and maybe try mono

ToneBooster's TB_Isone has a preset that sounds just like a tv speaker.

These are all great ideas--thanks.
 
I was hoping someone could recommend corner frequencies for the top and bottom cuts (and frequency/Q for mid-boost, if any).
 
I can get close with HPF and LPF, but really don't know the best cut-offs or slopes to make it authentic.
 
By the way, there is a very cool reason for this.
 
Thanks.

This might work, and it's free;
 
Pushtec is a 6 band EQ VST plugin. It comes with a lot of presets and sounds great. As with posihfopit, you can use it to create "radio effects" or "phone effect"
 
http://www.wavosaur.com/vst/eq-plugins.php

I'm no expert, but I would hazard a guess that steep cutoff slopes would be more authentic.

just keep twisting until it seems right for you.  as others have said it was the crappy low fi speaker that produced most of what we remember as low fi.  and each company made their own inhouse until the late 70s or so.  so there is no scientific answer.

There are a few IRs available on the internet for small speakers. Maybe on of those would be more satisfying than an EQ.