Diaphragm Damping Agents

[Joe Alesi]

Hello All,

Hope all is well for you. I am interested in your experiences or thoughts around the idea of applying damping agents to compression driver diaphrams. Certainly Acquaplas is used and has been tried- anyone tried anything else? I do not have a specific project in mind, but I thought it might prove an interesting topic for discussion.

I have known of some audiophiles that have applied vaseline (petroleum jelly) to Dynaudio dust caps. Not sure that is so clever with a plastic, but food for thought anyway. Something like a 3M spray adhesive, latex or gum might be OK and even peel straight off if you didn't like it ??? Any before and after damping application, frequency responses or better yet cumulative decay spectra.

Of course this stuff will add some mass to the diaphragm, but probably no more than a few %.


Thoughts,

Best
JA

[Robh3606]

Hello Joe

The only material I have tried is aquaplas. I took some before and after measurements using an 035Ti tweeter. Will be doing some after market 2425 diaphrams when I get a chance. You can try anything however with cost of these diaphrams you have to be careful what you put on. In case you have not seen this thread

http://www.audioheritage.org/vbulletin/showthread.php?t=14236&page=2


Rob:)

[moldyoldy]

Hi, Joe,

If you think about it, you likely already know the answer to your question.

Does the diaphragm(s) you have in mind perform as if it's underdamped (exhibits ringing)? If not, adding mass will create a problem instead of fixing one.

It seems the instruction "if it moves, coat it" has been grossly misinterpreted by many.

(Add/edit) The pot life of most viscoelastic damping compounds is 6 months...;)

[Robh3606]

"if it moves, coat it"

More like if it's metal coat it. Although it seems JBL likes their cones well damped. The only metal domes that are not damped in some way are the compression driver domes. Tweeter domes have a foam pad. That said looking at the new JBL pro stuff if the tweeter dome is not fabric it's aquaplased.

Rob:)

[Mr. Widget]

I am interested in your experiences or thoughts around the idea of applying damping agents to compression driver diaphrams.

I have known of some audiophiles that have applied vaseline (petroleum jelly) to Dynaudio dust caps. JBL has had very good results using aquaplas on their titanium, aluminum, and beryllium diaphragms... TAD doesn't seem to use anything on their 4001/4002 beryllium diaphragms, however on the lighter 4003 beryllium diaphragms they have a very light oil on the surface of the diaphragm. I doubt they are using this because they are unaware of aquaplas... as they use aquaplas or a similar product on some of their cone woofers.


You can try anything however with cost of these diaphrams you have to be careful what you put on.Absolutely!

I personally wouldn't try anything... without far more knowledge and better test gear, any experimenting would be a simple trial and error crap shoot. I suppose duplicating what JBL does on their diaphragms is fine, but outside of that I wouldn't go messing around with random chemicals on other diaphragms.


Widget

[Joe Alesi]

Hello Joe

The only material I have tried is aquaplas. I took some before and after measurements using an 035Ti tweeter. Will be doing some after market 2425 diaphrams when I get a chance. You can try anything however with cost of these diaphrams you have to be careful what you put on. In case you have not seen this thread

http://www.audioheritage.org/vbulletin/showthread.php?t=14236&page=2


Rob:)
Thanks for that Rob, I am interested to see the before and after curves, but the link doesn't work for me-it say report it to the administrator- so I've got the right guy.;)

Best
JA

[Joe Alesi]

Hi, Joe,

Does the diaphragm(s) you have in mind perform as if it's underdamped (exhibits ringing)? If not, adding mass will create a problem instead of fixing one.


Haven't decided to use it on a particular driver yet, really just wanted to stimulate discussion on possible damping agents. Come to think of it maybe some aftermarket(can I say that here?:D ) 2425 diaphragms I have may benefit from something.

