I have recently received my 99 Noir in Peru, but sadly they've como defective. They have an unbearable distortion/vibration on the left speaker with all vocals independently of the source I use. Does Drop have customer support for this issues? They are unusable.
JorgeRI too have the imbalance on the left driver. It's much louder and bass is more boomy to a point you can feel the difference between the left and right side.
What I've done to fix this is to open up the left driver cover by removing the four torx screws and you'll see a piece of foam behind the driver. I added a piece of cotton wool behind this foam piece in the earcup and put the driver back together. I only did this to the left side. It tamed down the bass on the left and removed the imbalance to a point that it's a great listening pair of headphones now.