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For what it's worth....

I have written about this before, maybe many times. I modified my Sound Labs 845PX speakers, which in stock configuration had a nasty impedance dip at critical midrange frequencies, down to below 4 ohms, such that the impedance after the modifications is a fairly flat 20-30 ohms, from around 100Hz to 5kHz. Impedance falls gradually above 5kHz to 2 ohms at 20kHz (nearly unavoidable with a large ESL like mine, due to the capacitative nature of the speaker itself). In any case, the improvement in both speaker efficiency and in the capacity of my Atma-sphere MA240 amplifiers to drive them, and hence the pleasure factor, was nothing short of phenomenal and continues to gratify me every time I fire them up.

(Efficiency went up as a result of the mods independent of the fact that impedance went up, because the low impedance of the OEM configuration is in large part due to the fact that the crossover places a rather low value resistor, anywhere from 5 ohms to 10 ohms depending upon the year and model of the SL speaker, in parallel with the output of the amplifier. The resistor inevitably sucks amplifier power and converts it to useless heat. That resistor is now in the trash.)

I feel certain that any 50W tube amp would drive the modified SL speakers to ear-splitting levels with no strain.



Edits: 04/23/17 04/23/17

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  • For what it's worth.... - Lew 10:06:42 04/23/17 (0)

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