will do steve. it will be a while but I wont forget. My plan was to experiment with the thinnest foam core panels and see if a stacked and 90 degree rotated foam core (to even out directional stiffness) sounds any better than a single core with differing panel stiffness. I also wanted to experiment with some low density density eps. I will consult with you when the time comes to decide what types of coatings to experiment with. I have sanded down 1/2" low density eps to a 1/4" thickness and have found a source for 1/4" panels like this commercially. What density do you think will sound best at a thickness of 1/4"? thanks.
steve I wanted to ask you if when you removed the paper from the foamcore board did you then sand off the textured skin surface and then coat as usual with PVA? thanks.
Interesting material. Checking availability the US.
That said, still interested in any thoughts you or anyone have/has with respect to equal bendiness in all directions across the surfaces of a panel.
I have a memory of posts from instrument makers building DMLs from wood.
This got me thinking about what gets used in cello's
Emphasis mine.
Cello
A European Spruce Cello Tops
Thick for DML use, but interesting I think.
Any disqualifies?
This got me thinking about what gets used in cello's
Emphasis mine.
Cello
This very much interests me for my center channel project.
A European Spruce Cello Tops
Thick for DML use, but interesting I think.
Any disqualifies?
Moray.
Can you take a photo of the textured surface ?
I seem to remember that the foamcore had a couple of different layers before you reach the xps ?
Can you take a photo of the textured surface ?
I seem to remember that the foamcore had a couple of different layers before you reach the xps ?
Hello Sandasnickaren,
Inspired by your post I bought a Bambu printer, and today I tried this panel (PLA, overall thickness 2 mm). When I hooked it up it seems to have very low efficiency. I didn't mount it on a frame yet, but that probably won't make much of a difference loudness wise.
Could I be doing something wrong? Thickness (It's quite flexible)?
It's a shame it didin't work out yet, because it's quite magical to see the printer make this in an hour, and this size would be nice and compact if I could coax a bit more sound out of it..........
For now it's no match to my paper/nomex panels.
Greetings, Hans
That has been my experience with regular PLA as well. But of course there are a lot of parameters. How many and how thick layers, and what infill with what density? Which brand of PLA?
Mounting them should improve LF response, but wont help much with mid and highs.
Would be interesting if you would try the LW PLA to see how that compares.
Mounting them should improve LF response, but wont help much with mid and highs.
Would be interesting if you would try the LW PLA to see how that compares.
hope you can see these both skins can be sanded off. for the standard foam-core board the white core looks the same but the black core had better contrast in the photo. Hope this helps.
Attachments
I now tried different options. The infill accounts for a big portion of the weight. Making the walls and infill walls and surfaces very thin (.1 mm) didn't work The infill kind of crumbled and the surfaces sagged (with standard nozzle). My latest test panel is 3mm thick, has surfaces of .2 mm, walls of .1 mm and standard infill wall thickness, standard raster but only 7% percentage . That worked, but only just (the upper surface sags in between the infill raster).
The panel is 38 g - about 800 g/sqm , and still about 9 dB quieter than my big paper panel.
I don't believe unstressed plastic will ever be a candidate for skin material... By its very nature, it absorbs too much energy. I do however think it could work as a core grid with a suitable resonant facing material.
Tensioned Mylar film has been used with some success but that's entirely a different ball game
Eucy
Tensioned Mylar film has been used with some success but that's entirely a different ball game
Eucy
You could try sanding the xps and applying pva.
It might control the panel a little better, but this material has a lot to be desired.
You would have to sand the xps as the watered down pva would just run off of the panel , unless a thick undiluted coating was used
Epoxy would brighten up the sound a lot more, and as long as it is not too small it will not be too bright.
Pva works best on thin ply , veneer, card, eps, to name a few that I have tested, I have never recommend pva on xps.
Steve.
The round flueted polypropylene is a very good panel material.
I have made very good recordings on YouTube of this panel.
It does not need an added surface (except a loose polythene film if wanted ) it has a very good frequency response.
Practicality full range from 40hz to above 20k .
It would seem to be a good candidate for 3D printing in a smaller 3mm thickness to see if the efficiency could be improved.
Or the use of a more higher power exciter.
Steve.
I don't have experience with printing PP, but from the 3D printing tests I have seen it is more flexible than PLA. Like with most plastics there are many grades and blends, and for printing you are very limited and need a certain flexibility and low melting temp, so the materials are much more similar in the end. For example polycarbonate used when printing is not nearly as stiff as if you buy a PC sheet, since typically it is only around 50% PC to make it printable, and the rest is for example ABS to improve flexibility and printability of the filament.
The LW PLA being porous allows for lightweight structure onto which one can add a skin that does not have the properties of printable thermoplastics, so I'm hopeful that can make it viable. At least one should be able to make the skin hard enough for a decent HF response, but I'm a bit sceptical if it is possible to get good efficiency.
The LW PLA being porous allows for lightweight structure onto which one can add a skin that does not have the properties of printable thermoplastics, so I'm hopeful that can make it viable. At least one should be able to make the skin hard enough for a decent HF response, but I'm a bit sceptical if it is possible to get good efficiency.
