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Default 16 ohm amp -- 4 ohm speaker block (ex speakers)

Could a Crate BV120H valve amp really blow 4x 12 inch 16 ohm speaker box ?
Amp as received was set for 16 ohm output, I measured the speaker box
impedance at 13 ohm, or so, before connecting up just to be sure.
Very feeble and distorted sound. No signs of the reported burning smell,
output matching transformer primaries at about 50 ohm seemed ok and
secondaries not open circuit in the amp so turned to the speakers. The amp
o/p switch setting was set for 4 ohms instead of 16 ohms but as I measured
16 ohms I assumed a switch problem.
Taking apart 2 pairs of paralleled 16 ohm speakers so settable as series
pair of 8 ohm for 16, or 4 paralleled for 4 ohm.
3 of these speakers are open circuit leaving one giving the 16 ohm reading ,
and the fourth one driving from another source is distorting.
Can a valve amp really progressively burn out, in turn, 16 ohm speakers ?
Driving just one initially, I could understand, like the final remnant one
here.


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