[Abelma]

[

[hblester3]

Glad to see you are back, (Ziggy and everyone that is still working on it) still using regular eps 6 x 2 ft 1/2 thick with a back spine holding the exciters and the panels are supported only by the feet of the exciter. I used wood glue to attach a 2 in circle of alum. flashing and then glued exciter to that. It has held up well so far. I am powering with a gainclone 50 watts per channel but they sound good with cheap parts express t-amp 10 watt. I am ready to start work on podium clone so which exciter are you talking about from parts express and will start looking again for vh eps. Students are still amazed that much sound is coming from two styrofoam panels. I have this thread bookmarked and check in often. Here we go again.

Hubert

[zygadr]

Hi Hubert, good to see you and others are still using these panels. It is a great way to achieve very good sound quality at a low price. They are not perfect by any means, but you soon forget about that and just enjoy a huge , massive soundstage and enveloping sound.
After checking all the specs.on the the P.E. exciters, there were about three that had interesting attributes as contenders for the best exciter to use.
Two had 32mm voice coils and high power handling which had me interested. However, one is a 4 ohm unit with a mounting assembly that can accept a ''screw in'' exciter if you blow it up. This model however is really aimed at automotive use and is a ''balanced type''.
The second 32 mm voice coil one was also ''self supporting'' but was designed to be used on windows and other very high impedance materials. I have a feeling that sound quality would be compromised with such a unit.

Then I came across another more standard exciter which had a high BL/shove factor and was designed to ''be used to drive large panels''.
the exciter in question is : http://www.partsexpress.com/pe/showdetl.cfm?partnumber=297-2105
Notice that the ''HS'' at the end of the part number actually refers to ''HIGH SHOVE'' which is what makes this type of exciter much more efficient than the average run of the mill exciter. This is important as you do not need as much amplifier power to get very high sound pressure levels.This unit replaces the Hi Wave HIAX25C15-8/SF STEERED FLUX EXCITER which unfortunately, is no longer available

With this replacement exciter, especially a few of them wired together and fully supported on a spine, there should be a new breed of panel emerge from what we have had previously. The only way to tell is to order some and see.

Of equal importance, is the so called ''sound bridges'' that Podium use to ''tune'' their panels. I would say that using some form of solid rubber tubing that connects the panel to the frame in only four places, we can tune out any spurious resonances and self panel noise. Bass can also benefit greatly from correct positioning of these so called bridges.

On the subject of wood panels, I have tried this and initially liked the sound. However, the 3mm plywood I used had a LOT of self panel noise and buzzing that drove me mad. Also, the increased weight of wood against poly, was a severe decrease in efficiency and output 

So there we have it folks..............we can improve on what we have............I'm pretty confident of that. How much improvement needs all of our heads and brains to work together on this..........I'M EXCITED!!!!!(pun intended)

[zygadr]

The more I think of it the more I tend to want to give thin plywood another try.
I am sure and speaking from memory, the ''tone'' of the plywood previously tried was far better than VHEPS.

Iam not sure where the resonances and buzzing were coming from in the last test on the plywood but it was a very rough and dirty quick test so I don't think I gave it much of a chance.

Anybody else tried wood with good results?

[j gale]

I have tried 2 grades of EPS, gator board and various other plastic sheets. I have found the tone of 3 or 4 mm plywood pretty good but the loss of efficiency and weight is a problem. I keep coming back to cardboard. To my ears it has the most natural tone. A coat of shellac on both surfaces seems to improve it even more. A bonus is that the 3M tape sticks better. A large panel is needed at least 30"x48" or 2'x6' Lots of info on cardboard  in earlier posts. I think that cardboard is often dismissed as unsuitable because its too easy to come by and too cheap so it]can't be good.

[zygadr]

Hi j gale, good to hear from you again after all this time!

