awesome review, I wish everyone here would be as reasonable in judging sound quality as you.

Great review and I could not tell it was your first.  Very informative and I must say, I am now interested in L2, even though I was sold on the Momentum before.

Great review.
 
I had Sennheiser Momentum before. L2 is much better.

I must also say, L2 is great with EDM. I listen to a lot of trance, house, synthpop etc. and it's amazing with all of them.

I must also add that even though highs are very extended, they are not harsh at all. I'm very sensitive to harsh treble (thus I sold my AKG Q701 cause I couldn't stand the treble) but L2 doesn't have it, unless the recording is very low quality. L2 is not brutally unforgiving, but it's not as forgiving as HD650 either.

If the "screws" are like the "screws" on my Fidelio M1, they are not really screws, but rather plastic snaps with a hollow center.  On each earcup, one of them has the wire going through it to the headband for the right side.  Certainly they could make that piece out of metal, but perhaps it was easier to make it out of plastic.

Nice review, I agree on most points. To me they are a touch too bright to be called neutral (noticeable for instance with violins), and lack a bit of low end. Very different sounding than the bigger Fidelio X1, which is a rather warm headphone. I like them both.

Thanks for all the positive comments
The orange hinges are definitely filled with cables, since they are the only connection between the frame and the earcups. That might explain it indeed.
And I agree, they are a bit bright indeed and supprisingly smooth, although I don't think they lack in the low end. The bass is just quite controlled. Although that thought can also be caused by them having a more noticeable impact than my Shures...

Great Review and fully agree with You
Any issues they have with their apparent brightness can be sorted with a good Valve drive headphone amplifier, just adding a little warmth but retaining their crisp fun sound, also experimenting with different cables can be worthwhile, they need some burn in time too to get to their best. I eventually ended up using a Valve Pre amp into the Graham Slee SRGii , detailed , slightly warmer, big sounding fun presentation.... for £150 its hard to criticise them.
They are not ideal for on the bus, but hey that;s where the M1BT come into their own !!!!