Thanks & Best
JA

[Joe Alesi]

JBL has had very good results using aquaplas on their titanium, aluminum, and beryllium diaphragms... TAD doesn't seem to use anything on their 4001/4002 beryllium diaphragms, however on the lighter 4003 beryllium diaphragms they have a very light oil on the surface of the diaphragm. I doubt they are using this because they are unaware of aquaplas... as they use aquaplas or a similar product on some of their cone woofers.

Hello Mr W,

Interesting- The light oil on the TAD sounds like a similar treatment to the dynaudio dust cap vaseline treatment.

Thanks and Best
JA

[pocketchange]

If petro jelly is used, maybe LPS 3 would be useful.
pc

[Steve Schell]

Damping compounds such as Aquaplas are apparently applied to help tame misbehavior in the metal diaphragm. This may work to an extent, but I think a better approach is to begin with a better behaved diaphragm material. Composite diaphragms made from phenolic and cloth work great; they sound very clean and open, and lack the high frequency breakups typical of many metal diaphragms. Problem is that most phenolic diaphragms lack high frequencies altogether, having been designed rather thick and heavy for high power applications. If one finds a driver with a reasonably light composite diaphragm, it may provide just the sound one has been hoping for.

[Mr. Widget]

Damping compounds such as Aquaplas are apparently applied to help tame misbehavior in the metal diaphragm. This may work to an extent, but I think a better approach is to begin with a better behaved diaphragm material.I agree... that said, the approach I prefer is to use bandwidth limiting... i.e. don't try to make a two-way out of a driver exhibiting break-up. With care, adding the tweeter allows you to preserve the clarity and detail of the lower frequencies and if the tweeter does exhibit break-up it will only piss off the neighbor's dog or the unfortunate bat who flies by.


Widget

[4313B]

More like if it's metal coat it.The original statement was "If it's metal, coat it." It was later changed to "If it moves, coat it."

I need to stop posting these kinds of things.

[vince]

Hi guys, interesting question, like some of you, I'd be dubitative about applying something on the diaph itself (mostly because I don't know what I will want out of it...because for ringing problems I solved that simply in modifying my crossover ,ringing came , in my case, from fs around 500hz when I used a crossover that underdamped the system...) some resistors divider, put in a certain way(cf Pi crossover from Wayne' website) helped much in that way...althought I was convinced that it was only a diaphragm issue...(and it is of course , but can be solved many other way, electronically I mean...)
I'll be glad anyway to have inputs on what could be done to that diaph...but I also wonder if anyone tried modifying the damping material beside the diaph, in theory the rear charge of the diaph should be in adequation with the front(horn), did anyone tried to modify it? or damping it differently? for sure it has an influence on the cone motion, any input?
Vince:)

[pocketchange]

per diaphgram(s) and info from outside reading, notice was given concerning improved material and processing technique. Heat treating the typical material prior to forming the diaphragm. I have not noted anything added. Since [Al] in whatever spec is the choice for most diaphragm material, I'm wondering if there is a process after the stress generated in the forming of the diaphragm?

NOTE: I know nothing on how diaphragms are produced ... :blink:

There has been a great deal of headway made in post production processing including heat treatment of material(s) other than ferrous and non ferrous metal.
I'm talking stress relief here if there is any confusion.
pc

[Joe Alesi]

There has been a great deal of headway made in post production processing including heat treatment of material(s) other than ferrous and non ferrous metal.
I'm talking stress relief here if there is any confusion.
pc

Hello Pocketcahnge,

Yes I could easily imagine a stress relieving processes like annealing or heat soaking being used. Although, if the orginal forming process created any assymetrical residual stresses in the diaphragm, the relief of such stresses can result in a distorted part.

Come to think of it the diaphragm isn't all that deep compared to its diameter- It may even be formed and just let be.

Best
JA

[Ian Mackenzie]

If you do a search on google there are local firms that specialise in material vibration and damping agents used in structural engineering.

Check it out and contact a product manager for applications data.

I very seriously doubt acquaplas is the "only" solution to that particular issue.

