OB-4 Speaker and radio

The OB-4 is a portable Bluetooth loudspeaker designed and manufactured by Teenage Engineering. The design combines traditional audio playback with innovative digital features through a motorized user interface that includes a digital-motion controlled volume knob and tape reel. The speaker uses four tailor-engineered elements: two 4-inch bass drivers and two neodymium tweeters, powered by a 2 × 38W Class D amplifier, delivering a frequency range of 52 to 25,000 Hz. The construction features amorphous polymer glass fibre reinforced polycarbonate and milled aluminium, creating an ultra-thin form factor that belies its sound capabilities. A flow-optimized bass reflex duct delivers deep natural bass, while the folding handle doubles as a stand and houses an extended FM antenna. The device continuously records the last two hours of audio from any source, allowing users to rewind, loop, and manipulate live sound through the motorized tape reel interface. The OB-4 represents Teenage Engineering's approach to reimagining audio playback as an interactive instrument rather than a passive device. Released in September 2020, it arrived at a time when portable speakers were largely focused on convenience and connectivity, with few offering meaningful ways to interact with sound beyond play and pause. The motorized interface and continuous recording capability transform listening into a creative act, allowing users to manipulate radio broadcasts, loop music, and experiment with ambient soundscapes through the device's disk mode. The inclusion of FM radio alongside Bluetooth and line-in reflects a commitment to diverse audio sources, while the 72-hour battery life for FM listening positions it as a companion for extended listening sessions. Today, the OB-4 stands as a statement piece that questions why audio devices should be passive. It is both a high-fidelity speaker and a creative tool that invites users to engage with sound in new ways.