A Study of DMLs as a Full Range Speaker

Yes Steve that’s exactly the effect I get as well. I will post pictures when finished and in place. My old Samsung TV let’s the side down a bit but I hate throwing away anything that is still working well.

Burnt
We will all happy to see the panels in place. A picture has always a bigger impact than words... at least to me. I had to read twice your post to understand the panels show their edge to the listener. You are entering a new paradigme. It says a lot on my concentration while reading... Terrible... Sumimasen Burnt san.
About your TV, it is what my grand-parents, my parents teach to me too. You are just in advance as it will be the expected behavior for the next years.
To come to the technical side : I did some measurements at different angle including 90° (they are stored in my computer, I will see if I can find them again). I didn't detect in this measurement cession the null the theory is expected at 90°.
Christian
 
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We will all happy to see the panels in place. A picture has always a bigger impact than words... at least to me. I had to read twice your post to understand the panels show their edge to the listener. You are entering a new paradigme. It says a lot on my concentration while reading... Terrible... Sumimasen Burnt san.
About your TV, it is what my grand-parents, my parents teach to me too. You are just in advance as it will be the expected behavior for the next years.
To come to the technical side : I did some measurements at different angle including 90° (they are stored in my computer, I will see if I can find them again). I didn't detect in this measurement cession the null the theory is expected at 90°.
Christian

Not so new Christian, Steve has explored it before. I think the theory is probably correct but in practice any effect appears to be trivial. I would be very interested to see your measurements and it would be very helpful to DIYers to write an update to the theory if the effect is unmeasurable. It would come as no surprise to me if you can’t measure it. I suspect with a thicker panel like Steve’s 7 ft EPS panels the effect may be more detectable.
Your grandparents taught you well. In 1995 I bought a Mercedes coupe. I still have her.

Burnt
 
@BurntCoil
Re hello Burnt
Sorry for the flow of questions! At the level of the enthusiasm from your pictures?
About the plywood :
  • is it a 3 or a 5 plys?
  • which direction is the external grain?
About the exciter
  • which model ?
  • about the location, I understand the technique. Which position have you ended with?
Thank you
Christian
 
@BurntCoil
Burnt
Here are some measurements. It was a 20x30cm 9mm XPS I used for test purpose. It was indoor measurements at 1m. If I remember well, the panel was in a fixed position and I changed the mic position.
  • red = 0°
  • green : 45°
  • blue : 60°
  • orange : 80°
  • black : 90°
1/6 of octave smoothing, no frequency dependent window. Let me if you want another REW setting.

1665919889230.png
 
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@BurntCoil
Re hello Burnt
Sorry for the flow of questions! At the level of the enthusiasm from your pictures?
About the plywood :
  • is it a 3 or a 5 plys?
  • which direction is the external grain?
About the exciter
  • which model ?
  • about the location, I understand the technique. Which position have you ended with?
Thank you
Christian
@BurntCoil
Re hello Burnt
Sorry for the flow of questions! At the level of the enthusiasm from your pictures?
About the plywood :
  • is it a 3 or a 5 plys?
  • which direction is the external grain?
About the exciter
  • which model ?
  • about the location, I understand the technique. Which position have you ended with?
Thank you
Christian
No worries Christian.

The exciter is the Dayton Audio EX32EP2-4 Thruster 32mm 2-Hole Exciter 40W 4 Ohm

Position from the base is 625mm and 103mm from the edge for one panel and 618mm by 120mm on the second. A sane person would probably rationalise that by taking the average.

You really have to experiment though because of the many differences between boards. If you look at the earlier photographs where strong sunlight is illuminating the boards you can see the variation in grain density. It’s pretty random and on a large scale.

The panel is a three layer ply with the external grain orientated along the long axis.

I hope that helps

Burnt
 
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@BurntCoil
Burnt
Here are some measurements. It was a 20x30cm 9mm XPS I used for test purpose. It was indoor measurements at 1m. If I remember well, the panel was in a fixed position and I changed the mic position.
  • red = 0°
  • green : 45°
  • blue : 60°
  • orange : 80°
  • black : 90°
1/6 of octave smoothing, no frequency dependent window. Let me if you want another REW setting.

