H. J. Leak & Co. Limited was founded in London in 1934 by Harold Joseph Leak. They specialised in manufacturing audio components, but were most well known for their amplifiers and loudspeakers. With the help of Ted Ashley, the company became a market leader of affordable but high performance home audio equipment. They developed amplifier technology, loudspeakers, pickups and turntables.

During the Second World War, like many audio equipment manufacturers during this time, they turned to public address systems. This developed a new expertise in loudspeakers for the company. During the 1940s, they used this new expertise to pursue hi-fidelity systems which proved to be very successful for them. However, during the Second World War, their factory in Shepherd's Bush was destroyed which led them to move to the new Westway factory estate, Brunel Road, London.

In 1945, the company released their LEAK Type 15 amplifier which became known as the original 'Point One Amplifier', and in 1948, they released their LEAK TL/12, their first hi-fidelity piece of equipment. Due to the marketing endeavours of H. J. Leak which involved a tour of presentations to show a comparison between live and recorded music through their hi-fi system, the LEAK TL/12 became a global success. It became a BBC standard in 1951 and was adapted for the BBC to incorporate input attenuation and a new balancing transformer.

The company's success continued throughout the 1950s, releasing many new amplifiers, and into the 1960s introducing their range of loudspeakers with their massively successful LEAK SANDWICH introduced in 1961. During the 1960s, the company moved to the Downham Market factory in Norwich due to the high demand for the LEAK SANDWICH loudspeaker and the diversification of their product portfolio.

In 1969, H. J. Leak retired and sold the company to the Rank Organisation. Although the company continued beyond this date through the Rank Organisation, it began to face increasing overseas competition and eventually succumbed. In 1989, H. J. Leak died, and in 1996, the Downham Market factory was demolished. This was the end of the company.

However, in recent years, the company was acquired by the IAG Group and in 2020, they returned. They have started reproducing their classic styles of home audio hi-fi equipment and have released the LEAK STEREO 130, and the LEAK CDT, the first digital CD playback device.