Yes, I remember my initial cardboard panels that were the first panels I made. They did sound good apart from some H.F. loss at first. After treatment (I also used Shellac)the high frequencies were dramatically improved.
Don't really know why I strayed away from it................guess I was convinced that there was something better which I don't really think was the case in the end

As I began to surf the net and revisit all the technical papers and articles, there was indeed a recommendation by NXT to use cardboard as a panel material. I also recall that this was also the case in one of my many emails to NXT in the initial stages of experimentation.Gator board was also recommended and I spent a lot of money getting it.

The problem with DML's is that the exciters will showcase the tone of the panel material very easily. I guess that's why Podium used paper honeycomb for their panels. It sounds more natural due to the make up being mostly phenolic hardened paper. Remember my link ''BYOB Mother of tone''?...........seems to make sense that paper is the closest relative to the make up of our bodies/ears. Plastics and metals don't really fit if natural tone is the ultimate goal..........supposedly?

Well, cardboard sheet is no trouble to obtain and it's cheap. I have plenty of high quality Shellac flakes left, so I'll give it a go again

[j gale]

Hi Zygadr,  I'm very pleased that you are back to experimenting with this technology. I would like to get my hands on some honey comb cardboard to experiment with but haven't been able to. There is also the various configurations of the regular stuff, double and triple layers. Having said that I would love it if someone stumbled across the perfect exotic material. I just haven't found it yet and so far, to me good old cardboard has sounded the best over time. I hope the others that have been using it will chime in with their experience and especially if they have gone to something else. I'm also very tempted to try the hi shove exciters you linked to.  So keep stirring the pot. Good things will come from it. I've continued to play with open baffle speakers etc. but keep coming back to these panels because they do things that other technologies can't match. So again welcome back and thanks for starting all this.

[zygadr]

Hi j gale. It is indeed a pleasure to be back!
 Yes, you have nailed the true majic benefits of these panel speakers. They are like no other in what they do for such little outlay.
I have ditched my horn speakers when I fired them up again in a shoot out with the panels and compared some micro dynamics on a particular cello CD I have.
 The panels totally blew them away!! .........what was barely audible on the horns became blatantly obvious on the panels!!!...........go figure!!

I will be getting back in to building the ''next generation'' of panel, even if it means going back to an already tried panel material.
I have still got the injection of shellac in to the cardboard corrugations at the back of my mind. My doctor has supplied me with the bare syringes, but I can't wait to see the expression on his face when I ask him for large gauge needles!!

The ''High Shove'' exciters will be interesting no doubt. They are designed to move large surfaces that are heavier than usual and should be magic with cardboard sheets that are noticeably heavier than EPS.

There is mention of using a table top from Ikea recently that has apparently good sonic properties. I have discovered that within the interior is a vertical pattern of cardboard that stiffens and holds the two veneered sides together. Interesting stuff, but probably not what we are after. The honeycomb paper panels are hopelessly out of our reach unfortunately. Yes, you can get them, but they are costly and freight from another part of the world would be a deal breaker.

Is there an ultimate material?...............if there was, Podium Sound would have found it and created a ''super version'' of their speaker by now??

Anyhow, feedback from forum members is welcome.
Let the fun begin!!

[zygadr]

By the way, here is Hi Wave's most powerful, and highest BL/SHOVE FACTOR exciter they make. It is even more powerful than the discontinued ''steered flux '' exciter used on the Podium 1 speaker!!!!

http://www.partsexpress.com/pe/showdetl.cfm?partnumber=297-2114

if you look to the right of the page, click on the blue highlighted part number, and check out the ''BL''. It's force factor is 7.8 Tm !!!!!!.................that's nearly double BL from my previously linked exciter!!!
As a bonus it has a 32mm voice coil and max power handling of 30W and is self supporting and balanced so it will allways remain perfectly attached to the panel.

WOW!!!

[doug s.]

do a websearch for "honeycomb sheet"  or honeycomb panel"  there's a ton of stuff out there that looks like it would be good.  not cheap, but some is not too expensive, either.  this company has stuff that looks promising - honeycomb and balsa cores, w/fiberglass or carbon fiber skins:

https://www.acpsales.com/Sandwich-Panels.html

doug s.

