My boyfriend and I just bought America's oldest drive-in movie theater (Shankweiler's Drive-In Theatre, which I suppose is, in itself, a weird and wonderful secondhand find).

In the shed, we found this enormous speaker. I can't find any clear photos of it in use, but it was the original source for sound for the drive-in when it was first built in the 1930s - pre-dating even speaker poles!
No banana for scale, but here's a 5'8" gentleman and a water bottle.
Holy macaroni, the response to this has been such a wonderful surprise. I can't get through all the comments but to answer a few key questions:
The drive-in has been in continuous operation since 1934! It's been immaculately cared for and updated. We decided to keep it open in the winters now, too, so I actually made this post while hanging out in the projection booth.
We did not try out the speaker and do not intend to! We will clean it up and find a way to display it, since it's an important piece of cinematic history.
Related to the first point - as several people have noted, the first drive-in theater was in Camden NJ and built in 1933. Shankweiler's was built less than a year later, in Pennsylvania. Unfortunately the drive-in in Camden closed shortly after opening 🙁 so for the majority of its 88 (almost 89) years, Shankweiler's has been widely regarded as the oldest. (But not the first!)
Thank you everyone for your support and interest!!!