I think you would have to go for profiled aluminium or steel pipe (the lightweight stuff used in lighting trusses.)
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I have been building EPS panels for about 12years now.
EPS is my favourite material so far , nothing I have heard can quite match it.
Steve.
Yes I've also been doing intensive testing using EPS. Of course the problem is its compressive strength: It's too soft to transmit HF from the back of the panel through to the front. So unless you're using hard, low density pucks in front of the driver in the panel, then HF does suffer.
But yes, as far as efficiency and self damping go, it's good.
I've found the best result skinning it with ultra lightweight Dyneema and cold glue.
Andre.
If you want an EPS panel that radiates HF above 10k from all over the panel surface , you will need to use a higher grade EPS .
The lower grades only radiate the hf above 10k from the central area about two or three inches max.
I took these pictures on NXT Rubbish forum in about 2014.
The first picture shows the response of a 5ftx2ft x 25mm panel 12inches in front of the exciter area.
The second picture shows the panel response at 12ft distance.
Notice the response drops sharply a good 6db or so after 10k but stays constant up to 10k.
This is the in room response including the dip below 300hz.
Picture three shows the in room response with my TLs subs running below 300hz.
The comment below this picture says although the hf flat lines above 10k it radiates this all over the room, which sounded natural, so I do not bother to EQ or add a tweeter.
Although I do now days increase the hf output from the centre without too much effort .
I try to do as little as possible, to try and not add any extra mass.
Adding paper and glue will damp the panel and add mass.
Steve.
If you want an EPS panel that radiates HF above 10k from all over the panel surface , you will need to use a higher grade EPS .
The lower grades only radiate the hf above 10k from the central area about two or three inches max.
I took these pictures on NXT Rubbish forum in about 2014.
The first picture shows the response of a 5ftx2ft x 25mm panel 12inches in front of the exciter area.
The second picture shows the panel response at 12ft distance.
Notice the response drops sharply a good 6db or so after 10k but stays constant up to 10k.
This is the in room response including the dip below 300hz.
Picture three shows the in room response with my TLs subs running below 300hz.
The comment below this picture says although the hf flat lines above 10k it radiates this all over the room, which sounded natural, so I do not bother to EQ or add a tweeter.
Although I do now days increase the hf output from the centre without too much effort .
I try to do as little as possible, to try and not add any extra mass.
Adding paper and glue will damp the panel and add mass.
Steve.
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Higher grade than EPS... Do you mean higher density or do you mean XPS?
What density EPS are you using?
Using 25kg/m3 10mm EPS I got very very good efficiency. But it rings like a bell. Spectrograms expose resonant tails at multiple frequencies.
I applied kraft paper both sides with diluted cold glue and the efficiency increased slightly over-all, with slightly better highs, and nicely-controlled bass.
But it's still not good enough for live PA use. And too fragile anyway.
Jmproject.
I think that what Andre is hinting at is that I came up with the idea of the 50x50 pva mix on EPS over on NXT Rubbish some years ago.
The guy that posted that project used my idea( he did reference me ,which was nice) but he used a totally different material , XPS.
which I would not use pva on, as this has a totally different effect.
I was a little disappointed, as everyone ,even tectonic now use XPS instead of EPS .
The deed is done, and everyone seems to go along with it😱
If using XPS I would recommend an epoxy to skin the surface, this would bring up the HF and impove the sound.
And you should not sand the shiny XPS surface , but thinly spread the epoxy over this shiny surface.
If you sanded the XPS the epoxy would sink into the surface and make the panel too heavy.
EPS and XPS are not the same, and should not be treated the same.
Steve.
I think that what Andre is hinting at is that I came up with the idea of the 50x50 pva mix on EPS over on NXT Rubbish some years ago.
The guy that posted that project used my idea( he did reference me ,which was nice) but he used a totally different material , XPS.
which I would not use pva on, as this has a totally different effect.
I was a little disappointed, as everyone ,even tectonic now use XPS instead of EPS .
The deed is done, and everyone seems to go along with it😱
If using XPS I would recommend an epoxy to skin the surface, this would bring up the HF and impove the sound.
