The match between amplifier and speaker for single-ended operation is critical, which is why John Atkinson suggested I let Wavelength's Gordon Rankin lead when it came to choosing a speaker to partner his special-edition Cardinal amplifiers. If you're not talking roughly 92dB sensitivity and a fairly benign load, say no lower than 6 ohms, you're just not talking single-ended. That precluded running the Cardinals on the big Avalon Ascents with their lowish 86dB sensitivity (in spite of the relatively benign impedance curve).
After more discussion it became evident that the best speakers to use were the very ones Gordon employed in his own reference systemthe Swiss-made Reference 3A Royal Master Control loudspeakers.
Silicon Valleybased Velodyne was founded in 1983 to develop a range of subwoofers that used servo-control to reduce non-linear distortion to vanishingly small levels. They succeeded in this goal to the extent that Velodyne is now perhaps the best-known subwoofer company in the US, currently employing 65 people. At the 1994 Winter CES, Velodyne launched the subject of this review: the DF-661 ($1800$2600/pair), their first full-range loudspeaker (the "DF" stands for "Distortion-Free").
The three-way DF-661 was designed from the ground up to continue the Velodyne tradition of ultra-low distortion. "We had developed the technology and resources to attack distortion elsewhere in the audio chain," wrote company President David Hall, "and started with the premise that, by definition...distortion in loudspeakers is wrong." (His italics.) "We went to the laboratory for a solution, with the living room as the ultimate goal." Velodyne calls this attention to technological detail "The Silicon Valley approach to sound."