Sanyo M9990
The M-9990 was a 4-speaker boombox produced by Sanyo in 1979. It measures 49cm across. It features 2 big VU meters and a digital alarm clock. It has slots in the upper left and right corners for a pair of Sanyo microphones, but those are very rare and hard to find. At only 3.5 watts per channel, this model was not very powerful, but it's still a very good quality boombox, with good sound, solid build, and nice-feeling controls. It takes eight D-cell batteries, and one AA battery for the clock. The service manual can be purchased HERE.
Note, there is a "K" version of this model (M9990K) with shortwave on the tuner. There were also 2 re-branded versions sold in Europe: The Thomson MRK-470, and the Nordmende Globecorder 4084.