Unknown type of audio interface/connector/cable

I found it in my grandma's attic, so no loss :))

This is how the cassette deck looks, it has a dolby noise reduction button on it, so it's definitely made for recording. 
It has a power outlet and that connector, whose only use i suppose would be for audio playback.

I did also find another Akai radio/amplifier/tuner with a graphic EQ which in the meantime I plugged into my computer to test and it does work perfectly.

I attached photos of both here: https://imgur.com/a/Yp9TVec .

It's really hard to tell what that is in the photo and I am with stereo5 a tape deck would go into a preamp or integrated not a speaker.

While I have never seen that type of connector before, shouldn't the tape deck go through a preamp and not directly to the speakers?