I should have done this mod sooner! I've had the resonators for over a year, and finally installed them today. I hadn't realized how much I'd gotten used to the shelved up treble of the HD800, and the headphones sounded dark at first, but after a few minutes of listening, they sound great. What's surprising is how much more articulate the HD800 sounds with the resonators in place. This is a much bigger change than the Tyll mods I previously had (and removed in order to get a baseline for the SDR's changes), and I think makes the headphones sound better instead of kind of different.