Re: Which Taps for the 7ES3?
In truth I don't suppose it will make much sonic difference whether you chose the 4 ohm or 8 ohm tap since the speaker's 6 ohm load falls mid way between.
The rule of thumb is that the source impedance (the tube amplifier's output setting) should, in theory, be lower or the same as the speaker's impedance. In that case, the 4 ohm tap would meet that rule.
However, this is a really fine argument: you may prefer the sound (in the bass) on the 8 ohm setting. What matters is what sound best to you, not the grand theory. Either way, no damage will be done to the speaker or the amplifier.
Alan A. Shaw
Harbeth Audio UK