A Study of DMLs as a Full Range Speaker

Alaska 129.
This patent has been posted a few times, it is a bit wordy, but has a lot of useful information.
It's not an easy read but the information is there.

https://patents.google.com/patent/US7158647B2/en?assignee=New+Transducers+Ltd

Steve
Hi Steve;

Well, I’m up to pg. 62 on the pdf, starting in on the Brief Description OF Drawings. Worth the read. It explains some

background, ratios, materials etc. This journey into DML has/is

an education. I’d like to thank you, Leob, Hkguy6,Christian, Veleric and others for tolerating my juvenal questions. I look back at posts from Veleric when he made his first Rev. Ply panel and said damn it sounds good. I look forward to doing that with EPS or any material… I truly long to hear the DML sound and share the music with my grand children. Thank you all.

Pete
 

spedge

Member
2009-09-03 3:41 pm
DontHertsMe.
It is difficult to recommend something when you do not know how it is going to be used ?
Especially for teenage girls .
Is it for computer station, wall mounting freestanding ,full range, method of XO, and so on ?
You didn't say which exciters you have purchased ,how many watts ?
I would be easier to narrow down the materials if this is known.
Recycling free materials is probably the best to start experimenting with like corrugated cardboard, or used serial boxes.
The beauty of the serial box is you get a free Blue Peter badge with it(UK only joke) 😂
Which ever material you use ,I hope it goes well.
Steve.
 
Hi all,

I recently received a pair of Dayton exciters, with the intent of building some DMLs with my partner and her daughters during the upcoming vacation time. Her teenage girls have shown to be surprisingly interested in the concept, so I'd really like to achieve a good result, and hopefully engender further interest in engineering concepts.

I've got a few options for panel material. I've read around 100 pages of this thread but my brain is now turning to mush. Given the following, what would you guys recommend?

Extruded polystyrene 150cm by 60cm, but only available in 3cm thickness (is this too thick?)
Acrylic 100cm by 50cm, 3mm thickness
PVC foam board cut to size, 3 or 5mm thickness
"Litewood" plywood cut to size, 3 to 15mm thickness (same density as poplar ply, which I can't find here)

I'd like to keep the total cost low, so foam board would be my last choice (it's strangely expensive here) unless its by far the best option sound-wise.

Thank you for any advice you can provide :)
Hi Hertz

Welcome to the great chase

Personally, I'd try the 3mm ply followed by the XPS.. I've tried 30mn and it works ok...if you're masochistic, you can also use a router to thin it down, or a hot wire cutter if you can make or get hold of one

Cheers
Eucy
 
Hi DontHertzMe,

For beginner, my suggestion is EPS > Polywood > Canvas.
Especially if you don't have a woofer. EPS maybe the only choice to get good result at the first time. And it is not exciter picky. Just don't over 150g is all fine.
Start from middle size. Within 40 to 60cm is more easier to control the variable.

Enjoy your first success with your girl.

Thanks hkguy6 - do you mean XPS (extruded) rather than EPS (expanded)? I was under the impression that expanded was sub optimal. I do have an old Polk powered sub that I'll be giving them to handle LF duties (because I know the youngsters will be all like "Ew there's no bass, man!" ;) ).

DontHertsMe.
It is difficult to recommend something when you do not know how it is going to be used ?
Especially for teenage girls .
Is it for computer station, wall mounting freestanding ,full range, method of XO, and so on ?
You didn't say which exciters you have purchased ,how many watts ?
I would be easier to narrow down the materials if this is known.
Recycling free materials is probably the best to start experimenting with like corrugated cardboard, or used serial boxes.
The beauty of the serial box is you get a free Blue Peter badge with it(UK only joke) 😂
Which ever material you use ,I hope it goes well.
Steve.

Thank you spedge. Yep, I'm going to first show them various household items (tupperware, cutting board, cardboard boxes etc.) so they can see how these affect the output. Sadly no badges with cereal here in South Africa since the 1990s :D.
The exciters I got are the 40W Dayton DAEX32QMB-4 - I was hoping to get the DAEX32EP but they were out of stock with a lead time of 6 weeks at my supplier.
The speakers will be suspended from the ceiling in their lounge, used for music as well as TV. Happily, WAF is not an issue, so panel size isn't a factor. I have a simple SMSL AO100 for amplification duties. No XO as such, just capacitors inline with the exciters as high pass filter (probably 300uF for a pole of ~130Hz) and an active sub connected to the amplifiers sub out.
The setup does not have to be high end - anything is better than the awful integrated TV speakers they've been using up until now. This is primarily a fun and educational project but I'd like the best result I can reasonably achieve. If things go well I'll may look into a proper DIY dynamic speaker project with them at a later stage, budget dependent.