And you should not sand the shiny XPS surface , but thinly spread the epoxy over this shiny surface.
If you sanded the XPS the epoxy would sink into the surface and make the panel too heavy.
EPS and XPS are not the same, and should not be treated the same.
Steve.
I think Steve means a higher grade of EPS. Basically it comes in five different densities. The highest density one I've bought is 'Ultra High Density' - 30kg/m3 I think. I've yet to turn it in to a serious functioning panel as I'm getting very good results from 2mm ceiba plywood fixed to a softwood frame. However, when I nave tried it (including the obligatory sanding and PVAing, I've never been fully convinced. My panels are 30x40cm and sit above an open baffle bass unit, soon to become an H frame. I XO at around 400hz. The 15" Monacor bass drivers are good to 2.5khz.
Oh I never knew that! But it's a very nice treatment, it seems to act like a stiffening membrane when it's cured. I see it's regularly suggested all over these threads.
I'm still looking for XPS in this backward country of ours. Nobody seems to even know what it is... eish.
Those are fairly big panels for a 400Hz HPF? I'm sure they could probably do 200Hz quite easily unless you're driving them really hard.
I've discovered that I can very VERY good bass from small panels if I use a less stiff, low density material. But this is where compression strength and bending stiffness have to fight each other.
I'm currently experimenting with expanding foam skinned with carbon fibre or alu foil (260mm x360mm, variable thickness.) Both gave me very surprising bass and decent tops. Next step is to crank up the kW and see how loud they can go.
I somewhat cringe silently when I see a 15" driver going anywhere higher than 200Hz...
Hello Lordtarqin,
Which thickness are they?
For now, I have had only standard density EPS which suffer for a low HF extension. What the HF extension of your EPS panels?
Regarding your pursuit of expanding foam and Toddincabo's cooler foam, this may be of interest - DIY expanding urethane foam, with strength/stiffness doping: https://www.kitplanes.com/making-sandable-foam-glue-filler/
I was thinking about making an aluminum skinned (pop can material) 4" circle for highs, like you did on the DML PA forum. What thickness would you suggest?
Thanks for that great background information, Spedge. So all these years later, where have you landed on the ideal build? From your last few comments, it sounds like you prefer EPS to XPS, is that right? What is an example of high grade EPS - R-Tech from HD? It also sounds like you no longer treat the surface? Is that right?
I didn't understand that statement, how is it that you're increasing the hf output from the centre?
Also, it seems like there are two schools of though on DML -- spines and spineless. Have you built panels with frames and spines?
I'm not going to be able to try epoxy on xps for a while, I'm already in trouble for the epoxy I used a couple days ago to mount an exciter to a spine. So I'm game for trying a less intensively treated route on EPS...
spedge said:
I didn't understand that statement, how is it that you're increasing the hf output from the centre?
Also, it seems like there are two schools of though on DML -- spines and spineless. Have you built panels with frames and spines?
I'm not going to be able to try epoxy on xps for a while, I'm already in trouble for the epoxy I used a couple days ago to mount an exciter to a spine. So I'm game for trying a less intensively treated route on EPS...
Spine... I'm assuming you mean the brace or the support behind the exciter?
Larger exciters, such as the DAEX 30HESF, are too heavy to be supported by adhesive tape and supporting legs. They might work ok for a short while supported only by adhesives, but eventually they either fall off, or the voice coil gets misaligned and starts rubbing against the magnet.
These exciters have a tapped hole in the back of the magnet that will accept a threaded rod to be fastened to a brace for the sole intention of supporting the magnet. They might also have screw holes around the sides of the magnet also to be fastened to support (not to the panel!!) Such units are designed to run with bracing, and they might benefit sonically from such support.
Smaller drivers, with or without tapped holes on the back, might have three or four flat legs, with adhesive tape on their feet, extending out and around the magnet to be adhered to the panel. These legs are there simply to support the magnet, and have nothing to do with the sound. I normally chop them off and support the magnet with bolts or with adhesive to a brace. It seems that some of these units prefer their magnets to vibrate freely (with their legs only for support) while others benefit from the magnet being fixed to a brace.
Very small drivers don't need additional support and rely only on the adhesive ring on the voice coil. These units are designed to have their magnets vibrating freely.