With a few rare exceptions (aka M1 mid/hf driver) a compression driver was never designed for hi fidelity and nor was a horn for that matter.

But we still like to play with the First Watt.

If you want something really good consider a Scan Revelator tweeter loaded with a properly designed low profile wave guide.

[pocketchange]

I'll step up to the plate on this... FWIW

In making most anything but a pancake, stress is induced. This is the reason for post production processing, if the item in question is metal (and this includes many other materials as well).

Over the last 40 years NASA has spent a potload of funding learning how to get things to last longer. Read this to include getting things to bend, slide, stretch, flex, cut longer etc., etc., and sound BETTER.
Technology is moving forward all the time.

I'm just wondering if the diaphragm producing Industry around the world are playing with these various processes. You sleep, we loose...

Keep in mind, most of us would be a little happier if our razor blades lasted longer... unless you have stock in Gillette or Shick. pc ;)

[Ian Mackenzie]

Oh I get it,

Well Space Shuttles must be their forte.

[pocketchange]

Nope, I somehow doubt it.

[hjames]

Over the last 40 years NASA has spent a potload of funding learning how to get things to last longer. Read this to include getting things to bend, slide, stretch, flex, cut longer etc., etc., and sound BETTER.
Technology is moving forward all the time.


nah - NASA has spent a potload of money maintaining a status quo - nursing along a second rate space delivery system that was old tech before it was built. A typical federal agency concerned more with continued Employment rather than Innovation.
Not my words, read the aerospace engineers who know better at:

http://www.jerrypournelle.com/slowchange/SSX.html

as well as

http://www.jerrypournelle.com/reports/jerryp/gettospace.html

[pocketchange]

No Question about it, "they" know how to pi$$ "it" away...

[Ian Mackenzie]

A quick search suggests some other manufacturers are using laminate diaphragm structures.

Again this is not new.

I spent 10 years in the polymer coating and laminating industry with outfits like 3M and Du pont. A lot of damping agents are used in automotive, civil and mechanical engineeriing applications.

Getting the coating to stick the base material is the key.

[pocketchange]

Reference my inq. to post production processing.
I'm up on coating(s), I do use them and have for 20 years, was also in the "biz" and consult from time to time.

www.300below.com

Check this out if you care to.

[Ian Mackenzie]

Yes,

I landed the Tardis once a 1km below the surface of Mars and my companion stepped out the front door before we checked the outside temperature.

The poor girl's been stuck on hi beam ever since. ...not that I mind..LOL

[moldyoldy]

Ian's correct in saying there are many alternatives to Aqua****, most are more affordable and readily available. Forget the brand name and search out the product(s) that meet your particular requirements. Viscoelastic damping products are commonly used in industrial mfg., HVAC, automotive, and aircraft industries, to mention just a few.

This, of course, requires one to KNOW the requirements, as the application of random goops to diaphragms, horns, or enclosures with hopes of improved performance is very unlikely to be successful.

[Thom]

Yes,

I landed the Tardis once a 1km below the surface of Mars and my companion stepped out the front door before we checked the outside temperature.

The poor girl's been stuck on hi beam ever since. ...not that I mind..LOL

?

[richluvsound]

Yes,

I landed the Tardis once a 1km below the surface of Mars and my companion stepped out the front door before we checked the outside temperature.

The poor girl's been stuck on hi beam ever since. ...not that I mind..LOL

Ian,
I trust you mean she is now incredibly bright !!!!:)

interesting stuff.

Rich

[Ian Mackenzie]

Rich,

I think you get it. The yanks wouldn't.

[4313B]

Rich,

I think you get it. The yanks wouldn't.Um, actually we would; On the first reading to boot!

[Ian Mackenzie]

I forgot you get your share of cold weather.

Probably one of the few reasons you get out of bed some (chilly) mornings!

[richluvsound]

Giskard ,
how do you apply aquaplas ? Is it something a rookie could do ?

