This is one one of the few early 80s loudspeakers I remember listening to (back then): very "muscular" rendition, tight and controlled, far from a "romanticised" sound. It's written on them: MONITOR. What is not written on them (but is if one attempts to move them) is their weight : 85kg - each.
The honeycomb structure of the drivers were Technics' staple, just like Sony's earlier APM square drivers - the structure, however, is very different

The three controls set the level for the tweeter (+1/-6dB), high-mid (+2/-6dB) and low-mid (+1/-6dB) respectively, with an added but non-descript "min." setting for each pot. A relay-activated protector sets in if the tweeter temperature goes too high ; a related LED is present on the front panel for indication.

The regular SB-M1 was available in a "civilized" dressing as well : it is the M version, made with a real wood enclosure and weighing even more than the regular SB-M1S (Studio) version ; the M version was not made available in Europe and I wonder if it even got produced at all, besides the one or two samples for the ads.