I have given a try yesterday to DIRAC. I'll not hide it was not conclusive, but it's not due to the software itself...
I'll just share the few impressions I had on the program, although I didn't go through all the process.
Registration is easy, download pretty fast (around 30-35 MB).You must make sure your computer is connected to the internet, as it checks permanently you are a registered user when activating your license, but also when measuring the room! Rather than that, installation is hassle free.
Surprisingly, like ARC 2, the package consists into two softwares - one for measurement (DIRAC Live Calibration Tool), and the other one for managing the filter correction (DIRAC Audio Processor). This split was understandable for ARC 2, since the correction must be used under a VST host, but it was a bit more difficult for me to understand it with light and standalone DIRAC.
ARC 2 is stereo only. DIRAC allows more flexibility - up to 7.1 and even more through manual configuration.
Measurement in itself it rather easy. you have the choice between three configurations - chair, soda and auditorium. I selected the sofa and went for the 7 measurements -
To be noted unlike ARC 2, which generates "plops" into your speakers, DIRAC is using this deafening pink noise. Process is done fairly quickly. I used my Behringer ECM8000, but you can used whichever microphone you want (including USB ones). To be noted my microphone is not calibrated, and DIRAC was proposing calibration files for the XTZSOUND Pete was mentioning only.
Measurements are quite interesting -
... to be compared to what I got with ARC 2
A lot of similarities between the two measurements, as you can see - what makes it difficult to compare is DIRAC consolidates both channels on one graph whereas ARC 2 is showing two curves.
Process is then exactly like to ARC 2: you build your own correction curve, either by default - as suggested by the software - or by implementing some modifications in the "target" curve. As for me, I tried without any modification -
You will notice the default target curve (orange) is not flat - it boosts bass frequencies, and tends to minimise treble ones. This is precisely what I have done with my ARC2 target by the way, after a few experimentations - a real flat curve feels lifeless to me. Correction (in green) looks graphically as impressive as the one obtained on ARC2 (herebelow in white)
Alas, I cannot go any further. I didn't want to affect the Reaper + ARC2 setting, and obviously, it was preventing DIRAC to work properly - when I tried to listen to the sound after correction under DIRAC, it's as if nothing had been done. Most probably I've done something wrong for setting the DIRAC Audio Processor on my Mac. I have the feeling though the result must be very similar to ARC2, considering all other aspects are alike. By any means, it's worth trying for those interested to explore the acoustics correction world - no trial is possible with ARC2.