K-77-D repair

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Yesterday, I was swapping back in the K-77-D tweeters into my La Scala II's after running CT120's all Summer.  Noticed some of that sshhhh sibilance that I remembered on the stock La Scala II's.  But this time, I have REL along with a calibrated UMIK-1 in my toolkit.  Did some measurements and comparisons.  SPL graphs looked normal for K-77-Ds.  Then I hit the distortion button on REL and the graph the left K-77-D looked out of whack compared to the right.  Notice the distortion peak on the left tweeter starting at the crossover point 4500hz.

 

          

 

Re-checked all my connections - still the same.  Removed the tweeter and checked it alone - distortion still there.  Removed the four screws and separated the magnet assembly from the horn, reseated the bug screen and gasket, blew some air in there, tightened everything back down, and distortion is gone.  Wonder if the bug screen wasn't seated properly and was resonating?   (Looked at my REL data from a few months ago, and the distortion was present back then so I wonder if this was my problem with the K-77-D all along....)  Everything is buttoned back up and sounding great.  Going to run the stock K-77-D's again now for a while.  Anyhow, I hope this info helps somebody.

 

   

 

 

 

[Schu]

Hmmm.... I hear sibilance from my 2's also.

 

Everything else is great but there just seems to be some high frequency directivity and/or sibilance happening.

 

Not sure I wanted 120's or not, but I do like high frequency extension and longer decay times in that area of the listening spectrum... but you know, without sibilance or beaming.

[Panelhead]

  I heard this in my LS ii 70th. But it was not output dependent. Played around with several items and it was digital front end related. At least that is how I got rid of the edge.