bdjohns.
Thanks ,it's nice to know that someone is interested in my designs 😀
I usually only use the lower grades of eps , but ziggy loved his large HD eps panels.
Although I did manage to get some samples of 40cm square panels .
The HD should have a better hf to 20k.
Do you have a block of eps , if so what size?
EPS would be very good for drum reproduction, it's like having the drum kit in your room.
Maybe pm me for discussions.
These exciters seem similar and are a good price at the moment.
They are 25watt exciters.
Now you have made me buy 4 of them 🙄😅
https://www.soundimports.eu/en/dayton-audio-daex25fhe-4.html
Steve.
Thanks ,it's nice to know that someone is interested in my designs 😀
I usually only use the lower grades of eps , but ziggy loved his large HD eps panels.
Although I did manage to get some samples of 40cm square panels .
The HD should have a better hf to 20k.
Do you have a block of eps , if so what size?
EPS would be very good for drum reproduction, it's like having the drum kit in your room.
Maybe pm me for discussions.
These exciters seem similar and are a good price at the moment.
They are 25watt exciters.
Now you have made me buy 4 of them 🙄😅
https://www.soundimports.eu/en/dayton-audio-daex25fhe-4.html
Steve.
Jmproject.
This looks very similar to this old patent.
He uses this method to vary the damping applied to the panel.
Cohen, was way ahead of his time.
If we had paid more attention to his design instead of cones, where would we be now ?
https://patents.google.com/patent/U...=priority:19610101&oq=inventor:+A+Cohen++1961
1961 👍
Steve.
Thanks for the historical note, Spedge. I hope his worked better than mine. Actually, it's good for the job of getting the bass just right, but not sure beyond that. But, I await a mic and we'll see if I can figure out how to do a test.
my boatload of fhe-4's came in. On the panel in the recent pic, I put one of those on in place of the thruster and then later wired it and the thruster in series, and the sum total of those experiments is that it all sounds about the same to me.
Because I just have that one birch panel and the others are somewhat torn apart, I wanted to get some stereo going. So, I took the 10" x 48" piece of birch left over from cutting the main panel, inserted it sideways and about 1" deep into the frame of the panel in that last pic and tightened the bolds lightly. Then put a fhe-4 near either end. Unbelievable how good even that sounds with the right sub mix and a little help from a couple small junker xps panels. There is a use case here -- I need a light, long, thin panel that I can put up behind my recliner in the shop here for rear surrounds on occasion, since I found a place for the Denon here rather than haul it back to the house after the testing over the holidays.
Just the single 10" x 48" piece of birch though with 2 exciters sounds better than the rears I paid $110 a piece for in the 2000s and its portable.
my boatload of fhe-4's came in. On the panel in the recent pic, I put one of those on in place of the thruster and then later wired it and the thruster in series, and the sum total of those experiments is that it all sounds about the same to me.
Because I just have that one birch panel and the others are somewhat torn apart, I wanted to get some stereo going. So, I took the 10" x 48" piece of birch left over from cutting the main panel, inserted it sideways and about 1" deep into the frame of the panel in that last pic and tightened the bolds lightly. Then put a fhe-4 near either end. Unbelievable how good even that sounds with the right sub mix and a little help from a couple small junker xps panels. There is a use case here -- I need a light, long, thin panel that I can put up behind my recliner in the shop here for rear surrounds on occasion, since I found a place for the Denon here rather than haul it back to the house after the testing over the holidays.
Just the single 10" x 48" piece of birch though with 2 exciters sounds better than the rears I paid $110 a piece for in the 2000s and its portable.
Jmproject.
I can't say I am a fan of tall thin panels, but maybe you should try my idea of only clamping the panel in a vice at the bottom , leaving the rest of the panel to vibrate.
I would recommend a couple of sturdy pieces of wood to clamp in the vice each side of the bottom of the panel.
I recently showed a picture of a tall panel with the bracing at an angle in red.
The angle will remove most of the standing waves bouncing up and down the panel, dispersing them.
I would probably not use foam damping in the clamping, to increase the reflections, not reduce them.
Although it would be easy to compare the two, or to use as variable clamping pressure, as in the patent?
Steve.
I can't say I am a fan of tall thin panels, but maybe you should try my idea of only clamping the panel in a vice at the bottom , leaving the rest of the panel to vibrate.
I would recommend a couple of sturdy pieces of wood to clamp in the vice each side of the bottom of the panel.
I recently showed a picture of a tall panel with the bracing at an angle in red.
The angle will remove most of the standing waves bouncing up and down the panel, dispersing them.
I would probably not use foam damping in the clamping, to increase the reflections, not reduce them.
Although it would be easy to compare the two, or to use as variable clamping pressure, as in the patent?
Steve.
