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Carbon fiber + nomex honeycomb sandwich DML panel construction project
Carbon fiber + nomex honeycomb sandwich DML panel construction project
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Old 31st December 2016, 01:06 PM   #21
lowmass is offline lowmass  United States
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electrostatic drive is very weak. not really suited to driving higher mass panels.

As well the type of speaker talked about here works by actually encurraging resonances. so driving from a "point" is nessasary.

Last edited by lowmass; 31st December 2016 at 01:08 PM.
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Old 31st December 2016, 04:16 PM   #22
bentoronto is offline bentoronto  Canada
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Carbon fiber + nomex honeycomb sandwich DML panel construction project
Quote:
Originally Posted by lowmass View Post
As well the type of speaker talked about here works by actually encurraging resonances. so driving from a "point" is nessasary.
OK, I wandered in here by mistake and now I will hasten out. But "encouraging resonances" sounds like a really wrong-headed concept to a conventionally-minded speaker builder.

And if in repeated asking, nobody has been able or seen fit to post an answer to the question of weight or weight compared to films, it is hard to think this thread is achieving adequate technical depth.

Ben
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Old 31st December 2016, 07:41 PM   #23
altie is offline altie
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What is the usefulness of that statement about "adequate technical depth"? I hesitated responding to your initial question about weight because it struck me as entitled. Look it up if you want to see how much a panel like this weighs. Google would give you the answer quicker than I would. After leaving it sit for a few days I got over that and decided I'd try to help you out, even though ESL is totally, way off topic.

I don't know much about loudspeaker design but you're probably right that exciting modes is precisely the wrong way to approach a conventional speaker design. Look up some details on DML and maybe check your attitude and have some sympathy and flexibility around what other people might or might not want to get out of a thread like this before pontificating on what's "adequate".
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Old 1st January 2017, 12:54 AM   #24
bentoronto is offline bentoronto  Canada
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Carbon fiber + nomex honeycomb sandwich DML panel construction project
A sq foot piece, a half-inch thick might be in the vicinity of 50 gr. Comparable to the cone part of a domestic driver although vastly stiffer (but stiffness per se in a cone does not necessarily lead to great sound). Of course today, so many drivers are made for cars and megawatt power handling, the moving weight can be anywhere even a pound.

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Old 1st January 2017, 10:15 AM   #25
TNT is online now TNT  Sweden
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Quote:
Originally Posted by bentoronto View Post
A sq foot piece, a half-inch thick might be in the vicinity of 50 gr. Comparable to the cone part of a domestic driver although vastly stiffer (but stiffness per se in a cone does not necessarily lead to great sound). Of course today, so many drivers are made for cars and megawatt power handling, the moving weight can be anywhere even a pound.

B.
Yes thats how it works. It is obvious that your technical depth doesn't reach far enough.

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Old 1st January 2017, 01:40 PM   #26
anji12305 is offline anji12305  United States
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Rather than preceding through a list of unavailable materials chosen for ideal properties - yet unobtainable - why not experiment with things you can purchase?

So what if the result isn't ready for a mass market? Once you've made something yourself, no one can deny your achievement.

Rough panels for archtop guitars would be my choice, for a trial run...

http://www.stewmac.com/Materials_and...htop_Tops.html

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Old 1st January 2017, 01:42 PM   #27
majerjack is offline majerjack  United States
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Thanks to Altie for this thread. It seems that we all lead busy live these days, and I appreciate the time you spent in constructing your panel and reporting it to this forum.

I have been intrigued by DML panels for some time and am considering a bi-amplified version with a large flat panel crossed over to a conventional sealed-box bass driver. In your research have you come across any rules of thumb for flat panel size and low frequency extension? It appears that larger panels produce better bass response, but has this been quantified in any way? It also appears that a flat panel mounted in a stiff frame (similar to a framed painting) gives a flatter frequency response. Is that your opinion also?

Due to space restrictions I am considering putting panels against wall surfaces. Would you suggest some kind of cushion or absorption between the panels and the walls?

Finally, I have at my disposal a variety of hardwoods and softwoods that can be used to make flat panels. In your research have you read accounts of solid wood being used to make DML speakers?

Thanks for your attention to my questions, and thanks again for your work on this thread.

Last edited by majerjack; 1st January 2017 at 01:45 PM.
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Old 1st January 2017, 01:50 PM   #28
lowmass is offline lowmass  United States
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well DMLs are not conventional loudspeakers. And yes NXT types operate not on trying to eliminate resonances but on encurraging them with control. very carful balance of material properties to get level response.

Resonances are really only a bad thing when non linear across the range. Linear spring bending modes over a wide freq range will result in low distortion and generaly high sensativity.

The diference in mass between panels and film is huge.
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Old 1st January 2017, 01:51 PM   #29
anji12305 is offline anji12305  United States
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JMC luthierie has a nice looking product which is clearly "proud" of the rear wall. It also appears gently curved which creates a cavity behind the assembly.

https://youtu.be/NTfl7o5xbyI

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Old 1st January 2017, 05:17 PM   #30
altie is offline altie
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Quote:
Originally Posted by anji12305 View Post
Rather than preceding through a list of unavailable materials chosen for ideal properties - yet unobtainable - why not experiment with things you can purchase?

So what if the result isn't ready for a mass market? Once you've made something yourself, no one can deny your achievement.

Rough panels for archtop guitars would be my choice, for a trial run...

Archtop Tops | stewmac.com

Sent from my Nexus 6 using Tapatalk
Agreed that the fun is in the building and experimenting.

The main reason for the first handful of posts in this thread, in particular the ones talking about sourcing carbon fiber from scrap and honeycomb from radiator protectors, was to show that the current ideal materials may not be as unobtainable as has been assumed. Total cost for two panels with Dayton 40W exciters is around $100, and is not particularly hard to build. With that said, lots of people are happy with the results from cheaper and easier to find materials.

Birch and spruce are probably particularly good woods to try. I'd also be interested to find out how the curve affects it. Is there a characteristic difference in sound between arch top and flat top guitars that we might speculate would either color full range sound or allow it to come through more clearly?
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