Bench tool
Speaker Impedance & Cabinet Wiring Calculator
Wire multiple speakers in series, parallel, or series-parallel and see the resulting load — with a visual wiring diagram and a check against your output transformer's taps.
Match against output transformer taps
Most tube amp OTs are tapped for 4, 8, and 16Ω. Pick whichever tap sits closest to your total load.
Running a load slightly higher than the selected tap is generally safe — the output stage sees a bit less current and power transfer drops slightly. Running lower than the tap raises reflected plate current and stresses the output tubes and transformer; avoid it, especially on amps without a fixed load already installed. This assumes matched speakers of equal impedance — mixing different speaker impedances in one cabinet skews power distribution unevenly between drivers.