[zygadr]

Thanks doug s. Great link.
It would be very interesting to try some of these configurations of materials available, but that is probably not going to happen.
Unfortunately, making a couple of large panels is still a bit costly for me, especially as we don't know what the end result will sound like.
Anyhow, the link is there should we wish to take matters in that direction.

[zygadr]

O.K............found a local supplier of Phenolic infused paper honeycomb...............big deal!!!!

After a lengthy conversation, the honeycomb material itself is 16mm thick(nothing thinner), not that expensive, but it is flexible .........quite flexible!
It's only after you sandwich it between fibreglass, carbon fibre, or various metal sheeting that it becomes rigid ..........and much, much, heavier.........too heavy in fact for our purposes.

There is no Mylar coated option as in the Podium speakers which as stated by the reviews, ''there is only one company in Germany that can make these panels to Podium's specifications''.

So, in my opinion, we can as d.i.y.'ers, forget about honeycomb panels for good as it just ain't going to happen I'm afraid.

I would suggest that with the high power/high shove exciter I linked previously, we can still experiment with cardboard, and thin plywood as the best sounding materials.
I will be once again looking at coating and infusing the exterior and interior of cardboard sheets with Shellac using new methods to avoid delamination (a problem previously).
As the panel material itself is critical to the tonality of the sound produced, a paper based panel seems to be the logical way to go.

[doug s.]

O.K............found a local supplier of Phenolic infused paper honeycomb...............big deal!!!!

After a lengthy conversation, the honeycomb material itself is 16mm thick(nothing thinner), not that expensive, but it is flexible .........quite flexible!
It's only after you sandwich it between fibreglass, carbon fibre, or various metal sheeting that it becomes rigid ..........and much, much, heavier.........too heavy in fact for our purposes.

There is no Mylar coated option as in the Podium speakers which as stated by the reviews, ''there is only one company in Germany that can make these panels to Podium's specifications''.

So, in my opinion, we can as d.i.y.'ers, forget about honeycomb panels for good as it just ain't going to happen I'm afraid.

I would suggest that with the high power/high shove exciter I linked previously, we can still experiment with cardboard, and thin plywood as the best sounding materials.
I will be once again looking at coating and infusing the exterior and interior of cardboard sheets with Shellac using new methods to avoid delamination (a problem previously).
As the panel material itself is critical to the tonality of the sound produced, a paper based panel seems to be the logical way to go.

ok - so this isn't cheap.  but, you can get a 48x48 1/4" thick panel for $250.  or a single 48x96 1/4" panel for $418 - make a pair out of 'em - 24x48 or 24x96.  while not cheap, it doesn't break the bank either. 

https://www.acpsales.com/OnlineStore.php?cat=5084

if you keep searching, you will find something you can get nearby w/o breaking the bank.  some day, when i get out of my studio apartment, i have a couple of speaker ideas i wanna check out...   

doug s.

[zygadr]

The panels aren't expensive over here either, but once you apply a fibreglass skin, the weight goes up significantly.
Yes, I could order from the company in your link, but what about freight cost..........I live in West Australia.

[bobloblob]

The honeycomb material I’ve seen - honeycomb paper interior with kraft-paper like sheets covering it - is not flexible at all.  It is used in some cardboard crates as reinforcement.  It can dent or crush under a lot of stress, but bends very little.  It is also ½ inch in single sheets and relatively heavy, and is often glued together to make blocks to put under heavy items shipped in corrugated cardboard crates.  I think there are probably several types of honeycomb cardboard constructed to serve different purposes, so one has to be careful with ordering this blind.  $418 would be less of a problem if the results were guaranteed.  To experiment with, it’s a bit too pricey for me.

I like the idea of corrugated cardboard because of weight and availability and cost, but it has a major problem.  The stiffness is in one plane only, and even there mostly on end along the length of the corrugation.  The corrugated elements inside are like having thousands of tiny leaf springs and serve to  cushion, as leaf springs do, and secondarily to give some strength and resistance.  This cushioning effect will absorb a lot of what should have been acoustic energy moving through the panel.  Sonic Impact made some folding cardboard speakers with an exciter in each one and packaged them with their Sonic Impact T-amp.  They were okay for their purpose, though not really hifi.

