Hey Marco. On paper you are correct about doubling power results in a 3 db increase in sound. But there are no standards in rating power in amps; and keep in mind that this non-standardized spec is derived under laboratory conditions.
Other factors such as headroom and power supplies factor into the amount of juice an amp can provide in the real world setting of our audio systems, whose requirements (complex impedances) change by the microsecond. And thus, it is possible that a little under 20 watt Viva SET amp can drive the hell out of power hungry Sound Lab M1s, which typically is an amp killer.
In my view, most specs in audio components should be ignored, at least ignored in the sense that they cannot be used to compare one component to another. It is much better to plug something into your system and verify performance 1st hand.
Other factors such as headroom and power supplies factor into the amount of juice an amp can provide in the real world setting of our audio systems, whose requirements (complex impedances) change by the microsecond. And thus, it is possible that a little under 20 watt Viva SET amp can drive the hell out of power hungry Sound Lab M1s, which typically is an amp killer.
In my view, most specs in audio components should be ignored, at least ignored in the sense that they cannot be used to compare one component to another. It is much better to plug something into your system and verify performance 1st hand.