Damping metal baffles

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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.
 
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.
 
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?
 
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.
 
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.
 
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.


Note that the edge connection point (to the enclosure) will likely damp most of the ringing. The addition of the caulk just kills the rest, particularly with a heavy layer on the other side as well.
 
Gilbert Briggs the founder of Wharfdale, built a “knuckle wrapping”, fixture back in the 50's

This consisted of a device to clamp a section of panel and an inclined plane to roll down a steel ball to strike the panel, and a microphone to record the event.

3mm. Steel is about as stiff as a 15mm. MDF panel, and will flex about as much with the same loading, but it will ring with higher q with an impulse applied to it.

The point about constrained layer damping is that the panel has to flex quite a lot for the damping layer to be sheared enough, and this has to do with how much force you need to deform it in the first place.
Typical polymer type coatings have very little resistance to shear for low velocity small displacement panel movements such as this since viscosity is a “square law” effect, and panels such as this can be more effectively damped by simply putting a mass in the center of them.
Rcw.
 
I've used 10 mm thick steel for an open-baffle.
Each side was bonded with two 6 mm layers of cork i.e. 24 mm altogether (sort of the opposite of constrained layer damping).
The baffle was extremely dead, and very rigid!
I've previously used sand filled baffles, and this was better.
The drivers (woofers) were mounted directly onto the cork, and bolted through.

David
 
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