Hi Steve
I've been revisiting some 12mm thick high density EPS panel material and although I'll persist for a while, I find it has a large amount of harsh self noise at reasonable listening levels... almost like vibrations within the depth of the panel... Have you found this with your lower density panels, and if so, how did you treat it?
At this stage I haven't coated it, but have put masking tape in a few spots, mainly directly over the exciter position to see if it tones it down... Marginally is all I'd say
Eucy
This could be a decent exciter if you want good sub extension 
https://kinxsound.com/shop/speakers/562
https://kinxsound.com/shop/speakers/562
Hi Eucy.
The hard skin is one of the main problems with EPS.
It has a pretty awful sound.
If your panel is fairly small below 60cm it is quite easy to sand off this skin, if a little messy, larger panels are a pain in the neck .
I then coat the panel with splash of a 50x50 mix of pva and water.
This should rid the panel of this noise.
If not enough you can add another splash of pva mix.
With this mix ,most of the liquid will evaporate leaving a very thin coating, which has also soaked into the panel a little bit .
You will probably also be suffering from the the noise from the centre of the coil area, which can have a very harsh sound especially on female voices, very painful sometimes.
You could also make a small concave cone shape in the coil area for a little more midrange clarity.
What size panels were you thinking of using?
Steve.
The hard skin is one of the main problems with EPS.
It has a pretty awful sound.
If your panel is fairly small below 60cm it is quite easy to sand off this skin, if a little messy, larger panels are a pain in the neck .
I then coat the panel with splash of a 50x50 mix of pva and water.
This should rid the panel of this noise.
If not enough you can add another splash of pva mix.
With this mix ,most of the liquid will evaporate leaving a very thin coating, which has also soaked into the panel a little bit .
You will probably also be suffering from the the noise from the centre of the coil area, which can have a very harsh sound especially on female voices, very painful sometimes.
You could also make a small concave cone shape in the coil area for a little more midrange clarity.
What size panels were you thinking of using?
Steve.
Hi Steve
I've done that with XPS and it gets noticeably softer after the skin is removed
I just tried a bit of the EPS...With a coarse(ish) abrasive paper it cuts with just a small amount of pick up (pull out) which can be smoothed with a fine paper. , but the transition from skinned to skinless is not as pronounced as with the XPS. Unusually for EPS, this stuff can be sanded smooth on the end grain.
I'll try on the panel ..it's a 600 X 400 test piece.
Wrt to the voice coil noise, I know this has been mentioned a number of times previously, but on other materials I have never experienced it, so is it a feature of EPS in particular?
Eucy
I've done that with XPS and it gets noticeably softer after the skin is removed
I just tried a bit of the EPS...With a coarse(ish) abrasive paper it cuts with just a small amount of pick up (pull out) which can be smoothed with a fine paper. , but the transition from skinned to skinless is not as pronounced as with the XPS. Unusually for EPS, this stuff can be sanded smooth on the end grain.
I'll try on the panel ..it's a 600 X 400 test piece.
Wrt to the voice coil noise, I know this has been mentioned a number of times previously, but on other materials I have never experienced it, so is it a feature of EPS in particular?
Eucy
Thanks Leob
I have used latex on XPS previously, along with tissue to stiffen...EPS I've asked away from so far after testing some cheap stuff and not liking the sound. I then bought some high density material but put it aside again, now I'm trying again
Eucy
FINALLY >
I've had a great break in the weather, and with a trailer I finally have all my building materials.
(off the shelf insulation panels are huge)
To my surprise, the 10mm panel material (with thinly bonded aluminum) is not XPS, but EPS.
From all I have read > I am glad about this!
Due to its incredibly light weight, I am expecting very fast 'transient attack' and nice quick decay.
Also, due to the thin aluminum, I am expecting some pretty good high frequency extension.
I am now excited, but being a slow project builder, please be patient for updates with pictures
I've had a great break in the weather, and with a trailer I finally have all my building materials.
(off the shelf insulation panels are huge)
To my surprise, the 10mm panel material (with thinly bonded aluminum) is not XPS, but EPS.
From all I have read > I am glad about this!
Due to its incredibly light weight, I am expecting very fast 'transient attack' and nice quick decay.
Also, due to the thin aluminum, I am expecting some pretty good high frequency extension.
I am now excited, but being a slow project builder, please be patient for updates with pictures
Hello Eucy,
It would be interesting if you want to share a synthesis of your different tests of materials.
About panel noises, this topic was shared in different previous posts.
I would list :
- the membrane self noise due to the non linearity of the membrane material, all the noise created by the deformation. About it, I suggested to run a self contamination test. See for example #6131.
- the voice coil noise which is due to the air in the former area that can't escape quietly. I was shared here the countermeasure for cone speakers with radial holes in the voice coil former but I have never seen a countermeasure for DML. If I remember (Steve correct me if it is wrong), Steve experienced a change in this noise with the membrane material. This noise is around a frequency, not spread along the spectrum as the membrane self noise but it can be strong and coming from the rear side of the membrane (the use of a spectrogram in REW can help in identifying it)
- the central disk area which in my idea is more an unexpected resonance with solution like a central additional mass, higher rigidity of the central area, Eucy's dome?
