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Background: Dirac Live 2 – Calibration software for home use

Dirac Live 2 - Calibration software for home use: In this article, we take a look at the new version of Dirac for home use, Dirac Live 2 .x. 
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Dirac was already one of the best room correction solutions available. A thoroughly revised version now makes the software more accessible to a wider audience. That is good, because at the same time appear more surround and stereo devices with Dirac on board. Arcam, NAD and Rotel, among others, have recently embraced the new Dirac software. It can of course also be used with existing Dirac partners, such as miniDSP and Storm Audio. In this article, we take a look at the new version of Dirac for home use, Dirac Live 2 .x. 

We have written before about this software of Swedish origin, which is being built into more and more audio products, but which can also run separately on a PC. Both in the form of a background piece about what Dirac is and in the margin of tests of AV receivers such as the Arcam AVR-550 and NAD T 758 v3. Why that we now devote a longer piece to Dirac again? Because the software is now getting a major update to version 2, Dirac Live 2. What is immediately striking is that the interface has been completely adapted. That’s a bonus, but just as important is that Dirac now gets a new architecture so that it can easily be expanded and improved in the future with new modules that do something specific. The module approach sounds special, but you don’t need those extra parts to get started with Dirac Live. The software is completely functional and useful for the end user. 

What is Dirac?

A first question is of course: what is Dirac exactly? Simply put, Dirac is software that allows you to tackle the acoustic reproduction in a room so that your music and movie sound sound better. In most cases this is really necessary. You rarely come across a room without problems and speakers that are really perfectly positioned. This may be a dedicated cinema space designed by an expert. A typical living room or home theater almost always needs some software help.

Dirac is thus a competitor for the calibration software found on AV receivers from Denon and Marantz (Audyssey), Yamaha (YPAO), Onkyo and Pioneer (AccuEQ), Sony (DCAC), and others, and stereo devices such as the Micromega M- One M150 (MARS) or the Lyngdorf TDAI-3400 (RoomPerfect). It is certainly not the only solution to make sound sound good in your room.

Dirac Live 2 - Calibration software for home use

For the sake of completeness, we should mention that the Dirac software comes in other forms as well. For example, it is used by car manufacturers such as Bentley (together with Naim), BMW (in the M series), Volvo and Rolls-Royce. Because Dirac has a strategic collaboration with Harman, we suspect that this list will soon become much longer. After all, Harman is the most important player in automotive audio and systems, with partnerships around brand names such as Bowers & Wilkins and Bang & Olufsen. Dirac is also working hard to become a big name in the mobile segment. It has all kinds of software to improve the audio reproduction via smartphones and tablets. Finally, the company is also looking into virtual reality, with solutions around 3D Audio. It is an exciting company that has recently succeeded in attracting a lot of venture capital.

A different approach

A typical example of an acoustic problem that you can tackle with Dirac is a so-called room mode: a low frequency that is amplified by the shape of your room. This creates a woolly bass that takes away detail in the bass and possibly also makes things like dialog and fine surround effects disappear. With an AV receiver, a typical calibration function will do one more thing: measure the distances between the different speakers and the listening position. After that, the software eliminates the differences in distances. This is done by slowing down speakers that are closer compared to speakers that are a little further away. As a result, the sound effects and music of a soundtrack arrive at your ears at the right time. That distance compensation is really useful. After all, a situation with less optimally placed speakers often occurs in living rooms. For example, the stereo speakers are often closer than the center placed just below the TV screen. In summary: typical calibration software intervenes in the frequency domain (by amplifying or suppressing certain frequencies) and in the time domain (by delaying speakers if necessary).

Dirac Live 2 - Calibration software for home use

Dirac does all this too, but takes it one step further. It is also concerned with impulse response. It is not entirely correct to say that this is the reverberation of a tone, as perceived at the listening position, but it does help to understand the impulse response. Due to the properties of speakers and the room, a tone is not just played. Certain frequencies may arrive a little later at the listening position, for example because basses are still vibrating or because there are strong reflections. It can also come through the speaker. A speaker with multiple drivers will – if it is well developed – put together in such a way that the frequencies coming from the tweeter arrive at your ears at the same time as the mids and basses. But this phase coherence is not easy to achieve,

What’s new Dirac Live 2?

