Panzerholz - its application in audio systems

[Taiko Audio]

I general woods self resonance main modes are typically somewhere between 1000 and 3000Hz, softer/lower density closer to 1K, harder/higher density closer to 3K. It will also attenuate frequencies above it's own resonance a bit. How much it amplifies as self resonance and how much it damps above depends on its internal damping properties. Panzerholz is wood, but with very high internal damping, it's self resonance is relatively benign and around 2.5K, above that it damps pretty strong. If used with a turntable where vibrations are directly translated into sound it may end up muting the top end and amplifying a bit around 2.5K giving it a hard/harsh quality with a muted top end (dead sound). How strong this effect is all depends on if these high frequencies being damped are part of the "magical" sound tuning and how it is used. What we use it for is to deliberately damp resonances, we machine specific cut outs into the panzerholz to move lower frequency resonances up to higher frequencies (above self resonance) which get damped pretty effectively by the material again and we managed to get rid of the 2.5K self resonance. This is all good for solid state electronics, but with any type of equipment where its resonances are part of the tuning, basically everything labelled as "tuned by ear" and/or very microphonic in nature, like turntables, a lot of tubed gear and a variety of loudspeakers, it may impact the chef's delicate seasoning of his dish. Bottom line it's all about application, like in a piano where you can used panzerholz to "decouple" the toneboard from the piano chassis, but you most definitely should not use it as a toneboard.

 

[Rensselaer]

I general woods self resonance main modes are typically somewhere between 1000 and 3000Hz, softer/lower density closer to 1K, harder/higher density closer to 3K. It will also attenuate frequencies above it's own resonance a bit. How much it amplifies as self resonance and how much it damps above depends on its internal damping properties. Panzerholz is wood, but with very high internal damping, it's self resonance is relatively benign and around 2.5K, above that it damps pretty strong. If used with a turntable where vibrations are directly translated into sound it may end up muting the top end and amplifying a bit around 2.5K giving it a hard/harsh quality with a muted top end (dead sound). How strong this effect is all depends on if these high frequencies being damped are part of the "magical" sound tuning and how it is used. What we use it for is to deliberately damp resonances, we machine specific cut outs into the panzerholz to move lower frequency resonances up to higher frequencies (above self resonance) which get damped pretty effectively by the material again and we managed to get rid of the 2.5K self resonance. This is all good for solid state electronics, but with any type of equipment where its resonances are part of the tuning, basically everything labelled as "tuned by ear" and/or very microphonic in nature, like turntables, a lot of tubed gear and a variety of loudspeakers, it may impact the chef's delicate seasoning of his dish. Bottom line it's all about application, like in a piano where you can used panzerholz to "decouple" the toneboard from the piano chassis, but you most definitely should not use it as a toneboard.

1. I do not want any part of my plinth to act as a "tone board"!
2. The use of Panzerholz to "decouple" the motor vibrations from the tonearm/cartridge is exactly why I am choosing Panzerholz as my plinth material.
3. The plinth will be further decoupled from the rack (and foot traffic) by Townshend seismic pods underneath.
4. My turntable will have a new solid machined from aluminium billet chassis (to which the turntable motor is mounted as well) which (as you spell out) stacks different materials, so as you say, acts as further physical impedance, so in effect, I will have Panzerholz sandwiched between aluminium and Townshend pods in a way that is similar to the Clearaudio Statement V2 (at a fraction of the cost)?
5. My turntable will also have a heavy duty bearing/spindle assembly holding a 20Kg brass (another material change) platter, adding solidity and weight like (but to a lesser extent) the Rossner and Sohn Mott (325kg) and J.C. Verdier La Plantine Magnum (400kg), and further decoupling the engine rumble from the record groove.

Taiko, and Ovenmitt, I have read and re-read your explanations and hope that my comments above prove that I understand what you are saying and have answered concerns, however I still have no idea how some vibrations from the turntable motor being allowed to get through to the tonearm and cartridge improve sound (less deadened). I am beginning to wonder if you are used to a little even-order harmonic distortion coming through which, like that from valves, sounds warmer, and when missing seems "over deadened"?

 

[dwhistance]

Hi Rensselaer, I don’t want to distract from the main theme of this thread, ie Panzerholz (or similar compressed wood composite materials) but can I ask a couple of questions about the Classic Turntable bits you are using please?

