Hello! Thanks for reading and for the question!
I’ve had luck powering both models with a phone…although I don’t listen at super high levels.
However, I have an important question.
Do you listen with the phone in your pocket?
If that’s the case…neither the 250 ohm nor the 80 ohm DT770 is probably the best choice, in my opinion. The 250 ohm model has a coiled cable and the 80 ohm model has a long 10-foot straight cable. Both cables are best suited for desktop/seated use, and are a little tough to walk around with.
The HRM-5 is easier to power with a phone. I don’t think it would sound better necessarily, just a little bit different. If you’re way into sub bass/sparkly treble, you’ll think the DT770 sounds better. The HRM-5 is a little flatter and less aggressive.
However, the HRM-5 has a cable issue again. It includes a coiled cable and a 10-foot straight cable, so it’s best for desktop use. They do also sell a short straight cable for it, and Pioneer bundles that cable in with the more expensive HRM-6.
If you’ve got your heart set on a Beyerdynamic model (and I certainly wouldn’t blame you for that!) I’d consider taking a look at the Custom One Pro Plus and the 32 ohm version of the DT770.
The Custom One Pro Plus (my review HERE) is more fun than the DT770, with less aggressive treble, but I think it sound is still good enough to use for some production. And it’s very suited to phone listening. It has two detachable short cables which are both better suited to a phone in a pocket, and one even has a built in remote and mic.
The 32ohm DT770 (my review HERE) has a very similar sound to the other 770 models, but includes leatherette pads and a shorter cable which is, again, the perfect length for phone listening.
I hope that helps you out!