In‑ear “Pipe Phone” Earphones HP-V21

Compact in‑ear stereo earphones featuring Aiwa’s “Pipe Phone” acoustic system. The HP‑V21 uses 1.2‑inch (30 mm) U‑shaped bass resonator ducts to enhance low‑frequency performance, marketed under the POWER BASS label. The model includes an OFC (oxygen‑free copper) cord and a mono/stereo switch for compatibility with portable cassette players, radios, and dictation devices. Right‑angle 3.5 mm plug. Supplied with foam earpad covers.

Technical Features

• 30 mm U‑shaped bass resonator ducts
• POWER BASS tuning
• OFC cord
• Mono/stereo switch
• In‑ear “pipe phone” acoustic design
• L/R marked housings
• Right‑angle 3.5 mm stereo plug

Notes

Likely sold as an accessory for Aiwa portable cassette players and “Sports” series units. Not listed in main Aiwa headphone catalogues; appears to be a region‑specific or bundled model.

Difference from HP‑V14

Although the HP‑V21 shares some external styling cues with the HP‑V14, the two models are fundamentally different. The HP‑V21 is an in‑ear “pipe phone” earphone using internal bass‑resonator ducts and designed for direct insertion into the outer ear, while the HP‑V14 is a lightweight supra‑aural on‑ear headphone with 30 mm drivers and a headband. The HP‑V21’s mono/stereo switch, resonator system, and earbud‑type form factor clearly distinguish it from the HP‑V14’s conventional on‑ear design.

In questo link sono elencati 970 modelli, di cui 921 con immagini e 182 con schemi.
Elenco delle radio e altri apparecchi della Aiwa Co. Ltd.; Tokyo