1 - I’m interested in your platter which I think is much heavier than his regular oversized brass platters which weigh in at a still fairly heavy 12kgs. Can you tell me a bit more about it please? Also given your sound priorities that you have set out above I am interested in the choice of brass as opposed to stainless steel for your platter which I understand has a “cleaner” sound? I should say that I use a Stefano Bertoncello oversized, heavy, bronze platter on my 401 so have gone down this route some way myself.

2 - For your new chassis is the motor hanging on springs as is standard with Garrards or has Ray developed a new motor mount? I know Bob Cusworth has a metal frame to hold the motor in his plinths and my Bastin plinth has the motor mounted from below albeit using a plastic assembly but I’m not aware of any others yet (though I think there is another under development). If he has a new mount for the motor that would be really interesting.

It will be interesting to hear your thoughts when the new plinth, etc is delivered and assembled.

David Whistance

 

[Robert Young]

1. I do not want any part of my plinth to act as a "tone board"!
2. The use of Panzerholz to "decouple" the motor vibrations from the tonearm/cartridge is exactly why I am choosing Panzerholz as my plinth material.
3. The plinth will be further decoupled from the rack (and foot traffic) by Townshend seismic pods underneath.
4. My turntable will have a new solid machined from aluminium billet chassis (to which the turntable motor is mounted as well) which (as you spell out) stacks different materials, so as you say, acts as further physical impedance, so in effect, I will have Panzerholz sandwiched between aluminium and Townshend pods in a way that is similar to the Clearaudio Statement V2 (at a fraction of the cost)?
5. My turntable will also have a heavy duty bearing/spindle assembly holding a 20Kg brass (another material change) platter, adding solidity and weight like (but to a lesser extent) the Rossner and Sohn Mott (325kg) and J.C. Verdier La Plantine Magnum (400kg), and further decoupling the engine rumble from the record groove.

Taiko, and Ovenmitt, I have read and re-read your explanations and hope that my comments above prove that I understand what you are saying and have answered concerns, however I still have no idea how some vibrations from the turntable motor being allowed to get through to the tonearm and cartridge improve sound (less deadened). I am beginning to wonder if you are used to a little even-order harmonic distortion coming through which, like that from valves, sounds warmer, and when missing seems "over deadened"?

In my experience, you definitely want to decouple the motor from everything else as much as possible, whether you are using idler or belt. DDs have their own rather intriguing issues that brings into play the idea of coupling the tonearm to the bearing or not. One important thing to consider, as Taiko explained, is that one must pay attention to how the material behaves across the entire spectrum. That it damps well above its resonant frequency is good, but if the application amplifies the self resonance at 2500 Hz, then the higher frequencies may seem over-damped in comparison. There are many ways to move the resonant frequency around, including mass (as one increases mass its resonant frequency decreases), and by selective cutting/modification of the surface (again, see Taiko). As in much of life, it is about finding the appropriate balance.

Panzerholz is a superb material, but it certainly does not come down to how well it damps solely. That's just a part of the equation, as Taiko has discovered and implemented beautifully in his products. In particular, there are charlatans (actually, only one, really) on many fora who pretends to have tested all materials for their damping characteristics and concluded that 20mm of Panzerholz is the perfect plinth. No more, no less. Apart from the testing methodology being beyond laughable, the rest of his "science" fails basic physics 101. But for some reason, people listen. Dunning-Kruger has that effect on some people...He once got furious for the suggestion that the new SME plinths had a combination of materials, including phenolic resin. Phenolic resin is another really amazing material, and just because it is also used to make high-impact resistant toilet partitions doesn't mean it is somehow a degraded material....Panzerholz, by the by, is made of highly compressed wood and.....phenolic resin. It is fancy plywood.

The long and the short of this is that, as one can see by the broad range of solutions that many amazing turntable manufacturers have developed with spectacular results, there is no magic solution. There is thinking through the problem, then experimenting. In the end, it has to sound good to you.

For those curious, Delignit (the German manufacturer of Panzerholz) also makes a few other rather interesting materials, including Festholz, which claims sound deadening characteristics (not claimed by Delignit for Panzerholz!), and Carbonwood, which is compressed Beechwood and carbon fiber reinforcing. It's hard to come by in the States, but I would be interested to try it.

 

[Ovenmitt]

Dear @Rensselaer

We all have our own preferences and tastes (sonic and otherwise) in life, then follow the path we feel best gets us there….. I’m confident you will enjoy your new turntable.

I have had an interest in Classic Audio’s Garrard remakes for a long time - I think it’s called the “Ultimate”- and look forward to reading your impressions once you’ve had a chance to hear it.

