High sensitivity (99) with mid powered (50 to 100 wpc/tube) amps?

I think, however, if something happened in my life that allowed me to start (somewhat) fresh, I'd like to go the low powered SET route (I was specifically thinking about some of the Dennis Had stuff) with speakers in the high 90s.

@immatthewj If you use a lower powered SET (up to 7 Watts or so, which might be a 300b), the speakers really should have sensitivity/efficiency in the 100s.

Zero feedback SETs have about 20-25% usable output power (relative to full power) because higher ordered harmonics show up above those power levels, causing the amp to sound 'dynamic' (since power is most needed on the leading edge of transients) because the ear uses higher ordered harmonics to figure out how loud sounds are. When the 'loudness cues' are only on the transients you get that 'dynamic' quality but its really how distortion is interacting with the ear.

Also if you push the amp it will sound 'loud' because of these harmonics, which is why so many people say they really don't need that much power. There are sound pressure level apps for your phone that will winnow out the truth of that- you find that 'loud' is considerably lower than you might expect.

So if you really want to hear them do what they do best, you need a very efficient speaker!

When the amp has less higher ordered harmonics its very natural to turn the volume up higher and use greater power; its the mark the better systems that they do not sound 'loud' at any volume! There are lower powered PP amps (5-20 Watts, class A) that have considerably higher usable power (90-95% instead of 20-25%) and are every bit as involving and musical as the best SETs, but with wider bandwidth and greater detail as well.

I have no problem running my CW4's with a 50wpc Moonriver integrated, with no noise, dead quiet.  They are also happy with Ralph's Class D Ganfets and a pair of Belles Aria Monoblocs.  All quiet.  But, if I try to use my Sugden A21SE class A integrated, the noise is very apparent, and not very enjoyable.  Just goes to show, you never know until you try it.

Thanks @atmasphere  , @doni  and thanks to all.  I did finally get off of the fence, but I felt a bit nervous about the Forte IVs after all I have read here, and sending them back would be a bitch.  As I just typed, I did get off the fence and I just got through hooking up a pair of Revel M126Be's which are on the other side of the sensitivity spectrum at 86 with 8 ohm minimal impedance.  They were B stock from MD, and I have 60 days to decide, and at 22 Lb.s each, if I do send them back it won't be so bad.  They are lookers, but there are some things I didn't know that may have made me consider not ordering them.

But, I'' listen with an open mind.

Thanks again.

I run a pair of 101db 16 ohm 15” coaxial Altec 604Cs with a pair of NYAL Julius Futterman OTLs, converted to triode and rated 135 watts each.

It’s worked for me for 39 years.