One of the hottest subjects in the industry right now is room correction, taking high-performance systems and tuning them specifically for the environment they are to be located in. But, how do they work? Which one is the best? EI invited those in the know to explain the benefits.
As the owner of DALI loudspeakers, Peter Lyngdorf was disappointed that customers didn’t hear the speakers they bought at their best in their homes. This led to his research into room correction for high end stereo systems in 1990. Three years later they released the world’s first full range digital room correction system.
The system was very complex to set up, but the biggest problem was that it changed the sound of the loudspeakers that were being used. The measurement process took a reading with a mic at the listening position, firing towards the ceiling. This process was then repeated across the seating area.
This process didn’t capture the sound of the speakers, so their characteristics couldn’t be preserved. The system works by changing the sound of your speakers to try and match the target curve that the correction system has stored. In a home cinema this may not be an issue, but where people have spent years finding their favourite speakers, customers were not happy that the sound of their speakers had changed.
This approach is the one all correction systems still use. Demonstrating the technology in his stores, listeners commented that all the speakers sounded virtually identical after set-up. This led to a complete rethink of their approach to room correction.
After four years research and an investment of $9,000,000, RoomPerfect was patented with 54 separate elements protected by one of the largest patents in the history of audio. RoomPerfect requires the mic to be pointed at the speakers for the first reading.
This captures the characteristics of the speakers with the addition you would expect from the room they are used in. Then the full height, width and length of the room is captured. Room errors are a three-dimensional problem so measurement across all of the room is required.
The process typically takes 15 minutes for stereo and under an hour for the largest Dolby Atmos systems. RoomPerfect is also unique in measuring and correcting the speakers with the subs so they are perfectly integrated.
In systems where dual subs are used, RoomPerfect is unique in seamlessly blending the right-hand sub to all speakers on the right of the room and vice versa. This gives true stereo bass down to 20Hz. Steinway Lyngdorf and Lyngdorf products with RoomPerfect are totally silent.
Lyngdorf created the first fully digital amplifier, the Millennium, in 1998 which reproduced music with none of the noise inherent in analogue amplifiers. Because the signal was in the digital domain, room correction could be added without the noise of extra A/D and D/A to the signal path.
While room correction is an essential addition to any surround processor, most processors add noise to a system that high quality stereo pre amps don’t, another barrier for use in systems with great stereo performance.
In the stereo world, room correction has not been accepted because the systems available add noise to the system and change the nature of the speakers. With RoomPerfect, these reservations are removed with Lyngdorf TDA amplifiers costing as little as £2,200.
RoomPerfect is included on a wide range of price points in the Lyngdorf and Steinway Lyngdorf families including the entry level TDAi1120
Tom Garret, International Sales Manager at Trinnov Audio, which delivers its Trinnov Optimizer technology.
Trinnov Audio started research on loudspeaker/room optimisation in 2003 and released its first multichannel processor featuring its Optimizer technology in 2005. The first Optimizer processor was primarily intended for studios and Trinnov built its reputation with this technology while winning the trust of some of the most demanding sound engineers in broadcast, music, and post-production studios around the world.
The Optimizer has been gradually refined over the years and is now the only ‘room correction’ system widely used throughout the production chain, from studios to some of the finest commercial and private cinemas. It is used daily in over 1,500 studios worldwide to produce some of the content you enjoy every day.
The Optimizer is also used in over 1,500 commercial theatres. Unique in many ways, the Optimizer relies on Trinnov’s iconic 3D Microphone to localise speakers and capture sound in three dimensions. This microphone is designed by and unique to Trinnov, and each one is individually calibrated for accuracy to ensure the most reliable acoustic measurement.
Indeed, because Trinnov feels nothing should be left to chance, they keep the entire signal path within a Trinnov-controlled environment (in their processor) rather than relying on external software, operating systems and audio interfaces.
The Optimizer captures a huge amount of acoustic information in each measurement and performs time/frequency analysis to better understand and characterise the behaviour of the speakers in the room. Indeed, without the time domain, frequency response alone shows irregularities in response but doesn’t provide enough information to correct the errors properly, with the appropriate method.
The highly-detailed information is then processed using Trinnov’s proprietary algorithms, providing a full acoustic analysis of the room and revealing more information than any other automatic system.
As an example, the acoustic graphs generated by the Optimizer for each measurement point include the phase response, group delay, and impulse response of each speaker, all of which are important to understand what is occurring in the room over time.
Most people understand that time-aligning speakers is important; but the point Trinnov has made since 2005 is that time-aligning frequencies is also essential for improving sound staging and transient reproduction.
This is an area where passive acoustic treatment, although extremely important, cannot help. The sophistication of acoustic analysis performed by the Optimizer may sound like overkill for the consumer world.
However, Trinnov is understandably proud of its pro audio background and believes consumers deserve no less. The Optimizer simply can solve problems that other systems cannot, and this is an area where Trinnov reigns supreme.
Fortunately, Trinnov introduced a setup wizard to simplify the initial measurement and calibration process. Trinnov has also introduced a step-bystep calibration assistant to simplify the whole process including Active Crossover calibration.
However, the manufacturer remains clear about the fact that every system is unique. Many acoustic parameters come into play, whether they are related to room acoustics, electroacoustics or psychoacoustics.
The best possible results can only be achieved by a trained ear and experienced calibrator. This fact is not specific to Trinnov but is true for any system, regardless of its sophistication.
Trinnov really shines with respect to the level of integration of the Optimizer within its products. The Optimizer does not require external equipment beyond the microphone. It takes only a few clicks to make the system sing, whether you do it locally or remotely over the internet.
