The wicker I know makes a lot of creaking noise and is very porous. It would need to be cast in epoxy to work without internal noise. You may as well just use carbon fiber at that point.
most epoxy coating take about 21 days to achieve most of their full cure a few as long as a month but I would say if you are not happy with the hardness at three weeks try another product/brand
Has anyone tried gold leaf on HD EPS? I'm not sure how if it will affect the sound much being so thin but could look nice for a bit of bling in the lounge.
@JoskaNZ I read somewhere about a mic manufacturer doing testing of the same microphone, but one with gold plating and one without. The one with gold plating was considered the best by the listeners, even if sound was exactly the same. So in reality, it should sound better then a similar material like aluminium 😀
Both aluminium and gold are quite soft, and definitely does not have a high stiffness to weight ratio, which seems desirable to a degree at least. But they are also not stretchy, and can perhaps work when a thin skin bonded to a core that is stiff. I think I saw some commercial manufacturer of DML using composite with aluminium skin.
Both aluminium and gold are quite soft, and definitely does not have a high stiffness to weight ratio, which seems desirable to a degree at least. But they are also not stretchy, and can perhaps work when a thin skin bonded to a core that is stiff. I think I saw some commercial manufacturer of DML using composite with aluminium skin.
That's interesting, if it wasn't a blind test it would be easy to put down to audiophile tomfoolery. The gold leaf is less than 0.2microns thick apparently so it would be probably hardly noticeable I guess the adhesive would add more to the panel than the leaf itself.
I was going to ask Leob if you had compared the SPL output of a single exciter to the 4 you use on the same panel?
Mine sound pretty composed up to about 96-100db (at 1m) but then start to distort, I can't tell if it's the panel and its fixing or the exciter that is being overdriven, the DAEX25FHE so only 24w but on EPS (which in theory should be around 92db+ sensitivity) that would only be getting around 10Watts at 102db. My thought was maybe it's the small attachment area and I need to prep the EPS surface more than 1/2 strength PVA glue.
I forgot to mention they are high passed with a 24db slope at 150HZ so it'n not low bass distorting them.
I 'discovered' something recently that seems obvious, but I never really thought about it with big DML panels: adding a baffle significantly improves bass response. It's a pretty fundamental concept which is thought about a lot with cone speakers, and unsurprisingly it applies to DML panels as well. I did some experimenting and I definitely noticed more bass output when I moved my test panel edge right up to a baffle face. My test panels are usually around 13"x20" - 16"x24".
Months ago while experimenting with foam panels I found that I definitely prefer XPS over EPS. The 1" thick purple XPS project panels work pretty well, significantly better than all of my EPS experiments. EPS is too floppy. I tried a whole lot of surface treatments and dimensions and I used REW to measure the results. The best result overall was when I hot-wire sliced the XPS to about 5/8" thick and about 16"x24", and then I heat-skinned it.
What does heat-skinned mean? While testing different surface treatments and cutting foam I noticed that heat makes the foam shrink and harden. It occurred to me that this might be better than any glue or paint because it can be very hard and light, and it applies some tension as it shrinks, much like hide glue. I found a heat gun to be the best approach and with lots of experimenting I learned the right temp and speed to use to slowly 'toast' the surface without creating holes or extreme webbing. I also found through experimenting that hardening the edge faces along with the main faces improves the sound quality.
So for anyone considering PVA, shellac, acrylic paint, or hide glue on foam panels I'd recommend instead to use XPS foam with heat to harden the skin. It can be tricky to control the heat-skinning process so practice on lots of scraps first to get an even and consistent finish. Make it as dark and hard as you can without creating holes or tearing with the heat. The heat creates some very toxic gases so make sure you do it in a very well ventilated space with adequate protection. This doesn't work well on EPS because of the space it has between spheres of foam - that space causes tearing very quickly.
I did try other methods to harden the polystyrene but I couldn't find a way to get a better finish than with careful use of a heat gun. I tried an oven, hot spatula, and hot plate, but heat gun worked the best. I thought about trying to liquify polystyrene and bake it till it starts turning dark, then pour it out, cool a bit, and then set a panel on it, but that is too difficult a process for me to try at home and without precise control of the temperature it would likely leave pockets of air/gas between the hard layer and foam resulting in a fragile bond.
