Marty (Viridian), note that the speakers are different models, one being rated at 4 ohms and the other at 8 ohms. Series connection of different models will usually result in significant sonic degradation.
How the voltage and power being output by the amp at a given frequency at a given time will divide up between the two speakers depends on the relation between the impedances of the speakers at that frequency. Therefore the frequency response of each speaker will be affected in an arbitrary manner by how the impedance of the other speaker varies as a function of frequency.
Another factor that might also be an issue with a series connection is that the 8 ohm speaker will receive considerably more power overall than the 4 ohm speaker. Based on the oversimplified assumption that the impedances of the two speakers are purely resistive and correspond to their 4 and 8 ohm nominal ratings, the 8 ohm speaker would receive twice as much power as the 4 ohm speaker.
Regards,
-- Al