[zygadr]

Oh c'mon guys!!!!!!   
It's a hell of a lot easy to make an A3 size Balsa wood laminate than a large full range panel!
Gobel is a mini DML wit a Subwoofer...............not what we are all about!

I've gone back to using  "full size" Corrugated Cardboard sheets with only one exciter per panel.
The VH EPS has been binned with pleasure!!!!!!!!!!!!!

Now, here is a fact......the stupid Visaton base plate (and Dayton knock off) with the the big square 2 inch chunk of flat mounting plastic as it's base is a very poor substitute for the small round voice coil coupling that other exciters including the el- cheapo exciters of the past!
There is a vast improvement in using the small round version as there is far greater energy transfer compared to the square lump of crap on the others..... Trust me......I have clearly heard the difference!

[zygadr]

100 pages! !!!!!!!!!!!!!!wooooooooooohoooooooo

[sedge]

zygadr
happy 100th

I think you have misunderstood the points I made. there is nothing that can't be easily  fixed or improved on your panel.
I could give advice on how to do this ,but if you are worried about making alterations to your panel that can't be undone you could buy a 8x4ft 25mm panel which are easy to get hold of and cheep (7 pounds a panel over here)the panels do sound similar so you could do the alterations to this panel and if you liked how it improves this panel you could do the same to your vh's.
you might even find you like the 25mm panel , as I do.
hope this clears up the misunderstanding.
I did do a more in depth post but just lost it again
steve

[oldschoolVlad]

You know, guys, those Göbel panels have hooked me. The materials and technology are pretty handy.
Suggest to go 2 ways finally:

1) natural skins (veneer/paper) / synthetic core (xps, nomex honeycomb)
2) synthetic skins (carbon webbing, mylar?) / natural core (balsa)

A panel is self-damped in both cases; the mass of a panel will be approximately equal in both cases. The thickness must be about 1/8” for proper highs. Most likely, the 1 way will give less bending rigidity. No problem, a slightly curved panel is far more rigid. Maybe the use of some ribs will be needed.

Some thoughts on balsa core. It's a thin, light but very stiff core, perfect for highs. Actually, those balsa cubes on video above don’t like me much because of overall core inhomogeneity, which may cause additional wave reflections on the cube joints. Maybe that is the cause of those additional tuning incisions on a panel. Also, bear in mind that balsa core grains must lay in transverse direction. That way the highs transfer is just perfect. Nevertheless, to glue a puzzle of 4"x4" balsa cubes is not a big problem for the real hi-fi, IMHO.
I am thinking now about another wooden core, maybe a bit odd one. You would newer guess. A plywood honeycomb(!) An even-perforated birch plywood. Thousands of drill holes can decrease the plywood mass by half, so 2 times less exciters will be needed. Not so simple one, but it will be a perfectly damped, stiff and homogeneous core, I think… And no need to make a puzzle of balsa cubes...

[xit]

concerning the goëbel panel i found this infos:

"The edge of the panel is well cut by lasers in order to reduce the reflection from the boundaries thus achieve
the infinite panel approach. Besides, it also can be use for adjusting the moment of inertia I, or the bending stiffness B.
The panel of this bending wave loudspeaker consists of 9 layers, which is mainly made of a special
tropic wood, with a remarkable property of anisotropy. The in-homogeneity of the wood avoids distinctive resonance
occurring on the panel. It is claimed that “the particular mass density and damping characteristic of the panel also enables the panel
to radiate well even below the critical frequency”; however, it is not surprising. As one remember, it is already pointed out in            Sec 2.4.2 that for any plate apply infinite approach, there will be some leakage occurring below critical frequency.
The question left is that how well is the frequency response below fc. Is it flat enough?
How is the efficiency at LF? It is a pity that no information about these details is given from their website.
One who is curious may try to contact with them. More for the panel, the clamping consists of sophisticated damping made of rubber, aluminium, silicon, foam rubber and so on, to have a well-controlled frequency limit. Strictly speaking, the design principle of this bending wave loudspeaker is nothing more than an infinite panel approach. The distinctive thing of the loudspeaker is the art of producing, including the clamping, manufacture of the panel and especially the material selection. If the resonant frequencies really can be eliminated by using this 9-layers design, then one can expect that the sounds it reproduced should be very clear. "


also in another side maybe we can use this kind of paper honeycomb, coated and filled with shellac:

http://stouls-conservation.fr/medias/photos/basse_def/341-1.jpg
http://stouls-conservation.fr/FR/boutique.asp?cha_id0=284&cha_id1=334
(sorry it's in french ... museum conservation panel stuff)
or this one ?
http://www.alibaba.com/product-detail/honeycomb-panel_364624057.html

[sedge]

hi xit
notice how goabels head is in the way of the hi end of the fr plot in the video not that there are any fr markings,but what is there could be smoother.
you don't spend that sort of money on building a panel system unless it sounds good, but I would still like to hear It first just to make sure it works ,not that I have the money to buy one.
steve

[zygadr]

Hi xit and all,
Your links look very much like Re-Board which is not that great sounding unfortunately. Also, there is what looks like corrugated polypropylene which I have also used.
However, if I recall correctly, corrugated polypropylene did not have self damping problems at all and may deserve another try perhaps?   

