Density mostly seems important for efficiency, and doesn't need to mean bad FR. My first experiments was with polycarbonate sheets which also gave a quite full response, but bad efficiency.
PLA is one of the stiffer thermoplastics, so probably a good choice. PC by itself is very stiff, but also very hard to print, and filaments like PC Max are blends so they can be printed on normal consumer printers, and as you can see from the sheet, often not much stiffer than regular PLA. Additives like carbon, glass fibre or diamond can give significantly stiffer prints. For example here is a PC CF filament with much better stats
https://nanovia.tech/en/ref/nanovia-pc-cf/
Also the PLA CF from Polymaker is much stiffer then their plain PC.
Of course stiffness is not everything, but I think the main problem with thermoplastics is that they are not that stiff in relation to weight. So PLA or PC with fiber additives, or perhaps LW PLA, are probably best alternatives unless you start looking in to very expensive materials that needs very hot nozzle and bed. I did test some PETG in my early experiments, and it was worse than the PLA resulting in a much more flexible plate.
PLA is one of the stiffer thermoplastics, so probably a good choice. PC by itself is very stiff, but also very hard to print, and filaments like PC Max are blends so they can be printed on normal consumer printers, and as you can see from the sheet, often not much stiffer than regular PLA. Additives like carbon, glass fibre or diamond can give significantly stiffer prints. For example here is a PC CF filament with much better stats
https://nanovia.tech/en/ref/nanovia-pc-cf/
Also the PLA CF from Polymaker is much stiffer then their plain PC.
Of course stiffness is not everything, but I think the main problem with thermoplastics is that they are not that stiff in relation to weight. So PLA or PC with fiber additives, or perhaps LW PLA, are probably best alternatives unless you start looking in to very expensive materials that needs very hot nozzle and bed. I did test some PETG in my early experiments, and it was worse than the PLA resulting in a much more flexible plate.
I tested the CC3D PC filament on a different project, and was impressed by how tough it is. It prints easily, gives a fine finish if set correctly, and will be great in well designed parts for a workshop etc..
In thin layers, it is tough rather than stiff, and when bent springs back into shape.
Stiffness though can come with the design of an object, as with PC twin wall sheets, but PLA or PLA+ being inherently stiffer may be a better choice for a core material.
I still fancy trying a grid, cubic or honeycomb core and hard resin treated Kraft paper...A poor mans Nomex sandwich ... I'll do a small 300x300 test and see how it goes... Maybe 4mm thick with the thinnest stable core wall. The infill pattern chosen may also affect the response.
In thin layers, it is tough rather than stiff, and when bent springs back into shape.
Stiffness though can come with the design of an object, as with PC twin wall sheets, but PLA or PLA+ being inherently stiffer may be a better choice for a core material.
I still fancy trying a grid, cubic or honeycomb core and hard resin treated Kraft paper...A poor mans Nomex sandwich ... I'll do a small 300x300 test and see how it goes... Maybe 4mm thick with the thinnest stable core wall. The infill pattern chosen may also affect the response.
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Hello Eucyblues, I think that making only the honeycomb is not very practical, as it is the glueing of the paper to the honeycomb that is the challenge (using just enough glue to bond). Better would be to mimic the Nidaplast, but printing the "scrim" might be impossible because of the minimum layer thickness.
Best would be Nidaplast be available, but that seems to not be the case.....
For now I'll stick to nomex and paper, but will also try printing a panel (just bought a Bambu A1 printer, and learning to 3d design - inspired by the post of Sandasnickaren).
Greetings, Hans
Best would be Nidaplast be available, but that seems to not be the case.....
For now I'll stick to nomex and paper, but will also try printing a panel (just bought a Bambu A1 printer, and learning to 3d design - inspired by the post of Sandasnickaren).
Greetings, Hans
A while since I've visited/posted, but I thought that I'd show my latest DML experiment (see snaps attached).
Home theater / audio setup.
Several earlier posts have followed the experiments with my found aluminum honeycomb panels.
Their performance (using a single Thruster on each panel) still astonishes me every time I play music.
I've found the biggest challenge to getting the full audio on films comes from center channel speakers.
I've experimented with using a pair of speakers rather than a single one to reproduce the center channel.
