Jump to content
The Klipsch Audio Community
Sign in to follow this  
we_doyle

Coatings on paper cone drivers (woofers)

Recommended Posts

Is there any advantage (or disadvantage) in applying a shellac or other similar type coating to woofers for the purpose of protecting the paper from deterioration? It would seem like the coating would help protect the paper cone. However, I wonder if there are some drawbacks to doing something like this. Would it actually hurt the driver?

Would it affect the sound negatively?

If so, how?

If it is a good thing to do, what product do you use?

Is there a particular product to use and/or is there a particular brand?

Share this post


Link to post
Share on other sites

There are plenty of folks on here with drivers that are 30-40 years old, still going strong. What would hurt would be direct sunlight.

A very light coat won't hurt, and some have done that with a black, to make the woofers match better aesthetically (like having bought some off ebay and one was faded). Too much coating and the compliance will change as you are adding mass to the cone.

Bruce

Share this post


Link to post
Share on other sites

Try Dammar from an art suppy store. Two very thin coats are better than one heavy coat. Spelling is Damar in the USA.

Do a search for Dammar/Damar and speaker cones.

Share this post


Link to post
Share on other sites

Mine are 42 years old and they are still flopping around pretty good. The Cornwall 15" even has a pencil hole in the edge and I can't tell the difference.

JJK

Share this post


Link to post
Share on other sites
Guest " "

There are different coatings rumored to provide some value in one form or another.   These coatings, if they dry out,  can warp the cone, causing voice coil rubbing due to the cone now being out of alignment.

Interestingly, one of the treatments highly reguarded on the audiokarma forum...of all things...is the use of brake fluid on the surrounds.  Brake fuild is though to be one of the few chemicals that does not have a negative effect on the surrounds while helping to preserve and restoring the texture of the surround.

I persoanlly would leave things be and not apply anything.


Share this post


Link to post
Share on other sites

I dolled up some very old Heresy woofers for decorator models using SEM satin black spray paint- this particular paint is intended for refurbishing auto vinyl tops. It's lightweight, black, very flexible. Worked great. As a test I sprayed some paper and strip of masking tape, I could crinkle it up and the paint would not flake off.


See Mr. Paint (Michael Hurd) for more info. Or SEARCH SEM, I'm sure that thread is here somewhere.

EDIT NOTE- I only would do this to horribly old, aged woofers where there was a reason for upgrading appearance and where frequency response was not absolutely critical- that is why only the occasional nasty pro woofer gets this treatment. That's all. END EDIT



It worked so well I used it on my Heresy HIP's where the cone was practically grey/white from exposure over 30 years.


I'd avoid that 'wet look' stuff, looks thick and heavy. The last thing you want to do is add substantial mass to the cone.

Share this post


Link to post
Share on other sites

Polyethylene Glycol is what's in brake fluid. It has a nasty habit of stripping paint, staining and making wood look greasy, and corroding metal. It can be used to preserve wood and other materials though.

Share this post


Link to post
Share on other sites

Protect from WHAT?? coatings on the cone will change resonence and add unneeded mass....The brake fluid was used on JBL Lansalloy outer surrounds to soften the old foam...It works for awhile but you dont want it to leach onto the paper cone.....Paul Klipsch added a special chemicle to outer surrounds to bring resonence down on very early woofers.. But when he found woofer manufacteres that met his requirements this was discontinued.. And now you want to mess with changing the free air resonence???? what are your qualifications to do this..Do you have proper Measurment equip.. to verify? Thats an awful suggestion to make unless you have alot of money to burn to recone to bring back to origional spec.

Share this post


Link to post
Share on other sites

Wouldn't coating the woofer add quite a bit of mass to it? Wouldn't that in turn lower it's sensitivity rating because it would take more force to move the woofer? Wouldn't that in turn un-balance the woofer's output compared to the tweeter? You would probably have to tweak the cross-over to deaden the tweeter slightly or bi-amp and adjust the output levels on each channel.

I wouldn't do it to an existing speaker, but if you're building one it would be a fun project. I don't know if it would have a favourable outcome. If you try it you'll have to repost your results.

