This makes sense, and together with my observation about how even a UHD EPS panel develops a porous layer after sanding, would seem to suggest that diluted PVA is pretty well essential regardless of EPA grade.
Once dry, the firmer surface is restored. My experience with a medium density sanded and PVAed EPS panel is that treble goes to 20khz easily - and this was with an inferior panel with lots of flex and wobble. There really is a very big difference between medium grade EPS and UHD EPS in terms of compressive strength and rigidity.
If my new UHD EPS panel works well (and my quick and dirty test was encouraging), it would seem to me that its light and stiff properties make it the perfect inexpensive and easy to work with panel material.
Sorry, I presumed as everyone talks of applying my 50x50 pva mix ,that they understood why ?
It is obviously lost in the depths of the NXT RUBBISH forum.
As you can imagine ,sanding and applying this mix on a 7 foot panel was a pain in the neck ,very messy.
I still have a 6 foot sanded panel that I never got around to coating in pva.
Even now when I hook it up and play it ,it leaves a light white powder on the floor.
The beauty of the 50x50 pva mix is that when the water evaporates you are left with a pretty hard surface,but which has practically no weight.
A gentle use of a hair dryer will have a 50x50 mix of pva dry to the touch in no time,unless you have a 7 foot panel
But it still takes at least a couple of days to fully cure,until then the hf will roll off above 10k.
Paints and such like,leave heavy deposits which do heavily damp the sound,if something like silicone is used it will produce a sort of rubbery sound ?
I am always on the lookout for a better performing coating ,which is why I am trying out the epoxy.
But it is still a very heavy material,no evaporation !
So far ,I think the sound is pretty good,but it has a few issues with the exciter.
It sets off the exciters 2.5k and 9k resonances badly,and becomes a bit shouty on the vocals.
There are a few easy ways to prevent the 9k resonance,but the 2.5k is a bit more complicated.
Obviously the resonances would be different on different exciters.
I think I might have to at some point ,try out my fabric dome ,somehow ?
Steve.
It is obviously lost in the depths of the NXT RUBBISH forum.
As you can imagine ,sanding and applying this mix on a 7 foot panel was a pain in the neck ,very messy.
I still have a 6 foot sanded panel that I never got around to coating in pva.
Even now when I hook it up and play it ,it leaves a light white powder on the floor.
The beauty of the 50x50 pva mix is that when the water evaporates you are left with a pretty hard surface,but which has practically no weight.
A gentle use of a hair dryer will have a 50x50 mix of pva dry to the touch in no time,unless you have a 7 foot panel
But it still takes at least a couple of days to fully cure,until then the hf will roll off above 10k.
Paints and such like,leave heavy deposits which do heavily damp the sound,if something like silicone is used it will produce a sort of rubbery sound ?
I am always on the lookout for a better performing coating ,which is why I am trying out the epoxy.
But it is still a very heavy material,no evaporation !
So far ,I think the sound is pretty good,but it has a few issues with the exciter.
It sets off the exciters 2.5k and 9k resonances badly,and becomes a bit shouty on the vocals.
There are a few easy ways to prevent the 9k resonance,but the 2.5k is a bit more complicated.
Obviously the resonances would be different on different exciters.
I think I might have to at some point ,try out my fabric dome ,somehow ?
Steve.
Panel Tap Test
Steve
Yes, the reasons for PVAing are rather lost in the old threads, although I've picked up on bits and pieces on the parts I've read. And yes, the thought of rounding, sanding and PVAing large panels is far too daunting - which is probably why it seldom seems to be tried. 600x400mm is probably the largest I'd ever want to do.
The UHD EPS panels are now dry, if not fully 'cured'. I've just done a tap test. The raw panel exhibits a slow decay time when tapped. In other words, the energy imparted to the panel takes time to dissipate. This manifests itself as a kind of 'ringing'. Taking this further forward and thinking about playing music, the impact will be detrimental with more smearing of the sound and poorer transient performance.
The sanded and PVAed panel on the other hand has a very fast decay time with very little overhang and ringing. One tap and the energy dissipates quickly. This has very good implications for playing music. Transients will be faster and there will be less smearing. In fact, the thud it makes is rather reminiscent of the sound you get when you tap the cone of a traditional driver, especially a big one. The cured PVA will provide a firm surface - better than either the raw panel or an un-PVAed sanded one. In fact it's probably more like a treated paper cone.
The treated UHD EPS panel has less overhang than my sanded and PVAed 3mm ply panel too.
I'll try to record the differences, but afternoon cricket photography beckons.
Steve
Yes, the reasons for PVAing are rather lost in the old threads, although I've picked up on bits and pieces on the parts I've read. And yes, the thought of rounding, sanding and PVAing large panels is far too daunting - which is probably why it seldom seems to be tried. 600x400mm is probably the largest I'd ever want to do.
The UHD EPS panels are now dry, if not fully 'cured'. I've just done a tap test. The raw panel exhibits a slow decay time when tapped. In other words, the energy imparted to the panel takes time to dissipate. This manifests itself as a kind of 'ringing'. Taking this further forward and thinking about playing music, the impact will be detrimental with more smearing of the sound and poorer transient performance.
The sanded and PVAed panel on the other hand has a very fast decay time with very little overhang and ringing. One tap and the energy dissipates quickly. This has very good implications for playing music. Transients will be faster and there will be less smearing. In fact, the thud it makes is rather reminiscent of the sound you get when you tap the cone of a traditional driver, especially a big one. The cured PVA will provide a firm surface - better than either the raw panel or an un-PVAed sanded one. In fact it's probably more like a treated paper cone.
