Claude wrote:
Doesn't powering multiple speakers simultaneously from one amp increase the
load significantly (more than arithmetically)?

It increases it arithmetically. This is why the speaker switchboxes have
some big series resistors that they swap in and out to make sure the amp
sees an appropriate load.

When you parallel impedances, you add reciprocals. So two eight ohm speakers
in parallel gives you 1/8+1/8=1/4 for a total of four ohms.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."