Sennheiser Sennhesier MM 100 Bluetooth Stereo Headset Neckband Wearing Style (504111) "mm400" Questions

Hearing from Left Side only Brand New Headphones, had about one week, now the sound is coming from left side only even when using the AUX jack Sounds defective to me.. Most stores have a 30 day return

Connection bluetooth between MM400 and Sony VAIO serie Z with Window7 not working: driver needed I dont owe one.