I'm not saying that bolting the disc to the panel would be any better or worse, just interesting ?
the more of the disc that is glued to the ply the more the ply will damp the disc and vice versa.
having the disc with a small bolt may cause the disc to vibrate too much , or even ring ?
but it is easy enough to test.
If the disc is needed or not is a matter of taste ,I should think.
Steve.
the more of the disc that is glued to the ply the more the ply will damp the disc and vice versa.
having the disc with a small bolt may cause the disc to vibrate too much , or even ring ?
but it is easy enough to test.
If the disc is needed or not is a matter of taste ,I should think.
Steve.
Jaxboy.
well , we can all guess what you had for Christmas😁
I got socks and a jumper(whooopeeee) the excitement was killing me !
What is the thickness of the card and What is the type of exciter you are thinking of using ?
They are an easy build so you shouldn't get too not under the collar 😁
And hopefully you won't get shirty with me if it all goes wrong 😂
Steve.
well , we can all guess what you had for Christmas😁
I got socks and a jumper(whooopeeee) the excitement was killing me !
What is the thickness of the card and What is the type of exciter you are thinking of using ?
They are an easy build so you shouldn't get too not under the collar 😁
And hopefully you won't get shirty with me if it all goes wrong 😂
Steve.
Christian,
I heard it exactly the same as you. He says 3.5 to 4 mm, so definitely not thinner, which is what I was thinking.
I expect you are correct that the efficiency information is another clue, but I'm afraid I also don't know how to use it.
Thanks for the link to the soundboard thesis. The comment about the D/mu^3 applying for a fixed thickness is interesting, and something I never read before. I'm going to have to give that closer read, and some of the references as well. Maybe some other factor (D/mu?) is actually a better "index of merit" in general. The old patents by Heron all reference the D/mu^3 criteria, while at least one other (Warnaka) references D/mu.
https://patentimages.storage.googleapis.com/9a/43/32/b09245ff903cac/WO1992003024A1.pdf
https://patentimages.storage.googleapis.com/d7/c4/c9/cbd405fcdd75ae/US3247925.pdf
Eric
Pepe, In my experience, the midrange to upper mid range (500 Hz to 4 Kz) is easiest.
Eric
Thank you Eric for the reply.
So I guess that within that range is where the magic happens with DML panels (?)
What panel material and exciter would you preferably choose for that range?
Christian,
I have mentioned balsa before, maybe it was a post of mine you recalled. I have been playing around with balsa in different ways. First, as a core material with carbon fiber or fiberglass skin layers. And secondly, balsa alone, made up like a plywood.
For my balsa plywood, I made a panel 24" x 16" (sorry for the units!), using three layers. Each of the layers is 1/16" (1.6 mm) thick. For the outer layers, the grain is running in the long direction, for the inner layer, the grain runs in the short direction. I glued the three layers together using spray adhesive.
It is hard (if even possible) to get balsa any wider than 12". So I made each layer by gluing the edges of pieces together using wood glue (PVA). I made the center layer by gluing together two pieces, each "16" x 12". One face was made with two 8" x 24" pieces, and the other face was made with one 8" x 24" piece with 4" x 24" pieces on either side. This way, the "seam" in the top and bottom faces were in different places, so as to avoid a possible weak spot down the center. I sanded the top and bottom of each of the three layers (gently) to smooth out the seams before laminating them together with the spray adhesive.
This balsa plywood panel is currently one of my two favorites. The other is balsa core (also 1.6 mm thick) with carbon fiber skins (spread tow twill weave, 0.23 mm) thick on each side. In this cf/balsa panel the grain of the balsa is in the long direction of the panel (16" x 23"). I would have used "end grain" balsa instead, if I could get it so thin. But the thinnest end grain balsa I could find was too thick, 6 mm or more as I recall).
Compared to my revply plywood panels, the cf/balsa panel has the greatest efficiency. Perhaps about 7 dB higher than the revply plywood. The balsa plywood is between them, about 4 dB above the revply, and 3 dB below the carbon/balsa.
The carbon/balsa also has a slightly flatter frequency response, while the balsa plywood has a bit of a hump at 200-300 Hz. However, in spite of the 200-300 Hz hump (or perhaps because of it??), and the slightly lower efficiency, I find the tone of the balsa more pleasing, for reasons I don't understand. I only know that whenever I play music on it, the sound makes me feel good!
