Plus [DeVore] was aiming the impedance/load characteristics [of the DeVore O/96] at people who like using tube amplification, as well as producing a sort of throw-back visual aesthetic. For the audience he was aiming (which included himself) he nailed it.
From the Stereophile
measurements, the impedance characteristic of the DeVore O/96 has three impedance minima: 7.8 ohms at around 42 Hz, 7.2 ohms at around 195 Hz, and 7.9 ohms at around 8.2 kHz. The impedance peaks are significant, considerably exceeding 20 ohms in height in conjunction with the ported enclosure design, and also just a bit over 20 ohms at 1.6 kHz in the crossover region. In the sense that the impedance never falls below 7.8 ohms, yes, this loudspeaker might be regarded as being easy to drive, with much lower current demands than other loudspeakers with 6-ohm or even 4-ohm minima. It has a fairly high sensitivity, which is estimated to be 91dB(B-weighted)@2.83V/1m. Of course, that places lower power demands on the amplifier than do many other loudspeakers, helping the O/96 to be easy to drive. Those particular elements of the design do help to make it work reasonably well with tubed amplifiers, which are often low powered devices.
Unfortunately, tube amplifiers are generally characterised by having a low damping factor. This makes their frequency response extremely sensitive to the impedance variations posed by typical loudspeaker systems. The O/96 is relatively typical, albeit it has some very high peaks in the impedance. The wide range in the impedance values between the minima and maxima will lead to large variations in the frequency response curve, adding to the relatively large variations in the frequency response curve of the O/96. Whether those additional colourations/distortions are euphonic is in the ear of the listener who might like to use tube amplification with these speakers.
If a loudspeaker were being truly aimed at use with tube amplification, in the sense of maintaining a flat tube amplifier frequency response, then the aim would be for a flat resistive impedance load of moderate value. This would ensure much less interaction with any amplifier, let alone tube amplifiers that have well-known idiosyncrasies that serve only to colour the sound. As the O/96 does not have a flat resistive impedance curve, to say that it is somehow aimed at use with tube amplification doesn't seem to hold up under even a minimal degree of scrutiny.