 

[Rensselaer]

Hi Rensselaer, I don’t want to distract from the main theme of this thread, ie Panzerholz (or similar compressed wood composite materials) but can I ask a couple of questions about the Classic Turntable bits you are using please?

1 - I’m interested in your platter which I think is much heavier than his regular oversized brass platters which weigh in at a still fairly heavy 12kgs. Can you tell me a bit more about it please? Also given your sound priorities that you have set out above I am interested in the choice of brass as opposed to stainless steel for your platter which I understand has a “cleaner” sound? I should say that I use a Stefano Bertoncello oversized, heavy, bronze platter on my 401 so have gone down this route some way myself.

2 - For your new chassis is the motor hanging on springs as is standard with Garrards or has Ray developed a new motor mount? I know Bob Cusworth has a metal frame to hold the motor in his plinths and my Bastin plinth has the motor mounted from below albeit using a plastic assembly but I’m not aware of any others yet (though I think there is another under development). If he has a new mount for the motor that would be really interesting.

It will be interesting to hear your thoughts when the new plinth, etc is delivered and assembled.

David Whistance

Hi David,

Ray Clark at Classic Turntable suggested the aluminium chassis (he has brass too, but although the brass might be a tad better than the aluminium, it is most expensive, and they are both so much better than the stock chassis that it didn't seem worth it for a tad more improvement). If his slightly oversize brass platter is only 12kgs, then I got the weight wrong. I am unaware of stainless steel platters. The motor of the 301 is rebuilt and mounted on the chassis as the stock arrangement (with springs). My plinth is being built soon, and I do not know how far the rebuild of the Garrard has occurred, but I will write about it when all finished and playing, probably on the Linear-Tracking Tonearms thread because of the Reed 5A tonearm I am attaching.

 

[Rensselaer]

Dear @Rensselaer

We all have our own preferences and tastes (sonic and otherwise) in life, then follow the path we feel best gets us there….. I’m confident you will enjoy your new turntable.

I have had an interest in Classic Audio’s Garrard remakes for a long time - I think it’s called the “Ultimate”- and look forward to reading your impressions once you’ve had a chance to hear it.

Sure Ovenmitt, as I said to dwhistance, check on the Linear-Tracking Tonearms thread periodically. I am hoping to have it up and playing before the Ypsilon phono stage arrives in June so I can hear it with the old system before the upgrade. The top classic is called a Reference I think, mine will be slightly less expensive having a chassis machined from aluminium instead of brass.

 

[Rensselaer]

Hi Rensselaer, I don’t want to distract from the main theme of this thread, ie Panzerholz (or similar compressed wood composite materials) but can I ask a couple of questions about the Classic Turntable bits you are using please?

1 - I’m interested in your platter which I think is much heavier than his regular oversized brass platters which weigh in at a still fairly heavy 12kgs. Can you tell me a bit more about it please? Also given your sound priorities that you have set out above I am interested in the choice of brass as opposed to stainless steel for your platter which I understand has a “cleaner” sound? I should say that I use a Stefano Bertoncello oversized, heavy, bronze platter on my 401 so have gone down this route some way myself.

2 - For your new chassis is the motor hanging on springs as is standard with Garrards or has Ray developed a new motor mount? I know Bob Cusworth has a metal frame to hold the motor in his plinths and my Bastin plinth has the motor mounted from below albeit using a plastic assembly but I’m not aware of any others yet (though I think there is another under development). If he has a new mount for the motor that would be really interesting.

It will be interesting to hear your thoughts when the new plinth, etc is delivered and assembled.

David Whistance

Hi David,

I had a chat with Ray Clark of Classic Turntable about the stainless steel platter option, not something he does, and didn't know about different sound. He said normal steel would be out because of its draw on the magnets in the cartridge, but stainless should be ok. I am choosing brass as that is the best he has, and is totally inert as far as the magnets are concerned. He has a new spindle bearing design that he feels is better than his old one, apparently can adjust height of platter as well. I said I was a little concerned that more complicated could spell out problems in future but he assures me it is better in that the weight of the platter is on bearings at the chassis level and not deep on the base of spindle bearing only secured from the chassis end. I also decided to get the brass chassis and the PSU that comes with the Reference level upgrade.

I will write it up when I get it up and working, but I am worried that the new tonearm will colour that evaluation (changed from Groove Master II to Reed 5A tangential tracking). If anyone in this group can explain to me how any heard improvements can be allocated as being from the turntable upgrade, vs the tonearm upgrade, please do.

