ATC SCM12 repair (tweeter exchange and more....)

I got a pair of SCM12 for repair, major issue was that stereo imaging was moved to a side. I took measurements of the original state. It was clear that one of the tweeters was reversed, but even after correction of polarity the FRs of both loudspeakers were not matching. It was quite clear that something was wrong with tweeters or crossover components.
One of the graphs show impedance of new tweeters D26NC-56-06 (blue and purple), original were D26NC-55-06 (other 4 curves). It was not sure if 56 is really drop in replacement.
Measurements after repair showed that 56 is good drop in replacement. Resulting horizontal responses are good, though there is impact of raised edges, as expected.
Overall, this was successful repair.

ATCSCM12 :: Pkaudio
 

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