It is the bass-reflex system floor type speaker developed in 1955 (Showa
It is said that composition is a Woofer and a tweeter
and became a prototype of 2S-305.
It is said that those days, evaluation
of the carry top was obtained for the speaker and blind test in the world in the
NHK technical research center by open viewing and listening by 3000 persons
involved in sound.
Henceforth, change of 2S-205, 2S-206 type, and
details is repeated, and 2S-305 type will be born in 1958.