Share this post


Link to post
Share on other sites

I heard about doping the woofer on AK also. I have a pair of 1968 KLH Six that has the waxy/oily woofer surrounds, and

I believe this was recommended as the old coating would dryout/wear off. I have not done it as of yet.

Share this post


Link to post
Share on other sites

In addition to its hydraulic function, brake fluid is designed to preserve rubber seals in the brake system and absorb moisture. That's why it needs to be changed periodically. DOT3 fluid is clear when new, and the colour of tea after it has absorbed its limit of water. It contains alcohol to absorb moisture, so it strongly attacks most kinds of paint. It might temporarily do something good to an old surround, but it won't make it new. Brake fluid belongs in brake systems, not in speakers.

Share this post


Link to post
Share on other sites

Brake fluid is really nasty on paint. Drop some on your new car and the drop will penetrate down to the metal. I believe but not sure that it is polyproylene glycol and not polyethylene. Anyway don't drink it.

JJK

Share this post


Link to post
Share on other sites


There are different coatings rumored to provide some value in one form or another. These coatings, if they dry out, can warp the cone, causing voice coil rubbing due to the cone now being out of alignment.


Interestingly, one of the treatments highly reguarded on the audiokarma forum...of all things...is the use of brake fluid on the surrounds. Brake fuild is though to be one of the few chemicals that does not have a negative effect on the surrounds while helping to preserve and restoring the texture of the surround.


I persoanlly would leave things be and not apply anything.



I'll verify that, Brake fluid has a tendency to absorb into rubber and rehydrate it. An old trick to make a transmission stop leaking is to add brake fluid to the Trans fluid. The leaking gaskets absorb the brake fluid causing them to swell and stop leaking.

Share this post


Link to post
Share on other sites

My JBL 4311s have the black, almost sticky coating on the surrounds... still very sticky and flexible since I bought them new in 1972..

There is a huge difference between what Michael was saying about that thin coat on the cones to improve appearance (doesn't take much) to putting stuff on the surrounds.

I wouldn't paint them just to be doing it, but you probably aren't going to change the compliance very much, I imagine almost no one could tell without test equipment.

Bruce

Share this post


Link to post
Share on other sites

I imagine almost no one could tell without test equipment.

I bet the test equipment wouldn't tell much of a difference either.

It's not like every cone coming off the manufacturing floor is

precisely 108 grams (or whatever the moving mass of the woofer is rated

at). The window is probably around 10% and a small touch up should fall

within that window.

But to answer the question, adding mass to the cone lowers the mass

roll-off frequency (resulting in less highs from the driver) and then lowers the

resonant frequency of the driver (doubling the mass of the cone would

lower it by an octave). More mass also reduces the overall

efficiency. So basically you get an all around reduction, less highs,

and slightly reduced output low-end that might dig a bit lower

depending on the driver's alignment in the cabinet.

Basically, there is no way that adding mass can be a good thing.

Engineers work very hard to make the cones as light as possible (yet

rigid enough to not flex). Whatever mass happens to be there is used in

conjuction with the suspension to target an alignment for a specific

cabinet design. In some cases mass is added to help the system dig

lower, but is done in full knowledge of the tradeoffs (and usually involves suspension changes too).

For what it's worth, recone kits are usually inexpensive

so if any cone damage happens in the future, it would be trivial to put

in a new cone. Paper lasts for years anyway and is very rarely a cause

for repair.

Share this post


Link to post
Share on other sites

I've used anti-static treatment (the kind that you use on the platen glass of copiers) for cleaning surrounds. It's silicone based and very thin. First I carefully blow out the dust with an air compressor. Then apply a meager amount to the surrounds and gently scrub with a nice soft brush. Then remove all the excess with a lint free cloth. Blow with an air compressor again and your set. I believe the silicone if anything would help to preserve the surrounds. I've used it on very grungy paper cones too and it worked well with no detrimental effects as far as I could tell. I can't find mine right now and I don't want to go on safari looking for it but I can post the ingredients tomorrow from work. Mark

Share this post


Link to post
Share on other sites

I just checked the MSDS and it say's it contains .99% water and 1% Dow Corning 360 silicone oil. Mark

Share this post


Link to post
Share on other sites

I call it soggy swomp cone treatment ,,,Looks good sounds bad. measures the same as some older units i did years ago.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...