The treated UHD EPS panel has less overhang than my sanded and PVAed 3mm ply panel too.
I'll try to record the differences, but afternoon cricket photography beckons.
I've just made a recording of these panels ,for interests sake,which I hope to later processes ,for posting.
As you can see from the photo the conditions are not great,with all the rubbish around, and with the microphone resting on the rolled up rug, but hopefully it will give an idea of the sound produced when coated with epoxy.
This is with The 9k peak reduced but The 2.5k is still very prominent,especially from the back, the 9k peak is also less prominent on the newer more damped panel.
The new panel still rings less than the first messy panel , so has more damping, which is understandable as the front coat on the messy panel is much thinner and the top and bottom couple of inches is uncoated.
Steve.
As you can see from the photo the conditions are not great,with all the rubbish around, and with the microphone resting on the rolled up rug, but hopefully it will give an idea of the sound produced when coated with epoxy.
This is with The 9k peak reduced but The 2.5k is still very prominent,especially from the back, the 9k peak is also less prominent on the newer more damped panel.
The new panel still rings less than the first messy panel , so has more damping, which is understandable as the front coat on the messy panel is much thinner and the top and bottom couple of inches is uncoated.
Steve.
Attachments
Very very satisfied with the Aiyimas. Running 2 of the 20W 8 ohms per channel in parallel on ceiling hung 2x2 styrofoam panels with a Dayton 10" sub in my kitchen. I measured way off axis as we are all over the room and rarely right under a panel. They are definitely not full range, at least with my panels... F3 is probably like 350 Hz, but my panels have a big plateau from 400Hz to 10Khz it seems.
Anyways in combo with the sub and some heavy lifting above 10KHz I am very pleased with the sound. Crucially, the midbass clipping I was getting with the Dayton HFs is gone. My torture test for that issue- the poorly mixed bass solo on Bill Evans' "Nardis"- passed with flying colors.
Only gripe is I ordered 8 and they only sent 4. I need the other 4 for the remaining 2 panels I want to hang. But other than that I am very satisfied and recommend these if you are not squeamish about cranking up the high frequencies. It's possible the high end might be better with a more direct mounting method- I used the double sided tape they provided and might remove those and glue them to the panel.
Anyways in combo with the sub and some heavy lifting above 10KHz I am very pleased with the sound. Crucially, the midbass clipping I was getting with the Dayton HFs is gone. My torture test for that issue- the poorly mixed bass solo on Bill Evans' "Nardis"- passed with flying colors.
Only gripe is I ordered 8 and they only sent 4. I need the other 4 for the remaining 2 panels I want to hang. But other than that I am very satisfied and recommend these if you are not squeamish about cranking up the high frequencies. It's possible the high end might be better with a more direct mounting method- I used the double sided tape they provided and might remove those and glue them to the panel.
UHD EPS = Ultra High Density Expanded Polystyrene.
Look for a density of 30kg per cubic meter. 25kg/m3 is 'Extra High Density, 20kg/m3 = High Density, 15kg/m3 = Medium Density, 10kg/m3 = Low Density (packing grade).
I would have to remove the disc and insert a bolt ,so that the exciter could bolt directly to the panel in one spot and not have all the trouble I am having!
Steve.
https://m.alibaba.com/pla_detail.ht...usXWelhclJHVpcSlxBm4XPOCJl9R7VxRoCLyIQAvD_BwE
Steve.
https://m.alibaba.com/pla_detail.ht...usXWelhclJHVpcSlxBm4XPOCJl9R7VxRoCLyIQAvD_BwE
Did you get the version that screws to the panel, using the exciter holes, or did you glue it? Anything else you did on the panel.
The 2 x 2 is what? Feet?
I wonder if that would actually be a bit wobbly. Introducing three metal bolts to secure the plate may have sonic effects. There are other screw heads that look as though some kind of spacer may needed too - more variables! Good quality nylon ones could be worth considering.
I got the kind you glue to the panel. I'm using the very weak double sided tape they sent. I will glue them to my panel on Monday. Hoping that helps with high end extension and overall efficiency. And yes the panels are 2x2 feet. No treatments to the panel besides surface sanding and cosmetic stuff. W/2 little kids I don't have much time to experiment. Next thing I will try is very thin reinforced fiberglass.
That would be my worry as well. I think the ideal removable mounting method would be very thin double sided tape.
Lordtarquine.
I purchased 40 of my 10watt exciters as i thought i would need at least 8 per panel,I wasted £50 on a pair of hdn8.
I suppose I'm not expecting that great a sound from so much metal ?
I might just fork out for one as an experiment?
But I've got plenty on my plate at the moment to keep me busy.
Steve.
I purchased 40 of my 10watt exciters as i thought i would need at least 8 per panel,I wasted £50 on a pair of hdn8.
I suppose I'm not expecting that great a sound from so much metal ?
I might just fork out for one as an experiment?
But I've got plenty on my plate at the moment to keep me busy.
Steve.
Nylon screws with bolts might be a good idea too. Though I'm not sure if it wouldn't weaken the board on that place.
Which hard panel, of any material, has given better results?
I'm thinking of that green fiberglass used on pcbs, that can be bought on many sizes.
There's one that's very thin, but that would need something to keep it flat.
The regular kind could be tried with and without copper, single and double side. And even experiment with copper patches, in different shapes.
Has anyone tried this material? What do you think?