Yeah, I get the sense the TH-900 are less closed than the Z1R. I'm definitely looking for higher volume listening, my Shures are great until I turn them up and then they fall apart for me so the main reason for the purchase is headphones that not only sound great but continue to sound great at higher volumes. I'm just wondering about that treble spike that some seem to report on the Z1Rs and if that will cause issues at louder volumes (which is a similar issue to the Shures). I am like 90% certain but it's a lot of money to spend, mostly I'm at the stage now where I'm going to purchase the Z1Rs unless there's a better alternative, but I have a feeling that they're my best bet. Audeze look too big and bulky, ZMF are difficult to source, HiFiMAN have a lot of detractors over build quality and the TH-900s are probably not isolated enough for my needs.