Here's some ancient history about my speakers.
I bought the drivers from Gold Ribbon Concepts in Iowa about 20 years ago. A local cabinet maker built the cabinets in accordance with the plans provided by the system designers. They are constructed from high density particle board and are about six feet tall with a trapezoidal cross section that contains a rear vented folded transmission line.
The ribbon driver is about 40 inches long. It consists of a stretched gold plated mylar film element that is supported between rows of powerful magnets. There is a simple crossover at 300 Hz.
The bass drivers are two Focal eight inch cones also crossed over at 300 Hz. These drivers were designed to complement the efficiency of the ribbon driver. They have a hole in the magnet to allow air to flow freely behind the cones. They are loaded by the folded transmission which is filled with pillow stuffing to increase its effective length.
The designer (Alan?) claimed the ribbon driver is resonance free with accurate phase response throughout its 300 Hz to ultrasonic range. He used an instrument that excited the driver with a short burst of energy to measure its response using mathematical transform methods. But, everyone who listened agreed the ribbon driver exhibited a mid-range peak and sounded much too bright. A more conventual sweep test verified a peak at 8 KHz. I designed a simple resistive loaded parallel LC trap to attenuate the resonance. A friend, who talked regularly with Alan, convinced him to do the sweep test. The final crossover design included a midrange trap.
Overall, the speakers sound rather nice, The bass is somewhat mushy but not lacking in intensity. Trebles are delicate but the midrange is still a little too bright and revealing of digital artifacts when playing CD's. I almost always use my Haffler XL-280 for everyday listening but I believe my Velleman tube amplifier tames this effect somewhat. Vinyl, through my Sonographe SC-1 sounds much better.
There were reports of a major problem with the ribbons. The mylar diaphragm can strike the magnets which obviously results in a distressing tinny sound. I have just recently begun to hear some intermittent mechanical noises from my speaker system.
I just visited a 'high end' shop where I auditioned Magnepans, Martin Logans and several other brands new to me. Maybe my hearing is failing, but I believe my old speakers can still hold their own against anything I heard there.