Audiovox Acoustic Research AW827 Portable Wireless Speaker with Post Topper Included (Black) (Discontinued by Manufacturer) Single 3-inch down-firing driver for omni-directional sound; frequency response: 40Hz-15kHz Push-button, auto-lock tuning ensures crystal clear reception up to 150-feet Operates using four AA batteries per speaker Three selectable broadcast frequencies; stereo audio input Compatible with iPhone/iPod