I agree with Larry that in this case a parallel configuration would provide too heavy a load for most amps. And while a series connection won’t be a problem for the amp, it is likely to result in poor sonics.
The main reason for that is that since in a series configuration the voltage provided by the amp at any instant of time will divide up between the two speakers in proportion to their impedances, the variations of each of their impedances as a function of frequency will have unintended effects on the frequency response of the other speaker.
Therefore a series connection is only likely to be suitable if the two speakers are identical models. In that situation, putting aside whatever small differences might exist between their impedance characteristics due to component tolerances, each speaker will see half of the amp’s output voltage, at all frequencies.
Also, regarding Roberjerman’s point about damping, I used to think that also, but while it seems counter-intuitive, that is not an issue. See
this paper, which I must credit A’gon member Kijanki for calling to my attention here some years ago.
Regards,
-- Al