 

[montesquieu]

I think the main thing when trying to evaluate and allocate changes is - change one thing at a time, and give it a decent listen, before you change something else.

If embarking on a wholesale change I guess the only thing you can really assess is what you like about what you are hearing and what you don't like. Then at least you can go about trying specific things in specific areas to enhance or mitigate respectively.

When I upgraded my TD124 I had a semi-planned sort of order of progress: motor restoration; stepper motor pulley bushes; replacement of existing plinth with two-arm layered cherry wood plinth - this sparked a flurry of tonearm experimentation (including Audio Note Arm3/II, AT 1010 and 1503, Ortofon 309i, SME M2-12R and 3012, finally settling on Ikeda IT345 and 407).

Further changes included Townshend Seismic Pods; Schopper platter; Schopper main bearing; Hanze motor spring set; Longdog regenerating PSU; replacement of cherry plinth with Panzerholz-core/solid sapelle-wrapped plinth, individually swapping tonearms (Glanz replacing Ikeda).

Each step undertaken in a way that left a clear idea about what the new element did compared to the previous configuration.

Happy with the main setup, I've since tinkered with less profound/more easily changed elements like bearing oil, tonearm cables, alternative idler wheels, different weight headshells for each cartridge I'm using, and all sorts of different platter/mat/stablilizer combinations (varying weights and materials), finally settling after more than a dozen permutations on the Retrotone machined top platter with Origin Live mat and lightweight stabilizer.

The above describes an incremental/iterative process of about eight years' duration. I would venture to say that there probably aren't too many TD124s around that have been tweaked and improved to this extent. What's amazed me is just how much this deck keeps on giving, so long as you work sympathetically with what the deck is, to bring out the best in it.

Anyway, in summary, to answer the initial question, keeping things controlled is really the only way to get a handle on what's contributing what.

 

[dwhistance]

Hi, I'm sorry I thought the stainless platters were one of Ray's products, I see instead that they are sold by Peak Hi-Fi. A few years ago they both used the same supplier but I think now source them from separate places. I agree with Tom about taking an incremental approach as that allows you to judge each change in isolation. Having said that I'm sure your completed turntable will sound amazing. David

 

[Stacore]

Jarek, you should consider sharing your magnificent Lenco resto-mod with this group....Your science and many afficionado's audio coincide right there...

Hey Robert, not ready yet

 

[Rensselaer]

I think the main thing when trying to evaluate and allocate changes is - change one thing at a time, and give it a decent listen, before you change something else.

If embarking on a wholesale change I guess the only thing you can really assess is what you like about what you are hearing and what you don't like. Then at least you can go about trying specific things in specific areas to enhance or mitigate respectively.

When I upgraded my TD124 I had a semi-planned sort of order of progress: motor restoration; stepper motor pulley bushes; replacement of existing plinth with two-arm layered cherry wood plinth - this sparked a flurry of tonearm experimentation (including Audio Note Arm3/II, AT 1010 and 1503, Ortofon 309i, SME M2-12R and 3012, finally settling on Ikeda IT345 and 407).

Further changes included Townshend Seismic Pods; Schopper platter; Schopper main bearing; Hanze motor spring set; Longdog regenerating PSU; replacement of cherry plinth with Panzerholz-core/solid sapelle-wrapped plinth, individually swapping tonearms (Glanz replacing Ikeda).

Each step undertaken in a way that left a clear idea about what the new element did compared to the previous configuration.

Happy with the main setup, I've since tinkered with less profound/more easily changed elements like bearing oil, tonearm cables, alternative idler wheels, different weight headshells for each cartridge I'm using, and all sorts of different platter/mat/stablilizer combinations (varying weights and materials), finally settling after more than a dozen permutations on the Retrotone machined top platter with Origin Live mat and lightweight stabilizer.

The above describes an incremental/iterative process of about eight years' duration. I would venture to say that there probably aren't too many TD124s around that have been tweaked and improved to this extent. What's amazed me is just how much this deck keeps on giving, so long as you work sympathetically with what the deck is, to bring out the best in it.

Anyway, in summary, to answer the initial question, keeping things controlled is really the only way to get a handle on what's contributing what.

Hi Montesquieu, and thank you for sharing your experience. I need to say that I am not a rich person and can not go through eight years of experimentation with different plinths, platters and tonearms to arrive at nirvana, but must take a chance one time to get it right or suffer my mistakes forever. So I must take a chance here and hope that I will be lucky with my initial choices.

