how is it called?

No.9883202 ViewReplyOriginalReport
I once visited a electronic arts show where, in the middle of a room, there was a rotating donut-shaped speaker. the amazing thing was, that sound was not propagating from the speaker in a conical fashion. you could only hear the speaker if it was directly facing you.

I want to look up this phenomenon, but neither "linear speaker", "linear direction speaker" or "non conical speaker" yielded results. I just can't think of any more sophisticated terms to look for...