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Those are M80s, right?  Do you find the bass level on the XS to be (far) more restrained than the M80?  That was the impression that I got with my brief listen to the XS.  As mentioned by others the XS does seem to have less clamping force which might mean a weaker seal.  I finally gave my M80s away because the bass was just too much for me.  It might have been my imagination but the bass seemed to be getting worse (heavier) towards the end.  I was thinking that maybe the pads we just conforming and I was getting a 'better' seal.

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Those are M80s, right?  Do you find the bass level on the XS to be (far) more restrained than the M80?  That was the impression that I got with my brief listen to the XS.  As mentioned by others the XS does seem to have less clamping force which might mean a weaker seal.  I finally gave my M80s away because the bass was just too much for me.  It might have been my imagination but the bass seemed to be getting worse (heavier) towards the end.  I was thinking that maybe the pads we just conforming and I was getting a 'better' seal.

I've only heard the M80 at stores/meets, so I doubt I can accurately judge the difference. From what I remember of the M80, the XS actually has a greater bass emphasis, though this could be due to auditioning the M80 in fairly noisy places rather than at home as with the XS. Also getting a pretty solid seal with the XS, though this too could be attributed to their newness vs the other M80s and the fact that my head is larger than average. Both have good bass, but I wouldn't go so far as to say great. Both the DT1350 and the HP50 have perceptibly tighter bass. HTH

Yes and no. (incidentally this was in an LP, not M80 or XS)

I managed to fit the driver into the existing baffle, but the driver is too big and covers most of the holes to screw down the baffle into the cup. Only 2 out of 7 holes were available, which left the baffle poorly sealed to the cup. The cup is also really too shallow to hold the driver and there's no breathing room at all, and the little that's there is uneven anyways, and a rather herculean effort with a dremel grinding out practically everything in the shell is required. I imagine if one could use a 3d printer (or good plastic/woodworking skills) to make a new baffle with a bit more clearance and finagle a new way to attach it things would be a lot better.

I played with a few damping schemes and ultimately just went with some acoustic foam and fiber filler in the cup, and some soft felt in front of the driver for simplicity. Oh and drilled a small hole in the cup. I think there was something else I'm forgetting, but that's the gist of it. It was decent sounding; better than a regular LP (not saying much there), but not nearly as good as a typical modded T50rp.

I've been using the XS since launch. I got rid of my IEMs due to comfort issues for me. Feather light and can be worn for  3-4 hours at a time. These are my travel HPs and in the gym as well.

There is a touch of warmth but overall the SQ is very good with very decent extension both ways. The bass will kick in when present in the recording.