I will state that since my last entry I have agreed to a solid machined from billet brass chassis over the machined from aluminium chassis that I had declared previously. I can only hope that the added expense was worth it.

In the past I have tried floating Garrard on a ply plinth on squash balls with the chassis bolted down on rubber washers to satisfy Terry at Loricraft but found, now that I have MC step up transformers in line with the phono stage, that the slightest vibrations that were not heard with MM cartridges now sound out loudly with my MC cartridge, hence the change in solidity of the turntable plinth and chassis. I am trying to deaden my turntable like the Brinkman Basis, an absolutely behemoth platter on a heavy duty spindle bearing in a strong chassis on a dead plinth.

There are those here who claim that the plinth needs to resonate some, like the piano soundboard or guitar tone-wood but, though I am but an amateur, I disagree. I too play a guitar and agree that the choice of wood makes a huge difference in the tone of the guitar, but feel that the plinth is not a musical instrument and should not sound of any wood, such would be an aberration and would contaminate sound from the grooves.

I have yet to see any reasonable argument as to why some vibrations from a less "deadened" plinth (than Panzerholz or equivalent) would improve the quality of the sound of a turntable in vinyl playback, so if you have the science and the gift of gab, please enlighten me.

 

[ACHiPo]

Hi Montesquieu, and thank you for sharing your experience. I need to say that I am not a rich person and can not go through eight years of experimentation with different plinths, platters and tonearms to arrive at nirvana, but must take a chance one time to get it right or suffer my mistakes forever. So I must take a chance here and hope that I will be lucky with my initial choices.

I will state that since my last entry I have agreed to a solid machined from billet brass chassis over the machined from aluminium chassis that I had declared previously. I can only hope that the added expense was worth it.

In the past I have tried floating Garrard on a ply plinth on squash balls with the chassis bolted down on rubber washers to satisfy Terry at Loricraft but found, now that I have MC step up transformers in line with the phono stage, that the slightest vibrations that were not heard with MM cartridges now sound out loudly with my MC cartridge, hence the change in solidity of the turntable plinth and chassis. I am trying to deaden my turntable like the Brinkman Basis, an absolutely behemoth platter on a heavy duty spindle bearing in a strong chassis on a dead plinth.

There are those here who claim that the plinth needs to resonate some, like the piano soundboard or guitar tone-wood but, though I am but an amateur, I disagree. I too play a guitar and agree that the choice of wood makes a huge difference in the tone of the guitar, but feel that the plinth is not a musical instrument and should not sound of any wood, such would be an aberration and would contaminate sound from the grooves.

I have yet to see any reasonable argument as to why some vibrations from a less "deadened" plinth (than Panzerholz or equivalent) would improve the quality of the sound of a turntable in vinyl playback, so if you have the science and the gift of gab, please enlighten me.

Rensselaer,
I also am an amateur with limited funds and time for experimentation. I have a decent foundation of physics and a modest understanding of the dynamics involved in record playing. I agree that anything that deadens the spurious vibrations while enabling the vibrations created by the groove and stylus is good. I suspect that preferences for "live" plinths/suspensions are euphonics that make a system more pleasing to the ear, not necessarily more accurate (although it's definitely possible that the right vibration of the right frequencies can compensate from excessive loss in other parts of the system). I agree with your perspective.

I'm thinking through the vinyl/stylus/cartridge/tonearm/plinth/motor/platter system. Thoughts are free and relatively quick. Empirical learning takes time and money. When/if I am confident in an approach I will pull the trigger on a direct drive 'table and get to work designing and fabricating a plinth for it.

As an aside I found this material made in the US that looks comparable to Panzerholz (I understand PH is long lead time and requires purchase/shipping of a full sheet at a minimum. This company will provide pieces cut to size for a relatively reasonable price.

InsuLam Densified Wood Laminate | CK Composites

ckcomposites.com

Evan

 

[Rensselaer]

Rensselaer,
I also am an amateur with limited funds and time for experimentation. I have a decent foundation of physics and a modest understanding of the dynamics involved in record playing. I agree that anything that deadens the spurious vibrations while enabling the vibrations created by the groove and stylus is good. I suspect that preferences for "live" plinths/suspensions are euphonics that make a system more pleasing to the ear, not necessarily more accurate (although it's definitely possible that the right vibration of the right frequencies can compensate from excessive loss in other parts of the system). I agree with your perspective.

