Watts are watts?

What’s missing in watts is the output impedance of the amplifiers. This can behave in positive or negative ways depending on the speaker and it’s design.

Also, its important to understand how little watts have to do with loudness. Relatively. Doubling the power increases loudness only by 3 db. To get double the loudness, you need 10x the power. So the difference between 90 watts and 150 watts is less than 3 dB.

If you want to do the math yourself: 

change in dB = 10 x log ( powerA / powerB )


Best,

E

Good point! It’s the efficiency of the speakers. That’s why you only need 3 watts or whatever to drive horn speakers. Hopefully tube watts.

I powered my magnepan IIIa speakers with an Audio Research D125 (115 w/ch) tube amp for years with great results!

They played clear and very loud.

IMO, there’s no substitute for class A bias output, whether it be tubes or SS.  Think of a class b amp as a dragster idling at the start line and a class a biased amp reved up to 8K rpm. The flag drops. The idling car driver, then puts the throttle to the floor and can go quite fast, however, the car that was reved up to 8K rpm simply drops the clutch and is gone in a flash.  May be a weird comparison, but the class a amp is always wide open sitting there just waiting for a signal.  It’s very quick.  No pause or sluggishness to reproduce that cymbal, snare crack or bass drum.  You can heat your room with them in the winter, but oh what sound.

Actually I love the analogy, being that I'm a huge NHRA fan!
OTOH, I can't say I've ever experienced "sluggishness" in an amp. I think too many hears of being in the middle of live music has dulled my golden ears.