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RE: Driving Sound Labs with Atma's

In a word, yes. The fewer the output tube sections the higher will be your output Z and the worse will be the ability to drive low impedances.

It is not surprising that the impedance of your speakers, and possibly the SPLs you can measure, fall at high frequency. The speaker is a giant capacitor, so impedance is inversely proportional to frequency. I think it is a mistake to make a big deal out of the numbers you are getting. Each pair of our speakers was built at a different time by the factory. SL is known to be constantly experimenting with types of mylar, the frame, the electrodes, the resistive coating on the mylar, etc, etc. Thus each individual pair of speakers may be different from any other, but in small increments. Also, I believe the bias voltage will affect impedance. Further, using your Rat Shack SP meter to evaluate an ESL is fraught with sources of error, due to the directionality of the RS meter vs the relative lack of directionality of the panels and the sheer size of the radiating area. My advice: replace the bad tubes, enjoy the sound (which you told me you were indeed doing), and forgeddaboudit.


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