> Try 5-6x. I've met some blind people who listen to audio so fast, it sounds like noise to me. As someone who isn't blind, I regularly listen to lectures and audiobooks on 1.75-2.5x (depending on the base rate) without issues, but 6x is just something else entirely.

Yes, indeed. I was writing that original comment for someone just getting started. What ends up happening is no matter how fast the speech rate is, you'll eventually get used to it and your brain will grow impatient. So you'll bump the rate up another 0.25 and rinse and repeat. Pretty soon it's incomprehensible to anyone but you.

I'm pretty sure anyone can get used to 2X+ without much effort. After a while you'll wonder how you ever listened to speech at a normal rate. Be careful, though, as I've found myself grow impatient listening to people in real life and can trace it back to my high-speed listening habits.