View attachment 1100267
That is pretty clear, thank you homeswinghome. So it confirms there is in practice no drop off in output edge on for thin panels. I will share measurements when I make them.

Burnt
 
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@BurntCoil

Burnt - More questions !

1/ Why did you decide to use raw ply ? - (apart from appearance) - and have you tried coated poplar ?
I found the raw 3mm poplar ply very flexible (floppy even) - esp across the grain of course. Have you had any problems with panel flatness?

2/ With all projects, there are usually aspects you feel could be improved - if so in this case, what are they?

3/ How stable are the panels with the single foot? - How long is the foot?

4/ What specifically was the grille cloth material you used, is it stretchy, and can you tell if it causes any loss in sound fidelity?

Cheers
Eucy
 
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@BurntCoil

Burnt - More questions !

1/ Why did you decide to use raw ply ? - (apart from appearance) - and have you tried coated poplar ?
I found the raw 3mm poplar ply very flexible (floppy even) - esp across the grain of course. Have you had any problems with panel flatness?

2/ With all projects, there are usually aspects you feel could be improved - if so in this case, what are they?

3/ How stable are the panels with the single foot? - How long is the foot?

4/ What specifically was the grille cloth material you used, is it stretchy, and can you tell if it causes any loss in sound fidelity?

Cheers
Eucy
Good morning Eucy, good questions.

1. I have tried a wide range of materials in the past, EPS, XPS, Carbon fibre, A composite of Ply/Nomex honeycomb/Ply, Stretched canvas, Polar ply, Birch Ply,
To my ears to date Poplar or Birch ply give the more natural sounding response and I am happy to live with the efficiency compromise. These days equalisation is trivial with the tools we have available so the top end droop you get with ply is easy to correct. On floppiness I can't really comment because I have never experienced the problem you mention with Poplar. I have had it once with Birch ply when the grain was in the wrong direction. I made a pair of Tall Blondes for a friend of my son and one of the panels was very floppy because of this problem and needed to be redone. On flatness I always ask the supply to select for flatness and usually I get good straight boards. I tend to purchase from suppliers of laserboard where, as you can imagine, flatness is required.

2. It's early days yet but on construction for the frame I would definitely opt for hardwoods rather than plywood. Birch ply is a wonderful construction material and I have used a lot of it but for a product rather than a prototype hardwoods are preferable. You need to select carefully to make sure you are buying a sustainable wood but the information is readily available. On the panels themselves I am investigating composite materials searching for a better performance. This design was intended to use a 0.4mm Birch ply/ 10mm Nomex honeycomb core/ 0.4mm Birch ply panel but that experiment did not go well. I am investigating why. I am also interested in cover materials. The one I used is fine, but I am interested in the possibility of materials that can be attached directly to the panel. My brief experiment with using an art canvas and frame suggests this is very possible and that would open a very wide door to alternative cover materials.

3. I find the stability of tall panel speakers is inversely proportional to the number of pets and children you have. My destabilising force is my wife when she opens the curtains and she is relatively easy to restrain. The current design is stable enough for general use and as these designs are remarkably robust I am not worried. The foot dimensions are 300mm by 50mm and they are 3mm Aluminium extrusions like the back brace radiused and polished up by hand.

4. This is the link for the cover material supplier. The material I selected is slightly stretchy, I would estimate 10%-15%. I ran one panel with and one panel without a cover to test transparency and I could not hear a difference but I have not measured them.

I hope that helps

Burnt.
 
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Eucy.
Very flexible and floppy sounds interesting to me.
Although I think the crate ply is a cheap ply of some sort, I'm wondering if it is poplar .
The crate ply is very flexible and sounds very good, but does need a little damping to sort out the exciter noise.
Just glueing 4 strips to make a larger panel seemed to sort this out.
Burntcoil, where did you get your poplar sheets from ? And were they expensive?
Steve.
 
Eucy.
Very flexible and floppy sounds interesting to me.
Although I think the crate ply is a cheap ply of some sort, I'm wondering if it is poplar .
The crate ply is very flexible and sounds very good, but does need a little damping to sort out the exciter noise.
Just glueing 4 strips to make a larger panel seemed to sort this out.
Burntcoil, where did you get your poplar sheets from ? And were they expensive?
Steve.
Hi Steve,

I usually buy ply from laserboard suppliers.

