A Study of DMLs as a Full Range Speaker

The easiest way is with double sided mounting tape. Attach the tape to the frame and then attach the panel to the tape. The mounting tape I like best is 3M Extreme double sided mounting tape. It comes in a strip 1 inch wide but I prefer to use only a 1/4" to 3/8" wide strip. I prefer to use the tape around virtually the entire perimeter, except for a few inches (2 or 3) from each corner. But the only reason for leaving the corners free is because it makes it much easier to separate the panel from the frame later if you want too.
Instead of the mounting tape you can use foam like the gray Frost King window weather stripping, or EPDM foam. Those are typically about 3/8" thick and 3/4" wide. I use the full 3/4" width with those. Also, these usually only have adhesive on one side, so you have to use something else (double sided tape or spray adhesive) to mount the other side to the frame or panel. But which tape or foam works best, and which dimensions depends on the panel material. Finding the best combination is still trial and error for me.
In the images below I attached the foam to the panel first, instead of the other way around. I also used a bigger gap in the corners than I do now, but I think you can get the idea.
Eric

View attachment 1134339 View attachment 1134341
Many thanks Eric.
My approach is similar but a little different, with approx 25mm long strips of 6mm thick x 15mm wide neoprene foam attached with 25mm gaps all the way round including the corners. I PVA both sides of the foam & stick to the frame first, and then panel onto foam once the foam is stuck to the frame. My 2mm ceiba ply panels are only 30x40cm, so relatively modest in size. They are also very light for plywood. They operate mainly from 400hz upwards (XO set at 500hz, Butterworth 4th order 24db/octave) to help remove a peak around 400hz that's hard to EQ out.

I was wondering whether less foam and less sticking would give a better result with the panel edges being less constrained, or whether there would in fact be an increased opportunity for unwanted 'buzzing' and other artefacts. I know Steve goes for a very minimalist approach with his panel supports. I think I'll try 10mm wide neoprene foam next time.
Simon.
 
Further to post #8,828

Also, you have to make sure there's no pistonic motion transferred to the panel, other than the vibrations from the exciter, otherwise the panel would start to wobble, most times uncontrollably, which would give distortions/colourations. The vibrations have to be transferred to the panel from the perimeter of the exciter's coil former point-wise to the panel at 90 degrees -- only the vibrations, not the pistonic motion. Otherwise, it would not be a pure DML, but more or less a BMR, and because of the uncontrolled wobbling, a bad BMR.

The DML panel has to framed with a resilient suspension around the perimeter. The frame could be extend to an open box, or a closed shallow box. A free hanging, uncontrollably wobbling panel/sheet is not a DML.
 
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Lordtarquin.
The method I use is similar to this YouTube video at about 8mins in.
I have my deq set to peak hold not average as in the vidio.
when I am sitting on my couch in the listening position, I move the microphone to the left about 2ft then 2ft to the right and also up and down covering the whole couch area.
Do not move the microphones fast as in the video unless you have a wind shield, I move the microphone slowly anyway.
This will give me an average of the response in this seating area, which is most important.
If I took single point measurements they could be totally different and EQing one point could make the other points worse.
I hope this is of some use.
This is why I do not usually use EQ although I have the option.
Steve.




Thanks for this Steve. Fortunately, I have a miniDSP HD which has twice as many PEQ bands. My mic is attached to a tripod, so I can measure from multiple points around the listening position and do some averaging for each driver and panel.
Simon.
 
Further to post #8,828

Also, you have to make sure there's no pistonic motion transferred to the panel, other than the vibrations from the exciter, otherwise the panel would start to wobble, most times uncontrollably, which would give distortions/colourations. The vibrations have to be transferred to the panel from the perimeter of the exciter's coil former point-wise to the panel at 90 degrees -- only the vibrations, not the pistonic motion. Otherwise, it would not be a pure DML, but more or less a BMR, and because of the uncontrolled wobbling, a bad BMR.

The DML panel has to framed with a resilient suspension around the perimeter. The frame could be extend to an open box, or a closed shallow box. A free hanging, uncontrollably wobbling panel/sheet is not a DML.
Wobble, wobble, toil and twobble - rhubarb chdsl - just doesn't happen unless the panel is overdriven -

My apologies for being critical, but at this point I believe you really should temper your lecturing/sermons/opinions until you've actually made something.

Eucy
 
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Further to post #8,828

Also, you have to make sure there's no pistonic motion transferred to the panel, other than the vibrations from the exciter, otherwise the panel would start to wobble, most times uncontrollably, which would give distortions/colourations. The vibrations have to be transferred to the panel from the perimeter of the exciter's coil former point-wise to the panel at 90 degrees -- only the vibrations, not the pistonic motion. Otherwise, it would not be a pure DML, but more or less a BMR, and because of the uncontrolled wobbling, a bad BMR.

