Use the 4 ohm tap.
The 6 ohm speaker rating is a nominal number, which means it will drop below that somewhere in the frequency range. Your amp has an easier time running against a higher impedance, and using the 4 ohm tap will make it see the speaker at a higher impedance.
Regards
Paul
The 6 ohm speaker rating is a nominal number, which means it will drop below that somewhere in the frequency range. Your amp has an easier time running against a higher impedance, and using the 4 ohm tap will make it see the speaker at a higher impedance.
Regards
Paul