Rectilinear III buzz?

[JonGain]

I have a very nice set of Rectilinear III (not the tall ones) with a updated Dayton 8". At higher volumes I have a buzzing or rumbling sound which appears to be coming from the crossover? I have gone in & foam taped the resistors made sure that everything was neat and tidy but still have the sound? I am almost thinking that it is coming from inside the attenuators for the Tweeter & midrange? Anyone else have these problems?

[paulfx]

First, obtain a function generator. Hook it up to a high level input on your amp. Then get hold of a stethiscope. Make sure the tone generator is set on sine wave, don't want to blow the tweeters with a loud square wave. And go easy on the volume, you want just enough amplitude and the right frequency to excite the unwanted noise. If the noise is coming from a component fastened to the inside if the Rectilinear, or from a point in the cabinet, you should be able to pinpoint it with the stethiscope. This also works for finding gaps in the driver mount areas, from old gaskets or worn screw holes.
If the buzz isn't anywhere specific on the outside of the box, it might be a wire looped close the the woofer diaphragm. Low volume, no problem, but turn it up and...
Adding stuffing without wrapping it in cheese cloth can cause interference, but I think those Rectilinears weren't stuffed anyway, so that doesn't apply.
You might have an air leak in one the the mid or high driver enclosures, smacking their diaphrams back and forth. You hopefully have a known good speaker system on the other channel - since it sounds like you have already gone into these and updated drivers, you could mark and then swap connector, drivers and the crossover from the good speaker one by one until the resonant noise stops. If it does not, then it's somewhere in that cabinet! Ebay for the same model used so you can switch cabinets?
Hope that helps!
Paul

[paulfx]

Oh, I forgot, attenuators get loosey-goosey after a decade or two. Either bypass them with allegator leads or include them in the step-by-bloody-step swap from the known good system on the other channel.