Enclosures: mass, bracing, damping etc

[tsmith1315]

Chris, thanks for sharing the details- it's beautiful work. I was wondering how the ribs didn't show through after vacuum, the form explains that. You never know when such info might come in handy!

 

[planet10]

... it's beautiful work ...

And they sound very good too :^)

dave

 

[poflobo]

How about using Dyna-Mat or equivalent on the inside of enclosures? It should easily reduce the resonance of the cabinet. Works great in vehicles! Also, put some on the walls of midrange/ tweeter horns and framework of the woofers.

 

[chrisb]

Uh, if you’re talking about the mahogany Elipses in Dave’s photo, I lived with them for a while myself, and I don’t remember any issues that could be attributed to the enclosures resonating. While I think I prefer the combination of the higher priced A12PW and A7.3 as implemented in the MTM that has been posted elsewhere to that of the SDX7, I could have easily lived with their sonics, but the footprint of both was too awkward for the room.

 

[planet10]

… Dyna-Mat or equivalent on the inside of enclosures?

It adds mass without adding stiffness, lowering the frequency that might ring and broaden the Q of that resonance, both of those making it more likely a resonance will be excited.

Not the approach i take.

dave

 

[chrisb]

I've had great results with Dyna Mat or equivalent in auto installs, and to deaden resonances of thin metal chassis such as CD player and most recently a pair of ACA kits, but never tried it in plywood speaker cabinets.

 

[tmuikku]

I red about the issue some time ago here on diyaudio.com, lots of discussion. Most effective and easiest to build method seems to be bracing with shearing damping. Will dampen resonances most effectively. Remember, unless you build the box very heavy it is impossible to get rid of wall resonances.

If I remember Geddes uses some liquid rubber with added glass beads to bond the braces, or something like that. Example here of such construction a new (I think) cabinet damping technique.
Edit. from the linked thread: Geddes uses "two part polyurethane with a filler", "dampens like cracy".