Are there any sonic differences or performance characteristics of wiring speakers in serial vs parallel? I'm assuming in either instance one is properly loading the amplifier and has the choice of a parallel or series topology.
If there are any differences are they measurable via IR, FFT, RTA, etc?
Putting two 8 ohm speakers in parallel produces an overall load of 4 ohms. Putting two 8 ohm speakers in series produces an overall load of 16 ohms. The parallel scenario will generate about 4x the acoustic power all other things being equal. That's a 6 dB loudness improvement.
You may also need to consider the overall Damping Factor of the system when thinking about this, especially for the reproduction of the lower frequencies. Using series loading, ie a 16 ohm load can 'sound better' (yes, admittedly a personal and maybe controversial area), but a higher load impedance will give better cone control. Ultimately, it will depend on the whole chain, ie amplifier, cables (cross section, not any magic nonsense factor, like $$$ paid) and speakers.
