Good speakers less efficient?

My experience has been that high efficiency speakers are more likely to compress than low efficiency speakers...even at modest SPL levels. A low efficiency speaker often remains more balanced at various SPL levels whereas a high efficiency design often sounds balanced only within a much narrower SPL range.

I don't know why this is....but it is certainly my general observation...perhaps Duke can explain? (I am referring to regular box speakers here)

Duke,

Thanks, I am sure you are right about the causes or shifting tonal balance (from different driver sensitivities). My experience is probably not representative as it does not involve more than a few dozen designs.

However there is another angle. The Fletcher-Munson equal loudness curves. These also have impact on the perception of sound at various levels;

130 db at 20Hz sounds as loud as 100 db at 2 Khz.
110 db at 20Hz sounds as loud as 60 db at 2 Khz.

Notice that this implies that our ears compress the mid range relative to the bass as you go to higher SPL's (a 20 db increase in ultra LF requires a massive 40 db increase in mid range to maintain equal terms of loudness perception)

I guess this explains why rock mixes that are designed to play loud are usually mixed thin in the bass. It implies that to maintain consistency to our ears at various sound levels then the bass should be compressed as you increase SPL in order not to have too much shift in the balance.

Does this imply that relative compression between drivers might actually be desirable in a speaker?

Does this imply that there is fundamentally a SPL sweetspot for particular forms of music that is independent of the speaker used?

Thanks for your insights.