This is one supplier in the UK https://kitronik.co.uk/collections/plywood.
This is not a laserboard supplier but they do a 1220mm by 610mm by 3mm Poplar sheet for £11. https://www.timberite.co.uk/3mm-poplar-laser-plywood. Delivery will be on top of that.

I hope that helps.

Burnt
 
Burntcoil.
The crate ply Is very efficient which is handy as it allows me to use my 10watt exciters with no problems.
Also with my exciter I usually get a rising response above 10k with various ply woods, not a dip ?
Crate ply has a very lively sound which I do like, it's just trying to find out what it is ?
Steve.
 
Burntcoil.
The crate ply Is very efficient which is handy as it allows me to use my 10watt exciters with no problems.
Also with my exciter I usually get a rising response above 10k with various ply woods, not a dip ?
Crate ply has a very lively sound which I do like, it's just trying to find out what it is ?
Steve.
I am afraid I can't help Steve. I have never used crate ply, sorry!
 
Burntcoil.
That's OK, there is someone out there, probably in the fruit crate business who knows all about the product, I just have to find the right person 😀
But in the meantime there are plenty of choices.
I was trying to remember my experiments with my tall eps panels, and I think in the end I toed them out just a little bit to get a little more of the front sound field .
To get the best of both front and side effects.
As you say ,with the panels further apart, on each side of the tv, you can see more of the front surfaces and hear them, that is if the sides of the panels are pointing straight down the room?
The reflections from the walls on either side of the panels will be louder and will help spread the sound field.
You should be able to move the panels closer to the rear wall without the usual bad sounding problems below 500hz.
I have only used my small panels and the canvas panels this close to the rear or side walls, but I would expect similar results with larger panels ?
The rear wall or side wall problems tend to disappear using this method.
Steve.
 
Good morning Eucy, good questions.

1. I have tried a wide range of materials in the past, EPS, XPS, Carbon fibre, A composite of Ply/Nomex honeycomb/Ply, Stretched canvas, Polar ply, Birch Ply,
To my ears to date Poplar or Birch ply give the more natural sounding response and I am happy to live with the efficiency compromise. These days equalisation is trivial with the tools we have available so the top end droop you get with ply is easy to correct. On floppiness I can't really comment because I have never experienced the problem you mention with Poplar. I have had it once with Birch ply when the grain was in the wrong direction. I made a pair of Tall Blondes for a friend of my son and one of the panels was very floppy because of this problem and needed to be redone. On flatness I always ask the supply to select for flatness and usually I get good straight boards. I tend to purchase from suppliers of laserboard where, as you can imagine, flatness is required.

2. It's early days yet but on construction for the frame I would definitely opt for hardwoods rather than plywood. Birch ply is a wonderful construction material and I have used a lot of it but for a product rather than a prototype hardwoods are preferable. You need to select carefully to make sure you are buying a sustainable wood but the information is readily available. On the panels themselves I am investigating composite materials searching for a better performance. This design was intended to use a 0.4mm Birch ply/ 10mm Nomex honeycomb core/ 0.4mm Birch ply panel but that experiment did not go well. I am investigating why. I am also interested in cover materials. The one I used is fine, but I am interested in the possibility of materials that can be attached directly to the panel. My brief experiment with using an art canvas and frame suggests this is very possible and that would open a very wide door to alternative cover materials.

3. I find the stability of tall panel speakers is inversely proportional to the number of pets and children you have. My destabilising force is my wife when she opens the curtains and she is relatively easy to restrain. The current design is stable enough for general use and as these designs are remarkably robust I am not worried. The foot dimensions are 300mm by 50mm and they are 3mm Aluminium extrusions like the back brace radiused and polished up by hand.

4. This is the link for the cover material supplier. The material I selected is slightly stretchy, I would estimate 10%-15%. I ran one panel with and one panel without a cover to test transparency and I could not hear a difference but I have not measured them.

I hope that helps

Burnt.
The link for materials https://www.ebay.co.uk/itm/273030585149
 
Good morning Eucy, good questions.

