LS3/5a had greater continuous longevity in my systems than any other speaker so far. I ran a double LS3/5a system for over a decade (think a miniature version of TAS' double Advent system from the mid-70s) and later used them in in secondary systems of as alternate speakers in my main system, from 1976 to 2002. The 15 ohms load will make most solid state amplifiers sound smoother and more refined, albeit at roughly half their 8 ohms power (unless its a McIntosh autoformer output SS amp). And if the mismatch is with a tube amp with only 8 ohm taps, no harm will occur. The speaker is a great match for OTL tube amps, like Atmasphere or Transendent, today. I used my double LS3/5as for several years wired in series for 30 ohms driven by Futterman OTL monoblocks. Sensational.
The BBC monitor emulated the midrange beauty, tone and human voice realism of the original Quad electrostatic, in a dynamic speaker. It's inefficient and has limited power handline. You generally need 25w to wake them up, and getting much beyond 70w is risky unless you're careful to restrict volume below where you hear the B110 driver driven past its range on bass transients. The speaker was designed before the CD, so dynamic range in digital source bass can put the 4" driver past its limits. The speaker has a bass hump between roughly 80 - 100Hz, to give the listener an illusion of bass range that's greater than the speaker actually has, but it worked well as a tactic for making a very small speaker satisfying. Actual lower limit bass response trails off rapidly below 70 Hz. With the right amplication, LS3/5a can still produce beautiful sound, within its dynamic limits, 40 years after its original development for BBC field monitoring.
Phil
