Sensitivity question

8 ohm speaker rated at 88dB will produce 88dB/W at 1m distance.  At 2m it will drop to 82dB/W, but room reflections add 3dB and second speaker adds another 3dB, resulting in 88dB at 1W.  At 23W they will produce 102dB - should be loud enough.

Sensitivity is specified at 1W or 2.83Vrms.  It is the same with 8ohm speaker, but specifying 4ohm speaker at 2.83V (2W) shows better (by 3dB) sensitivity in specs.

Speaker's nominal impedance is specified usually at 1kHz, but might vary a lot at different frequencies.  As you stated lower impedance speaker is a little harder to drive, but the same goes for speakers that have impedance dip at certain frequencies.  My amplifier is specified for >2ohm speakers, while my 6ohm speakers' minimum impedance is 3.6ohm - so I'm OK.

You seem to be mixing concepts. "hard to drive" is usually reserved for speakers with very low impedences in certain frequency bands that need very high current. Not the same as sensitivity

Low sensitivity needs more watts of power, but isn’t necessarily hard to drive.

High impedence means less amps required and generally requires less current for the same watts.

Now if you’re looking for a speaker to pair with an SET at low wattage, the only thing you really need to look at is sensitivity. Then check that it isn’t one of the "problem" speakers that has impedence dips. 4 ohm or even 3 ohm is fine for most amps (the amp manufacturer will warn you if it is designed for 8 ohm only). Infinity speakers, especially the Kappa’s are known to have very low impedence dips and thus require huge currents and are very "hard to drive’. Lesser amps tend to fry.

If you're trying to match to a 23 wpc amp, you might look for 90 and above but 88 may work.  Do you listen loud?  Check that the 88 is not a "problem" load.  

Jerry

It will work fine just will sound small and have limits on peak SPL. After all, you selected a small speaker and lower power. You picked your limitations.

Your 23wpc class A amplifier should have no problem driving a 10 ohm speaker. How loud the experience is dependent on room size and distance one sits from speakers. 

@johnk +1

Mike