I'm working on a scene in a film where two actors are watching a video tape on a small (15"), vintage 1970s TV. I need to do some EQ on the sound that is supposedly coming from that TV. The director wants it to be just a tad exaggerated so that we can easily hear the difference in quality between the actors watching the TV and the TV itself.

Roughly, what would be the accurate audio frequency range of such an old TV that had, say, only one, cheap mid-range speaker in it?

To get the sound I think you want, you could use a small speaker from a 5:1 system, set it for a mid range only and mic it to record the sound. You could also add a touch of reverb to give it the perspetive of location in the room.

Try 4-6db boost somewhere between 1.5kHz and 3 kHz (depending on what your ears tell you) and apply -11 db to the bands above and below what you boost. The run it through a compressor, set to a good amount (4:1 or so) of compression, fairly fast (5ms) attack and a fair bit of makeup gain added. That should get you in the ballpark, adjust to taste.