Steve -
I sent some time this morning reading about the varnishes that instrument makers used to finish violins and cellos, finding the following:
Oil-Based Varnish
Traditionally used on high-end cellos and other string instruments.- Made from natural oils like linseed oil
- Applied in multiple thin layers
- Takes longer to dry between coats
- Creates a soft, flexible finish
- Allows the wood to vibrate more freely
- Develops a nice patina over time
- Often preferred for its warm, rich appearance
Spirit Varnish
Alcohol-based and have different properties:- Dries much faster than oil varnish
- Easier to apply in a shorter timeframe
- Creates a harder, more durable finish
- May slightly dampen wood vibrations compared to oil varnish
- Often used on less expensive instruments
I just wondered if you've tried anything like this on your various wood panels.
Seems like a natural thing for wood DML panels.
Thoughts?
I plan on trying an add mix of Plaster of Paris in with dilute PVA glue 20 -25% by volume to harden the glue. Easier to use than epoxy. Will be some time yet but I will post my findings.
It is difficult to compare a Luthier designing the sound of his instrument for a certain sound and designing a DML panel to have no sound of its own .
Yes different coatings will change the sound of a panel.
Softer coatings will soften the sound, while harder coatings such as epoxy will give a brighter but harsher sound to the panel.
Moray.
Adding plaster to a pva mix will thicken the coating and increase its weight.
When the water evaporates You will probably end up with a thin ish coating of plaster which might have a tenancy to crack.
Personally I would not go down this route ( although I did 🙄).
If you do try this ,let me know your thoughts and findings.
Steve.
@aagas, I like your latest experiments in finding centre channel speakers. I believe DML panels should be excellent for this purpose.
I am toying with the idea of adding two smallish DML panels as atmosphere speakers to my existing system, which is not DML panels, but full range transmission lines. Just to add some DML magic to an already great sounding point-and-squirt system. I have 3mm Albasia plywood for this, but I was wondering what your small Basswood panels sound like on their own? And can you hear them adding value to the rest of your system? You did not elaborate much on how they sound/perform or contribute. Just curious?
Btw, I still envy those Valcucine cabinet door panels of yours. What a great and lucky find. Glad to hear you are still enjoying them.
I am toying with the idea of adding two smallish DML panels as atmosphere speakers to my existing system, which is not DML panels, but full range transmission lines. Just to add some DML magic to an already great sounding point-and-squirt system. I have 3mm Albasia plywood for this, but I was wondering what your small Basswood panels sound like on their own? And can you hear them adding value to the rest of your system? You did not elaborate much on how they sound/perform or contribute. Just curious?
Btw, I still envy those Valcucine cabinet door panels of yours. What a great and lucky find. Glad to hear you are still enjoying them.
I haven't run the Basswood panels with a full left & right channel signal.
That said, they sound pretty good even without any DSP or real integration into the rest of the system.
I have an Emotiva BasX MC1 A/V receiver, struggling to integrate the center channel and a miniDSP SHD (over kill for this particular use but I had it already) handling stereo (DMLs + woofers). This cobbled together approach can't really do what I truly want it to do.
Time for an upgrade.
I ordered a miniDSP Flex HT which should arrive this coming Wednesday.
For my purposes (single Apple TV streaming source) the Flex HT will replace both the A/V receiver and the miniDSP SHD.
(I put the A/V receiver and the SHD up on Swap Meet - they each do what they do very well, just not what I need now).
For home theater use, I'll have all DSP and room correction controlled from the Flex HT and the ability to support up to eight speakers/drivers.
The Flex HT comes with Dirac Live, so I cautiously hope to finally integrate the center channel speakers into the system.
I will report once I've done so.
FYI - In case you haven't noticed I still very much love my aluminum DMLs ;-)
Hi Moray
As per Steve, I'd shy away from this idea
PVA is not a joy to sand because it's a bit chewy by nature and plaster isn't the best additive.
You'd be better off with shellac and a filler.
If you do want to try it, I suggest adding talcum powder or real talc instead of plaster.
Eucy
aagas.
You could try these weight positions on your centre channel panels.
This will hopefully increase the response in the lower midrange and reduce some of the panel and exciter noise.
This works well with my crate ply panels.
Mount the weights at the first four reflection points .
I used magnets to slide the weights around the panel.
You could move them around to find the ideal positions if you have a way of measuring the response in real-time.
Or just use your ears to listen to the increased lower midrange response and the reduction of noise.
If the panel is small enough you can use your fingers around the edges of the panel.
This is easy and it is free, if you do not like it, you can just take them off.
All the best.
Steve.
You could try these weight positions on your centre channel panels.
This will hopefully increase the response in the lower midrange and reduce some of the panel and exciter noise.
This works well with my crate ply panels.
Mount the weights at the first four reflection points .
I used magnets to slide the weights around the panel.
You could move them around to find the ideal positions if you have a way of measuring the response in real-time.
Or just use your ears to listen to the increased lower midrange response and the reduction of noise.
If the panel is small enough you can use your fingers around the edges of the panel.
This is easy and it is free, if you do not like it, you can just take them off.
All the best.
Steve.
