Has anyone tried a rubberized coating on older Klipsch tweeters?

Thanks everyone for your input.

Thanks for the mention, tomic. The horns on the RF3, and series 2, handle much of the midrange as well as the treble, as they are a 2 way, based on the crossover point to the woofers. Dynamat is a great material to use, but some of my clients wanted to do it a bit less expensive, so I used Peel and Seal, a roofing repair tape, found at Lowes and the HD. There are others you can use as well. IME, every horn, whether metal, aluminum or a poly material, gives the listener a smoother, more relaxed, less colored, cleaner, with greater detail, and a more dynamic presentation, when properly damped. Been damping horns for 50 years ( early on, I used clay, and mortite ). The RF3II is worthwhile, as long as you like them. Do the same as you did with your Quartets. Enjoy !, and be well, all.

I've always wanted to try some Quartets out.  The RF speakers aren't bad by any means.  I still have a pair of RF-3 I in my home theater setup and also a pair of RF-5.  I've owned RF-7, RF-3 II, and RF-82 II also.

Thanks, I own a great pair of Quartets I have upgraded with titanium drivers mid and tweet, more sound absorbing in the cabinets and rebuilt E2 crossovers parts for the Quartets. I did Dynamat the Tractrix horns and the woofer and passive frames. I just really like my old RF-3 lls. 

I have used Dynamat on the outside of the horns in some of my Klipsch Heresy speakers.  I'm not sure I'd bother with the RF-3s.  I'd encourage you to move to the Heritage line or see if you can find some second hand Epic (CF-X) or Legend (KLF-XX) series speakers if you want better sound quality and like the Klipsch sound.  Bob Crites sells replacement tweeters for Klipsch speakers that are less fatiguing, but I don't think he carries anything for the "Reference" line.  

Dynamat was the material I used as well. 

Thanks roxy54!

Not tweeters, but I have used a product similar to dynamat,  peel-off rubber like sheets meant for this purpose on the outside of the horns on my Epic CF-4's. I did 2 layers and it was effective, but I wasn't having an issue with brightness, I just wanted to make it more dead, and to compensate for the fact that it's plastic, not thicker wood.  

Thanks !

Mr Decibel here on audiogon has done some treatments 

I bought sheets of dampening material used for sound proofing autos and placed it all over the exterior of the horns. I found the results pleasing. Toned down the harshness of the highs.