As a fellow Caltech grad (went to school with Bill Gross), I saw the developmeht of GNP speakers and have listened to most of the different versions and owned a few.
I think the Valkyries with the laad cylinders were the last of the speakers designed by Bill Gross of GNP. The earlier ones were called 'Sound Mirrors' and featured rectangular particle board satellites with 5" Bextrene Midranges and 1" soft dome tweeters. These were sold with 'bass cubes' with 10" or 8" drivers, and an internal crossover (which accepted an input from the power amp and had an output for the satellite (with the low frequencies filtered out)
The key features of these speakers were outstanding phase accuracy/imaging, sonic accuracy and high efficiency. Not flashy, just perfectly real sounding. The key element was the manner in which they were phase corrected - not all drivers and electronic components with the same specs are created equal, and by measuring and carefully matching the drivers with the capacitors and resistors and custom winding the inductors, you could make a given speaker phase accurate (so long as you don't replace any of the drivers or parts of the crossover.
These sounded like incredibly more expensive speakers, did not challenge the amplifiers (over 100WPC was a waste and a 25WPC Class A amp was all you needed for great sound). Most of these were 6 ohms with efficiencies over 90 dB/watt.
These didn't sell that well since they were'nt well promoted and didn't have any sound characteristic that jumped out at the listener - people seem to like speakers that exaggerate sound part of the sound vs. provide extremely accurate reproduction. In fact, when playing a direct-do-disk LP the imaging is incredible - you can tell where all the musicians are sitting. Really.
