Speaker impedance on vibrochamp XD

[JimmieT]

the speaker jack says 4 ohms minimum. Does that mean you can put in an 8 ohm? I have a Jensen alnico 8 ohm that I'd like to try in there.
If it is compatable what effects might there be?

[Slow Reflexes]

General rule - higher impedance is okay, lower is not. The primary effect will be diminished volume.

[jefrs]

It's a 6V6 bottle job. Fender are notoriously catholic in their speaker impedance and play fast and loose with the laws of physics especially with their old amps which sound great despite this predilection. Do not expect 200% tolerance of old, do not go under 4ohm.
Eight (8) ohms will give you an impedance mis-match but is relatively safe i.e. nothing will blow up, but you will get maximum reduced power. Much depends on the output transformer, it may even sound better, probably will with a Jensen AlNiCo.

Do it.