Hello Eucy
Thank you for those additions.
About the stiffness, it leads to consider all the panels as square no? Square panels are said not to be the best choice considering how the modes are distributed in the frequency range.. it leaves me perplexed for the moment.
Christian
Hi Christian
Good point but no- the distribution I believe remains as for the rectangular shape, but the node 'shapes' in the lower registers become elongated like a football ( I found this while Chladni testing a 3:1 ratio solid Cedar panel). It allows the shapes to form 'properly' but you still won't get the absolute number of nodes laterally that you'd get with a square-ish panel.
Without anisotropy, the nodal amplitudes and shapes will be heavily affected by the lateral stiffness and side supports. In the very extreme case of a long thin strip, it will behave somewhat like a line source and would have to be supported at each end only. As mentioned above, the effect of this is most felt in the lower frequencies which are always the troublesome ones.
I discovered the dramatic effect of stiffening when I used strips of YellowTrace on both sides to stiffen a 1200x600x19 EPS panel - I overdid it and it certainly stiffened the panel - in the process I built the worlds biggest tweeter
- it was way too stiff to respond to the low frequencies. Lessen learnt.The effect of anisotropy is relatively poorly covered in research papers I find.
One thing I didn't mention is that for a thin panel limited suspension system, you can purposely build in a slight lateral curve with either the Shellac/lacquer by itself or in conjunction with the YellowTrace which will stiffen and provide more stability in the longitudinal direction. If using solid timber it can be done by jointing as you normally have to join boards to get the required panel width.
Cheers
Eucy
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Christian (and others) - I highly recommend this glue if you can get it - It's Styrene based - looks line PVA but isn't - adheres to more materials than PVA - quite strong and dries about the same as PVA - I have used it to glue exciters to panels instead of epoxy and it's worked well
Cheers
Eucy
Hi Eucy,Hi Christian
Good point but no- the distribution I believe remains as for the rectangular shape, but the node 'shapes' in the lower registers become elongated like a football ( I found this while Chladni testing a 3:1 ratio solid Cedar panel). It allows the shapes to form 'properly' but you still won't get the absolute number of nodes laterally that you'd get with a square-ish panel.
Without anisotropy, the nodal amplitudes and shapes will be heavily affected by the lateral stiffness and side supports. In the very extreme case of a long thin strip, it will behave somewhat like a line source and would have to be supported at each end only. As mentioned above, the effect of this is most felt in the lower frequencies which are always the troublesome ones.
I discovered the dramatic effect of stiffening when I used strips of YellowTrace on both sides to stiffen a 1200x600x19 EPS panel - I overdid it and it certainly stiffened the panel - in the process I built the worlds biggest tweeter
The effect of anisotropy is relatively poorly covered in research papers I find.
One thing I didn't mention is that for a thin panel limited suspension system, you can purposely build in a slight lateral curve with either the Shellac/lacquer by itself or in conjunction with the YellowTrace which will stiffen and provide more stability in the longitudinal direction. If using solid timber it can be done by jointing as you normally have to join boards to get the required panel width.
Cheers
Eucy
I can easily understood that a 19mm EPS becomes too stiff with 2 additional layers. I think it needs many trials to feel what is the "right" stiffness (at least for me!)
About anisotropy, I think we come to the same question about the suspension. Does the suspension play the role we want? I wonder as often a panel might be too stiff, the suspension is also to stiff (related to the panel). I have used a light 17x17mm foam for my plywood panel. I was surprised seeing the weight to apply on a 30mm long piece of this foam to half its height; some hundreds grams.
To find some papers, have you searched with "orthotropic"? I think I have some with that.
Nevertheless, you are pointing something I don't have in my tentative of calculation a difference of stiffness in the main direction. Having them equal is a specific case.
Do you have some tips to share about Chladni patterns? How to proceed? How to analyze? I had a tentative put not push further.
Christian
a recording of the 4 strip panel on the left with the 7inch x11inch ply panel on the right.
im thinking of putting a small frame around the 7 x11 panel and using a strip of masking tape as a surround to see if it matches the art panel ?
i had to roll off the 7 x11 panel at 100hz as the exciter was wobbling badly and buzzing, the exciter needs bracing because it is very out of balance because of the lead out wires.
sub used up to 300hz
listen on headphones only .
a very lively sound and dynamic.
i have done nothing as yet to alter the sound of these panels.
steve.
im thinking of putting a small frame around the 7 x11 panel and using a strip of masking tape as a surround to see if it matches the art panel ?
i had to roll off the 7 x11 panel at 100hz as the exciter was wobbling badly and buzzing, the exciter needs bracing because it is very out of balance because of the lead out wires.
sub used up to 300hz
listen on headphones only .
a very lively sound and dynamic.
i have done nothing as yet to alter the sound of these panels.
steve.
