Although being founded in 2007, the history of Four Audio’s products goes back to the mid 1980s. At the Institute of Technical Acoustics at RWTH Aachen University, first attempts to use FIR filters for loudspeaker equalization were made. At that time, due to limited processing power, relatively short FIR filters and a lot of special FIR-processors had to be used. With funding from loudspeaker companies, several researchers were involved in optimizing performance considering processing power as well as signal quality.

In the early nineties, the predecessor of the HD2 was released and sold successfully by the involved loudspeaker companies. The concept of generating steep crossover filters free of phase distortion and the ability to reproduce sound with almost perfectly flat amplitude response and overall linear phase based on the complex equalization of measured loudspeaker transfer functions was then made commercially available for the first time.

In 1997, precision parametric EQs and the option for cross-over design using IIR-filters with double precision processing were added.

A part of the researchers were eager to commit to the project even after they left university and spent a lot of their time with developing a second generation of the loudspeaker controller being more flexible and having improved communication abilities.
After fruitful discussions with loudspeaker manufacturers, 4 of the researchers decided to found a company for developing and distributing the controllers as well as audio and acoustics measurement software and hardware combining expertise in soft- and hardware development, signal processing, audio and acoustics measurement technique, loudspeaker design and sound installations.

Parallel to these developments, Monkey Forest evolved from being a laboratory tool for measurements and signal processing to a full-blown audio and acoustics measurement software with manyfold options for impulse response measurements, room acoustic evaluation, microphone calibration, Thiele-Small parameters, distortion measurements and many more.

The successor WinMF was launched 2012 and replaced Monkey Forest. WinMF is by now being used by countless companies, developers and consultants, e.g. for room-acoustic measurements, speaker development and quality control in series production.

In 2008, the ELF robot for measuring 3D loudspeaker directivity was added to our product portfolio and has since been sold successfully to many companies throughout the world. It is being used both as a research tool and a tool for series measurements of loudspeakers to create balloon data. As far as we know, there are no competing products available until today.

As a companion, the ANT – an ultra-flat, high torque turntable for 2D speaker measurements was developed in 2018 and is available for sale.

After becoming integration partner for Pascal amplifiers, our latest product, the DSP powered plate amplifier series PPA was developed, combining our knowledge in IIR / FIR filtering, crossover design, sophisiticated limiter concepts as well as good design of housing and intuitive user interfaces.

In a government-founded project, a new beamsteering approach together with complete MCU/DSP amplifier electronics, PC GUI software and a leading edge demonstrator line-array was developed within 30 months. Together with a multi-channel, IC-based amplifier module, this formed (and still forms) the basis for several successful OEM projects.

A complete range of beam-steering columns for speech and music together with additional subwoofers was developed to demonstrate the quality of our developments and to form a basis for rapid prototyping.

Besides this, several wave-field-synthesis systems were equipped with our modules, e.g. at the HfMT and HAW in Hamburg, the Humboldt-Forum in Berlin or the new building at the Royal Conservatoire in The Hague, Netherlands.

Today, our long-term experience in practice as well as good contacts to the loudspeaker industry and universities is an inspiration for improvements of our products as well as for new ideas.