1. I have tried a wide range of materials in the past, EPS, XPS, Carbon fibre, A composite of Ply/Nomex honeycomb/Ply, Stretched canvas, Polar ply, Birch Ply,
To my ears to date Poplar or Birch ply give the more natural sounding response and I am happy to live with the efficiency compromise. These days equalisation is trivial with the tools we have available so the top end droop you get with ply is easy to correct. On floppiness I can't really comment because I have never experienced the problem you mention with Poplar. I have had it once with Birch ply when the grain was in the wrong direction. I made a pair of Tall Blondes for a friend of my son and one of the panels was very floppy because of this problem and needed to be redone. On flatness I always ask the supply to select for flatness and usually I get good straight boards. I tend to purchase from suppliers of laserboard where, as you can imagine, flatness is required.

2. It's early days yet but on construction for the frame I would definitely opt for hardwoods rather than plywood. Birch ply is a wonderful construction material and I have used a lot of it but for a product rather than a prototype hardwoods are preferable. You need to select carefully to make sure you are buying a sustainable wood but the information is readily available. On the panels themselves I am investigating composite materials searching for a better performance. This design was intended to use a 0.4mm Birch ply/ 10mm Nomex honeycomb core/ 0.4mm Birch ply panel but that experiment did not go well. I am investigating why. I am also interested in cover materials. The one I used is fine, but I am interested in the possibility of materials that can be attached directly to the panel. My brief experiment with using an art canvas and frame suggests this is very possible and that would open a very wide door to alternative cover materials.

3. I find the stability of tall panel speakers is inversely proportional to the number of pets and children you have. My destabilising force is my wife when she opens the curtains and she is relatively easy to restrain. The current design is stable enough for general use and as these designs are remarkably robust I am not worried. The foot dimensions are 300mm by 50mm and they are 3mm Aluminium extrusions like the back brace radiused and polished up by hand.

4. This is the link for the cover material supplier. The material I selected is slightly stretchy, I would estimate 10%-15%. I ran one panel with and one panel without a cover to test transparency and I could not hear a difference but I have not measured them.

I hope that helps

Burnt.
Thanks again Burnt
Very useful feedback
I'm not really clear on how or what you mean to attach directly to the panels... Surely fixing art canvas directly to them will excessively dampen the panels?

Eucy
 
You are very welcome Eucy.

I think it probably would damp the panels depending on the material used and adhesive used. If it is a lightweight material glued using an epoxy that might be different. The painting canvas model I tried was using a ply disc glued to the canvas and the exciter applied to that. It was an approach pioneered by @OffGridKindaGuy and sounded good. I am planning another experiment where I use a large ply panel glued to the canvas. If that works then it may imply I can use a wider range of materials. It may not work of course.

Burnt
 
1. I have tried a wide range of materials in the past, EPS, XPS, Carbon fibre, A composite of Ply/Nomex honeycomb/Ply, Stretched canvas, Polar ply, Birch Ply,
To my ears to date Poplar or Birch ply give the more natural sounding response and I am happy to live with the efficiency compromise.
Burnt – great work on those Snow White panels! It is refreshing for me to see complete and successful builds that can be copied. And they have a name that can be referred to, remembered, and searched for in future. Most active members here are probably aware of your famous Tall Blondes.

Getting back to materials again, I see you have experimented with most of the DML materials used in this thread and found plywood to be a good choice, like many other members here. Problem is – not all plywoods are equal. You are using Poplar plywood, spedge is using crate plywood, others use Birch. In my part of the world, I cannot source Poplar plywood. However, searching for plywoods I came upon another option – called Albasia plywood. Albasia is wood from Indonesia, and I found the following comment: “Albasia plywood weighs only 320 kg/m³ – about 12% lighter than conventional poplar plywood, for which albasia plywood has proved to be an ideal substitute.” This sounds like a worthy plywood to try for my next DML project. Anybody else tried this yet?
 
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“Albasia plywood weighs only 320 kg/m³ – about 12% lighter than conventional poplar plywood, for which albasia plywood has proved to be an ideal substitute.” This sounds like a worthy plywood to try for my next DML project.

That sounds like a great option to me Twocents!
 
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