Klipsch RP150M odd buzz/Zzt sound

[Yawnny]

Hi There,

I have a pair of Klipsch RP150M Passive Bookshelf Speakers. I've owned them for about six months and have really enjoyed the sound so far.

This morning when I was playing some usual "It's-Saturday-so-let's-play-it-loud" music I heard an odd buzzing resonance at, what seemed, infrequent intervals out of one of the speakers.

Almost an electrical vibration of sorts.

 

The sound is akin to an electrical "Zzzzt" and would only ever happen in quick bursts.. it would never be a long drawn out electrical sounding buzz.

 

I first thought this was my lamp against the wall vibrating but then I replayed a portion of the song, then another song, and kept an ear open while holding the speaker.

These odd quick-burst electrical sounding buzzes would come from the back of the speaker, seemingly right where the binding posts are. 

 

This noise only comes out of one of the speakers and it only occurs when there is a constant bass frequency in a song. (ie: shortly after the 3 minute 30 mark in Bipolar Scientist's cover of The Scientist. Seemingly when there's a solid resonance of low frequency, and at a touch higher than your wife might want it listening levels.

 

I disconnected this left channel speaker and brought over the other speaker to connect in it's place. Same buzz/"Zztt" sound. Almost an ultra quick rattle.

I then connected the problem speaker to the right channel and still had the same bad noise.

 

I hooked up the speakers to another amplifier and same issue with the single speaker but not the other.

 

Again, the sound is coming right behind the speaker at the binding post area.

Not from the front of the speaker in any location.

 

At first I thought it might be some rattling of the binding posts but I tried banana plugs and screwing the plugs right down, then screwing them up, then trying no banana plugs and just use bare wire..I tried applying pressure with my hands around the binding post area and the binding posts themselves, all yielded no change in results.

 

The sound it makes is as if the lead of a hot wire is tapping something to make a Scrapey, Rattley, sort of buzz.

Pardon my use of not real adjectives but I'm trying my best to describe this pain in my a**

 

I attempted unscrewing the binding post area on the back of the RP150M but there isn't much to look at and the binding post section won't fully come out of the speaker because it seems to be attached to a circuit board that is too large to come out of the port.. I can't notice any wires to see if something looks loose.

 

Does anyone have any ideas what could be happening here? I was running these through a crappy Sony STR-DG720 receiver..which is rated for 100W per channel even though the THD is crap. Could this receiver have done some damage?

 

These RP150M's are super efficient (as most Klipsch seem to be) so I'd be really surprised if how loud I was pushing them was the peak at which the speakers could go, and if that was the case then wouldn't both speakers be affected in the same way. Would they not have the same limits?

 

This doesn't happen with all songs either. Only if a song has a sort of muddy base section ,or high pitched vocals plus bass with drawn out notes.

 

Any and all suggestions/advice is welcome. 

Thanks!