In our Vendor Voice articles last year, we examined how the UNIO ecosystem acts as a bridge for audio professionals working on both studio monitors and headphones, providing consistent, high-quality monitoring that empowers creative freedom. During the recent IBC exhibition, we developed UNIO further by unveiling the PRM, of which the 8550A headphones form a key element.

As part of the PRM, the 8550As are always uniquely paired with a 9320A reference controller, and together they provide an active calibrated headphone system. The 9320A controller acts as a powerful hub for managing both in-room and personal headphone-based monitoring environments, offering an intuitive and flexible solution for modern workflows.

The UNIO PRM elevates the quality of headphone monitoring so that it offers a similar capability as loudspeakers for recording, editing, mixing and mastering, and allows users to move back and forth between the two monitoring environments, with excellent translation in both directions. It seamlessly integrates our loudspeaker-based Smart Active Monitoring and GLM loudspeaker manager software with binaural rendering for headphones using our Aural ID technology. This combination allows engineers to maintain consistent audio quality across different working environments – whether in a studio, or on the go with headphones and the Aural ID App.

The 8550A Reference Headphones

We’ve taken a unique approach with our new headphone technology by ensuring that the individual calibration file of the 8550A headphones is loaded into the matching 9320A controller – making the two a unique pair. And with GLM software, this setup provides calibration of monitoring loudspeakers and headphones, enabling engineers to make confident decisions in both domains.

The 8550A headphones offer exceptional sound quality, featuring 40 mm neodymium magnet transducers and delivering a short-term SPL of 119 dB. Being a closed-back, circumaural design, the 8550A offers excellent sound isolation, enabling high resolution sound engineering even in somewhat noisy environments with over-the-ear cups providing comfort across a variety of head sizes. The headphones come with leather and velvet ear cushions, straight and extending coiled cables, and replaceable skin-touching parts, promoting longevity and sustainability.

The design principle of the 8550A is to create neutral-sounding headphones. A neutral headphone frequency response implies that the headphones reproduce audio without artificially boosting or cutting any part of the frequency spectrum, closely mimicking the sound of a well calibrated monitoring loudspeaker in an acoustically well treated room.

Creating A Neutral Headphone Experience

Now, while monitoring loudspeakers in a good room strive to deliver a flat frequency response – where audible frequencies all create the same pressure at the listening location – neutral-sounding headphones are not actually the result of a flat frequency response at all. Over the years, a lot of research has gone into understanding how the headphone frequency response should be set to create the sensation of being a neutral source of audio. When we look at this problem more closely, it becomes apparent that the precise neutral-sounding frequency response in a headphone is slightly unique to each listener. This is because the shape and size of each person varies slightly, and this gives rise to small differences in our unique head-related transfer function (HRTF), which are the acoustic features that determine how we detect direction and the colour of sound. As individuals, we have grown to thoroughly adapt to our unique HRTF.

However, the frequency response of traditional headphones does not usually follow the individual's HRTF, but is typically set to the average measured for a sufficiently large group of individuals.

Closely matching our aim to offer neutral sound character on headphones, the ‘diffuse field equalization’ finds the frequency response for headphones that will provide an experience similar to listening to a neutral loudspeaker. The diffuse field equalization compensates for the head and ear filtering effects, leading to a sound signature that simulates a loudspeaker in a realistic spatial environment. This is typically a room with a relatively low reverberation time and constant rate of sound decay across frequencies, and this therefore creates a listening experience that attempts to emulate listening to high quality monitoring loudspeakers. While this is valid on average, we all differ slightly in our HRTF, so even after achieving this equalization, our individual experience may vary slightly, calling for additional steps of personal calibration.

More recently, some proposed headphone target curves have attempted to define a headphone sound that replicates the "preferred" frequency response that balances accuracy with what most listeners find enjoyable or convincing. While this target leads to a somewhat higher level at low frequency, the curve is an average across a large number of people, again not representing the individual personal HRTF.

In order to enable accurate reproduction at a personal level, the 8550A headphones pair with a 9320A reference controller to offer tools for personal calibration. The slope across the audio frequencies can be set, in addition to two parametric filters that enable control of details in the midrange frequency response, contributing to a neutral experience at a personal level – or to align the headphone frequency response with that of a loudspeaker-based monitoring system. So, while the 8550A headphone frequency response is subjectively neutral on average to begin with, the complete PRM system offers additional tools to improve personal sonic accuracy.

Getting Personal With Aural ID

A unique element of UNIO is Aural ID technology, which further personalizes the listening experience based on the user's HRTF, enabling accurate binaural monitoring through headphones. This system replicates the spatial effects of in-room monitoring, giving users an immersive and precise audio experience on the go. 

Aural ID technology uses the external ear, head and torso shape of an individual to calculate the person’s unique HRTF. This is achieved using the Aural ID Creator mobile app which enables you to submit 360-degree video footage of your head, ears and upper body, which is then used to create your personal profile. This Aural ID Profile enables externalized rendering of audio on headphones, and the direction of audio and sound colour are both highly accurate. The subjective calibration tools in the new Aural ID 2 app provide an unmatched level of personal customization for improved accuracy. The Aural ID 2 app converts the monitor loudspeaker channel feeds to virtual loudspeakers, which are then audible in the corresponding locations over headphones. The personal calibration in the Aural ID 2 app also allows the interaction of the headphones with an individual’s HRTF to be accounted for, by allowing each virtual monitor location azimuth, elevation and level to be personally calibrated. The complete monitoring system audio colour can then be adjusted for maximum accuracy, making the Aural ID 2 app ideal for consistent mixing and mastering of audio in environments that normally could not be used for audio engineering work.

The UNIO ecosystem integrates GLM loudspeaker manager software with the Mac-compatible Aural ID 2 app, enabling rendering of immersive audio over headphones with a personally accurate listening experience. Here, the Aural ID 2 app appears as a virtual sound card that can provide the number of channels required to enable DAWs and other audio software to deliver the monitoring formats for Aural ID processing. The number of channels and how they map to the virtual loudspeakers appearing on the headphones can be configured by the user. At the moment, the Aural ID 2 app supports any monitoring system from mono and stereo to 9.1.6 channels, and from 2 to 64 input channels of audio. As the virtual monitor locations can be configured and calibrated by the user, the Aural ID 2 app is able to support most existing monitor loudspeaker layouts. Being a virtual sound card instead of a DAW plug-in, the Aural ID 2 app can accept audio feeds from any source and can be easily used with other rendering software, such as the Dolby Atmos Renderer – or can even render binaural presentation in real time for multichannel audio streams.

Conclusion

At Genelec we’ve spent decades developing and refining our Smart Active Monitoring technology to minimize the room’s acoustic influence and deliver truthful mixes that translate consistently. Now, with UNIO, we’ve set out to bring that same level of accuracy and reliability to headphone monitoring too, and this has involved overcoming significant technical challenges. We’re really excited about the possibilities that UNIO PRM – with our 8550A headphones – represents, and hopefully this article goes some way to de-mystifying the elements required to achieve the seamless integration of in-room and personal headphone monitoring.