What is the benefit of low efficiency speakers?

BTW, my friend is selling his Silverline and Cayin 300B.
I'd never sell my combo.

Some low efficiency loudspeakers sound very very good. Chario academy 1's are very inefficient, about 82 or 84 db 1 watt/1 M, 4 ohms. Some very efficient speakers sound rather, ah, bad in some ways; JBL L-200's at around 96 or more db/1w/1m. I own a pair of both. If you want efficiency, it usually means very very large units, not easy to deal with in small houses or apts, not easy to move around.

I think Xiekitchen is finally beginning to touch on the substance of the issue.

I believe that the vast majority of speaker designers don't WANT their speakers to have low sensitivity, they choose the drivers for OTHER characteristics. Remember when 'air-suspension' speakers were introduced (in the '50s? by Acoustic Research?)? The goal was good bass response from small enclosures. One way they did that was too decrease the stiffness of the cone's double suspension so that cone travel could increase. Increased travel required more space between the voicecoil and the magnet structure. Increasing the gap reduced sensitivity. So for better bass from a smaller box, we get lower sensitivity. The other drivers (MR, tweeter) have to be of approximately the same sensitivity, so now we have speakers with typical sensitivities of less than 90dB/2.83v./1M instead of 95 - 105dB sensitivity.

BTW, there's a difference between the terms sensitivity and efficiency, but for this discussion, the terms are interchangeable.

1. Low efficiency is a trade-off towards the full range and power handling.

Okay, I asked the question wrong! I was almost asleep when I did it so please forgive me.

The question I have has nothing to do with efficiency. What I wondered about was the load of the speakers; or why are some speakers designed at a nominal 8 ohm while others drop as low as two or even one ohm. The lower being more difficult to drive. Are these differences based on the individual drivers or on crossover design? Why doesn't everyone design their speaker to be a nominal 8 ohm, or higher? What are the benefits of 4, 2, or even 1 ohm speakers?