Charles and Ray Eames had nothing to do with the Sonab headphones, this connection was only made as a sales trick in a recent ad (“Eames era”).
The modernist Sonab designs were masterminded by Lars Lallerstedt from 1969 to 1974, in all probability also including the H10 and H20 headphones. These high quality headphones were only in production a few years, from 1972 to 1974, according to the Sonab catalogues I’ve seen. The headphones were manufactured by German MB (Mikrophon Bau), which may explain the short lifespan of the headphones as MB ran into financial difficulties in 1974-1975 after the world-wide introduction of electret microphones (see Wikiphonia).
I’m listening to the H10 as I write this, and would describe the sound as punchy and forward, typically 70s, with deep bass roll-off. Still, the frequency balance is OK, with some midrange unevenness. The pads are aged, the foam all but gone, which means that isolation and distance to driver is not optimal. The drivers are also acoustically filtered by the plastic baffle which leaves only three small openings for the driver. I’m sure there is room for improvement here, both concerning damping and shape/size of the driver opening.
The headphones were originally supplied with tone filters (“klangfilter”), foam donuts that you put into the pads for a softer sound.
The bigger brother H20 had a higher sensitivity and wider frequency response according to specifications. They’re 400 ohms and need good amplification.
A design very typical of the 1970s, stylistically, which may or may not appeal. I, for one, would not wear them in public, but if you do you'd certainly attract attention.
