulk
3. Steel

[rcw]

With a steel baffle any kind of mastic type layer might as well not be there.

A steel Aluminium steel structure bonded with aircraft type adhesive will provide damping.
Rcw.

[sdclc126]

Any of the self-adhesive damping materials from PE, Madisound, Solen etc. should do, or Dynamat from your local auto parts store. You can apply multiple layers if desired.

[Curly Woods]

I would not think that you would want to use any type of really compliant material to sandwich between the outer layers. Maybe MDF as the inner material. Any thing flexible in between the sandwiches would not be good IMO, even if it does a superior job of dampening the metals. Maybe a very thin sheet of a hard rubber instead, but again i would worry about rigidity of this material.
Now if it were only applied as a backing then that would be different.

[454Casull]

I didn't clarify, but the baffle mount will not be affected by the constrained layer in any way.

Some of you are recommending a soft constrained layer, some a (relatively) hard constrained layer. Why? Won't the soft layer convert more of the shear energy into heat?

[ScottG]

Originally Posted by 454Casull

I didn't clarify, but the baffle mount will not be affected by the constrained layer in any way.

The "baffle mount" - is this baffle to enclosure OR driver to baffle (in your clarification)?

[Curly Woods]

Originally Posted by 454Casull

I didn't clarify, but the baffle mount will not be affected by the constrained layer in any way.

Some of you are recommending a soft constrained layer, some a (relatively) hard constrained layer. Why? Won't the soft layer convert more of the shear energy into heat?

Yes the softer material will "dampen" better, but it is also extremely "compliant". You do not want any movement of the driver frame, just the driver cone or dome. The movement may seem minor, but any movement is a "no-no".

Same thing as spiking your speaker to the floor. It helps to eliminate any movement of the speaker cabinet and couples the speaker to the floor tighter.

As all things DIY, do both and see what you like the best.

[454Casull]

It is impossible for the frame to deflect more after the damping has been added. You are not subtracting material, and I really do not think that there could be any resonances present in the new vibrating system that would be any worse than just the plain steel baffle.

Now if I was going to try both I wouldn't have bothered making this thread; I simply would've reported on the results.

I think I'll stick with a soft layer - hopefully caulk will do it, but if Green Glue will be significantly better I'll just go with that instead.

[David_Web]

There are special damping materials made for metal to damp any vibrations. Targeted for ventilation systems, cars and the like. Some better than other.
I don't know their prices or where you can get them, but their damping glue seems well regarded from the people I have talked to.
http://www.swedac-acoustic.com/