Dirac was really ready for a new version. The software dates back to 2011, which you immediately saw in the interface (see the old versus new interface below). It was clearly designed by engineers, not usability experts. As a result, the threshold to use Dirac was higher than with other calibration software. That was the case anyway because you needed a computer to take measurements, instead of just plugging in a microphone on an AV receiver and then following a step-by-step plan.

Dirac Live 2 - Calibration software for home use

We will take a closer look at the new interface of Dirac Live 2 .x in a moment. But when it comes to making the software more accessible, we can already say that the mission has been accomplished. Thanks to the clear menus and the graphic elements, for example, it becomes clearer how to measure. Important, because performing the measurements according to the rules is the key to a good correction at Dirac. Completely new is that the software can now also be used via a mobile app – although there are limitations compared to Dirac Live on a Mac or Windows machine.

The core of Dirac, the Dirac Audio Processor, has remained largely unchanged, says Dirac. The company does not solve an incredible amount about its algorithms, perhaps because it fears competitors running off with knowledge. Dirac does say that the new software has a modified phase correction algorithm that improves stereo reproduction. The Audio Processor used to only look at the phase coherence of individual speakers, now it is also measured in pairs. This makes it possible to create filters in which the phase response of a stereo pair is matched.

Testing with the new Dirac, Dirac Live 2

We tried the new Dirac version extensively while testing the Arcam AVR-850 . It was also intended to test the impact for stereo using the brand new NAD C 658 that has been in our test room for a while, but unfortunately the firmware update that added the Dirac function was delayed for a while making this impossible . However, the update would be available in the foreseeable future. So be sure to read the review of this streaming preamplifier from NAD on Hifi.nl soon. The NAD is a special thing – and we suspect that the combination of BluOS / Roon and Dirac will make it a much sought after addition to the music systems of many hi-fi enthusiasts.

We also foresee a test of the NAD M10 a little later in the spring, a compact but high-quality stereo amplifier with Dirac built-in. For this article, we ran all tests with the Dirac app on a MacBook Pro and on a Microsoft Surface Pro. It was also installed on an Android tablet and an iPad, but those mobile apps did not find compatible audio devices. We asked Dirac why this is, but unfortunately the company did not respond to our questions. If there is a response, we are happy to add it to this article.

Get started with Dirac Live 2 .x

Dirac works in two phases: measuring and creating filters. You take measurements in several places (nine are recommended). You need a measuring microphone for that. If you do not have a suitable device with a Dirac-compatible device, we would recommend a USB measuring microphone. We use the UMIK-1, a measuring microphone with USB connection that costs around 80 euros. You can buy a more expensive model, but Dirac himself also likes the UMIK. Which microphone you purchase, it is important that an individual calibration file is available from the manufacturer. This file describes the properties of the microphone, so that they are not included in the measurements.

Broadly speaking, measuring with Dirac Live 2 .x remains the same as before. The software first detects whether there is a compatible device on the network, after which you can choose the microphone. During the measurement itself, an extensive series of test tones is played by each speaker. A surround setup can involve a collection of speakers with very different sensitivities, which is why you must first find a volume level that is suitable for all speakers before measuring. You do that in a screen that is much brighter than before with Dirac Live 2 .x. The method is simple: you can play white noise with each speaker, so you can adjust the volume so that a bar indicator turns green (not too loud, not too quiet). To match the speakers you have a master volume and a mic gain slider, but also an adjustment per channel. It is best to start by properly adjusting the least sensitive speaker (perhaps the rear speakers or the height channels) and then the more sensitive speakers (possibly left and right at the front). The sensitive speakers will immediately receive a signal that is too loud, but you can then reduce that at speaker level.

Dirac Live 2 - Calibration software for home use

Measuring itself is also much more user-friendly than before. You can choose to measure broadly or more focused (depending on whether you listen with 1-2 people or an entire family). The app now clearly shows where to measure and it is possible to choose which measuring point to measure when. There are thirteen measuring points in total, but you can also work with less. You can always go back and take a measurement again.

