Cabinet Dampening Materials

[Cyclotronguy]

The Seattle Zoo used to sell "Zoo-Doo" in any species you might want.

Word on the street was that big cat "Zoo-Doo" was wonderful for keeping the local stray pets out of one's yard.

Mixed up with something to make it stick to speaker cabinets and one could argue that you could not only make for an inert cabinet but one that "Kitty" would avoid.

Cyclotronguy

[Ian Mackenzie]

Next we'll see it sold on Ebay out of .............

Acquadump..........the best damping for your 4345's..................

[richluvsound]

Macka,

are you trying to say my speakers sound "CRAP"?

Rich

[Ian Mackenzie]

I think we have been though all that in another thread.

When I get around to re building mine I intend to look at this again.

There is HD MDF out there and other high density laminates used for sound proof doors. The problem is this material is both very heavy and expensive.

Soi if someone can do some investigations using std mdf it would be very useful.

Ian

[Andyoz]

Guys,

I really think you are heading down the wrong track with the thin brush applied layers referenced in those links. They will work on relatlively thin metal sheets but not on the much heavier (and inherently better damped) MDF or plywood boards.

You should be looking at something like this (constrained layer damping) - the 32mm layer, not the 15mm one:

http://www.cdm-uk.co.uk/CDM-UK_SDS/M...ORE-MARINE.pdf

We deal with this company in Ireland and have found them one of the few in the industry to have realistic pricing. These products actually are not rocket science.

Rich...not sure how it would go on your curves (p.s. if it works, can I get a discount of a pair of your new creations!!).

[richluvsound]

Ian , the word "crap" was a pun !!!!

Andy ,

this stuff looks very interesting !

I'll phone for a sample today .

Rich

[richluvsound]

Cheers Andy,

I just spoke to Roger, the UK rep. They are sending me a sample sheet to play with. As well as the ISO-CORE they supply the membrane only. He will hook me up with some Italian company that laminates it into curved panels for the marine industry. Adhesives are going to be the issue for curved panels though. I think this would work really well. I will make two test boxes, one with one without , suck it and see !!!!

Rich

[Andyoz]

They are a very helpful company. The supplier here in Ireland does a lot of business here so we should be able to pull some favours if you need.

I am just wondering exactly what we are trying to dampen here. The constrained layer damping really works best at the "critical frequency" (or coincidence freq.) where there is a resonant wave travelling in the same plane as the panel. For 20mm plywood it's normally at around 1000-2000Hz. For MDF it's around 1500-2000Hz but not as bad as plywood. Every material has it - you commonly hear it in a glazed office on a rainy day when the high freq. tyre noise from cars is filtered by the dip in performance and is heard as a "swishing" sound as the car passes (p.s. it essentially dissappears with laminated glass which is a form of constrained layer damping).

The low freq. resonance is more a function of the panel size, stiffness and mass. Not really sure how much the constrained layer damping helps that TBH. That's more a bracing and mass issue.

The only way you will ever truely know what each of your prototypes is doing is to do FFT analysis of panel vibration using an acceleromoter. If you lived nearby we could do it!!!

Rich, how did you go with the Green Glue? I really like the way they research their stuff. Check out this..

http://www.greengluecompany.com/soundAbsorption.php

[Ian Mackenzie]

Andy,


I agree with the theory.

Have you heard the joke about the guy who was in bed with his wife and yelled out "Babe your as big as a house". She said "what did you say?" He said "your as big as a house" again. She said "Oh I can hear the echo...I get it". Go figure!

The theme is that any damping is a good thing...apparently!

In the other thread this is why I challenged the much mooted function of the Goop used by a certain loudspeaker manufacturer who we will not name here.

I believe it was a lossy absorbant at "lower frequencies" and a panel damping agent only at "higher frequencies".

One member said he could hear a difference in the bass after application of the Goop in a bass reflecx enclosure. The question is was it the bass, the upper bass or the midrange that was being effected?

One explanation would be reduction of panel borne reflections that congregate in large enclosures used in such systems which would tend to mask the actual bass. This occurs as a result of transmission of the destructive sound waves to the listener through a large cone(s) that operate in the 20- 800 hz range.

The asborbed energy is converted to heat through frictional losses.The application of various absorbants is well documented for this purpose.

If the absorbant is sufficiently lossy it will add virtual volume to the enclosure and this can effect bass tuning of reflex systems at Fb. By controlling the lossy factor "K" and the frequency "F" at which it is active you have an interesting means of applying asborbant.


Ian

[Andyoz]

This occurs as a result of transmission of the destructive sound waves to the listener through a large cone(s) that operate in the 20- 800 hz range.

That's a good point and one that's often forgotten. You have a very lightweight cone that can actually transmit internal energy that is not correlated with the electrically induced cone movement.

[grumpy]

You have a very lightweight cone that can actually transmit internal energy that is not correlated with the electrically induced cone movement.

Hi Andy,

If by "not correlated", you mean delayed with a complex transfer function, then OK, but
if other drivers are sufficiently isolated (e.g., via doghouse or non-resonant baffle), the
energy coming from and through the cone should correlate-able. -grumpy

[richluvsound]

Fella's

those last few posts left me feeling pretty stupid. I'm just a Lumber Jack , I'll leave the Nasa stuff alone and take the imperical approach. Although , it seems to me that if a box can be made to HELP solve any distortion issue , then its worth a crack

Rich

[grumpy]

Fella's those last few posts left me feeling pretty stupid.

No need for that... just job-specific-speak.

I'm just a Lumber Jack

and you're OK.

, I'll leave the Nasa stuff alone and take the imperical approach. Although , it seems to me that if a box can be made to HELP solve any distortion issue , then its worth a crack

works for me. Identifying distortion mechanisms gives one something to chase
after with a (hopefully) appropriate test box.

[richluvsound]

I will never admit to wearing womens cloathing though

I think it will be very interesting to build A-B boxes just to hear the difference. All the graph stuff can be done by Guido.

Rich

[grumpy]

looking forward to it (cab comparison, not your wardrobe selection).