What is Dirac Live Room Correction?

Optimise your room's acoustics

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What is Dirac Live Room Correction?

When it comes to setting up a sound system, the biggest impact to the audio quality comes from the room itself. No matter how good or expensive the equipment, a challenging environment can result in poor sound quality.

There are numerous methods of mitigating a room's negative effects, from optimal speaker and subwoofer placement, to using absorption panels, diffusers and bass traps. There's no doubt that carefully installing speakers and subs in the best locations will help eliminate certain room issues, but using panels and diffusers can get expensive and intrusive.

These days the most effective way of addressing the impact of a room is to use some form of room correction software, and one of the most popular is Dirac Live. This particular system has been licensed by numerous mid-range and high-end manufacturers and integrated into their products. These companies include Arcam, Emotiva, Datasat, Focal, Monoprice, miniDSP, NAD, Rotel, Storm Audio, Wisdom Audio, JBL Synthesis, and Thetal Digital.

What versions of Dirac Live are there?

There are two variants of Dirac Live aimed at two different markets: one for the home market; and another for the professional audio market. Both versions share the same Dirac Live room correction calibration tool, with the key difference being that the professional audio/studio version includes an audio plugin, and therefore does not require compatible hardware to store and apply the filters like the home version does.

The version of Dirac Live aimed at home audio market currently has two key features: Room Correction and Bass Control. For both of these features there are tiered offers, leading to variations in Dirac Live's capabilities. For example, when using the room correction feature, end users can choose to upgrade from limited frequency range correction (Limited) to full frequency range correction (Full). For the bass control feature, end users can choose to upgrade from single subwoofer bass management (Limited) to multiple subwoofer bass management (Full).

What does Dirac Live seek to achieve?

Dirac Live aims to enable users to customise their acoustic experience, ensuring that their sound system performs at its best with minimum impact from the listening environment.

Dirac believes that the reproduction of transients is critical for a truly natural and transparent sound. For example, the stereo image is critically dependent on the time-domain differences and similarities between the sound at the left ear and the right ear. As such, Dirac Live's impulse response correction improves the depth, the positioning and distinction of individual voices and instruments.

How Dirac Live basically works:

The end user installs software on their PC or smartphone (available on Windows, MacOS, Android and iOS) to connect to a Dirac Live-capable system over a network. They then follow the on-screen instructions, allowing them to perform the set up procedures, which include selecting the device, selecting the recording device (including any calibration file for the microphone), setting the calibration volume, selecting the speaker arrangement, taking the actual measurements, designing the filters, and exporting them to the device to create the desired sound.

Measure: The user takes measurements of the room and the audio systems with a microphone (either provided with the device or bought from a third-party) by following the instructions in the Dirac Live calibration software. Dirac Live uses several measurement positions (typically 9) in the listening room, making it possible to accurately locate and correct acoustic problems. These measurements are presented in a clear and easy to interpret graphical interface.

In terms of the impulse response, this means optimisation of the direct wave and very early reflections. Generally, at higher frequencies there is less consistent time-domain behavior. Dirac Live room correction automatically finds consistent problems in a frequency-dependent way and corrects for them. After addressing consistent time-domain behavior, there may still be some late reverberation in the room that causes subtle colouration. Dirac Live corrects these in the frequency domain to achieve just the right resolution.

Filter design: The user then adjusts and sets the desired frequency response using the breakpoints and target curve feature. However, the user doesn't have to do anything with impulse response correction, because that is carried out automatically. The software can show the measurements before and after the application of the filter, either for each individual speaker and subwoofer or all together as a system.

Why is it that the same frequency response can sound so different from room to room? The answer lies to a large extent in the time-domain aspects of the measured frequency response, as well as critical differences in the spatial (angular) domain. By addressing time-domain problems as such, and not as minimum-phase spectral problems, frequency response correction becomes more effective. After conducting time-domain correction, Dirac Live treats the spectral colourations in a room. By paying particular attention to the variations across different measurement positions – not just the average – Dirac Live makes sure not to overcompensate.

