professional audio, Professional recording studio, Public address (PA) and sound system accessories, including, electronic power amplifiers, pre-amplifiers, musical instrument pre-amplifiers, AM/FM stereo tuners, car audio stereo systems, stereo hi-fi systems, radios, wireless transmitters and receivers, headphone amplifiers, phono preamplifiers, loudspeakers, subwoofer speakers, headphones, wireless headphones, wireless speakers, electronic switchers for audio and video signals, ground loop noise isolators, microphones, equalizers, crossovers, noise gates, audio limiters, audio signal processor duckers, audio compressors, optical compressors, digital voice signal processors, dynamic processors, analog and digital audio signal and effects processors, audio reverb effects processors for emulating the audio of different types of rooms, audio effects processors for simulating the sound of different types of speaker cabinets, direct signal boxes, audio and digital signal switch boxes, vacuum tubes, electrical transformers, audio and video cables, and digitally stored instruction manuals, sold as a unit

Flexible, mechanically-operated doors (not of metal) with frames entirely or partially of metal; industrial rolling doors (not of metal) with frames entirely or partially of metal

Scientific and electrical apparatus and instruments (including wireless) including audio transformers, tuners, amplifiers, preamplifiers and loudspeaker systems