Koss Porta Pro

The Porta Pro is a pair of small, open on-ear headphones built around a split headband: two thin bands of steel arch over the head to a pair of light plastic earpieces, each faced with a round foam cushion. A switch sets the fit light or firm, and the whole thing folds down small enough for a bag or a pocket. It weighs very little and looks, as What Hi-Fi? put it, as though it comes from the 1980s, because it does.

Its maker invented the category it sells in. In 1958 John C. Koss and the engineer Martin Lange showed a stereo headphone, the SP/3, at a hi-fi show in Milwaukee; until then headphones had been used almost only for communications. Other manufacturers soon copied it, but by the 1970s Koss dominated the market, with Telex its main rival. The Porta Pro came in 1984, according to the company, as a headphone for listening on the move.

It arrived at a bad moment. Koss had spent the early 1980s trying to diversify into other electronics, lost six million dollars, and filed for bankruptcy protection in 1984. It came out of Chapter 11 the following year, and the headphone it had launched in the year of the filing went on to become, in the company's words, one of the most popular headphones in the world.

Koss has since added versions with a microphone, with a detachable cord and, from 2018, with no cord at all, presenting each as the same headphone brought up to date. The wired original is still sold beside them, with its 3.5mm plug, its foam cushions and its limited lifetime warranty, and at around thirty pounds it remains one of the cheapest objects in this catalogue. What Hi-Fi? found it a great deal of fun, and very hard to beat at the price.