What is Dirac Live Room Correction?
Dirac Live impulse response

A loudspeaker’s impulse response affects clarity, detail and all spatial aspects of the sound. Dirac Live corrects the impulse response throughout the listening area, not just at a single point. By focusing on consistent problems across the measurement positions and correcting only these anomalies, Dirac Live can achieve a faster decay time. Typically, the power ratio between the direct wave and the tail (later-arriving echoes) is improved by 6 dB or more, representing a vastly improved overall sound.

A flat frequency response does not necessarily sound neutral due to the ratio between direct and reverberant sound and the frequency-variable propagation loss. Dirac Live can’t remove late reflections, because they change too much between different positions. Therefore, a slight roll-off is often appropriate when listening at a distance. The Dirac Live algorithm suggests a target response appropriate for your listening environment and speakers, which you can of course adjust to your taste using the simple graphical interface.

Export filter: The user then exports the filter they have created into the compatible hardware or audio plugin.

Apply the filter: The filter is then applied to the audio signal via the hardware (Dirac Live for Home) or audio plugin (Dirac Live for Studio), and adjusts the frequency and impulse responses to eliminate the more egregious aspects of the room.

The beauty of Dirac Live is that you don’t have to be a signal processing or computer expert to enjoy its benefits. All of the measurements, processing and correction is automatically managed by the audio calibration software, making it easy for all kinds of users. All you to do is position the microphone and press “Play” – the software wizard will take care of the rest. Advanced users are free to edit the target response as desired using a simple graphical interface. Otherwise, just press “Optimise” for immediate results.

What’s Bass Control and how does it basically works?

Dirac calls this feature Bass Control, instead of bass management, because it is fundamentally different from simple bass management. The Dirac Live bass control feature works by co-optimising all the speakers and subwoofers in the same system. The speakers, subwoofers and the room are all regarded as a complete system.

To ensure that the system’s bass reproduction is accurate, and the performance is the same at all locations in the room, it aligns the phase between the speakers in correlation. In technical terms, Dirac Live Bass Control reduces the spatial variability of the frequency response in the lower frequencies when more than one subwoofer is available. It also reduces any out-of-phase behaviour between paired speakers in a frequency band around the crossover point. The Bass Control also reduces out of phase behaviour between the full-range speakers and subwoofer(s) in a frequency band around the crossover point.

What makes Dirac Live different from the competition?

Dirac Live room correction uses mixed phase technology with advanced impulse response and phase correction. This is one of the main features in Dirac Live’s room correction software and enables Dirac Live to deliver impressive room correction.

There's a look-ahead buffer that enables impulse response correction. In addition, minimum-phase and linear-phase room correction filters can’t physically optimise the acoustic impulse response in a room. At best, they can minimise problems caused by the application of a filter. Room-acoustic responses are non-minimum-phase, which is why Dirac Live uses mixed-phase correction.

Most other room correction systems use minimum-phase, which means they try not to add any time-domain distortion, whereas Dirac Live actually reduces time-domain distortion. Mixed phase technology enables Dirac Live to address some of the key room acoustic problems other solutions struggle to address efficiently. The results are audible in terms of imaging, clarity and bass tightness.

For in depth knowledge about the mixed phase approach, you can read an article written by Dr. Mathias Johansson, CEO and co founder of Dirac.

Traditional EQ systems use IIR (infinite impulse response) filters for the lowest processor usage, and many room correction filters use FIR (finite impulse response) for ease of implementation and sound optimisation. IIR and FIR filters both have their pros and cons. Dirac Live uses a proprietary filter structure that achieves maximum performance at much less processor usage than regular FIR filters. This filter structure also has improved numerical properties, so it doesn’t produce any digital noise, and thus achieves enhanced sound optimisation.

It is also worth to mentioning that although Dirac Live is sophisticated and delivers a high level of performance, it is very easy to run with its intuitive user interface, visual filter design feature and step-by-step guide. This, together with its leading performance and capability, makes Dirac Live attractive to many processor and receiver manufacturers. It also makes it a great choice for consumers of any kind, whether they're AV enthusiasts or average users. 

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