Magnepan had explored this idea some years ago.
It works.
I have gone through a number of iterations of DMLs for these center channel speakers.
Until this latest iteration, mounting the DMLs whether by clamping one edge or trying to clip them to a frame (both with foam between the clamp, clips and panels) still transferred far too much energy to the supporting frame.
This latest experiment has the panels hanging by thread.
You can also see how I've support the Thrusters.
The Thrusters probably overdrive these small thin bass wood panels and the earlier versions had a harshness to them as variously clamped.
These seem lovely. Clear. Efficient. Curiously well matched and integrated (at least by ear) with the rest of the system.
No measurements yet, just going back to listen to passages in films that I've missed because of poor centre channel reproduction.
I made my little stands from stuff I had in the workshop:
Next thoughts - I might switch out the wood for thin aluminum with silicone dampening (silicone adhesive + acetone -> sprayed on) as I described in an earlier post.
Just having fun.
.
Home theater / audio setup.
Several earlier posts have followed the experiments with my found aluminum honeycomb panels.
Their performance (using a single Thruster on each panel) still astonishes me every time I play music.
I've found the biggest challenge to getting the full audio on films comes from center channel speakers.
I've experimented with using a pair of speakers rather than a single one to reproduce the center channel.
Magnepan had explored this idea some years ago.
It works.
I have gone through a number of iterations of DMLs for these center channel speakers.
Until this latest iteration, mounting the DMLs whether by clamping one edge or trying to clip them to a frame (both with foam between the clamp, clips and panels) still transferred far too much energy to the supporting frame.
This latest experiment has the panels hanging by thread.
You can also see how I've support the Thrusters.
The Thrusters probably overdrive these small thin bass wood panels and the earlier versions had a harshness to them as variously clamped.
These seem lovely. Clear. Efficient. Curiously well matched and integrated (at least by ear) with the rest of the system.
No measurements yet, just going back to listen to passages in films that I've missed because of poor centre channel reproduction.
I made my little stands from stuff I had in the workshop:
- Base - pieces of aluminum shelving cutoffs
- Verticals - Ikea closet door pulls
Next thoughts - I might switch out the wood for thin aluminum with silicone dampening (silicone adhesive + acetone -> sprayed on) as I described in an earlier post.
Just having fun.
.
HvdZ... Sounds like you're doing the same thing... Nomex honeycomb is aramid fibre and your gluing it to paper??
Same process as building a double top guitar.
For reference, I printed a 75 X 75 X 4 test grid with 0.1 mm walls in PLA+
It was quite rigid through the plane
It weighed 3.3g vs 15.75g for 4mm poplar of the same size..Add some for the surfacing and it's still incredibly light
The reason for only printing the core is that it can be made in 300x300 panels and glued together, then the facings are not constrained by the available print size
Time will tell if it's viable but it's worth a shot
Eucy
Hi aagas.
Can you give information of the construction of the panel and its thickness?
I tried to look back but couldn't find this information.
Steve.
Center channel speakers:
- Basswood
- 3 mm x 260 mm 165 mm.
- Aluminum honeycomb core with aluminum skins
- 10 mm x 1800 mm x 720 mm
Each aluminum panels weighs 13 lbs (5.91 kg).
Room has 12' (365.75 cm) between the pilasters in the photo.
TV sits in front of the aluminum panels.
Panels sit on 4" L-brackets and angle towards the wall with a single bit of dense foam at the top.
Just easy to do and may prevent standing waves with the DMLs so close to the wall.
In earlier incarnations I had the panels oriented vertically and placed about 2.25' (68.58 cm) from the back wall.
I don't have an explanation, but they sound (to the ear) better now.
You've been conducting quite a few experiments with exciters affixed to flat panels. The voice coil, which is blocked from movement, transmits vibrations to the upper part of the exciter, which then conveys those vibrations to the panel surface. This, in turn, generates sound waves that travel through the air.
The persistent issue has always been (and continues to be) the weight of the exciter. The panel must be suspended in such a way that it doesn’t wobble about. Regardless of the setup, the panel tends to exhibit some degree of wobble, necessitating some form of restraint. This could potentially be achieved through a suspension system, much like that of a conventional speaker, where the suspension is anchored to a stable frame or enclosure. However, the challenge of the exciter's weight remains a significant concern.
