I think it's more a fine tune about drivers or completely other drivers swap (or from silver plated to OFC cable swap, maybe) because the docomo shells have nothing extraordinary (from first sight), they use standard MX500 shoes cotton (damper?) tuning on the behind stock holes which have extremely low porous air to pass. But I will remedy about that soonYeah, those Docomos are more than decent earbuds. The Black version are are more audiophile while the white ones has more mid bass.
Not sure if its due to different drivers or just more damper on the the whites. But both sounds great.
Btw, I forgot to say that for a normal use, PK1/2 drivers snaps already well (not by much) on those docomo shells, so for DIY tries, this is perfect (no need to use glue if care enough).