That's the beauty of good damping, that it effects all frequencies in a good way. Undamped panels have a strong preference to vibrate at particular frequencies, but not at the frequencies in between. Damping reduces the amplitude of vibration of a panel at its natural frequencies and increases its amplitude of vibration at the frequencies in between resonances.
Here is a comparison of a "close mic" measurement of two identical panels, one hanging freely with no added damping, and the other attached to a frame around the entire perimeter with an effective damping foam. The "close mic" measurement gives a result that approximates the measurement you would get from an accelerometer and gives you an idea of how the vibration amplitude of the panel varies with frequency at the location of the mic. In these particular measurements, the mic was placed directly opposite the exciter, but other locations give results with the same basic character. That is, with an undamped panel (red curve), the vibration amplitude varies wildly with frequency. In contrast, the vibration amplitude of the damped panel (green) varies much less as a function of frequency. Basically, damping reduces the sensitivity of the panel to frequency, reducing its amplitude at resonances, and increasing its amplitude between resonances.
So yes, it affects the panel at all frequencies, and in a good way. With effective damping, there's no need for haphazardly adding weights or cutting angles, hoping (mostly in vain) that it will help reduce a nasty resonance at one frequency without simply moving it to another.
Spectrograms of the same two measurements are show below (undamped above, and damped below). Everyone should decide for themselves which is more likely to faithfully reproduce a recording.
And just to be complete, the final plot below compares the impedance curves for the same panels (again offset for clarity). It should be clear which is which. Both results, (close mic, and impedance) suggest that the impact of damping is strongest at lower frequencies. If you use your panel only for higher frequencies, maybe you can get away without damping. But if you want to use your panel in the lower range, where modal density is low, I suggest to consider added damping,
Eric
I thought it might be easier if I made a drawing of the problem, hopefully to clear this up once and for all.
This is an old corrugated cardboard panel 1mm thick.
I had removed the exciter , which left the ring of pva ,as shown in the picture, so I thought I would show what happens when the coil foot vibrates ,using arrows to show the direction of the travelling waves.
The arrows pointing outwards are no problem as they disperse .
But the arrows pointing inwards have a problem, they end up crashing into each other trying to get to the other side of the coil foot.
If you can imagine the peaks and cancellations going on in this area, you can understand how bad this will sound.
I would not consider using a panel that is suffering from this problem.
Some panels suffer more than others.
On this panel I made a hole in the centre and filled it with a very small blob of blu-tack , I would probably use this method on ply or similar solid heavy panels or the strip of paper technique ,or both, depending on performance.
Or a film layer.
on similar card and veneer panels, I used a fabric dome, this is easy when the panel is only 1mm thick.
This method does not work well for EPS.
I have a policy of adding nothing unless I take something away.
I prefer EPS panels, but that does not mean that heavier panels cannot sound good too.
It is in the small detail, that makes a good sounding panel.
Steve.
This is an old corrugated cardboard panel 1mm thick.
I had removed the exciter , which left the ring of pva ,as shown in the picture, so I thought I would show what happens when the coil foot vibrates ,using arrows to show the direction of the travelling waves.
The arrows pointing outwards are no problem as they disperse .
But the arrows pointing inwards have a problem, they end up crashing into each other trying to get to the other side of the coil foot.
If you can imagine the peaks and cancellations going on in this area, you can understand how bad this will sound.
I would not consider using a panel that is suffering from this problem.
Some panels suffer more than others.
On this panel I made a hole in the centre and filled it with a very small blob of blu-tack , I would probably use this method on ply or similar solid heavy panels or the strip of paper technique ,or both, depending on performance.
Or a film layer.
on similar card and veneer panels, I used a fabric dome, this is easy when the panel is only 1mm thick.
This method does not work well for EPS.
I have a policy of adding nothing unless I take something away.
I prefer EPS panels, but that does not mean that heavier panels cannot sound good too.
It is in the small detail, that makes a good sounding panel.
Steve.
Attachments
jmproject.
By all means, try everything that Spedge suggests. Trying for yourself is the only way to find out what works and what doesn't.
Also, however, I do want to clarify that my initial recommendation for a 14x48 panel as a good size applies only in the specific case that I described. That is, mounted to a sturdy braced frame, attached to the frame on all four sides (not just two). I'm not saying that you can't get good results with some other size or mounting, (maybe you can), but only that the size and mounting that I recommended is the one that works best of all the things I've tried.
I also suggest wating until you have your mic and REW running before you commit to a particular design. Once you know how to use it, it'll help you learn what changes have what effect.
Eric