Thanks Chris...yours is the definitive answer on this topic
I think I've gone as low as 7.3V, but certainly never lower than that. I seem to get a lot of use out of a single 9V alkaline, so I can't complain one bit. I've also recommended these mics (CA-14c) to several people, a couple of which told me, after hearing my recordings with them, that they were going to pick up a pair. I find them to be excellent stealth mics.