Everything I tried for the title was too long so I decided for this. How to mix your vocal to make it sound like it's sung through a intercom, or and old mic, or just filtered? What freqs do I need to add, what do I need to cut?

Like this


Or this


Or this


I'd appreciate your help!
play around with Cutting the Low and High ends. Cut them to your desired level.
Should work, I've heard adding a touch of distortion spices it up a little
Telephone mids are what you need my friend. Boost 1.2K with a wide Q, add some saturation (for example Massey Tapehead Medium) and have vigorous HP/LP settings.