I just experienced a really spooky phenomenon while using a multimeter to measure the outputs of my SRM-252s. After plugging the L300 into the amp and unplugging, if I placed the common lead, hooked to the meter, into one of the four non-bias jacks, I could still very faintly hear the music through the L300!! But it's unplugged! It's quiet in the beginning and quickly loses energy, until you can no longer hear anything, over a span of several seconds. I repeated it over and over again, wondering what could be the cause. If I moved away from the amp and meter, the effect quickly wears off, but comes back if I return. This lead me to think it could be an electromagnetic radiation thing. However, when I touched only one of the pins with a finger, the effect would be enhanced (the sound got louder—but was still faint), so my body could somehow be playing a role? Sometimes I heard it more from the left transducer, and sometimes more from the right, but it never seemed to be quite balanced, and it seemed to be independent of which jack is in contact with the lead. The only thing I'm certain about is that by plugging in the earspeakers, you charge the capacitors and diaphragms, which convert the energy into sound as the phenomenon goes on. It seems to lose energy pretty quickly, not unlikely how a resistor-capacitor circuit exponentially loses voltage when the switch is closed.
Also, when I touched all 5 pins at the same time, the effect immediately cut off. Obviously, it was due to my finger serving as a conductor/resistor to drain the capacitors and diaphragms.