When I first posted on "that other forum"' I was using a bare piezo cone that produced a remarkable volume output for what it was.
I am not sure of the weight difference between CCP and CCC ?

I also recall that I had no noticeable self panel noise/damping with black Gatorfoam( which NXT themselves informed me that they have used this material in many of their designs!

If we are going to meddle in multi/complex balsa wood sandwich designs, I can only see a defeat in the purpose that this thread was originally started in the first place.............a simple lightweight panel driven by one or more exciters that had some superior qualities to your Magnepans and Electrostatics.

So, where are we going guys?.........????????

[oldschoolVlad]

Rob, I think every one of us have to go Stradivari slightly to build our own beautiful Violins. Cause its obvious there is no ones in our next hardware store. The Magnepans and Electrostatics are the hi-end ones, truly full-range, detailed and "airy". Nothing simple-n-cheap can beat them, IMHO...
I plan to try both ways I wrote above. Will order some HIAXes, some rohacell and balsa. Will make some SPL measurements. Will post it here. The longer the road is, the better is satisfaction...

Vlad

[xit]

Hello to all


here's more infos about gobel panels:
http://goebel-highend.de/technology.html
what it amazes me are the small dimentions of the panel and the pretty good bandwith + supposed very good THD
 
I had once reboard in hand and i think it seems to me more thick and heavy than the honeycomb paper i linked
I'm sure there's something to do with honeycomb: Amina, Tectonic, Podium and even NXT uses honeycomb material

Also, I have the chance to get my hands on a warfedale NXT panel, and i can confirm you that this is a 8 mm foam panel
with a thin and in rigid resin + paper like sandwich outside, i'll try to open it more and check it really in the inside but it looks like
VH XPS sandwiched between a thin white clay/paper substance ... (white gatorboard ?)
Anyway, this sounds good for a normal everyday listener, but not really "Hifi" to my hears, but i'll try to make some new
listenings and some measurements soon

[sedge]

vlad

If you were to offer me a pair of electrostatics ,  Magnepans or any other speaker for free, but said I had to throw my panels away, the answer would be NO. a properly treated panel does things other speakers do not, realism.
as my friend said the other day(How the hell did you get those cheep crappy old exciter stuck to a bit of plastic to sound so good?).
he now wants to build a pair to go with his 15inch eminence open panel bass units, should be interesting. he was thinking of buying an expensive full range driver.
But if anyone wants to give me their old elec's or mag's ,don't let me stop you
steve

[oldschoolVlad]

Ok, no more "dreamouts", just useful facts (from me) 

[sedge]

have just got this old 40cm 10mm thick panel down from the loft and treated it using my new techniques, so far sounds good but am waiting a day or so till the glue hardens properly .the self noise and harshness has already gone but the hf will improve more when fully dried.

steve

[sedge]

this is the fr response of a 40cm panel 10mm thick with discs still attached before mods ,the mic is about 12ins in front of the panel.

[j gale]

Sedge, Can you explain or link us to your mods? Are your panels the extruded poly styrene or expanded? Are you referring to the PVA glue or shellac? If the glue, have you tried shellac? are you still experimenting or have you settled on one particular panel or set of mods? Have you modded cardboard in a similar way? I was never completely happy with the poly styrene but only listened to it as is. I hope you have the patience to ans. all this.  Jim

[zygadr]

I am sitting here listening to two 6 foot x 3 foot 6mm thick single cushion, untreated sheets of corrugated cardboard and have forgotten about all the problems with thin plywood and VH  Polystyrene.
The sound is "NATURAL" and I am getting involved in the music rather than worrying about colorations and self panel noise within the panel material.
With only one el-cheapo  exciter per panel, the sound is astounding.....and way too good to make sense to me!!!!! ?????.

A word of warning from someone that has tried almost every possible thing to make this damned technology work!!.............be weary of fancy manufacturers B.S..........I believe that amongst the distraction and confusion out there, the simplest of materials can equal or rival the complex laminates and exotic materials they promote..............????!!!

[sedge]

jim

I will gladly explain what  I do to my panels, .and why. but my daughter has just given birth last night, so it's all gone a bit mad !
I only set up the vh panels to stop me staring at the phone waiting for it to ring, give me a few days and I'll get it sorted.

steve

[j gale]

Thanks sedge will look forward to it. For Zygadr a word of warning. I have had the same experience and you are right. If you're like me it won't be long before what if or could I get something more if this panel or this exciter etc. Or something more exotic has to be better. I think this sickness of mine is contagious, so be warned.   Jim

[zygadr]

Thanks sedge will look forward to it. For Zygadr a word of warning. I have had the same experience and you are right. If you're like me it won't be long before what if or could I get something more if this panel or this exciter etc. Or something more exotic has to be better. I think this sickness of mine is contagious, so be warned.   Jim

j gale.................I like you pal...............you are very wise...............and funny !!

Rob. 

[sedge]

1st mod 40cm 10mm thick panel with cone shape in centre aprox 2ins wide(this panel is a few years old and has the exciter in the centre but still performs well)

40cm 10mm thick panel with cone shape in centre response at 12ins (still needs some work)

[sedge]

5mm thick foam type panel with cone .

5mm foam type panel response at 12ins