I'm thinking through the vinyl/stylus/cartridge/tonearm/plinth/motor/platter system. Thoughts are free and relatively quick. Empirical learning takes time and money. When/if I am confident in an approach I will pull the trigger on a direct drive 'table and get to work designing and fabricating a plinth for it.

As an aside I found this material made in the US that looks comparable to Panzerholz (I understand PH is long lead time and requires purchase/shipping of a full sheet at a minimum. This company will provide pieces cut to size for a relatively reasonable price.

InsuLam Densified Wood Laminate | CK Composites

ckcomposites.com

Evan

Hi Evan,

The plinth material is actually "Permali", which I am told is much the same as Panzerholz except the layers are thinner so more of them. It is what is available here in the UK (also available with different materials/substrate for different applications). I have been assured that the outcome will be the same. It is bullet proof, sinks in water like a rock and deadens vibrations better than anything else.

Perhaps, if you are in the States, you could check to see if Permali done with birch plywood and phenolic resins is more available (or less expensive) than Panzerholz there?

 

[montesquieu]

Hi Evan,

The plinth material is actually "Permali", which I am told is much the same as Panzerholz except the layers are thinner so more of them. It is what is available here in the UK (also available with different materials/substrate for different applications). I have been assured that the outcome will be the same. It is bullet proof, sinks in water like a rock and deadens vibrations better than anything else.

Perhaps, if you are in the States, you could check to see if Permali done with birch plywood and phenolic resins is more available (or less expensive) than Panzerholz there?

My plinth is done with permali rather than panzerholz. It's a little finer (more layers, thinner sheet) but most of the measurements on density/resonance etc are similar.

 

[ACHiPo]

My plinth is done with permali rather than panzerholz. It's a little finer (more layers, thinner sheet) but most of the measurements on density/resonance etc are similar.

I’ve heard of Permali, but have not seen it in the US.

 

[montesquieu]

I’ve heard of Permali, but have not seen it in the US.

It's UK manufactured.

 

[ACHiPo]

It's UK manufactured.

Yes. I have not seen Peramli imported. I can get Panzerholz in the US, but it is expensive, long lead time, and generally only available in large quantities. The InsuLam I posted above is available in individual plinth-sized sheets. Eg 18” x 24”. I don’t (yet) have any experience with any of the phenolic impregnated ply products.

 

[Ovenmitt]

Yes. I have not seen Peramli imported. I can get Panzerholz in the US, but it is expensive, long lead time, and generally only available in large quantities. The InsuLam I posted above is available in individual plinth-sized sheets. Eg 18” x 24”. I don’t (yet) have any experience with any of the phenolic impregnated ply products.

Working with Panzerholz requires powerful tools with carbide blades and bits (if you're routing or drilling) - I assume the InsuLam product would be similar. 2-part epoxy is also needed for any glue-up. It's pretty tough stuff to work with. Having said that, it does finish up nicely. The fact that it's so stable can also help... Just make sure you have an upgrade from the usual Home Depot grade tools.

 

[ACHiPo]

Working with Panzerholz requires powerful tools with carbide blades and bits (if you're routing or drilling) - I assume the InsuLam product would be similar. 2-part epoxy is also needed for any glue-up. It's pretty tough stuff to work with. Having said that, it does finish up nicely. The fact that it's so stable can also help... Just make sure you have an upgrade from the usual Home Depot grade tools.

Well I've got a reasonably well equipped wood and metal shop, so I should have tooling covered. I knew about the carbide tooling, but forgot (or never knew) about the glue requirements.

I'm actually thinking about something like this between the panels (at least a couple of them). It is not glue and stays rubbery so should be pretty effective as a constrained damping layer.

RoomDamp2 constrained-layer damping compound | A/V RoomService, Ltd.

RoomDamp2Constrained-layer damping compound Primarily used to control noise from being transmitted to or from adjacent spaces, RoomDamp2 also offers huge sound quality characteristics. Sold in five gallon pails, it is easily applied with a low-nap paint roller to the back-side of a second layer...

avroomservice.com

Or this which is glue, but should work?

Green Glue Soundproofing Compound - 28 Oz Tube

At SoundAway, we carry the very best soundproofing composite adhesive of its kind, Green Glue, to help you soundproof your home, studio, and vehicles saving you time and money. Green Glue is durable, versatile, and easy to apply. Order online to take advantage of our affordable prices and fast...

www.soundaway.com