I had a look on what is available here (in France)... not easy to find for sure and quickly equivalent product. The brands are different. The products behind the commercial names are not easily related to what is inside.
By the way, I found a family of glue I haven't considered for now. It is for example under "Pattex" brand under the name "ni clou ni vis" (means "no nail no screw") which is not PVA, works on most of the material. the technical document says formula = Flextex(R)-polymer. Behind Pattex it is a Henkel product. It looks more like a mastic. No mention of styren (Prep Multi-Use Adhesive). To be continued.
Christian
Hello Steve
Very good.
Lively and dynamic are also the words I have.
May I suggest a standardization of the sound tracks that we could listen on our system? Sometimes ago, I came across Archimago's Musical Performance Track (AMPT). I was really impressed by the dynamic of the Stravinsky's extract.
It is also what I saw here with this glue... just trying to search some equivalence to what Eucy pointed.
I suspect it's and SBR based adhesive - BASF mention this technology here :
https://www.basf.com/au/en/products/dispersion-resin/adhesives/adhesive_technologies.html
When I searched for styrene butadiene adhesive this popped up on Amazon : Could be worth a try
I'd stay away from the no-more-nails stuff - wrong usage
Eucy
It was actually XPS but the same result I'm sure.
The experimentation required for this is a killer - try and try again.
Yes - I have some but they're filled with matrices and generally only try to compare theoretical models with tests which offer no practical information
I was thinking that if you wanted to test the effect, a simple way would be to make 2 smallish 3ply panels @ 3:1 ratio - one cut longitudinally, one transversely. Support the full length of each along the long sides the same as each other and test them. I believe you'll find that the transversely cut panel lacks low frequency response comparted to the longit panel.
There are lots of examples on the web - the only difficulty is that the in testing flat, the mass of the exciter affects the results, but it's a guide and can be used to determine F0 etc. I put masking tape on the piston of the exciter and just moved it around - if you're concerned about getting the exciter contaminated, put it in a ziploc sandwich bag - Run it up and down the frequency scale. It's fascinating to watch the patterns. I used tea leaves from tea bags - Any fine light material will do - spices, coffee grounds etc - have fun.
Eucy
johnnoG
thanks again for sending the panels.
the panels are pretty heavy and as i said they look like polypropylene ?
my exciters are going to have a lot of trouble trying to drive these.
i might have to get out the hdn8 exciters.
but i should be able to get a frequency plot at least.
Ive just got to decide which panel to rip off the exciter from.
steve.
thanks again for sending the panels.
the panels are pretty heavy and as i said they look like polypropylene ?
my exciters are going to have a lot of trouble trying to drive these.
i might have to get out the hdn8 exciters.
but i should be able to get a frequency plot at least.
Ive just got to decide which panel to rip off the exciter from.
steve.
leob
https://archimago.blogspot.com/2020/01/an-inexpensive-hi-fi-class-d-stereo-amp.html
i noticed this ,from christians post.
steve.
https://archimago.blogspot.com/2020/01/an-inexpensive-hi-fi-class-d-stereo-amp.html
i noticed this ,from christians post.
steve.
Thanks Steve,
Hypex NCore seems to be excellent, but not sure how easy that particular board is to get hold of since it is OEM. The plate amps I'm leaning towards using has two of these NCore modules in it though: https://www.hypex.nl/product/nc500-oem/50
The only NCore board I found for sale to consumers is this, but seems very cost inefficient compared to the amp plate: https://www.soundimports.eu/en/hypex-nc400.html
Been starting to order stuff for making composite panels, and didn't really plan to play around the EPS plates more for now, but exciters started falling off the one plate I used the 3M 9088 tape on, so was forced to do another panel today. This time using 25mm Neopor and only one thin coat of hide glue. In my previous attempt with hide glue I did two coats, and that was too much I think. Also, this time I glued the exciters using hide glue as well instead of using tape. Not much difference in FR, and still lacking treble. But like the last attempt with Neopor and hide glue, it does respond much better to EQ if I try to boost the HF, and has a tight and detailed sound that I find superior to the PVA coated panels.
What really surprised me though was the efficiency of this panel. I measure more then 4dB above the 20kg/m2 EPS with PVA, which been the most efficient I tried otherwise so far. Very surprising with such a big difference...can really the skin make such a big difference, or could it have more to do with using the glue to fix the exciters?
JohnnoG.
Two quick pictures .
The first of the frequency plot ,which was unexpectedly good.
The second of the exciter on the panel, held on with double sided tape ,so the hf should improve when glued on properly,and some masking tape to support the magnet.
My exciters are getting slightly warm, but I am using them full range so far.
So looking and sounding not too bad, I'll have to get another exciter from one of My other panels again.
Then I'll make a recording of the two panels.
