05-21-14: DougdeaconDoug, "industry standard" is probably ambiguous in this context these days, as specifying speaker SPLs relative to an input of 2.83 volts rather than 1 watt is pretty common. Measurements presented in reviews often do that as well.
So they're actually just 81db efficient when stated with industry standard specs? Ouch.
For an 8 ohm speaker (that is really 8 ohms) it makes no difference, as 2.83 volts into 8 ohms corresponds to 1 watt. But 2.83 volts into a 4 ohm speaker corresponds to 2 watts, which results in the SPL number being 3 db higher if the input is 2.83 volts rather than 1 watt.
Since a high quality solid state amp will usually approach or equal being able to supply 3 db more (twice as much) power into 4 ohms than into 8 ohms, specifying relative to 2.83 volts arguably has a somewhat reasonable basis. But tube amps can't do that, of course, so the 2.83 volt "specmanship" can be particularly misleading when a tube amp is paired with a low impedance speaker.
Best regards,
-- Al