Hi Hertz

Welcome to the great chase

Personally, I'd try the 3mm ply followed by the XPS.. I've tried 30mn and it works ok...if you're masochistic, you can also use a router to thin it down, or a hot wire cutter if you can make or get hold of one

Cheers
Eucy

Thank you Eucyblues99. I was indeed thinking of thinning the XPS panels but I lack the tools to do it properly :p

Edit: I've started reading that patent document too. Lots to digest!
 
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hkguy6

Member
2022-01-22 3:30 pm
Thanks hkguy6 - do you mean XPS (extruded) rather than EPS (expanded)? I was under the impression that expanded was sub optimal. I do have an old Polk powered sub that I'll be giving them to handle LF duties (because I know the youngsters will be all like "Ew there's no bass, man!" ;) ).
Yes EPS as Expanded Polystyrene board. Spedge is the expert on this material you should ask him for more suggestions such as the sanding and coat finishing.
All XPS I tried gave me toy sound. An absolute NO for me.

DAEX32QMB-4 seems idential as my favourite PUI ASX05404. Just the number on the magnet different (1519 vs 2051).
It's a very good sounding all-rounded exciter. However maybe a little heavy for EPS board. The good news is you will get luxy sound when pair it with 2-3mm plywood or canvas. Especially you have a sub. Now I will suggest plywood instead EPS to try first. Your exciter is a best match with plywood. Even a free hanging 30x50cm small ply board will give you luxy nature timbre sound.

But DAEX32QMB-4 it's external spiders maybe a negative. You should try them first or if you don't like the result you can simply cut them off.


 
DontHertzMe
when you say the panels will be suspended from the ceiling do you mean facing you , or facing the floor ?
how far out from the walls can they be.
The exciter looks fine ,but for best sound I would eventually cut off the feet after finishing experimenting.
Steve.

Facing me, hanging vertically on fishing line from the ceiling's timber beams. Distance from the wall is unfortunately quite small, around 10cm / 4in.
What do you recommend for the finishing of polystyrene?

Yes EPS as Expanded Polystyrene board. Spedge is the expert on this material you should ask him for more suggestions such as the sanding and coat finishing.
All XPS I tried gave me toy sound. An absolute NO for me.

DAEX32QMB-4 seems idential as my favourite PUI ASX05404. Just the number on the magnet different (1519 vs 2051).
It's a very good sounding all-rounded exciter. However maybe a little heavy for EPS board. The good news is you will get luxy sound when pair it with 2-3mm plywood or canvas. Especially you have a sub. Now I will suggest plywood instead EPS to try first. Your exciter is a best match with plywood. Even a free hanging 30x50cm small ply board will give you luxy nature timbre sound.

But DAEX32QMB-4 it's external spiders maybe a negative. You should try them first or if you don't like the result you can simply cut them off.

Interesting! I'd always thought that the open-cell structure of EPS would compromise the sound performance. Polystyrene sheets are cheap enough that I can try both XPS and EPS. When you say plywood, do you mean poplar ply specifically? I can get pine plywood very cheaply, but it's heavy (around 50% more than poplar). Is this heavier ply still worth a try?
 

hkguy6

Member
2022-01-22 3:30 pm
Interesting! I'd always thought that the open-cell structure of EPS would compromise the sound performance. Polystyrene sheets are cheap enough that I can try both XPS and EPS. When you say plywood, do you mean poplar ply specifically? I can get pine plywood very cheaply, but it's heavy (around 50% more than poplar). Is this heavier ply still worth a try?
Your thought was exactly what I expected. But the truth is EPS much better. You can also try XPS. Everybody have different preference.
Get higher density of EPS if you can. 18kg/m3 up. Not lower then 13. I means their actal weight, not the shop "labeled" weight.

I tried many wood within 2-3mm. They are all have sound different but not much (except the Balsa).
Plywood yes the poplar ply, is sound good enough and easy to get. So that's what I suggest.
2mm is a good start for free hanging. Over 3mm the efficency is not good for your exciter (in single). I prefer single instead of multi exciters sound.
Is this heavier ply still worth a try? If you can get them easy it always worth the try. But I prefer light instead of heavy. Just not light as Balsa.
 
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DontHertzMe.
Only 4inches from the back wall is going to be a big problem for a large panel, of any type.
The panel will have an odd sound to it and will loose the low frequencies below about 400hz or so.
I presume you have a TV on the wall, and want to have your panels each side ?
Do they have to be large ?
Steve.
 
Sorry pete, I did say it was a bit wordy.
you could probably fit the relevant information to you on 2 pages.
It is patent talk.
I still keep an eye out for the patent I lost, which was much more understandable and interesting.
Steve.
Hi Steve;
Just a bit wordy mmmm ya :ROFLMAO:
Wondering when you do PVA coatings be it on card stock, EPS , corrugated cardboard etc., do you do the whole panel at once to avoid cupping ? Oh and how big are your 10w exciters or is there an equivalent in Dayton Audio?

