calling all Guru;s, Ideas on audiophyle high effeiciency speakers solicited


Wanting to enter the "Tube system" realm. After extensive research I've come to realize that my current low efficiency speakers B&W 803D2 require a lot of power and may not cut the mustard using tube gear. Although I truly love the speakers I may end up swapping them out in the future to accommodate my new found rabbit hole. Tube amps in general provide only minimal power certainly not enough for my listening habits. 
Anyway what , by any standard, constitutes a high efficiency speaker? is it a rating of 80....... 90, 92,......97? just what is it. Do speaker manufacturers fudge the number on occasions? How do we know? Is a 2 way design inherently more efficient than a 3 way? Does  the amount of speakers in a cabinet affect efficiency?
Last of all what are some audiophile grade speakers? 
128x128gillatgh
How did you feel when the Krell worked ? I do not feel tubes are a match with your speakers.
Loved the sound with the Krell, would not mind trying a more efficient speaker with a tube sys but need to know what to look for

You're speakers allegedly have 90db sensitivity with a nominal impedance of 8 ohms. In theory, that's fairly efficient by today's standards, and should work with a tube amp of about 50 watts. After all, B&W recommends a minimum of 50 watts. However, it seems most B&W owners end up settling with powerful SS amps. 

If you want to try tubes with your B&Ws, I have no doubt that a Rogue Audio Cronus Magnum will drive them to sane volumes. That's about the most glass power one can get for the money. If your heart is set on low power SET amps, you'll need different speakers, ideally some of 94db sensitivity or greater.

 Some will tell you that tubes necessitate 3-digit sensitivity. That's complete rubbish. I can drive my 87db spec speakers to loud volumes with 45 tube watts. Also, room gain, listening distance, music genres, particular amp design, and desired headroom play a significant role.
Contrary to untutored belief tubes are NOT inherently better than transistors! I own many amps of both types! Your 803D2's are truly excellent speakers and capable of better sound than ANY high-sensitivity types. I can recommend a New York Audio Labs NYAL Moscode 300 (tube/MOSFET hybrid) to power the B&W's. A superb amp designed by George Kaye - and capable of handling difficult loads! And being a hybrid it will give you a nice taste of tube sound - without the drawbacks of an all-tube amp!
I can speak from experience, owning a NYAL Moscode 150 (half the power of the 300)!