New type of baffle construction

madisonears · 8th January 2009, 02:52 AM

I am currently in the prototype stage of a pair of OB tweeter/mids MTM that will eventually mate with a pair of sealed bass bins.

Because the mids I selected are 4" and have very little space at the rear for the backwave, I wanted to use a thin material that would be stiff, dense, and not ring or vibrate excessively.

Every enclosure builder's dream, right?

Thought about solid hardwood, aluminum, phenolic, molded epoxy, polyurethane or fiberglass, even ceramic, but all of them have drawbacks.

So now I am using PVC sheet: a 1/8" thick and 1/4" thick sheet with a 1/16" layer of Dynamat laminated between them. I must say that this is filling the requirements pretty well. It vibrates very little, even at the unsupported edges. It doesn't seem to be coloring the sound at all, unlike 1/2" plywood and MDF. It is dense yet easy to work with, and very stable and strong.

I don't know how well this material would work with larger drivers, but with these 4" mids (which have useful response down to 200hz) mounted on a simple, flat piece, I feel almost no vibration transmitted to the tweeter flange. With any kind of stiffener attached, I'm sure this configuration would be suitable for heavier duty applications.

It's not cheap, and the hardest part is gluing the layers together. I used standard PVC glue, but there are probably better types. At least the glued panels seem to be fairly sturdy: the Dynamat pulls apart before the PVC breaks loose.

Just an idea for you all to ponder.

Peace,
Tom E

jupiterjune · 9th January 2009, 12:54 AM

I found CPVC to be one of the most well damped materials I ever found. I would bet that PVC performs simularly.

JJ

mayhem13 · 9th January 2009, 03:15 AM

3/4" cast acrylic is really inert as well. Just tap the panel next time at the bank and listen to the 'THUD'. Relatively inexpensive for a 1x2 piece as well. Routes well when frozen. Been working on an OB MTM for a WHILE now with it. Currently sand blasting the rear panel with an airbrush/beader and cut friske. Should turn out well with some blue LED lighting.

8th January 2009, 02:52 AM	#1
madisonears diyAudio Member Join Date: Sep 2007	New type of baffle construction I am currently in the prototype stage of a pair of OB tweeter/mids MTM that will eventually mate with a pair of sealed bass bins. Because the mids I selected are 4" and have very little space at the rear for the backwave, I wanted to use a thin material that would be stiff, dense, and not ring or vibrate excessively. Every enclosure builder's dream, right? Thought about solid hardwood, aluminum, phenolic, molded epoxy, polyurethane or fiberglass, even ceramic, but all of them have drawbacks. So now I am using PVC sheet: a 1/8" thick and 1/4" thick sheet with a 1/16" layer of Dynamat laminated between them. I must say that this is filling the requirements pretty well. It vibrates very little, even at the unsupported edges. It doesn't seem to be coloring the sound at all, unlike 1/2" plywood and MDF. It is dense yet easy to work with, and very stable and strong. I don't know how well this material would work with larger drivers, but with these 4" mids (which have useful response down to 200hz) mounted on a simple, flat piece, I feel almost no vibration transmitted to the tweeter flange. With any kind of stiffener attached, I'm sure this configuration would be suitable for heavier duty applications. It's not cheap, and the hardest part is gluing the layers together. I used standard PVC glue, but there are probably better types. At least the glued panels seem to be fairly sturdy: the Dynamat pulls apart before the PVC breaks loose. Just an idea for you all to ponder. Peace, Tom E

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9th January 2009, 12:54 AM	#2
jupiterjune diyAudio Member Join Date: Nov 2006	I found CPVC to be one of the most well damped materials I ever found. I would bet that PVC performs simularly. JJ

9th January 2009, 03:15 AM	#3
mayhem13 diyAudio Member Join Date: Sep 2008	3/4" cast acrylic is really inert as well. Just tap the panel next time at the bank and listen to the 'THUD'. Relatively inexpensive for a 1x2 piece as well. Routes well when frozen. Been working on an OB MTM for a WHILE now with it. Currently sand blasting the rear panel with an airbrush/beader and cut friske. Should turn out well with some blue LED lighting.

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