Stiffening the corrugations I think is even more important than strengthening the sheets covering them.  Shellac will only be partially effective as it is a surface treatment - the shellac will mostly sit on the surface, and the medium, alcohol, will continue soaking into the paper.  It is also is very hard to get into the corrugations very far from where they are exposed on the ends.

What this needs is something to get inside the paper  and harden there.  There are two products that I know of that do this, but they will still be difficult to get down very far into the center of the panels.  One is an epoxy made to strengthen rotted wood.  I’ve put this on a 4x4 rotten plank and watched a pool of it completely disappear into the wood.  It set up very hard in a day, and the wood, which had been mushy, was hard as a piece of oak.  Unfortunately this epoxy is quite expensive, but maybe not so much as a 4x8 sheet of honeycomb.  Another product that I did try on cardboard is Minwax Wood Hardener.  Much less expensive and it doesn’t need to be catalyzed, though the stuff really stinks while it is drying.  I still didn’t get it into the innards far enough, but I think repeated applications might do it, since each new application will flow past the areas that have hardened.   Perhaps it can be injected into some areas with a hypodermic needle; the small puncture holes probably wouldn't be a problem.  I may try again on a small piece, though my time, energy, and finances are still tied up for a few months on a project other than audio.  I really hope someone finds a way to work with corrugated cardboard to make these panels.

Anyway, just some thoughts I was pondering, for what it’s worth.  Hope it’s more of a help than a hindrance.

[zygadr]

Hey bobloblob!......thanks for your input..........allways welcome, I'm sure all will agree.
I know what you mean about the honeycomb paper. It is true that there are many forms of it. They even use it in interiors of doors in housing.
I was once shown a different type of sample a while back that was promising, but the sound from the exciter had a hard time penetrating the highs through it(or should I say exciting the panel sufficiently). I would guess that it was too heavy for the job?

I agree with the problems trying to stiffen corrugated cardboard. Your input reminded me of my past attempts and now I'm not so confident about a second try using Shellac. There was a problem with the Shellac in that if applied too liberally, it would cause delamination of the edge of the panel. You really need to work methodically and slowly with great patience. Don't know if I have that patience anymore.

If using a syringe, the corrugations can be penetrated first from one end, let dry, and then turn the sheet over and start on the other end.
However as you have mentioned, maybe Shellac is not the right material to use?
The problem with the corrugations is that they are stuck to the outer sheets with ''starch glue'' I believe. That is why they can easily delaminate with spirit based varnishes.

What we must not forget is that the high shove exciter in my second link can and will effectively make a 1/4 inch window in to a speaker!!............it IS that powerful. Until this ''super exciter'' is tested, we do not know what it will perform like with cardboard or even wood. Perhaps there may be no need to coat the material at all with all that ''force'' available?

[doug s.]

The panels aren't expensive over here either, but once you apply a fibreglass skin, the weight goes up significantly.
Yes, I could order from the company in your link, but what about freight cost..........I live in West Australia.

yes - you need to keep searching for something local.  and me personally, i would stick with 1/4" (6mm).  re: the weight, it's 3.9oz/sq.ft.  that's under 2 lbs for a single panel...

doug s.

[Abelma]

[

[zygadr]

Great stuff Abelma!..................will be very interested to see how these go with wooden panels. If they can drive 1/4 inch glass, then wood should be a peice of cake!

[doug s.]

Great stuff Abelma!..................will be very interested to see how these go with wooden panels. If they can drive 1/4 inch glass, then wood should be a peice of cake!

the company i linked also has laminated end-grain balsa wood, which is even cheaper - i wonder how that would sound...

and the carbon fiber would be my first choice, but that's quite expensive - a 48x48 1/4" thick honeycomb panel is $370.  but the balsa wood isn't too bad, at $99 each for two 24x48 1/4" thick panels.  all this (and the other prices i quoted are for 1-ply carbon fiber or fiberglass; additional plies are more expensive.  not sure you would want more, tho, if using for speakers.

doug s.