Now, what if we were to consider the two primary components of the exciter separately: the voice coil and the magnet(s)? If we were to transfer the flattened voice coil to the suspended surface of the panel, while keeping the magnet(s) fixed to the frame itself, just a few millimetres away from the panel.
The flattened voice coil, connected to an amplifier and adhered to the surface would emit sound or music when the magnet(s) are brought close. This concept was practically a school experiment once upon a time. Our goal is to make the flat panel resonate beautifully, one way or another. And it certainly doesn’t imply that a hefty exciter needs to be suspended from the panel itself. I have mentioned this few times earlier. What do you think?
The persistent issue has always been (and continues to be) the weight of the exciter. The panel must be suspended in such a way that it doesn’t wobble about. Regardless of the setup, the panel tends to exhibit some degree of wobble, necessitating some form of restraint. This could potentially be achieved through a suspension system, much like that of a conventional speaker, where the suspension is anchored to a stable frame or enclosure. However, the challenge of the exciter's weight remains a significant concern.
Now, what if we were to consider the two primary components of the exciter separately: the voice coil and the magnet(s)? If we were to transfer the flattened voice coil to the suspended surface of the panel, while keeping the magnet(s) fixed to the frame itself, just a few millimetres away from the panel.
The flattened voice coil, connected to an amplifier and adhered to the surface would emit sound or music when the magnet(s) are brought close. This concept was practically a school experiment once upon a time. Our goal is to make the flat panel resonate beautifully, one way or another. And it certainly doesn’t imply that a hefty exciter needs to be suspended from the panel itself. I have mentioned this few times earlier. What do you think?
Had a little time today and rethought the center channels... (still playing ;-)
aagas have you considered moving the DML panel backwards to vertically align them with the centre of the woofer top plate? this ought to provide time alignment with the woofer. so I assume that you prefer this new set up over the previous one? thanks for posting.
I have (following fond memories of my first Dahlquist DQ10s).
That said, I have the capacity to time align outputs electronically if they need it.
Note, both DLM sets and the woofers stand in different planes.
I've already time aligned the woofers and the large panels.
I'll tweek time alignment for the center channel DMLs once I've settled on them.
Currently preparing an aluminum alternative to the Basswood.
Too early to tell, but even just clipped together they sound pretty good.
aagas.
When you say base wood, is it a single layer of wood or is it a ply?
I only ask as I have ordered base wood in the past ,and always ended up with ply 😖
Steve.
When you say base wood, is it a single layer of wood or is it a ply?
I only ask as I have ordered base wood in the past ,and always ended up with ply 😖
Steve.
Technically "basswood". Single layer. Solid wood. Heavier/denser than balsa wood (but not by a lot).
aagas.
I like the idea of different flexibilities in different directions with solid wood or ply with the grains going in the same direction.
I prefer the sound of the panels I have tried.
I did complain to Amazon about the wrongful advertising, they said they would look into it, but they are still doing it, and not just the one company.
I gave up in the end and thought I might try flexible ply as it seems close the the crate ply panels I have made.
Too much going on at the moment for me, so practically all projects have stopped.
Steve.
I like the idea of different flexibilities in different directions with solid wood or ply with the grains going in the same direction.
I prefer the sound of the panels I have tried.
I did complain to Amazon about the wrongful advertising, they said they would look into it, but they are still doing it, and not just the one company.
I gave up in the end and thought I might try flexible ply as it seems close the the crate ply panels I have made.
Too much going on at the moment for me, so practically all projects have stopped.
Steve.
Steve -
Not certain what we in the US would call "flexible ply".
I actually thought that the basswood would have a lots of similar characteristics to your various found crate panels.
I get it from an art supply store (2 blocks from my home in lower Manhattan). It gets used for things like architectural model building and sculpture.
I last purchased 24" x 8" sheets for $US 8.00.
- A
aagas.
Can you feel the difference in bending in different directions.
The crate ply could bend very easily in the short direction but harder in the long direction.
I did show pictures.
Steve.
Can you feel the difference in bending in different directions.
The crate ply could bend very easily in the short direction but harder in the long direction.
I did show pictures.
