The Blasting Brick amplifies the audio from your digital devices. Place and play your music, no Bluetooth or cables are required! The Blasting Brick is compatible with mobile phones or digital media devices that include an external speaker. Rechargeable lithium battery and charge cable included. Frequency Response:100 Hz – 18 KHz. Total Harmonic Distortion (THD) 0.2 %. Sensitivity 90 dB. Impedance 4 Ohm. 2 in 1 USB/3.5 mm audio to mini USB (80 cm)