Some further comments on the amplifier-to-speaker impedance compatibility issue:
It can be calculated that the interaction of the speaker's impedance dip to about 4 ohms at 20 kHz and the amplifier's 2 ohm output impedance will result in a frequency response rolloff of about 3.5 db at 20 KHz. The impedance dip to about 8.5 ohms in the area of 250 Hz will result in a frequency response dip of less than 1.8 db.
Neither number seems to me to be all that large. Furthermore, it seems very conceivable that the speaker was voiced with tube amps in mind, which would mean that its design may anticipate and compensate for those impedance interactions. Note in Figure 5 of JA's measurements, which shows nearfield anechoic frequency response, that the response is shelved upwards by about 3 db in the 10 to 20 kHz region!
The review noted much larger frequency response deviations due to interaction with the output impedance of the Shindo Haut-Brion amplifier they were using. My guess is that the output impedance of that amp is considerably higher than 2 ohms. The review indicated that the Shindo provided only a single output tap, which was nominally rated for use with 16 ohm speakers. That would seem consistent with it having a significantly higher output impedance than most tube amps provide.
Regards,
-- Al
It can be calculated that the interaction of the speaker's impedance dip to about 4 ohms at 20 kHz and the amplifier's 2 ohm output impedance will result in a frequency response rolloff of about 3.5 db at 20 KHz. The impedance dip to about 8.5 ohms in the area of 250 Hz will result in a frequency response dip of less than 1.8 db.
Neither number seems to me to be all that large. Furthermore, it seems very conceivable that the speaker was voiced with tube amps in mind, which would mean that its design may anticipate and compensate for those impedance interactions. Note in Figure 5 of JA's measurements, which shows nearfield anechoic frequency response, that the response is shelved upwards by about 3 db in the 10 to 20 kHz region!
The review noted much larger frequency response deviations due to interaction with the output impedance of the Shindo Haut-Brion amplifier they were using. My guess is that the output impedance of that amp is considerably higher than 2 ohms. The review indicated that the Shindo provided only a single output tap, which was nominally rated for use with 16 ohm speakers. That would seem consistent with it having a significantly higher output impedance than most tube amps provide.
Regards,
-- Al