[Peter J]

Rich, I'm fascinated by the whole thing, perhaps because I don't know a bunch about resonance in general, but interested none-the-less.

Could you elaborate some on what exactly you see and interpret from the samples? In particular, you call out "damped resonances". What are you looking at that gets you to that conclusion?

Not expecting a thesis, but some rudimentary interpretation for the neophyte(me) would be appreciated.

[HAL]

Peter,
I am an amateur at materials.  This was to learn about what happens when you apply impulse response testing to materials and what can we learn.

The higher the graph level the less damping the material provides.  Lower level is better. 

Any peaks in the graphs are some type of resonance.  Narrow bandwidth peaks are resonances that are not well damped.  Broader peaks are more damped.  Damping is what you want.

Look at the HDPE graph and that is a very interesting well damped material. 

Looking at the materials responses, there are frequency ranges that work better than others.  That might help choose the materials for cabinets or baffles for use in specific frequency ranges. 

These tests do not show strength of materials.  Just internal damping of the material. 

Adding constrained layer damping material to the surface does increase the material damping for the MEDEX sample tested with CAE VB-2.

Hope that generates interest in how to make improvements in wood working for speakers and other things.

[brj]

What about No-Rez encased in Baltic birch (as SETman suggested earlier)?

No-Rez will help absorb the backwave from drivers, but is likely to do little for cabinet resonance aside from the impact contributed by it's added mass.

Blackhole 5 implements constrained later damping, however, and therefore should show some improvements to cabinet damping, in addition to absorbing the driver backwave inside the cabinet.

It would actually be really interesting to see both of these tested to assess exactly that impact.

(Note that CLD is best engineered to the application.  The mass/unit area of the damping layer, the percentage area to cover with CLD, the viscosity of the constraining layer, etc.. are all parameters that one would vary depending on what type of signal you're trying to damp.)


HAL, what size are your test samples?  I wonder what I have lying in my basement...

[HAL]

The samples are basically 1" x 3" x standard depth from whatever the source material originally had. 

Understand about CLD materials.  This just gives some ideas for folks to think about. 

I do not have any BH5.  Do have some scrap norez to try.