I'm currently debating with myself about which of these to use to build my next complete speaker pair.
Eric
Steve,
Oh, you punny guy! It's .45mm. 2 pva'd together would give you a just under 1mm panel. I'm up to my ears now in speakers and DMLs and no room for any more, so I won't be doing any more DMLs. I am pleased with the ones I have. Besides, my daughter thinks I'm crazy already, and ANOTHER speaker pair would just prove it to her!
Oh, you punny guy! It's .45mm. 2 pva'd together would give you a just under 1mm panel. I'm up to my ears now in speakers and DMLs and no room for any more, so I won't be doing any more DMLs. I am pleased with the ones I have. Besides, my daughter thinks I'm crazy already, and ANOTHER speaker pair would just prove it to her!
I have not tried CF on its own. It may indeed be good, and I think 2 mm is a good thickness. But I wouldn't expect it to be particularly efficient. According to my model, for whatever its worth, it should behave similar to 5 mm thick plywood, at least with respect to efficiency.
For most applications, the real benefit of CF comes when it's used in a structure, like a hollow tube (as for a bike frame) or a sandwich composite with a lightweight core. I think the same is true for a DML panel. But I don't know for sure the best construction. That is, core material and thickness, cf layup and thicknesss, and size.
Eric
The beauty of a card panel is it is free, and small, and easy to hide from prying eyes 😁
If you had a spare exciter you could make a single test panel, if you don't like the panel sound you can just throw it in the bin, nothing lost.
My draught and wife, already knows I'm crazy but are happy that I have a hobby, even if the eyes do start rolling if I say I've made another panel😃
small panels I can stash under the bed in a small box.
Large panels are hidden behind curtains or in the loft.
Large heavy ply panels I have to store in my room.
I think I'm perfectly sane 😜
Steve.
Pepe.
as it is so easy to build a panel that has a full frequency response from 100hz to 20k given the right materials and exciter.
it seems strange to want to split the panel into small wave bands ?
If you are asking what panel frequencies sound the best , this would depend on the panel material.
Steve.
as it is so easy to build a panel that has a full frequency response from 100hz to 20k given the right materials and exciter.
it seems strange to want to split the panel into small wave bands ?
If you are asking what panel frequencies sound the best , this would depend on the panel material.
Steve.
The thinking behind comes from me missing the late night listening experience I got from the Final Sound 600i electrostats when I had them. I sold them because the bad low end, narrow sweet spot and lack of punch. So my thinking was that I could just use the dml panel in the range that they do best. But I see now that I would just over complicate things by splitting the freq. to a separate tweeter.
One other thing I’ve been interested to try is the Layered sound principle, by using my Stag Accompany monitors in conjuction with dml panels and maybe get the best of both worlds.
With the Stage Accompanys (12” woofer + planar mid tweeter xo 1000hz) I miss the clear midrange that the esl gave me. Maybe layered sound could be the solution?
Thank you Steve for putting me in the right direction.
Has any one here tried to play conventional cone driven speaker fullrange + dml panels fullrange.
Thank you Steve for putting me in the right direction.
Pepe.
actually, you have just reminded me that I originally wanted to use my 2inch bandor drive units on an OBs panel so that the dml panel was at the top of the OBs panel.
15inch unit at the bottom, the bandor in the middle and the dml floating on top.
I wanted to be able to turn on and off the bandor and dml and have them playing together, for the best of all three possibilities.
This still might happen but I will probably use my TLS at the back and use time delay to match with the bandor and the dml ?
The flexibility appeals to me especially as I intend to have at least 3 dml panels that I intend to be able to switch between at the flick of a switch.
Steve.
actually, you have just reminded me that I originally wanted to use my 2inch bandor drive units on an OBs panel so that the dml panel was at the top of the OBs panel.
15inch unit at the bottom, the bandor in the middle and the dml floating on top.
I wanted to be able to turn on and off the bandor and dml and have them playing together, for the best of all three possibilities.
This still might happen but I will probably use my TLS at the back and use time delay to match with the bandor and the dml ?
The flexibility appeals to me especially as I intend to have at least 3 dml panels that I intend to be able to switch between at the flick of a switch.
Steve.