Thank you, psilonaught.
Eyeballing Stereophile’s impedance curve of the MG-20, it looks like 4 ohms nominal (for the mid/tweet section) with a ballpark 12-ohm peak a little south of 2 kHz. That’s a 3-to-1 peak; not horrendous, but not insignificant within the context of tube amps. And assuming the 20.1’s impedance curve is similar, and that it was designed with constant-voltage (solid state) amps in mind, imo that impedance peak is worth paying attention to.
You see, a solid state amp will deliver 1/3 as much wattage into that 12-ohm peak as what it delivers into 4-ohm portions of the impedance curve. The designer presumably took that into account when he "voiced" the speakers.
Tube amps tend to deliver much closer to the same wattage into that 12-ohm peak as into the 4-ohm-nominal rest of the spectrum. So a tube amp may result in a frequency response emphasis in that region, because there the speaker will be getting more wattage than the designer anticipated. Imo one solution is to make the impedance curve more tube-amp-friendly.
EVERY TIME I have been able to thoroughly investigate someone trying a specialty tube amp and not liking it, I have found a plausible explanation in the loudspeaker’s impedance curve. I’m NOT saying "don’t try it" - quite the contrary; Maggies + tubes can equal MAGIC - but I suggest that you work with someone who is at least aware of the issue.
(The 3.6 was a particularly tube-friendly Maggie. It had a relatively small and narrow impedance peak at about 1.5 kHz, which also happened to be where it had a frequency-response DIP with a solid state amp, so the synergy with tubes was really good.)
Best of luck to you.
Duke
Reference: http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html
Eyeballing Stereophile’s impedance curve of the MG-20, it looks like 4 ohms nominal (for the mid/tweet section) with a ballpark 12-ohm peak a little south of 2 kHz. That’s a 3-to-1 peak; not horrendous, but not insignificant within the context of tube amps. And assuming the 20.1’s impedance curve is similar, and that it was designed with constant-voltage (solid state) amps in mind, imo that impedance peak is worth paying attention to.
You see, a solid state amp will deliver 1/3 as much wattage into that 12-ohm peak as what it delivers into 4-ohm portions of the impedance curve. The designer presumably took that into account when he "voiced" the speakers.
Tube amps tend to deliver much closer to the same wattage into that 12-ohm peak as into the 4-ohm-nominal rest of the spectrum. So a tube amp may result in a frequency response emphasis in that region, because there the speaker will be getting more wattage than the designer anticipated. Imo one solution is to make the impedance curve more tube-amp-friendly.
EVERY TIME I have been able to thoroughly investigate someone trying a specialty tube amp and not liking it, I have found a plausible explanation in the loudspeaker’s impedance curve. I’m NOT saying "don’t try it" - quite the contrary; Maggies + tubes can equal MAGIC - but I suggest that you work with someone who is at least aware of the issue.
(The 3.6 was a particularly tube-friendly Maggie. It had a relatively small and narrow impedance peak at about 1.5 kHz, which also happened to be where it had a frequency-response DIP with a solid state amp, so the synergy with tubes was really good.)
Best of luck to you.
Duke
Reference: http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html