Hello! Thanks for reading and for the questions!
The coiled cable on the 250 Ohm DT770’s is more or less identical in length to the one on the 7506’s. I think it might also be a touch thicker and heavier, but that’s going on feel. I don’t have an easy way to measure cable weight.
As for volume, yes, you’ll have to crank both 770’s a bit higher to achieve the same volume as the Sony headphones. I don’t listen at super high volumes either. I can achieve a good listening level out of my Galaxy S8 on my 250 Ohm 770’s at about 70 percent volume.
I think both pairs sound decent without an amp, and both are also revealing enough to show the small benefits that a dedicated amp can provide.
Now. The sound differences between 770 versions. They are incredibly minimal.
All of the 770’s are tuned to the same diffuse field compensation curve. The 80 ohm version is slightly more bass-heavy because of the way the interior of the cup is damped. But the 250 ohm and 32 ohm versions sound very similar to each other. This is all by design, so that you can match the impedance you need to different types of equipment across a studio environment and still get the same sound signature.
In fact, here’s a look at some comparison measurements from headphone.com’s handy graphing tool.
As you can see here, the 32 ohm version measures nigh-identically to its bigger brother. The bass hump is in a slightly different place due to the leatherette pads, so with the velour pads you should get basically the same response. If the velour version is cheaper, go for that one!
The upgrade question is tougher. Both the 7506 and DT770 are very good headphones. It’s more like it’ll be different. I prefer the 770’s sound by a little bit, but you might not. Let’s look at another graph.
The DT770 has a much stronger/more correct sub bass response, and a bit more air in the treble. The 7506 sounds like it has pretty impressive bass when you listen to it, but a lot of that energy is actually coming from the midbass region.
Looking at headphones on paper is one thing, and listening to them is another. They both have different characters, but until you hear it for yourself, it’ll be hard to tell which one you prefer. The graphs are useful because they at least show you’re going to be in the same overall ballpark.
I hope that helps you out or at least points you in the right direction! Thanks again for stopping by!