I’m in total agreement here.Yes, the ER4 certainly is, for a very neutral (+/- slight bass boost) sounding IEM. It also provides superb isolation, if willing to have deep insertion IEMs. It is still a reference product.
I know it sounds crazy, but If I were forced to keep only one IEM in my collection it would probably be the ER4XR. To me, it sounds more pleasing than the ER4SR. I like the slightly elevated bass. Definitely needs a tight seal and deep insertion to sound correct. But for a more reference tonality, its tough to beat for the price. Even Crinacle and some of the other reviewers have it pretty high up their lists.
For now though, I am loving the UM 3DT. I’m almost obsessed with it at this point. And….it is definitely sounding better over time. My only negatives are 1) the difficulty I’ve had finding eartips that work well with it for me due to my ear structure. 2) getting a great seal is critical to having the proper bass tonality with it. 3) Both IEM metal nozzles have come off and needed to be reglued which makes me wonder if UM needs to rethink how this part is engineered/attached.