Specs are community starting points - verify against your amp's manual. (Tube amps: set this to match your impedance selector.)
Tube
Solid State
Cabinets
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cabinet load
Add a cabinet to calculate
Wiring diagram
What does this wiring mean?
Power distribution
Valid speaker hookups for this amp
Tube amp rule: Never go below the rated output impedance - it stresses the output transformer.
Going higher (e.g. 16Ω cab on an 8Ω output) is safer but affects tone and power transfer.
Exact match is ideal.
Summary
Your rig
Speaker sensitivity is on its spec sheet - typical guitar speakers are 96–100 dB.
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estimated SPL at the listener
To get noticeably louder
Change
Power needed
Sounds…
+10 dB = 10× the power. That's why 100W barely edges 50W - speaker sensitivity matters more than chasing watts.