Speaker Impedance ... nominal 6 ohms

One key to this is the word....'nominal'....
If the speaker is +- a couple ohms of the rating, the test would be OK.
If there are some wacky peaks / dips, you may have some problems. Again, testing and paying attention to the amps heating will be key.

The other part of the equation is Phase Angle of the load. If the phase gets high, say 50 degrees or higher at the impedance minima, than you may also have problems....especially if such double dip occurs at frequencies which require lots of power..... Tubes generally don't like this kind of behavior.

Hi Kossi

Thanks for posting a thread about this topic. I always wondered about this. I always thought that if your speaker had a 6 ohm nominal impedance that either your receiver (if possible) would have to be set to 4 ohms or the 4 ohm taps on a tube amp had to be used. Good to know.

Kossi...yes you can use either amp to drive these speakers. On the amp that has 4ohm and 8ohm connections, try them both and see which one sounds better to you. You should get a little better bottom end control through the 4ohm taps but try them both and see which you prefer. Good luck.