The DML panel has to framed with a resilient suspension around the perimeter. The frame could be extend to an open box, or a closed shallow box. A free hanging, uncontrollably wobbling panel/sheet is not a DML.
I was wondering myself if the above is the rest of the NXT quote from the post you referenced, or rather your own interpretation, commentary? It seems more like your own commentary to me.

Though I agree that a free hanging sheet is not my kind of DML, nor probably what NXT would call an NXT DML either. But we do call them DMLs here on this forum.

I would say, however, that, a free hanging panel is a sort of modal bending wave speaker, in any event.

Eric
 
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Further to post #8,828

Also, you have to make sure there's no pistonic motion transferred to the panel, other than the vibrations from the exciter, otherwise the panel would start to wobble, most times uncontrollably, which would give distortions/colourations. The vibrations have to be transferred to the panel from the perimeter of the exciter's coil former point-wise to the panel at 90 degrees -- only the vibrations, not the pistonic motion. Otherwise, it would not be a pure DML, but more or less a BMR, and because of the uncontrolled wobbling, a bad BMR.

The DML panel has to framed with a resilient suspension around the perimeter. The frame could be extend to an open box, or a closed shallow box. A free hanging, uncontrollably wobbling panel/sheet is not a DML.
thank you all for the suggestions,
I wanted to ask you what do you mean by elastic suspension which material? Do you have any photos to better understand everything?
thank you
 
Spedge came in #1,302
I was wondering myself if the above is the rest of the NXT quote from the post you referenced, or rather your own interpretation, commentary? It seems more like your own commentary to me.

Though I agree that a free hanging sheet is not my kind of DML, nor probably what NXT would call an NXT DML either. But we do call them DMLs here on this forum.

I would say, however, that, a free hanging panel is a sort of modal bending wave speaker, in any event.

Eric
Everyone got caught to the Tech ingredients nonsense, me included at the beginning. Lot of us here are still promoting that, one way or another. Some even become "gurus" on that. They should actually write patents on that. :) I couldn't ever imagine hanging EPS sheets on strings in the living room. The result is that most of them get banished from home to sheds.

Anything you stick an exciter to (or a voice coil), would sing. But, that doesn't make it a distributed mode loudspeaker. It is just a singing and most times wobbling sheet -- the cabinet door didn't wobble, but sang. :)

A DM is a different kind of animal. There's a lot of maths and physics involved in that, but not everything is freely available for us. Some companies sell consumer products (speakers, bread, milk), and some companies sell intellectual property, or even whole companies. NXT was the latter kind, a scientific research lab -- sold licenses, and later sold the renamed divided companies. Most of the scientific/engineering staff went with them to the new companies, Tectonic Labs and Google. Some even created their own companies that sold DML and related products (Dr. Graham Bank).

Anyway, I decided to get the info from the source, that is, from what's freely available -- NXT, Tectonic patents and related documents. I also search for the work by individual people of that inventor group. Sure, I post interesting/relevant parts from their patents, for those who are interested, for the newcomers and for myself. Sure, I use their own words, for that gives a real outlook. There's no need to reinvent the wheel. Sure, they didn't exactly say that free hanging panels by strings, or hung from the exciter on stand with open edges etc, are not DMLs, but that info is all over those documents.

@Sandasnickaren first Göbel clone project opened my mind, then @Veleric's (he kindly gave me the links), and after reading about Veleric's project, I said I'd start reading Azima's patents, which then lead to the rest. All kinds of interesting information is opening up. It's always best to get the info from the from the horse's mouth.:)

Your product is also quite interesting, quite stunning, by the way. It has actually four sides that resonate, so is it a DML or a resonating box, I'm not sure, but I am thinking about that. :)
 
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thank you all for the suggestions,
I wanted to ask you what do you mean by elastic suspension which material? Do you have any photos to better understand everything?
thank you
Like rubber, or like window isolating strips Tesa Moll type, or even soft foam, something that could damp the edges, at the same time hold the panel in suspension. Suspension/surround like that you see in 'normal' cone speakers. If you have a spare or damaged cone speaker, check how it sounds without the suspension/surround. It'd sound terrible.
 
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Like rubber, or like window isolating strips Tesa Moll type, or even soft foam, something that could damp the edges, at the same time hold the panel in suspension. Suspension/surround like that you see in 'normal' cone speakers. If you have a spare or damaged cone speaker, check how it sounds without the suspension/surround. It'd sound terrible.
In the Dm 500 ecc tectonic panels seems to be connected to the frame only on 4 points on the long side, I'm not sure about this but it seems like this, instead you say to insert soft material between the panel and the frame but basically it is a fairly rigid connection. Another thing is to use the suspensions of the normal loudspeaker but isn't this in contrast with what you were saying that if it is free it is not a DML? In any case, the suspension of the loudspeakers is complex
 
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I apreciate your enthusiasm in research! Can you post NXT paper where they mention angled cutting on the membrane?
Here's another mention of cuttings (it is in the patent I linked)
cuttings.jpeg

It is a NXT finding. I have no knowledge of the scientific reasons for that, except what NXT says. :)
 
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Further to my post #8,851

The Google page of that patent gives the NXT claims, and how to choose the panel material, how to size the panel, where to place the transducer/exciter etc. You can choose an elliptical shape, instead of a rectangular panel. If you are only interested in a rectangular shape, you can omit sections 11 to 14 and 16 and 17. Every claim is thoroughly explained within the patent.

