Audio Advent Day 24: How DIRAC Works

Having attended multiple DIRAC training courses and completed over 100 Dirac calibrations on many systems, I have a wealth of practical experience in the day to day uses of Dirac.

The first and most important part of any DIRAC set up is to the get the basics of your system right before you even start to use the software.
To start off, set up your system to the ITU standards for home cinema systems, which is the basic standard to which all multichannel mixing studios adhere. This means that any engineer can travel to any studio and expect the system to be set up in the same way. It is easy to replicate in your own system with a simple chart and a laser guide to help you get all your speakers toed in the same amount and the same distance away from the listening position as each other.

Secondly make sure all your speakers are level and if they are floorstanders that there is no wobble, and that they are making good solid contact with the floor underneath your carpet if you have any. If you are using standmount speakers then make sure your stands are filled so they are inert but not totally dead and are again nice and level.

Thirdly, make sure as much as possible that none of your signal cables or speaker cables are wrapped around any mains cables and that all your cables are running in the right direction. Try to make sure that all your big power supply units are as far away as possible from your important source components.

These are all very simple things to look at but can achieve a surprising step up in performance in your system without spending a penny.

DIRAC as a room calibration tool is an incredibly powerful piece of software and DIRAC Live 3 is the latest incarnation, but it's only as good as how well you know the software and how to achieve the soundstage you are looking for whilst retaining the things you loved about your system before applying DIRAC.
Paying attention to the measurements is key and the first measurement is always the most important as this is the basis to which all the other measurements are compared.

You want to try and get the noise level in the room as low as possible, so turn off your projector if you're using one, any aircon units should be switched off as they are very noisy, and anything else you can think of that would cause a coloration to the measurements. If the calibration mic can hear it then it is going to affect your measurements.

Once you are taking your first measurement if anything noisy happens during the process, it's best to just abort the measurement and start all over again.
In the case of most DIRAC set ups now I always use the sofa in the wide configuration mode which takes 17 measurements, in larger systems for example a 5.1.4 system this means the system will run through 170 different measuring signal sweeps so make sure you give yourself plenty of time to do your DIRAC set up!

I use an XTZ calibration USB microphone that's significantly more accurate than the microphone that will come in the box with your DIRAC capable amplifier and certainly helps achieve the best results.

With the newest version of DIRAC it autosaves your project pretty regularly but it's still best to save once you have completed all your measurements so you have a starting point to come back to if you want to do a different calibration.

Now you are ready to start designing your EQ curves for your system in your room.

If a room is generating plenty of energy below 50hz this is very much like free information that we want to keep, as it will make the system sound big and strong. If, for example, there is a significant peak at 130hz this is the room reacting badly to the speakers in the room and could swarm the room with muddy bass so this is something we want to use DIRAC to help manage.

Some speakers have a nice 2k to 5k peak which is the characteristic of the tweeters in particular brands of speakers that make them sound interesting and have plenty of detail. If we followed DIRAC's standard speaker curve this would try to make the speakers sound like the perfect speakers in the perfect room and would in essence take away one of the characteristics about the speakers you chose since you liked the presentation of them. So we have to work with DIRAC software to keep this tonal characteristic in place or they wouldn't sound like your speakers anymore.

Another thing to bear in mind with DIRAC is the high shelf cut off. This is where the software thinks your speakers will start to roll off at the high frequencies at about 10khz, but many good speakers will go over 20khz so making sure you pay attention to following the roll off of your speakers is the key to a nice open sound stage.

Atmos speakers are something to look at quite carefully as you often need to be careful about how much bass information is sent to them. Even if you're using ceiling speakers and they are a full range speaker, if you give them too much bass information then they can start to agitate the plasterboard in your ceiling. You will often be able to tell this is happening when you do your measurement tone sweeps as it will cause your ceiling speakers to buzz at low frequencies. This is again something that DIRAC has the power to help you deal with in its low shelf cut off.

As I'm sure you can tell by now DIRAC is an incredibly powerful piece of software and in the right hands and following good basic principles with the set up of your system can achieve magnificent results with a more focussed soundstage, better dynamic control and greater detail.

DIRAC also does a huge amount of work in time alignment and phase control, this in essence is how well your speaker recovers after moving its drive unit and then ready for the next sound it's going to produce. DIRAC helps the speakers recover faster and deal with post impact distortion so that the speaker is ready for the next sound it has to produce. This will often help uncover more detail and lost information.

A great example of this is Dolby's own Atmos demonstration disc where there is a track called Rainstorm. By the time you have used DIRAC and got your system calibrated it sounds as if there are twice as many raindrops as to when you have DIRAC turned off.

If you have a DIRAC capable amplifier or you are thinking of getting one, have a look at the new Arcam range of amplifiers that we have taken into stock recently.

If you would like to chat about room calibration or simple set up tips then please feel free to drop us an Email and I would be happy to talk to you about DIRAC and system set up, we will also be offering a full DIRAC calibration service.


Happy DIRAC'ing 

John Nelson (General Manager)



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