Here's what I'm using at gigs. That's 4x20w drivers per side. I've taken off the bracing that supports the drivers since this is a temporary setup.
I drove them very hard last night, red-lining 150w per side, and I noticed that the drivers do not heat up the same. Some get really hot, while others just get a bit warm.
I suspect that the drivers sitting on panel modes at low frequencies get a lot of voice coil movement, and hence cooling, while those on nodes don't move so much, and over-heat.
I drove them very hard last night, red-lining 150w per side, and I noticed that the drivers do not heat up the same. Some get really hot, while others just get a bit warm.
I suspect that the drivers sitting on panel modes at low frequencies get a lot of voice coil movement, and hence cooling, while those on nodes don't move so much, and over-heat.
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25kg/m3 and 30kg/m3 seem quite hi densities to me .
I have never tried anything this high.
70 grade is about 14kg/m3, this is the material used for the 5ftx2ft x 25mm measurements I just posted.
This is the same type of material leob used for his pa speakers, except his were carbon impregnated .
150 grade in the UK, is about 22kg/m3 .
It is very expensive to get hold of EPS with a higher grade than 70 in the UK, you have to bulk buy plus delivery.
I would never spend this sort of money on an untested material.
I am at the moment testing an EPS panel which is possibly in the 40 grade area, 9kg/m3 using a 3watt exciter to see what sort of performance can be expected.
This is for home use ,not PA work.
Steve.
I have never tried anything this high.
70 grade is about 14kg/m3, this is the material used for the 5ftx2ft x 25mm measurements I just posted.
This is the same type of material leob used for his pa speakers, except his were carbon impregnated .
150 grade in the UK, is about 22kg/m3 .
It is very expensive to get hold of EPS with a higher grade than 70 in the UK, you have to bulk buy plus delivery.
I would never spend this sort of money on an untested material.
I am at the moment testing an EPS panel which is possibly in the 40 grade area, 9kg/m3 using a 3watt exciter to see what sort of performance can be expected.
This is for home use ,not PA work.
Steve.
The wires are not heavy enough nor short enough to distort the positions of the VC's and especially not to influence the Mms. I specifically cut the wires to length and suspended them in such a way as to not interfere with the VC/gap positions, nor to rattle at high SPLs.
I don't think they would. While they were nicely braced a week or two ago, I did not have the opportunity to drive them really hard for 4 hours at a time like I did last night. But common sense seems to suggest that the magnets, if fixed to the same brace, would force the drivers and the panel to all move similarly.
When I say 'over-heat', I mean that they heated up, I mean some got hot. But they did not reeely over-heat as-in blow up. I did not burn any voice coils... they all still smell quite fine.
I suppose @BurntCoil could give us some insight here...
I cannot remember how they measured, unfortunately. They were 10mm thick ultra high density ones. When I've rehoused my bass drivers in H frames, I may have another go with EPS.
Andre, the bass drivers are in asymmetrical topless U frames, so they do behave a little differently from if they were in a sealed or ported box. Mind you, back in the day, the usual XO point for 12" bass drivers in sealed boxes was around the 400hz mark.Oh I never knew that! But it's a very nice treatment, it seems to act like a stiffening membrane when it's cured. I see it's regularly suggested all over these threads.
I'm still looking for XPS in this backward country of ours. Nobody seems to even know what it is... eish.
Those are fairly big panels for a 400Hz HPF? I'm sure they could probably do 200Hz quite easily unless you're driving them really hard.
I've discovered that I can very VERY good bass from small panels if I use a less stiff, low density material. But this is where compression strength and bending stiffness have to fight each other.
I'm currently experimenting with expanding foam skinned with carbon fibre or alu foil (260mm x360mm, variable thickness.) Both gave me very surprising bass and decent tops. Next step is to crank up the kW and see how loud they can go.
I somewhat cringe silently when I see a 15" driver going anywhere higher than 200Hz...
I've checked the response curve of my 30x40cm panels. They will certainly go down to 250hz, below which they get very messy. When I've built my H frames for the bass drivers, I'll reassess. Hopefully they will be done within the next month.