speaker cone doping?

I found a wonderful pair of AR-2ax speakers in very good condition at a friends apt used as lamp stands. I have them at the moment and enjoy there ease that it takes to drive them. I noticed the bass drives are made of paper and wondering because of age would it make sense to dope them using a solution of thinned out white glue to stiffen them? Is this mod still being done and wondering will it help the sound in anyway? Thanks

Showing 2 responses by minkwelder

The AR's are an acoustic suspension design which uses very compliant woofers that have a cloth surround. The cloth was doped to maintain the acoustic seal. Sometimes the sealant fails over time and develops pinholes which allows for excessive cone movement. One way to test the acoustic seal is to lightly press in on the cone evenly and release. If it pops back immediately like it's spring loaded, the cabinet has lost its seal and the surround sealant MAY be the reason. If the surrounds need sealed, the trick is to apply something that's just enough to plug the pinholes, but not screw with the compliance. Stiffening them is not what you want to do.

Several years back, I reconditioned a pair of KLH Seventeens that needed doping. I followed some advice from Audiokarma and used a siliconized latex caulk thinned down to the consistency of heavy cream. It sealed the surrounds and seemed to do the job just fine, but I don't know if I screwed with the compliance or not.

There is much information on this subject on Audiokarma and Classicspeakerpages. RoyC is a member who is very knowledgeable on the subject. There is a seller on eBay named vintage-ar that may be able to help you.
I should revise my first statement above to say that SOME of the early AR's, including the AR-2ax, had cloth surrounds. If they're foam, forget everything I said!

I do not think it is advisable to put anything on the paper cones.