My thinking is that Sensitivity + Impedance + Phase angle = Efficiency. My understanding of these factors are not complete.
This is correct. However, there do exist some high sensitivity speakers that have rather tough impedance phase angles. Also, keep in mind that there is no real standardization for how manufacturers can rate their sensitivity. Some brands claim to base their spec on anechoic performance, while others include boundary/wall gain. Some manufacturers are altogether dishonest about their products’ sensitivity and/or nominal impedance. It’s not uncommon for brands to inflate the sensitivity spec by 5+ dB.
What is your ultimate goal? To use flea-watt tube amps? Better dynamics at low SPLs?
Given your room size, you are likely using less than 10 watts of power most of the time. This isn’t to say you wouldn’t benefit from speakers of higher efficiency, but it really depends on your goals. An efficient speaker is not necessarily a dynamic speaker either. Yes, higher efficiency does tend to correlate with better dynamics, but correlation ≠ causation. Some of the best low-volume dynamics I’ve achieved were from speakers of <85dB sensitivity.
Much of a speaker’s perceived dynamic range comes from its bass performance, and thereby, its woofers. In my experience, dynamic sounding woofers have high compliance suspensions, low-mass diaphragms, and a low nominal impedance, preferably all three. It’s for that reason that the DIY speaker community tends to prefer 4-ohm woofers, vs the 8-ohm version of the same woofer. But it’s also possible to make such woofers sound constrained and lifeless with poor implementation.
All this is to say that you can’t really judge a speaker by manufacturer specs. Even Klippel measurements are mostly useless for insight into subjective performance with your system, in your room.
