high-efficiency loudspeakers


 What is the best high-efficiancy loudspeakers? If you have it, are you  happy ?
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I had B&W 804s. I thought those were efficient. Then I got the Tekton DI upgrades. Made the 804s sound bad and inefficient in comparison. I now have the Tekton Ulfs. More efficient and even better sounding than the DIs. I think I've slain the speaker dragon. I'm not even looking anymore. Not a very Audiogonish statement, I know.
The Klipsch KLF-20. I bought it brand new back when they were out in light oak and I still have them. It's not the only speakers I own, but these KLF-20's will be with me for awhile.
@kqvkq with regard to Quad ESL 57s the recomended maximum amp size was 45 wpc as I had them and when Quad brought out their 405 current dumping amplifier they stipulated that you had to put current limiting resistors in it to limit the amp to 45wpc when using the 57s. I'm afraid I know this to my cost as twice I had to replace bass panels as I thought I would be smart and not use the resistors.
Ken Shindo gets the hammer green color that he uses in some of his amps from the Altec Lansing 604C. 

He actually once used a pair of 604Cs in a pair of floor standing cabinets that were being sold for $33,000 in a Manhattan audio salon, maybe two summers ago. 

The pair I have are in an identically sized pair of cabinets. I added the Mastering Lab crossovers, the whole package costing me $3,300, a mere tenth of what the “Shindo” pair eventually sold for, to some unsuspecting Wall Street sucker no doubt. 

I’ve had my pair for 35 years. Every 7 or 8 years or so I figure there must be something better, I go shopping for a month or so and decide well, yes, this or that may be better but is it $50K better, and the answer is always decidedly no. 

The speakers are 103DB. I run them with a pair of Julius Futterman OTL3s, converted to triode. The depth and detail are outstanding. 

I’m basically a happy camper. 
I own Spatial Audio M2 Turbos - 94dB?  They're wonderful.

I have a pair of the new Spatial X2s on order.  92dB? Clayton Shaw and the world tell me they'll be wonderfuller.  Impatient?  Me?

I run the M2s with a PS Audio Sprout.  It's wonderful, too, and what? 33w/channel?  And a good 'nuff DAC, and Bluetooth.  Lively and fun with the M2s.