This. I have an old vintage alarm clock that I put across the room. It’s set to my “if you aren’t up by now you will be late no matter what” time. If my phone alarms don’t get me up, this thing is so loud and unpleasant I will certainly get up.
Phone ringers are too pleasant sound and easy to snooze. I need to change the tone every few months as I adapt to them all. A harsh metal bell or mechanical buzz on an alarm with no snooze that I cant reach from bed has me wake up at the last phone ringer because it is so ear shattering when that alarm clock goes off, I can snap through all but the worst sleep deficit nights.
It also pisses off the girlfriend when that annoying thing goes off too, so then I have her mad at me for waking her up if I’m not up to shut it off before it lets loose.