Although I almost always agree with my esteemed Audiogon friends and colleagues Atmasphere and Charles, and although I am definitely a fan of tube amplification, I would be hesitant to pair a tube amp with these speakers, at least without an in-home trial having return privileges.
While the speaker’s published specs indicate a nominal impedance of 8 ohms, the measurements shown here indicate as follows:
The problem with the 3.75 ohm figure is not necessarily that value in itself, but rather that given the 8 ohm nominal impedance there is likely to be a wide **variation** in impedance between the bass region and the impedance at higher frequencies. And given also the likelihood that the speaker was designed with the expectation that it would probably be driven with solid state amplification that variation is likely to result in unintended tonal aberrations, such as weak bass, if it is driven via the higher effective output impedance of most tube amps. And the fairly severe -47.96 degree capacitive phase angle at 83 Hz would most likely add to the problem.
I can also say specifically that based on measurements I’ve seen in Stereophile many PrimaLuna models, especially the lower priced ones, have particularly high output impedances, even for a tube amp, which casts further doubt on their suitability for use with these speakers.
Good luck. Regards,
-- Al
While the speaker’s published specs indicate a nominal impedance of 8 ohms, the measurements shown here indicate as follows:
Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.While that information is not nearly as complete as I would have preferred to see (a graph of impedance magnitude and phase angle covering 20 Hz to 20 kHz would have been more informative), it is suggestive that these are probably not tube-friendly speakers, especially when it comes to tube amps in a price range that would make sense. (As opposed, for example, to a vastly more expensive Audio Research Reference series amp, which I suspect would do ok with these speakers).
The problem with the 3.75 ohm figure is not necessarily that value in itself, but rather that given the 8 ohm nominal impedance there is likely to be a wide **variation** in impedance between the bass region and the impedance at higher frequencies. And given also the likelihood that the speaker was designed with the expectation that it would probably be driven with solid state amplification that variation is likely to result in unintended tonal aberrations, such as weak bass, if it is driven via the higher effective output impedance of most tube amps. And the fairly severe -47.96 degree capacitive phase angle at 83 Hz would most likely add to the problem.
I can also say specifically that based on measurements I’ve seen in Stereophile many PrimaLuna models, especially the lower priced ones, have particularly high output impedances, even for a tube amp, which casts further doubt on their suitability for use with these speakers.
Good luck. Regards,
-- Al