mboxler Posted September 9, 2023 Share Posted September 9, 2023 This is a continuation of a thread started in the Alerts section. His La Scala's are currently stored in my garage, and I thought I'd post measurements. These appear to be completely original, except for what appears to be caked drywall dust everywhere. My first measurement was puzzling, as there were deep notches around 300hz, 700hz, and 3600hz (RED plot). Everything seemed to be wired correctly, but I decided to reverse the polarity of the woofer. I think that was the first time in 44 years that the spade connectors had been touched, as they were really stuck to the barrier strip. The Green plot is with the woofer polarity reversed. To my surprise, all the dips vanished. I did find an FR plot, and the RED plot does seem similar to the solid plot. Why the 3600hz dip vanished is even more puzzling. Thoughts? I plan on measuring individual drivers next. I'll be out of town all day so these will have to wait. I also plan on checking the woofer itself to make sure it was wired properly. Mike 3 Quote Link to comment Share on other sites More sharing options...
Bacek Posted September 9, 2023 Share Posted September 9, 2023 I would place something thick and soft (blanket, pillows) on the floor between mic and La Scala, some of those could be reflection effects. 1 Quote Link to comment Share on other sites More sharing options...
Deang Posted September 9, 2023 Share Posted September 9, 2023 I used to pay Mike to measure things for me, now I have to pay to make him stop. 7 Quote Link to comment Share on other sites More sharing options...
mboxler Posted September 10, 2023 Author Share Posted September 10, 2023 20 hours ago, Bacek said: I would place something thick and soft (blanket, pillows) on the floor between mic and La Scala, some of those could be reflection effects. I wondered the same thing. Last night I placed a moving blanket on the floor and got the same results. Today I'm going to place a capacitor across the woofer output just see "see" what happens. 20 hours ago, Deang said: I used to pay Mike to measure things for me, now I have to pay to make him stop. Your tab will be going up a little today 😎 I've always wanted to listen to La Scala's, and man they sound good. This is also the first time I can measure single phase plug K-55-V's. I did discover that one speaker was missing it's squawker gasket. Either it's always been missing or they are not as "untouched" as I had thought 😞 Quote Link to comment Share on other sites More sharing options...
OO1 Posted September 10, 2023 Share Posted September 10, 2023 12 minutes ago, mboxler said: I wondered the same thing. Last night I placed a moving blanket on the floor and got the same results. Today I'm going to place a capacitor across the woofer output just see "see" what happens. did you check to see if the woofers are the Original K-33 the lascala have either a bottom woofer access panel or an upper panel Quote Link to comment Share on other sites More sharing options...
mboxler Posted September 10, 2023 Author Share Posted September 10, 2023 44 minutes ago, OO1 said: did you check to see if the woofers are the Original K-33 the lascala have either a bottom woofer access panel or an upper panel Not yet. I promised @archdukeobvious I'd do as little damage as possible and these things are heavy. 1 Quote Link to comment Share on other sites More sharing options...
Bacek Posted September 10, 2023 Share Posted September 10, 2023 Flipping them over and unscrewing hatch it's not especially dangerous, but for sure takes some time. 2 Quote Link to comment Share on other sites More sharing options...
Marvel Posted September 10, 2023 Share Posted September 10, 2023 They could be stuck tight from a gooey gasket, too. Quote Link to comment Share on other sites More sharing options...
mboxler Posted September 23, 2023 Author Share Posted September 23, 2023 Here are the rest of my findings... One squawker gasket was missing, the other pretty compressed. New gaskets installed. Both AA tweeter inductors were secured with ferrous screws and measured 315uh. Replaced with non-ferrous and now both measure 265uh. One AA's woofer inductor measured 2mh, the other 2.5mh. Removed doghouse from one speaker. Woofer is K-33-E Square Magnet. Plots were made on just one speaker, as I wanted to see the how the crossovers measured. First, I was surprised how little the inductor difference made. White is 2.0mh crossover, green is 2.5mh crossover. Next I reversed the polarity of the squawker. Green is normal polarity, orange is reversed polarity. Next is a mod that I had to try out. I've always thought the AA tweeter filter peaked too soon, resulting in the SPL bump between 5khz and 6khz. I added a 4uf capacitor across the second 2uf of the tweeter filter and remeasured. It did decrease the bump by 4db, but it also extended the tweeter response (much flatter). Orange is 2uf, red is 6uf. Last is a comparison between the stock AA (Green) and the modded AA (Red). I plan on adding the notch filter to tame the 160hz bump, then I think I'm done! Mike 1 Quote Link to comment Share on other sites More sharing options...
Dr Morbius Posted September 23, 2023 Share Posted September 23, 2023 Fascinating, to be sure! Quote Link to comment Share on other sites More sharing options...
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