Ceiling speakers - single amp?

[Number 7]

I'm planning to install some ceiling speakers in a kitchen, fed from a stereo power amp with 2 sets of switchable speaker outputs. Ideally I would like the option to run all four speakers simultaneously when required, but having done a bit of research, I now suspect that this may not be possible.
My floorstanding Dynaudios are rated at 4 ohms, and the likely ceiling speakers are rated at 6 ohms, which I calculate would give a combined impedance of 2.4 ohms. The amp says it can run 2 sets of speakers provided that the combined impedance of the 2 pairs is not less than 4 ohms per channel. Have I calculated the combined impedance of 2.4 ohms correctly? If so, I could just use 1 set of speakers at a time. Or does this work: feed the ceiling speakers from the integrated amp that I'm currently just using as a pre-amp, and continue to feed the floorstanders from the power amp? Or am I just talking rubbish

Edited by Number 7 on Wednesday 17th November 15:43

[cjs]

Your pretty accurate on you impedance calcs. Most amps quote 4 ohms as a minimum, I have run many into 2 ohms without any real issue, main problem is extra heat but only when you drive the amp at high level.

Your other idea re using two amps will work, you may have an issue balancing the volumes though.

[Le TVR]

Number 7 said:

Have I calculated the combined impedance of 2.4 ohms correctly?

Yes but only if you wire the speakers in parallel.
Wire them in series and the impedance is the sum of the two.