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A Study of DML's as a Full Range Speaker
A Study of DML's as a Full Range Speaker
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Old 14th December 2019, 04:34 AM   #931
OffGridKindaGuy is offline OffGridKindaGuy  United States
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I built another quick and easy set tonight. The pictures are the plastic canvas and doesn't sound as good as the cotton canvas but overall.. No too bad..

A video..
YouTube
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Old 14th December 2019, 06:05 PM   #932
bradleypnw is offline bradleypnw
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Stevie Ray!
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Old 14th December 2019, 10:22 PM   #933
Veleric is offline Veleric  United States
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Has anybody tried applying constrained layer damping to DML panels?

In the giant Audio Circle DML thread I came across this paper:

https://eprints.soton.ac.uk/369232/1/Eprints.pdf

It seems counter intuitive, but the article shows that a panel with a sufficient loss factor will have greater radiation efficiency than a panel with a very low loss factor. This boost in efficiency occurs in the region between the fundamental frequency of the panel and the coincidence frequency. In addition, increasing the loss factor smooths out the bumps in the radiation efficiency in this same frequency region.

If correct, this would suggest that adding a damping layer to the panel could improve a DML.

I'm thinking of trying something like one of these products on the back side of my test panels:

Sonic Barrier UT-4 Ultra Sound Vibration Damping Sheets with Foil 15.5 sq. ft. 31.5" x 18.1" 4 pcs.

Boom Mat Tape Sound-damping tape — 2-inch wide, 20-foot roll at Crutchfield

Have any of you tried something like this, or know anyone that has?

Thanks
Eric
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Old 15th December 2019, 01:36 AM   #934
geosand is offline geosand  United States
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I believe in the second Tech Ingredients video the guy tried covering the back of a free panel completely with some kind of elastic damping material (don't remember what they called it). They even tested it with a freq sweep and showed the results so you could see and hear the difference between a panel without the damping material and a panel with. They must not have considered it an improvement because they did not choose it in their final build.

OK its in the second TI video at the 20 min mark. They used a "Silastic/Silicone" damping material...

geo

Last edited by geosand; 15th December 2019 at 01:40 AM.
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Old 15th December 2019, 01:49 AM   #935
geosand is offline geosand  United States
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Here's another DIY "wood" DML Panel...Sounds pretty good...


This is Home Depot 1/8th Birch cabinet plywood with water based poly urethane lacquer powered by a Dayton audio exciter. DAEX30HESF-4



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geo
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Old 15th December 2019, 05:24 AM   #936
gazzagazza is offline gazzagazza  New Zealand
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Quote:
Originally Posted by geosand View Post
Here's another DIY "wood" DML Panel...Sounds pretty good...


This is Home Depot 1/8th Birch cabinet plywood with water based poly urethane lacquer powered by a Dayton audio exciter. DAEX30HESF-4



YouTube


geo
Sounds great. What size is the panel?
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Old 15th December 2019, 05:30 AM   #937
geosand is offline geosand  United States
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Quote:
Originally Posted by gazzagazza View Post
Sounds great. What size is the panel?

Unfortunately, the guy didn't say, unless its buried in the comments.
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Old 15th December 2019, 05:08 PM   #938
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Default Canvas experiments.

So as the sun was going down on Great Britain

... for what feels like the last time, I thought I would try the canvas frame technique and share thoughts. I had a print I was given by an artist that I was not to keen on, his other work is great and I have bought a lot from him, but this one is not his best. I had to hand an exciter and about an hour so gave it a try. I fixed the exciter to a brace and used a 120mm ply disc as per the recipe.

First thoughts are:-

All the DML benefits are there, lots of clarity and attack, pretty smooth response similar to my ply panels, very engaging sound.
You get bass! I measured it down to 40hz. This is recessed compared to the midrange but this was just a first try so any deficiencies are down to me.
Your frame and brace needs to be well built and attachment to the exciter need to be solid. A lot of energy gets passed to the frame and I had some buzzing and rattles when I turned up the power. How much energy? Well the frame started ‘walking’ across the table on really bass heavy tracks e.g. Basshead from Far East Movement.
The canvas needs a good tension to perform well, I used inserts between the frame and the canvas to increase the tension and I got best results with a taught canvas which sounded 'drum-like' when tapped with a finger.

So its a very promising method and I look forward to exploring it further
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Old 15th December 2019, 09:37 PM   #939
OffGridKindaGuy is offline OffGridKindaGuy  United States
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@ BurntCoil..

I would suggest filling the gap where the canvas meets the frame on the inside to get rid of most or all of the "Buzz" problem. The frame is chamfered to the outside to avoid putting an impression in the canvas of the inside edge of the frame. A healthy bead of clear silicone sealer around the complete outer edge inside the frame where it meets the canvas works great and it isn't seen from the front. Just be certain the silicon sealer has good contact to the canvas and the frame..

I had an issue with the outer edge of the circle. A small bead of silicone sealer around the outer edge resolved it..

Last edited by OffGridKindaGuy; 15th December 2019 at 09:39 PM. Reason: 'cause I could..
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Old 15th December 2019, 09:42 PM   #940
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Cheers OffGrid!

I will try the frame bead when I get some new canvases as the one I am using just hasn't been stretched properly. I will try the disc bead tomorrow and let you know how it goes. Great discovery of yours!

Burnt

Last edited by BurntCoil; 15th December 2019 at 09:44 PM.
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