...or you could pick up one of those $20 B/W from Radio Shack or Best Buy. Telephone EQ presets work well for me, but what you are probably "missing" is the ambience of the TV body itself, which you could get doing what Bob suggests.

I wonder if you could create an AM impulse for something like that?

You could try some serious Eq, then add some distortion (not clipping) at the bottom end and some resonance filters to add a bit of a hollow wood or plastic box sound to it. But then you've got to place the thing in the sound field.
Yes, you could use AM for that, trick is to get a sample for AM to work with. Trick I think SPOT mentioned (or was it in Jay Rose's book), call for silence on the set, record the clapper near the sound source for AM sample and then 60 seconds of ambience. If you've just got the dry sound of the TV you still need the room ambience and the placement of your tweaked sound to take care of.
That's why my not so flippant suggestion before.
Of course doing it in post does give you more control.

Bob.

I just produced a voice-over for a 40's-style movie newsreel.

I've posted a .zip of the voice-over .mp3 and .veg that performed the processing.

http://michael-morlan.net/projects/vegas/vegas_really_cheap_speaker.zip

I used a Resonant Filter followed by a Track Compressor for the effect. You will find this chain in the Master Bus FX channel.

A note about the resonant filter effect. Some of the settings are quite easily changed when the mouse passes over them WITHOUT EVEN PRESSING THE MOUSE BUTTON. Be sure that the radio buttons for Filter Type and Filter Order are as follows:

Filter Type: High Pass
Filter Order: Second

Enjoy.

These all sound too complicated to get the result you need. I say just use the graphic EQ and cut down all the frequencies below 500Hz and find that right frequency (somewhere between 900 and 5000 Hz) and boost (them / it) and this will do good enough. Maybe even combine the para-metric EQ to find that perfect high frequency to boost. I doubt anybody will analyze the background sound fx that much unless it really sounds off.

Thanks everyone for the ideas. I'm a little afraid to go the way of playing through a cheap TV as the movie will be playing in a festival and speakers there are often a bit suspect. I did record a little bit of audio that way and now I'm thinking I may use the spectrum analyser to compare what I've done to the raw version that clip to what we got when recording off the TV.
TheGr8Steve, I think what I've done so far is fairly similar. The phone line effect cuts things off at 800 Hz and extends for 2 octaves (of course I still don't know what an octave is, but that's for another time).
I tried your formula and made a paragraphic eg where I made a low shelf for 500 hz and a high shelf for 5000 hz. So everything outside of that range was rolled off to nothing. You're right, it does sound pretty good. Strangely, now when I apply the reverb I had been using, it makes no difference- even applying a lot more of it. I'll try a different setting altogether, but I do think your suggestion helps and I appreciate it.

Yay! By the way, each octave is either double the Hz or 1/2 the Hz. Double meaning higher in pitch and etc. (Or in musical terms, an octave is the same note (like 'C' or 'A' or whichever) but either higher or lower in frequency. High 'C' or Low 'C', the Hz is either doubled(higher) or halved(lower) for each octave. An 'A' 440Hz is fairly standard, the next 'A', higher in pitch would be 880Hz or if lower in pitch would be 220Hz. All would be called 'A' notes, but octaves apart.) Now you know.