My voice is low. Like in the movie above. But I never 'purr' by default.
Though, I discovered myself doing a purr on auto pilot last week though. Music was loud. Girl pulled me back into her as I wanted to leave and she whispered something in my ear and I responded in her ear with a purr and I was like damn... Did I just sound like that?.. But that was because I was feeling like I was on drugs with this girl, so I thought I had to be aroused or something.
But right now I'm trying to recollect what I did and just found it is like keeping my voice clear and loud (as in trying to beat loud music playing in the room), but trying to get a lower pitch than normal. Then a certain resonance in my throat causes the purr. And if I can keep hold of that sensation, I can also go back to my usual pitch, but stilll purr on some words. Very interresting discovery