After tons of experimenting I decided that epoxy provides a tougher finish that is more controllable so that's what I'm working with now. Epoxy is much more expensive and takes longer to use but I think when done well it provides better results. The hardened polystyrene is pretty brittle and is prone to cracking when it is too thin. Epoxy can crack too when it is thin but it is easier to control the thickness, and fiberglass / CF can be added too.
What does heat-skinned mean? While testing different surface treatments and cutting foam I noticed that heat makes the foam shrink and harden. It occurred to me that this might be better than any glue or paint because it can be very hard and light, and it applies some tension as it shrinks, much like hide glue. I found a heat gun to be the best approach and with lots of experimenting I learned the right temp and speed to use to slowly 'toast' the surface without creating holes or extreme webbing. I also found through experimenting that hardening the edge faces along with the main faces improves the sound quality.
So for anyone considering PVA, shellac, acrylic paint, or hide glue on foam panels I'd recommend instead to use XPS foam with heat to harden the skin. It can be tricky to control the heat-skinning process so practice on lots of scraps first to get an even and consistent finish. Make it as dark and hard as you can without creating holes or tearing with the heat. The heat creates some very toxic gases so make sure you do it in a very well ventilated space with adequate protection. This doesn't work well on EPS because of the space it has between spheres of foam - that space causes tearing very quickly.
I did try other methods to harden the polystyrene but I couldn't find a way to get a better finish than with careful use of a heat gun. I tried an oven, hot spatula, and hot plate, but heat gun worked the best. I thought about trying to liquify polystyrene and bake it till it starts turning dark, then pour it out, cool a bit, and then set a panel on it, but that is too difficult a process for me to try at home and without precise control of the temperature it would likely leave pockets of air/gas between the hard layer and foam resulting in a fragile bond.
After tons of experimenting I decided that epoxy provides a tougher finish that is more controllable so that's what I'm working with now. Epoxy is much more expensive and takes longer to use but I think when done well it provides better results. The hardened polystyrene is pretty brittle and is prone to cracking when it is too thin. Epoxy can crack too when it is thin but it is easier to control the thickness, and fiberglass / CF can be added too.
Oh, and I should mention of course that based on all of my testing with different materials and dimensions and treatments, every kind of DML system will benefit significantly from EQ'ing. I certainly wouldn't use one without EQ. Some people say XPS is 'shouty' and that's because it is generally very loud in the 200hz - 1khz range, and an EQ can pull that down.
I'm using a mini-pc with Linux and CamillaDSP to give me all the control I need for a multi-channel setup.
I'm using a mini-pc with Linux and CamillaDSP to give me all the control I need for a multi-channel setup.
I've only done 4 or 5 epoxy tests so far and I've done it without any fabric. I just spread the epoxy on the surface of the foam after sanding. My testing is pretty crude so far and I'll be trying some fiberglass this week. I got some lightweight e-glass 'veil' off amazon yesterday. Prepreg will be too heavy I think, and because I'm putting it on foam I don't think the oven curing will be compatible? Idk, I haven't looked into what temp is required and I don't have any vacuum equipment (nor skill or experience) for doing this.
In this video they've got the gear and skill I wish I had:
That guy also shows some of the problems with epoxy on XPS, though his intended use is much different.
Interesting. I only heard the opposite, that EPS sounds better than XPS and that rather than creating a heat skin people use sandpaper to remove the skin formed when cutting with hot wire. So I have neither tried XPS nor heat skinning.
It is somewhat extraordinary claims, and while I appreciate the details about your method and your recommendation, I'm still wondering in what way is XPS better, and better compared to what?
Precisely what EPS have you tested with what additives and in what solutions? EPS varies a lot in density, and not only what you apply but how you apply it to the plate makes a really big difference.
Also you say "best results" are with XPS and EPS is "too floppy". Exactly what does that mean? Do you have measurements to compare that indicate issues with FR, sensitivity or something else? Or if subjective, can you try describing what you experienced?