According to Dirac, the distance between the measuring points is not crucial, but it is important that you always maintain the same distances. Unfortunately, the 3D drawing in the app does not make it completely clear that each measuring point is equidistant from another. A tip from a Dirac instructor we once received was to indicate the measuring positions in advance with a piece of masking tape. This way you can be sure that you always measure in the right place. A microphone stand with a loose arm is also handy. If everything is correct, you will be measuring for about 20-25 minutes with a 5.1.4 setup. Background noise can be annoying, so it may be better to repeat a measurement if a large truck accidentally thunders past during the measurement.

Create filters

You then use your measurement data to create a filter that is sent to your audio device after processing. With the Arcam AVR-850 you can forward one filter, but there are also devices with slots for multiple filters. But before you make a filter, you still have some work to do. A graphic representation shows the test data as a frequency display and as impulse response. You cannot adjust anything to the latter. Dirac optimizes the impulse response itself. However, you can manipulate the frequency response

The software will propose to adjust the measured frequency response so that it fits a target curve – ie a frequency response – that Dirac has devised. Everyone has an opinion about Dirac’s target curve; the consensus seems to be that the standard is too neutral and drastically affects the character of the speakers. Some audio manufacturers, such as NAD, therefore offer an alternative curve that will adjust the playback to their home sound.

But you can also get started yourself by adjusting the target curve. You do this by creating a point on the target curve and increasing or decreasing it by a number of decibels. You will notice that you do not adjust that one frequency, but that you make a hill or a valley that also affects surrounding frequencies. You can of course create multiple correction points. This way you adjust the curve (the pink line on the image) in its entirety. (In theory you could make a sharp peak, but in reality the speaker driver could not just reproduce that one frequency much louder because of its physical properties.)

A choice that some make is to have Dirac only function up to a certain frequency, for example 500 Hz. After all, room problems, such as room modes, are usually below this point. The advantage with this approach is that the character of your speaker is preserved in terms of detail reproduction. An alternative is to bring the target curve closer to the measured data at higher frequencies. You may only partially tone down unwanted peaks, but you will retain the character.

Dirac lets you adjust the target curve per pair of speakers, with the exception of the center speaker and the subwoofer. Logical, because your surround and height channels are always a pair and should be the same type of speakers. But if you wish, you can also adjust individual speakers. This may be desirable, for example, if you have a sub-optimal setup where, for example, one speaker is in a bookcase or closer to a wall than the other speaker in the pair.

In short, this aspect of Dirac is quite complex. You have to be quite an expert to immediately create a filter that really sounds the way it should and that sounds the way you like it. Both things are not always the same. In practice, you will create filters several times as part of your quest for the best sound. An audio device that has slots for multiple filters and allows to switch between filters while listening is really handy.

Fortunately, you don’t always have to measure again if you want to create a filter. You can use the data from one measurement session to create as many filters as you want – if you have thought of saving the data. That is why we recommend that you do that measurement really well and then save it. The measurement is the foundation – do it properly and thoroughly, and you can experiment with filters afterwards.

And the results? You can read more about it in the tests of devices with Dirac. But in summary: time and time again we hear a noticeably better result. Tighter – so a better impulse response – and often more detailed and in balance. We find Dirac very strong towards surround. By addressing the speakers and the room, the positioning of effects in the room becomes more accurate. A moment that stayed with us was the race in ‘Ready Player One’, a fragment that we have always used in surround tests in recent months, on a 5.1.2 setup. During that race you often hear coins rolling (the money that players drop when they die in the virtual world); suddenly we heard that sound right behind our heads – even though we had no surround back speakers set up. It was so realistic that we really looked up – even though we’ve watched this clip dozens of times. 

Conclusion of Dirac Live 2

In our opinion Dirac remains one of the best – if not the best – solution to improve sound reproduction. The fact that more and more manufacturers are integrating the software into their audio devices proves that we are not the only ones with that opinion. It remains a solution that requires time and knowledge to use correctly. Measurement takes longer and is more error prone than most calibration functions on AV receivers . In addition, adjusting the target curve requires insight and patience to do well. But all that effort is really worth it. Dirac then provides a better, tighter and more transparent sound than before. Provided you create a good curve that tackles the problems without affecting the character of your speakers, that speaks. Indispensable for the critical listener, we believe.

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