Watts are watts, tube amp just deliver more!
Amps are rated against fix loads (8, 4, 2) but speakers aren't!
Speaker impedance varies a lot, for a single driver it can be 8 Ohm at 200hz but raise to 48 or more at 40 Hz and at 16 or 32 at 15KHz. Multi way speakers tend to be conceived to maintain a leveled impedance but it is never completely flat.
Since Power equals Voltage Square over Impedance, P=V2/R.In a SS amp the voltage rail is fixed and if the impedance rises the power dissipated in the speaker is reduced.In a tube amp, the tube acts as a voltage regulator. Under rising load, the tube will reduce its internal resistance to allow more voltage to be drop on the load thus maintaining or increasing the power output.
Amps are rated against fix loads (8, 4, 2) but speakers aren't!
Speaker impedance varies a lot, for a single driver it can be 8 Ohm at 200hz but raise to 48 or more at 40 Hz and at 16 or 32 at 15KHz. Multi way speakers tend to be conceived to maintain a leveled impedance but it is never completely flat.
Since Power equals Voltage Square over Impedance, P=V2/R.In a SS amp the voltage rail is fixed and if the impedance rises the power dissipated in the speaker is reduced.In a tube amp, the tube acts as a voltage regulator. Under rising load, the tube will reduce its internal resistance to allow more voltage to be drop on the load thus maintaining or increasing the power output.