barnettk, I own an ARC Ref 150SE tube amp. Same issues have come up for me over the years. I find myself switching back and forth all the time. Right now, I am using the 8 ohm taps.
Both of us have power paradigm amps. As a result, the voltage output will change as a function of the speaker's impedance curves. IMO, your speaker's have pretty moderate impedance and phase angle plots. I surmise that your amp has little trouble driving the speakers.
What would be interesting to know is what the output impedance of your amp is off the 4 and 8 ohm taps. That would give you a clue as to how much the amp's output voltage with vary as a function of changes in the speaker impedance.
For example, the output impedance of my Ref 150SE is pretty low. As a consequence, the output voltage varies by +/- .8 db off the 8 ohm tap and about half that off the 4 ohm tap. See John Atkinson measurements here: https://www.stereophile.com/content/audio-research-reference-150-power-amplifier-measurements
Point being that your speaker output will be flatter off the 4 ohm tap and a little brighter off the 8 ohm tap because your amp will response to speaker impedance bumps with more output voltage. The reverse is the case with respect to speaker impedance dips.
So the bottom line is that what you hear will sound flatter and bass will be slightly tighter off the 4 ohm tap and a little more lively off the 8 ohm tap. Btw, I mention that bass will be tighter off the 4 ohm tap because I surmise that your amp's output impedance is lower off the 4 ohm tap. As a result, the amp's damping factor will be higher, thereby controlling the woofers a little better.
But the real bottom line is that you use whatever taps sound best to YOU!!
Both of us have power paradigm amps. As a result, the voltage output will change as a function of the speaker's impedance curves. IMO, your speaker's have pretty moderate impedance and phase angle plots. I surmise that your amp has little trouble driving the speakers.
What would be interesting to know is what the output impedance of your amp is off the 4 and 8 ohm taps. That would give you a clue as to how much the amp's output voltage with vary as a function of changes in the speaker impedance.
For example, the output impedance of my Ref 150SE is pretty low. As a consequence, the output voltage varies by +/- .8 db off the 8 ohm tap and about half that off the 4 ohm tap. See John Atkinson measurements here: https://www.stereophile.com/content/audio-research-reference-150-power-amplifier-measurements
Point being that your speaker output will be flatter off the 4 ohm tap and a little brighter off the 8 ohm tap because your amp will response to speaker impedance bumps with more output voltage. The reverse is the case with respect to speaker impedance dips.
So the bottom line is that what you hear will sound flatter and bass will be slightly tighter off the 4 ohm tap and a little more lively off the 8 ohm tap. Btw, I mention that bass will be tighter off the 4 ohm tap because I surmise that your amp's output impedance is lower off the 4 ohm tap. As a result, the amp's damping factor will be higher, thereby controlling the woofers a little better.
But the real bottom line is that you use whatever taps sound best to YOU!!