Thanks
Pete
 
Pete.
sadly , now they only sell this exciter ,which is very similar , but only in frog casing.
I looked on the tectonic site and it looks like they do not sell exciters directly to the public anymore ?
RS sell them in the U.K.for over £20 each !

https://www.parts-express.com

For small 1mm card panels I glue two 0.5 mm together using neat pva.
I place the card panel between two sheets of ply and place weights on top to keep the panel flat while drying.
Although it should dry pretty flat if left to dry on a flat surface, you can still use weights to flatten the panel when dry.
when dry you can splash on some 50x50 mix of pva on both surfaces, you can use a hair dryer which will dry the panel very quickly, when dry to the touch , place them inbetween the ply sheets again with weights to keep flat, if needed.
that is all that needs to be done for a basic panel .
I used a CD to round my 6x9inch panels, I had the exciter mounted in the centre to keep the balance but not sure if this is necessary if XOing higher up ?
Apart from the pva ,this is a free and disposable panel for experimenting, if you can get your hands on old 0.5mm card boxes, that is ?
This panel has excellent sound quality as a near field computer speaker, or a main audio speaker if used with an appropriate low frequency driver and XO.
Steve.
 
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A few pictures of the sort of mountings I have used for my various small panels.
In the last picture I include the original 3mm xps pizza base panels (no longer made in this country)I used to use many years ago over on NXT RUBBISH.
Plus the larger HD grade eps panel, which was square, but I cut one side at an angle, and glued it back on to the side shown so that now it does not have parallel sides🤗 and no waste (this panel cost money).
I will eventually do this to my square graphite panel for comparison.
Steve.
 

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A few pictures of the sort of mountings I have used for my various small panels.
In the last picture I include the original 3mm xps pizza base panels (no longer made in this country)I used to use many years ago over on NXT RUBBISH.
Plus the larger HD grade eps panel, which was square, but I cut one side at an angle, and glued it back on to the side shown so that now it does not have parallel sides🤗 and no waste (this panel cost money).
I will eventually do this to my square graphite panel for comparison.
Steve.
I wonder your panels with peel edges don't they cause flapping noise?
And did you measure and weight your HD grade EPS their actual kg/m3? I have no idea HD grade actual density. Thanks!
 
Hkguy6.
I purchased the high density eps about ten years ago, they are now coated in vinyl silk paint.
with a hole in the centre of the coil area.
I can't even remember where I got them from.
I might still have a 5mm HD that I did not use somewhere ?

the edges of the card does not peel or buzz ?
If that is what you mean ?
Steve.
 
Your thought was exactly what I expected. But the truth is EPS much better. You can also try XPS. Everybody have different preference.
Get higher density of EPS if you can. 18kg/m3 up. Not lower then 13. I means their actal weight, not the shop "labeled" weight.

I tried many wood within 2-3mm. They are all have sound different but not much (except the Balsa).
Plywood yes the poplar ply, is sound good enough and easy to get. So that's what I suggest.
2mm is a good start for free hanging. Over 3mm the efficency is not good for your exciter (in single). I prefer single instead of multi exciters sound.
Is this heavier ply still worth a try? If you can get them easy it always worth the try. But I prefer light instead of heavy. Just not light as Balsa.
Hello hkguy6
There are few posts about experiences with balsa as DML material. What is yours?
 
Hkguy6.
I purchased the high density eps about ten years ago, they are now coated in vinyl silk paint.
with a hole in the centre of the coil area.
I can't even remember where I got them from.
I might still have a 5mm HD that I did not use somewhere ?

the edges of the card does not peel or buzz ?
If that is what you mean ?
Steve.
Thanks.
I just curious the western standard Low Grade, HD, UHD their exactly weight. I got my EPS weight by measure their actual volume and weight to get the kg/m3. Even the shop(China) labeled as 25k but actual just around 18-20.

The peel I mean is your first pic the ply panel, especially the top left corner. Or you applied coating to fill the cracks and peels?
 
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Thanks.
I just curious the western standard Low Grade, HD, UHD their exactly weight. I got my EPS weight by measure their actual volume and weight to get the kg/m3. Even the shop(China) labeled as 25k but actual just around 18-20.

The peel I mean is your first pic the ply panel, especially the top left corner. Or you applied coating to fill the cracks and peels?
OK I understand now.
Well spotted.
That panel is a 1mm veneer which was from a very old draw in my shed, which peeled off .
It started to split when I rounded the corners .
I mentioned all this some way back on this forum when I built the panel.
I had to apply several layers of pva to fill the splits.
This was a very good performing panel , but I only had the one sheet of veneer.
Steve.
 
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