Rich

[4313B]

Is it something a rookie could do ?Yes, just like any of this stuff, anyone can do it.

[Robh3606]

With a paint brush. It spreads pretty easily and seems to cover well.

Rob:)

[richluvsound]

Cheers Rob,

I understand now..... anyone can do it !!!! I suppose its has to come through JBL ? It just so happens I aint too bad with the old paint brush !

thanks for your kind reply

Rich

[4313B]

Thanks Rob. Here's the one I got.
why are you so unkind. ? I guess I should have quoted the specific phrase I was responding to, which I've gone back and fixed.

I'm the unkind individual that stood in line at the Post Office to send him his horns.

I was thinking of doing a post on the process I use but it's too much work and I'd rather just get them done, shipped back and drop the subject once and for all. I've only got twenty more to do. My offer to do them all for everyone was a pretty dumb one. :rotfl: The real PITA is having to QC them with CLIO when I'm done with each one.

[richluvsound]

Giskard,
Indeed, that was a kind gesture. If your post office is anything like mine your deserve a silver star. I realise how much you do for people here on the forum. That is why I was asking about the process, not asking anyone , least of all you, to do it for me . I dont want people to do everything for me. I came here to learn to do this stuff for myself, and not from an armchair either.
I wish I'd done an E.E degree when trying to get my head around some of this stuff but, alas, I chose painting and french de-constructionist philosophy along with all the other hyper-sensitves . :p

Rich

[4313B]

If your post office is anything like mine your deserve a silver star.It's overrun.

[Ian Mackenzie]

If you Clio them can you send with a certificate..signed JBL bad ass?

Just kidding. But is the impediance changed from the stock dias in a way that the voltage drives need revision?

[Robh3606]

Hello Ian

Here's what happened when I tried coating with sample I have on an a beat up 035ti. There were changes but I don't think they were significant enough to worry about. That said I didn't run them and look for differences in LEAP. The Red and Blue for THD are without. The Green and Orange are with. The first impedance plot is without and last is with. You can see the shift in the resonace peaks. There were not real changes to the impulse and step respones plots. There were changes on the FFT plots as far as harmonic content. There was what appeared to be a reduction in the magnitude of the higher order harmonics. I need to try to confirm this at a latter date. I don't know if it was real or not and if the measurement was valid.

Giskard could you please post a before and after if you have them. I don't know if the aquaplas sample I have is the same exact material as the real deal you use. I added pigment to mine to make it black. I would love to see if our measurements show the same changes.

Thanks

Rob:)

[Ian Mackenzie]

Gee's Rob,

look what happened. Did you trowl it on?

[Robh3606]

Gee's Rob,

look what happened. Did you trowl it on?

No I used a shovel and a back hoe.

Rob:)

[Hoerninger]

Rob,

thank you for sharing.
Do you make waterfall plots as well?
___________
Peter

[Robh3606]

Hello Peter

I didn't but I can. I saved the MLS data files. I just went back to see what they look like but don't see that much of a change aside from the slight drop in level.

Rob:)

[Hoerninger]

Rob,

thank you for the pictures. Although I have not seen this kind of colored waterfall before (always sort of 3D in BW) these pictures seem to tell more than the frequency responses.
Around 3 kHz and 4,5 kHz the waterfall of the damped cone is less red in comparison to the region of ca. 10 kHz. For me it indicates a quicker roll off (and a cleaner sound reproduction).
[But I am no expert.]
___________
Peter

[Robh3606]

Hello Peter


[But I am no expert.]

Well I am not either. I will take a look at them again. The second file with the Aquaplas is about 1db lower in amplitude. I have to go back and see if this is the cause or not. Easy enough to find out. Differences on the standard plot are difficult to see.

Rob:)

[4313B]

The second file with the Aquaplas is about 1db lower in amplitude.G.T. does two thin coats of aquaplas diluted with water using a modeler's paint brush. One should see a drop of about 1 dB at the top end.

