PANASONIC 1994 VMSS ( Virtual Motion Sound System , Brain Shaker Xtreme VMSS , for very deep vibrating sensation like night club bass feeling , ( Frequency Response: 4Hz – 25kHz , Sensitivity: 125 dB/mW ) originaly wired with a 1 kg walkman RQ-SW20 , i make headphone wireless bluetooth , with incredible vibrations sensation , cristal sound from any source , pc , laptops , mp3′s without wire ! Autonomy of my Headphone 22 hours real hours !!!! i use him , 3h/day for my Jogging for about 5 months , 6day on 7 , this prototype work very well