I have built , tested and measured my 5mm xps panels on this forum.
There are also recordings that I have posted.
I did not sand the panel before coating with a thin layer of epoxy.
A sanded panel will absorb too much epoxy, and make the panel heavier than necessary.
Xps does not have the high frequencies ,without the epoxy coating.
Xps on its own suffers from early hf roll off.
Steve.
There are also recordings that I have posted.
I did not sand the panel before coating with a thin layer of epoxy.
A sanded panel will absorb too much epoxy, and make the panel heavier than necessary.
Xps does not have the high frequencies ,without the epoxy coating.
Xps on its own suffers from early hf roll off.
Steve.
moray james,
No, actually I was referring to panels made with a 1.6 mm balsa core with about 2.5 mm CF/epoxy skins.
And while it was an overstatement to call it the holy grail of panels (I was kidding around a bit), I do think it is a very good panel structure. Light and stiff for good efficiency, but not so stiff that the panels need to be huge to get low frequencies.
This panel structure has very low internal damping (similar to EPS and XPS), however, and hence needs perimeter damping even more than most other materials. Eventually I will try out a CF balsa panel with high aspect ratio (near 4:1) on a sturdy frame with good perimeter damping, but it's a fair amount of work to make these panels and I just haven't had the urge to make that much effort just yet.
Eric
Veleric what was the deciding factor for you to choose the CF/balsa over the three ply balsa? You said said the three ply balsa made you feel good when you listened to it. So I got the impression there was something about the CF/balsa that you were not happy with. Thanks.
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@Leob, yeah I spent weeks and months testing different foams primarily relying on REW for analysis rather than my ears. Through comparing what I heard to what REW said I learned a good deal about how to use my ears better, and how to use numbers to explain what I hear. I still don't know what I'm doing, really, but I just thought I'd share what I learned. It isn't really worth sharing my numbers because I did so many tests without documenting the test conditions well enough for the numbers themselves to mean much to other people. There are sooo many variables involved that greatly effect the test results... Panel support, location, and mic distance are the ones I did not document well enough nor keep consistent enough across weeks and weeks of testing :| I did enough testing for myself to validate my own subjective assessment though.
I don't have access to a lot of different EPS foams but I tried a few from Home Depot. One was 1/2" with foil on one side and plastic on the other. I tried intact, and foil side alone, and two glued together with foil out. I also tried 3/4" thick naked EPS, and two glued together. I tried PVA on outside too. Every EPS test was significantly more 'peaky' in frequency response and distortion, so that's why I prefer XPS.
FOAMULAR NGX F-250 2" thick provided the most stable frequency response for untreated foams that I tested. I think the thickness brings significant internal reflections at HF though causing greater distortion at HF, but overall it's still pretty good. Coroplast also provided very stable response but poor HF and much lower sensitivity. Elmer's foam board from Staples (XPS sandwiched with paper, I believe) worked very well, especially after I shellac'd it. Overall a thin XPS board with epoxy has been my best result though. Not good enough to stop exploring, just my best for now.
@spedge 5mm XPS is probably too thin w/o epoxy, but with epoxy it should be pretty good. I sanded with the intention of getting more surface area for the epoxy to bind to, hoping for better adhesion. My first good test still had some fuzzy foam sticking through the epoxy because it was so thin, but subsequent tests have been thicker, and e-glass will be thicker still. I'll have to see how it goes but the numbers show thin foam + epoxy is a good direction. For HF I've found that EPS and XPS average about the same, but EPS is more 'peaky' in response while XPS is more stable. I would definitely not say that XPS HF range or performance is any lower than EPS, based on my tests. Un-EQ'd HF typically isn't great from any panel (foam or otherwise) with my DAEX32EP-4 exciter though.
In my latest experiment with 4mm XPS epoxied board I cut it to a few different sizes to see how it would effect the results, I've attached a pic of REW from my favorite because the performance is pretty good for the size which can fit well into my living room. This is not EQ'd at all.
