Speaker switching with Mk III's

I have Dynakit Mk III amps wired in triode mode. I have 4 ohm speakers and am getting a pair of 8 ohm ones. I'll mostly switch between them but will be curious about what they sound like together, i.e. with both wired to the common speaker taps and one each to the 4 and 8 ohm taps. This will probably:

a) burn my house down

b) fry the amplifiers

c) not be a problem (except that the 8 ohm speakers, being more efficient, will probably drown out the 4 ohm ones)

Otherwise, when I switch between speaker pairs, I'll first switch one pair off and then switch the other pair on. Will the moment when amp output isn't going anywhere harm the amps?

Thank you,
John

What I would do if you want to switch from 4 to 8 ohm speakers for a A/B comparison is to get a DPDT switch (double pole double throw) and switch the common lead between both speakers but have the positive lead of each speaker connected to the 4 and 8 ohm terminals to their respective speakers. When you switch speakers, I would turn the volume down, flip the switch and then turn the volume back up. Now if you want to listen to both speakers at the same time, I would parallel them and connect the speakers to the 4 ohm screw. The resistance of the speakers in parallel is 2.66 ohms, I don't think it would hurt the amp if used for a short time. I am sure other more qualified experts will chime in with their opinions.

Take a look at the picture I just created to switch between the 2 speakers..

Sal

What a great forum! Thank you, Sal, for the excellent schematic. That's just the way I'll do it.

Can anyone offer an opinion on how long both speakers could be driven, at 2.66 ohms, before it would hurt the amps? What part would be hurt?

The other way to hook things up, I suppose, would be in series, which (I think) would present an impedance of 12 ohms to the amp. What would be the effect of that?

Thanks again,
John