Tuneslover
Headphoneus Supremus
I did the same and I agree. I know some are against it, strongly against it, but I like what I hear.
I put the Dekoni fenestrated sheepskin pads on my HD650's and am loving the sound
I put Dekoni Elite Velour pads on my HD650 and they sound very good with my detailed and bright sounding SMSL SU-8 and Jotunheim (all 3 in balanced mode). The Dekoni pads improve the bass but tend to slightly darken the overall soundscape which to me compliments my chosen DAC and AMP. I also have the HD6XX (with stock pads) which sound noticeably brighter than the HD650 with Dekoni pads, however the HD6XX sounds perfect (to me) with my Schiit Modi MB and Lake People G109S (slightly warmer than neutral sounding amp).
My point, the HD650/HD6XX can sound good (or bad) depending on the equipment they are being mated with. Also, pads are a worthy mod to tailor the sound you are seeking. Above all, flattened Sennheiser stock pads can take the life out of music. When you start questioning why your HD650/HD6XX don't sound as good as they once did then consider replacing the pads.