I use the same method as G.T. but then I hit each coat with a water mist to create a nice uniform coat. That just seems to work best for me personally. D.S. was concerned that any kind of manual method could cause pooling and I am extremely conscious of his concern. For concave surfaces one should wick away any pools that might form. As both G.T. and D.S. have stated, done correctly, there should not be a measurable night and day difference. I believe they were referring to a typical response curve. The resonant frequencies should shift downward somewhat but nothing dramatic.
Giskard could you please post a before and after if you have them. I don't know if the aquaplas sample I have is the same exact material as the real deal you use. I added pigment to mine to make it black. I would love to see if our measurements show the same changes.I suppose. It should probably be done on a PWT and I don't care enough to whip one up just for this. Of course we're also talking about a ferrofluid recharge here too so...

[Robh3606]

G.T. does two thin coats of aquaplas diluted with water using a modeler's paint brush.

That's the same method I tried to do. Good idea on the water mist between coats.


As both G.T. and D.S. have stated, done correctly, there should not be a measurable night and day difference.

What changes???


I suppose. It should probably be done on a PWT and I don't care enough to whip one up just for this.

Thanks, I understand about the PWT.

Rob:)

[Steve Schell]

Hi Rob, those are very interesting spectral decay plots. It would be nice if you could make them have identical vertical scales for a more perfect comparison, but they are still instructive. The main change I see is that the decay gets out of the red zone much quicker at most frequencies with the Aquaplas.

[4313B]

Thanks Steve.
What changes???Basically what you guys have shown. D.S. thought that under high enough resolution one might see a bit of roughness removed from any FR curves.
There were changes but I don't think they were significant enough to worry about.That's pretty much the consensus so far.

[Robh3606]

The main change I see is that the decay gets out of the red zone much quicker at most frequencies with the Aquaplas.

Hello Steve

Agreed but looking back they are not scalled the same one is at 0 the other at 1. I have to redo them to see if that is "real" or not. I will repost them once I get it worked out.

These are rescalled but also show a faster decay it subtle that's for sure look at the 12K peak as an example and the level of the 7th line. No coated first


Rob:)

[Earl K]

Rob

Nice Work ! ( with those Spectral Decay plots ) .

- Though I'm used to looking at the standard "waterfall" type / I do like the color versions . Once you work out the details / I'd enjoy seeing a repost of the "colored types" .

- Right now, the standard "waterfall" plots don't highlight much visible difference ( that I can easily find ).
- To find & view any differences , one would need to implement a finer scale ( ie ; within the time axis, something like 0 to 2.5 ms, & in db axis , and 0 to 10 db ) .

- FWIW: Pictures ( scales ) like these are all quite subjective. They usually end up reflecting the testers own biases. This happens through the choice of scales ( or colors ) that seem to show ( or not ) things that the tester wants to be seen. ( ie ; if I was convinced that I could identify the portion of the decay signature in a titianium diaphragm ( that I found irksome ) / I'd be high-lighting that area in red ). Of course, assigning "red" to a certain range of decay will also "assign" a subjective judjement, ( ie; good or bad ).

:)

[Ian Mackenzie]

The only other way would be to do an impulse amplitude test with the mic capsule in close proximity to the mouth of the horn or in a plane wave tube and look at the ringing after the inital pulse. I imagine the damping to effective well under 1 millisecond.

[UreiCollector]

I have known of some audiophiles that have applied vaseline (petroleum jelly)

I have found that KY applied to drivers, results in quite a 'slick' system.


sorry, I couldn't resist......:blah:

[Robh3606]

For all you curve junkies here are new plots with better resolution and the same scalling. First is no Aguaplas

Rob:)

[Russellc]

This is extremely interesting, I wish I had all the equipment for testing you guys had, and am very interested in aquaplas and other dampening agents and am trying to learn if they will do any good in my particular application. Thanks for the contribution.

Thanks for the info,
Russellc