I disagree. The seal is required to block out ambient sound, not to give better audio.
You can do both. I think my stock Apple headphones sound good compared to a LOT of the headphones people brag about…however, they are fragile and I replace them every other month. Do they sound great? No. They sound good.
The last in-ear monitors I had (years ago when I needed them professionally) were Shure ECs and they sounded AWESOME…I just couldn’t hear anything but the music within. I honestly thought of getting my ears poured again, but having some sort of acoustic tubes included so I could have a set of tips that I could use for ambient sound and one for stage.
