[halpsb]

The more I read about the Shure SRH1540's, the more I find myself wanting to own a pair. However, a good part of my listening happens on my LG G3 smartphone, often without even carrying my amp with me. I am just wondering if the upgrade would make sense in my situation, if there is any noticeable difference coming from the Sennheiser HD25-1 II or not. As for my go-to music genre, I listen mostly to techno. 
 
Thank you

 

[SteveHiFi]

I'm another who's reviewed them and I'm a big fan of the SRH1540 (and 1840) - they're lovely. I'd own them if I didn't already have too many headphones, and had more money.
 
Looking at the specs though, with 46 ohms impedance and 99dB sensitivity you might be wishing for more headroom/volume on your phone.
 
The HD25 you have has 70 ohms, but 120 dB sensitivity - I would stick with the HD25 if using the phone alone.