I think that the guys do definitely touch on key insights that are correct BUT most of what they talk about is lacking:
1) They are reviewing loudness in the context of Pedal Guys --- that is we generally want our guitars to sound like our pedals which is NOT the way amps were developed. Rather, pedals were developed to fit amps.
2) When comparing the AC30 vs. the AC10; they should have used the power section of the AC10 to drive the two Celestion Blues in the AC30 cabinet. Also, it takes a 6db increase to double perceived volume. In addition, assuming speakers are the same, it takes ten times the wattage to double perceived volume. So, to keep it simple, 1 watt, 10 watt, 100 watts are my key reference for this discourse. In fact, the AC30 will be much louder than the AC10 because the AC30 is moving more air. This guys are NOT hearing it because they are stuck inside a cubicle. To be anal about it, the AC30 is driving two speakers at least 10 watts while the AC10 plugged into the AC30 cabinet would only be driving two speakers at less than 10 watts. In fact the higher wattage on the AC30 gives you more headroom, mentioned by the guys but in passing. The AC10 pushing two Celestion Blues would immediately distort and NOT give you the chimey clean that Vox AC30s are ALSO known for -- thats why Joe Walsh uses an AC30 set at around 8-9 o clock volume when he tours with the eagles and NOT an AC10.
3) Rarely do I see guitar gear manufacturers specify IEC wattage on their amps and cabinets. IEC is the accepted audio started for measuring watts. So,anybody can claim any number of watts but fall short of the IEC watt rating of the equivalent numeral.
4) The voicing of an amp has a lot do with perceived loudness. My 100watt Soldano SLO is louder than my 120 watt Bogner Uberschall BECAUSE Soldano chose to voice the SLO with a more midrange to upper mid voicing whereas the Uberschall was designed to take on the scooped sound.
5) Again, I do agree with the guys that you need to own a lot of amps. But not necessarily small wattage amps. Small wattage amps -- much has been said about their advantages -- can sound less bassy and too midrangey. In fact, low wattage amps which sound louder than poorly designed higher wattage amps may still lack tightness in the bass end of the spectrum.
6) These pedal guys failed to test straight jack into the amps. This would have revealed that the AC30 would have more dynamics than the AC10 specially with regards to strumming. Since most of the time they passed their single coil guitars into highly compressed effects, they were not able to demonstrate the dynamism in single coils paired with high wattage amps. The guys did mention SRV but they failed to mention that SRV had on most occasions used high wattage amps to get the dynamics in his sound.
Given all the factors that affect loudness -- we even have not discussed how the room affects the loudness -- My only rule of thumb advice is match the number of 12 inch speakers to the size of your venue. Small club -- one twelve inch will do. Small Club and metal -- two twelve inches. Small Club and metal with a loud drummer -- 4x12. Small Club and metal with a deaf drummer or drummer who does not know how to bring down his volume -- Full Stack.
What's the moral lesson here? Simple: the drummer dictates how loud an amp you need.
