Von Schweikert VR4-JR

This sounds like a potential resonance issue at the tweeter during certain frequencies and sound pressure levels. I would check all connections, from amps to speakers, from pre to amps and whatever else you have. Use a set of headphones to see if you can isolate the noise specifically
to the speakers or a source.
Check your source material, perhaps playing the same song on CD and LP or whatever to make a comparison to see if the source is the reason. I had a similar experience with a song from the Eagles, Peaceful Easy Feeling, when the guitar riff would kick in I heard a resonance in the tweeter, after isolating the sound, I played with VTA and azimuth some to minimize it and then played a CD, then it happened again. Listening to this part of a song on friends stereo, I realized that the song itself also has distortion,,hmm. Sometimes, it can be a royal pain to isolate these types of distortion. After I made the adjustments to my equipment, I realized that I became hyper sensitive to this issue and now I am always listening for this type of distortion to appear so that I can attack it. Ciao,
Audioquest4life

Any chance you are over-driving your amp into clipping?

Given you say you hear it from ALL tweeters... I suspect you have tried turning off the rears.

the front & rear tweets are different from one another BTW. I'd have to say the thing in common with ALL of them is the crossover. if the connections to the speakers, and from the amps are tight and secure at both ends, it could well be in the Xover...

They are being run biwired, right? ...not using the data link?

you might also address a ground loop incident as a further precaution.

VSA replaced all the tweeters on my JRs at one point. Mine weren't buzzing however.

Easiest way to troubleshoot this is to try a different set of speakers. If the buzz goes away, it is the VR's. If it is the VR's, connect only the bass module and play bass heavy music. You may find that something on/in the cabinet is buzzing. If nothing, then connect only the MT module and play the song which causes the buzz. Get right up against the speaker and listen closely. My speaker input housing would buzz occasionally and I re-seated it and re-tightened all of the screws. The buzz was gone.

If you suspect the unwanted sound is a mechanical resonance from a speaker driver, try running a frequency sweep (though be careful with volume level as you get into the highs - you don't want to fry a tweeter.) If there is a resonant frequency you'll notice it as the sweep comes up to that frequency and then it'll go away as your sweep continues to climb.

You can probably find a sweep you can download as an audio file if you do a Google search.