Steve.
Similar to your crate ply.
Far more flexible parallel to the grain.
Hardly moves bending against the grain.
I noticed the other day that the art supply store I mentioned had some thin basswood ply.
Number of plys would matter if one wants equal bending in all directions.
I'll go visit them later today.
Hmmm....?
This discussion gives me even more incentive to look at taking thin aluminum as the base for a panel then spaying it with silicone/acetone.
While my aluminum honeycomb panels have extraordinary rigidity for their thickness, the original (in titanium) use of honeycomb panels saw construction of the SR-71 Blackbird providing uniform strength (and flexibility) across its surface.
Likely not an original thought to me, but it has me wondering.
Could the key to material selection follow uniform flexibility across the front and back surfaces of a DML?
If yes, would this argue for regular shapes: circle, square, equilateral triangle, ... ?
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aagas.
This was the sort of flexible ply that I was thinking of.
3mm would be my choice for a small panel ,say 6x9 maybe slightly larger ?
The crate ply was a very lively sounding panel, but needed small weights to damp out the panel exciter self noise.
the weights sorted out this problem and also filled in the suck outs in the lower midrange .
Steve.
https://www.ebay.co.uk/itm/16672564...ufhOXmeGx8V5W9KGZ+OivHbPY=|tkp:Bk9SR7r27K7OZA
This was the sort of flexible ply that I was thinking of.
3mm would be my choice for a small panel ,say 6x9 maybe slightly larger ?
The crate ply was a very lively sounding panel, but needed small weights to damp out the panel exciter self noise.
the weights sorted out this problem and also filled in the suck outs in the lower midrange .
Steve.
https://www.ebay.co.uk/itm/16672564...ufhOXmeGx8V5W9KGZ+OivHbPY=|tkp:Bk9SR7r27K7OZA
hello steve: I have been experimenting with foam ore art board the kind found at dollar stores which has an extruded ps foam core and laminated paper top coats. By soaking the paper in water for a few days you can easily roll the paper layers of the two sides as the adhesive used is water soluble. The foam core has a fine embossed surface texture which is easily sanded off with 100 grit open coat sandpaper. Core thicknesses vary in thickness but three of the samples I have the core is 5/32 of an inch thick and a fourth sample has a core thickness of 1/8 of an inch. So far the one black colour core foam board of the group has a core thickness which is 5/32 " thick. this black core shows a decent stiffness in the extruded direction while the stiffness in the opposite direction is quite flexible. the white core version of this board is a little less stiff in the extruded length compared to the black core but its stiffness in the opposite direction of the extrusion is quite a bit stiffer than that of the black core. the measured weight of the 5/32 core materials is all very similar and an 8"x4" sample of the 5/32" thick material (core only) weighs only 4 grams.
the thinnest core material I found was being used as the core of an rectangular board sole to be used as a dry eraser board (so it has a thin smooth plastic film on one side) this core material is 1/8 of an inch thick. /this core material has the most stiffness of the samples I tried and while the stiffness opposite to the extruded direction is les than in the extruded length it is the closest so far as stiffness goes in the opposite direction.
I thin this material with the surface texture/skin sanded off and then coated wit 50/50 water/white glue may have potential for a DML that may not require any edge damping like your card stock panels. hope this is of interest.
Hi moray.
Foamcore has never been one of my favourite materials.
Even with the paper stripped off.
And coating it in pva didn't seem to help much.
Coating xps in a thin coat of epoxy brings this material to life, and gives it a higher frequency response.
Some may think it sounds too bright.
But I am not sure if it would make a small rigid panel sound too bright and harsh.
Pva is not rigid like epoxy and has a softer more neutral sound which did not help the panels dull sound.
You will have to experiment.
Please let me know your findings.
Steve.
Foamcore has never been one of my favourite materials.
Even with the paper stripped off.
And coating it in pva didn't seem to help much.
Coating xps in a thin coat of epoxy brings this material to life, and gives it a higher frequency response.
Some may think it sounds too bright.
But I am not sure if it would make a small rigid panel sound too bright and harsh.
Pva is not rigid like epoxy and has a softer more neutral sound which did not help the panels dull sound.
You will have to experiment.
Please let me know your findings.
Steve.