Rick, some of the previous replies probably covered this, but it's more than just semantics as to what causes the increased current load on the bridged amplifier.Speaker impedance is set by its internal wiring and can't be changed by the amplifier. If in I=E/R it actually happened that R was halved, besides E being doubled, then current(I)would theoretically be increased four times and power(IxE)eight times. Despite the use of the "sees lower impedance" type of terminology(including in the Rotel reply)this isn't what's causing the increased current. The amplifier is supplying double the voltage(which the speaker can be said to "see")into obviously an unchanged speaker impedance. An article which discusses this in somewhat more detail is found in
secs. 3.5-3.5.4 here .
