... amplifier- Master volume and independent adjustment of each individual speaker volume - Fast separate microphone design(HDA-51A ) ... Headphones- The rear speakers: 2X30mm, 32Ω- Front speaker: 2X40mm, 64Ω- Surround sound speaker: 2X30mm, 32Ω- Bass: 2X40mm, 8Ω- Pre ... frequency response :25-18000Hz- Surround sound Frequency response :100- ...