But, you'd never find any mention about a bare radiator panel (a bare sheet) freely hanging from strings, or about an unsupported panel anywhere in it, or in any other patents, for that matter.
 
Wow, this thread is amazing. While a lot goes 'above my head' in terms of knowledge, It's great to see so many people trying to create the best DML based experience. I actually also want to start with a simple DML project. I'll be using two exciters per panel, and one panel per channel. (I'm going stereo) I think I'll use the DAEX25FHE-4 and DAEX32EP-4 unless I'm told otherwise. :) I know that two separate panels of a different material might be better, but the aesthetics are equally important for my project.

I'm looking at panels with a maximum size of 55x115cm (21.5" x 45") smaller is possible if that is to be advised.
I've looked at three possible materials. Mainly because of availability, costs and the ability to order them printed with a photo/design of my choice.

Could someone perhaps help me with deciding which material would be best? I have a windows PC as a source, and I am using an Umik-1 + REW and Windows APO to be able to EQ everything a bit.

The materials I've looked at;

3mm Dibond; https://company7.nl/en/product/print-op-dibond/
2.9mm Akylite: https://company7.nl/en/product/akylite-plex/
1/3/5mm Forex: https://company7.nl/en/product/foto-op-forex/

(The Akylite is the cheapest, the Dibond the most expensive.)
 
General Question...
Has anybody picked up rather disappointing performance from the Dayton DAEXHESF 40W High Efficiency drivers? I find their frequency response lacking on both the lows and highs. But yet on cheaper devices, like the DAEX25Q-4 (20W) , at half the price, I get very nice responses.
I've tried these drivers on various panels going through the whole spectrum of densities, thickness, stiffness, damping, dimensions and length/width ratios; I've also tried them as single, and as multiples; but I get the same basic variations in responses from the drivers: Very mid-heavy (almost unusable) on the expensive HESF, and almost decent on the cheaper 25Q-4.

Comments?
 
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Wow, this thread is amazing. While a lot goes 'above my head' in terms of knowledge, It's great to see so many people trying to create the best DML based experience. I actually also want to start with a simple DML project. I'll be using two exciters per panel, and one panel per channel. (I'm going stereo) I think I'll use the DAEX25FHE-4 and DAEX32EP-4 unless I'm told otherwise. :) I know that two separate panels of a different material might be better, but the aesthetics are equally important for my project.

I'm looking at panels with a maximum size of 55x115cm (21.5" x 45") smaller is possible if that is to be advised.
I've looked at three possible materials. Mainly because of availability, costs and the ability to order them printed with a photo/design of my choice.

Could someone perhaps help me with deciding which material would be best? I have a windows PC as a source, and I am using an Umik-1 + REW and Windows APO to be able to EQ everything a bit.

The materials I've looked at;

3mm Dibond; https://company7.nl/en/product/print-op-dibond/
2.9mm Akylite: https://company7.nl/en/product/akylite-plex/
1/3/5mm Forex: https://company7.nl/en/product/foto-op-forex/

(The Akylite is the cheapest, the Dibond the most expensive.)
I'm unfamiliar with the second two, but based on the specs, I'd be hesitant on the Akylite as the core seems to be what we term bubble wrap, which may have poor acoustic properties.

The Forex is PVC rather than the more usual polypropylene... It's heavier than Poplar ply but may be worth a try

Others have used Dibond or equal and may comment..I have a sample which I haven't tried but I think it's too heavy..

Googling shows there's also Formalite colour and Formalite x-press ...Of all of these choices I'd try Formalite colour...SG 0.4...cheaper than Forex..Interesting... Thanks for the info

Can you get samples to try... Even small samples will give you a good idea of efficiency


Eucy
 
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General Question...
Has anybody picked up rather disappointing performance from the Dayton DAEXHESF 40W High Efficiency drivers? I find their frequency response lacking on both the lows and highs. But yet on cheaper devices, like the DAEX25Q-4 (20W) , at half the price, I get very nice responses.
I've tried these drivers on various panels going through the whole spectrum of densities, thickness, stiffness, damping, dimensions and length/width ratios; I've also tried them as single, and as multiples; but I get the same basic variations in responses from the drivers: Very mid-heavy (almost unusable) on the expensive HESF, and almost decent on the cheaper 25Q-4.

Comments?
I have a pair of these but have only briefly tried them...I didn't notice anything unusual at the time but will take more notice now... Not much help at the moment I'm afraid
Eucy
 
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