Since the measurement data resides in the machine itself, subsequent tweaks are easily made, all with 64-bit floating point precision. All Trinnov products include the Optimizer technology, including the Altitude AV Processor range.
Trinnov Optimizer has been in the market since 2005
An audio system’s performance is always negatively affected by a room’s unique characteristics. The size and shape of the room, its construction, the furnishings, and other factors cause standing waves, resonances, and reflections that can colour the sound played by loudspeakers. Using proprietary algorithms developed by Anthem engineers, ARC Genesis creates custom correction curves that retain the favourable acoustic signature of speakers and remove negative room contributions.
These custom filters are then used to programme high-quality digital signal processing (DSP) technology embedded within compatible audio products. This third generation of ARC represents a major leap forward in room correction with the most comprehensive features ever.
ARC Genesis transforms the audio performance of compatible speakers or electronics to the unique characteristic of any room. Proprietary Digital Signal Processing (DSP) software works in tandem with the calibrated microphone provided with your ARC enabled product to provide an astonishing improvement to the sound you hear.
Key features include Demo Mode which offers access to the full suite of tools without having an Anthem, MartinLogan, or Paradigm compatible product connected. For products such as Anthem’s MRX audio/video receivers and AVM home theatre processors, ARC Genesis allows you to configure the assignable amp channels from within the software, making quick work of setting up your receiver for zone 2 or height effects channels.
For products such as Anthem’s MRX audio/video receivers, AVM home theatre processors, and STR preamplifier and integrated amplifiers, ARC Genesis not only optimises the performance of your system, it also lets you set up bass management from within the software.
To redirect bass to a subwoofer (below a speaker’s Crossover frequency), set the Send Bass to Subwoofer (or Low-Frequency Extension Slope) control to ‘Send bass to the sub’.
With ARC Genesis’ Professional Mode, the target curves for the system as a whole, are adjustable using room gain, deep bass boost, and tilt controls. Individual sets of speakers allow for the adjustment of high-frequency roll-off and crossover frequencies and slopes.
Subwoofers allow for the adjustment of high-frequency extension, low-frequency extension, and low frequency extension slope.
ARC Genesis also allows you to set a different maximum correction frequency for each set of speakers, up to 20,000 Hz. For example, you may want to use room correction on your dipole electrostatic front speakers up to 400 Hz and your small in-ceiling height effect speakers up to ARC’s default of 5,000 Hz.
Some devices also allow you to create multiple measurement sets (up to four, depending on the device). We recommend more than one if some significant transformation predictably takes place within the room that can alter the room’s acoustic response.
For example, take one set of measurements with a drop-down video screen deployed and another with the screen hidden, drapes up or down, doors open or closed, and so on.
You can also use multiple profiles to optimise your system; say, as a multi-channel home theatre with sub and another as a two-channel music system without a sub. If the system gets an upgrade with only one speaker being changed, you can retest just measuring the new component, you don’t have to start all over again.
ARC Genesis also allows you to examine graphs in detail and support for several languages is available (Chinese, English, French, German and Spanish). When creating multi-room music systems, it’s also possible to use Arc Genesis to compensate for all rooms in the system.
ARC Genesis recently received significant upgrades
Jakob Ågren, Head of Product Management, Dirac, creators of Dirac Live.
The Dirac Live room correction system celebrates its tenth year on the market in 2020. It was first introduced in the Datasat professional cinema product range and has since found its way into any system that aspires to be the best in room audio reproduction. Since its release it has been more or less alone on the market in being able to correct not only for the coloration of the sound (the magnitude response), but also for the phase.
While it is not conceptually difficult to correct for the phase, doing so while not introducing audible artifacts has proven much more tricky, which is why Dirac Live has been such a success with both consumers and installers; there is simply no other system that can achieve the same fidelity while maintaining ease of use. Being able to correct for the phase has several benefits.
It will improve the transient response, more accurately reproducing the harmonics in a system – this is important for all sounds, but perhaps especially critical for speech intelligibility.
Furthermore, it also improves the sound stage, the positioning of instruments in a stereo recording, and allows true immersion. Rather than listening to a bunch of speakers you become immersed in sound, the way it was intended to be by the content creator.
Dirac Live does not run using an onscreen display like room correction systems of old. Instead, you use your smartphone, tablet or PC to run the room correction software.
This allows significantly more computational power, and the calibration is partly performed in the cloud for additional compute horsepower. The Dirac Live calibration tool will connect to your equipment over your network, and you can optionally connect the microphone to your PC instead of, for instance, the AVR.
This is especially convenient for installers, who often face the problem that the equipment is sitting in a machine room somewhere, and not in the listening room, making it impractical or even impossible to perform a measurement based room correction if it requires the microphone to be connected to the AVR.
Dirac Live comes with multiple different feature levels and OEMs so end users can choose which features they want to include or use. The upper and lower frequency limits for where Dirac Live should perform room correction is end user adjustable, if desired. Between these two points the desired target response can be adjusted to achieve the optimal sound from the system.
Dirac Live also includes a measurement based multi subwoofer bass management system, called Dirac Live Bass Control. The main objective of the Bass Control feature is to reduce the spatial variations in the bass, so that regardless of where you sit, you will have the same amount of bass. This is extra useful for big installs, where the listening area is large, but also useful in your home.
Dirac’s plan for it’s Dirac Live product is to add a new and exciting feature every year, always pushing the limits of what’s possible to do, using digital signal processing and acoustic measurements.
Dirac Live is celebrating 10 years of innovation
StormAudio has been one of the manufacturers making maximum use of Dirac Live