I'll reserve judgment until I have both panels up and running, but first impressions are , I'm glad to say, very promising.
Steve.
Two quick pictures .
The first of the frequency plot ,which was unexpectedly good.
The second of the exciter on the panel, held on with double sided tape ,so the hf should improve when glued on properly,and some masking tape to support the magnet.
My exciters are getting slightly warm, but I am using them full range so far.
So looking and sounding not too bad, I'll have to get another exciter from one of My other panels again.
Then I'll make a recording of the two panels.
I'll reserve judgment until I have both panels up and running, but first impressions are , I'm glad to say, very promising.
Steve.
Attachments
If you do that I'd recommend some piano music in the mix. That seems to highlight distortion very well - a couple of times I've been listening thinking hmm, yea not bad, then ew oh, nope. Distortion makes a concert grand sound like a toy piano. And maybe don't use tracks that are overly impressive. I've been listening to a track someone shared earlier "walking on the moon, Yuri Honing Trio". Amazing track and good range for testing, but I suspect that boring, standardised isolated instruments result in a better judgement.
Hello Steve
A very promising start with the Material and again Thank You for your enthusiasm to keep on with the experimentation.
Whilst listening to your supplied recordings, there is a lot achieved already, no doubt hearing these for real would impress even further.
I sent the Panels in a dimension that was to give a option on a Larger Panel to be tried.
To save deconstructing another work, would it be better to reduce the Panels to a dimension that is a better match for the available exciters.
When the other better matched Exciters become available? I can send over a Pair of Ribbed Boards to a dimension of choice.
As suggested in my mail, I know that Helium and Sulfur Hexaflouride are gases that could be used with a Loudspeaker, as said, my Audax Gold Dome HD 3P has been modified, the deflation issue with this Tweeter caused major reliability issues and it was removed from production.
The Mod' carried out, has produced a Tweeter Foil is adequately tensioned and has remained adequately tensioned, the cavity now holds a charge of air, that is still present after a few years since the mod' was undertaken.
I have been tempted to use as a cavity charge material, either of the above gases, these would offer an alternative effect on the foils function in place of air.
I have seen tests where Helium used in a Loudspeaker Enclosure raised the db output for the same supplied power input as used with air.
Now I have taken to the concept of a DML and responded by immediately looking at materials for panels that were available.
The Ribbed Material with Cavities, set myself of pondering if a method to fill the ribbed cavities with an inert gas would have an effect that could be measurable and seen to be an improvement.
The air is exchanged for an inert gas as an alternative internal resistance within an speaker enclosure, where there is a change to the force that is usually in place behind the drivers.
Filling the ribs cavities on the board with inert gas, does create an alternative being filled with air.
To create the type of experiment I have seen, the board would need an inert gas filled chamber in place behind the DML Panel to produce an alternative rear force to impact on the function of the Exciter and flexion of the board.
This is all conjecture on my behalf for a DML Panel , but is quite achievable on the HD 3P Tweeter.
A very promising start with the Material and again Thank You for your enthusiasm to keep on with the experimentation.
Whilst listening to your supplied recordings, there is a lot achieved already, no doubt hearing these for real would impress even further.
I sent the Panels in a dimension that was to give a option on a Larger Panel to be tried.
To save deconstructing another work, would it be better to reduce the Panels to a dimension that is a better match for the available exciters.
When the other better matched Exciters become available? I can send over a Pair of Ribbed Boards to a dimension of choice.
As suggested in my mail, I know that Helium and Sulfur Hexaflouride are gases that could be used with a Loudspeaker, as said, my Audax Gold Dome HD 3P has been modified, the deflation issue with this Tweeter caused major reliability issues and it was removed from production.
The Mod' carried out, has produced a Tweeter Foil is adequately tensioned and has remained adequately tensioned, the cavity now holds a charge of air, that is still present after a few years since the mod' was undertaken.
I have been tempted to use as a cavity charge material, either of the above gases, these would offer an alternative effect on the foils function in place of air.
I have seen tests where Helium used in a Loudspeaker Enclosure raised the db output for the same supplied power input as used with air.
Now I have taken to the concept of a DML and responded by immediately looking at materials for panels that were available.
The Ribbed Material with Cavities, set myself of pondering if a method to fill the ribbed cavities with an inert gas would have an effect that could be measurable and seen to be an improvement.
The air is exchanged for an inert gas as an alternative internal resistance within an speaker enclosure, where there is a change to the force that is usually in place behind the drivers.
Filling the ribs cavities on the board with inert gas, does create an alternative being filled with air.
To create the type of experiment I have seen, the board would need an inert gas filled chamber in place behind the DML Panel to produce an alternative rear force to impact on the function of the Exciter and flexion of the board.
This is all conjecture on my behalf for a DML Panel , but is quite achievable on the HD 3P Tweeter.