(Note: my test volume was not very loud because of other people in the house, and there was significant noise in the background)
I don't have access to a lot of different EPS foams but I tried a few from Home Depot. One was 1/2" with foil on one side and plastic on the other. I tried intact, and foil side alone, and two glued together with foil out. I also tried 3/4" thick naked EPS, and two glued together. I tried PVA on outside too. Every EPS test was significantly more 'peaky' in frequency response and distortion, so that's why I prefer XPS.
FOAMULAR NGX F-250 2" thick provided the most stable frequency response for untreated foams that I tested. I think the thickness brings significant internal reflections at HF though causing greater distortion at HF, but overall it's still pretty good. Coroplast also provided very stable response but poor HF and much lower sensitivity. Elmer's foam board from Staples (XPS sandwiched with paper, I believe) worked very well, especially after I shellac'd it. Overall a thin XPS board with epoxy has been my best result though. Not good enough to stop exploring, just my best for now.
@spedge 5mm XPS is probably too thin w/o epoxy, but with epoxy it should be pretty good. I sanded with the intention of getting more surface area for the epoxy to bind to, hoping for better adhesion. My first good test still had some fuzzy foam sticking through the epoxy because it was so thin, but subsequent tests have been thicker, and e-glass will be thicker still. I'll have to see how it goes but the numbers show thin foam + epoxy is a good direction. For HF I've found that EPS and XPS average about the same, but EPS is more 'peaky' in response while XPS is more stable. I would definitely not say that XPS HF range or performance is any lower than EPS, based on my tests. Un-EQ'd HF typically isn't great from any panel (foam or otherwise) with my DAEX32EP-4 exciter though.
In my latest experiment with 4mm XPS epoxied board I cut it to a few different sizes to see how it would effect the results, I've attached a pic of REW from my favorite because the performance is pretty good for the size which can fit well into my living room. This is not EQ'd at all.
(Note: my test volume was not very loud because of other people in the house, and there was significant noise in the background)
@SapphireSloth
I'm the same, I do some measurements sometimes, but it is more of a passion and hobby than science for me 🙂
I think the typical building grade EPS has been dismissed a few times before in this thread. At least here in Sweden it seems impossible to find decent grade EPS in regular hardware stores. I think in general for building, XPS is the go-to for higher density and strength, and EPS is mostly used when you want good isolation but less weight. So unless you special order in bulk they only carry at best "EPS 100" which is around 20 kg/m3. "EPS 150" can be bought in bulk, and should be similar density to the EPS I use, and to your typical XPS plate. That is around 25 kg/m3, but has 50% more compressive strength and 25% more bending strength compared to EPS 100.
https://www.molygran.com/our-advice/polystyrene-grades/
My recommendation is graphite enhanced 25 kg/m3 EPS with very thin layers of hide glue and shellac, but I have only tried a few different densities of EPS, and never bothered with XPS due to the many bad opinions compared to high grade EPS. But I think perhaps you have been a bit early to dismiss EPS if you only tried what was available at Home Depot. Not sure about good sources for high grade EPS in US though.
I'm the same, I do some measurements sometimes, but it is more of a passion and hobby than science for me 🙂
I think the typical building grade EPS has been dismissed a few times before in this thread. At least here in Sweden it seems impossible to find decent grade EPS in regular hardware stores. I think in general for building, XPS is the go-to for higher density and strength, and EPS is mostly used when you want good isolation but less weight. So unless you special order in bulk they only carry at best "EPS 100" which is around 20 kg/m3. "EPS 150" can be bought in bulk, and should be similar density to the EPS I use, and to your typical XPS plate. That is around 25 kg/m3, but has 50% more compressive strength and 25% more bending strength compared to EPS 100.
https://www.molygran.com/our-advice/polystyrene-grades/
My recommendation is graphite enhanced 25 kg/m3 EPS with very thin layers of hide glue and shellac, but I have only tried a few different densities of EPS, and never bothered with XPS due to the many bad opinions compared to high grade EPS. But I think perhaps you have been a bit early to dismiss EPS if you only tried what was available at Home Depot. Not sure about good sources for high grade EPS in US though.