The reason you hear a lot about tube watts being more effective somehow is due to distortion- tubes make less of the distortions that the human ear finds objectionable- and so *seem* to have a greater percentage of usable power relative to transistors.
The effect is real enough on account of the way our ears work, but if you measure sound pressure levels for the most part watts is watts.
A lot also has to do with the load, in particular tubes in general behave differently from transistors, i.e. they do not double power as impedance decreases. Often though they may *increase* power as impedance increases. Sometimes this gives you more punch on certain box speakers that have a low frequency resonance.
Bottom line is that there are a lot of variables but with many speakers you do get the impression that tube power carries more 'weight'.
The effect is real enough on account of the way our ears work, but if you measure sound pressure levels for the most part watts is watts.
A lot also has to do with the load, in particular tubes in general behave differently from transistors, i.e. they do not double power as impedance decreases. Often though they may *increase* power as impedance increases. Sometimes this gives you more punch on certain box speakers that have a low frequency resonance.
Bottom line is that there are a lot of variables but with many speakers you do get the impression that tube power carries more 'weight'.