4 or 8 ohm with Harbeth

Ditto above,try both and decide for yourself. After all, you are the one that that's listening. If you're worried about damaging your speakers, don't.

Thanks for the replies. One of my concerns was the possibility of damage to either the speakers or amp. I will try both and listen.

You don't mention your amp, for one, so why are you thanking anyone for their replies? Their comments are useless without more knowledge.
Second, why would you be concerned of possibility of damage? if you bought from a decent dealer you shouldn't have to be asking....

It is the cross-over interaction with your amp that is affecting your sound and yes, your speakers will often fluctuate to 4 ohms. The lower impedance tap always tends to be safer on your outputs as this setting is made to handle more current demands.

Chashas1,
My amp is a Rogue Audio Tempest bought from a dealer that does not carry Harbeth. My thought in posting this question is to get input from those directly familiar with Harbeth and tube amps with 4 and 8 ohm taps. BTW all my current system- amp, cd player, speakers, turntable, phono preamp, and subwoofer has been purchased from dealers.