CES 2017: DIRAC VR Dynamic 3D Audio Rendering System
Man, is there a lot to talk about here. First of all, I think we're still a few years away from really convincing 3D audio on headphones. There are still too many unknowns that need sorting throughpersonalized HRTFs; better headphone transducers; how to economically get all number crunching with head movement in order to commercialize it. To my mind, any solution out there right now will be largely incomplete, bleeding edge technologies. Previous to CES, that idea tainted my expectations; I really didn't think I'd hear anything really impressive when it came to 3D audio. I was wrong.
Mathias Johnsson, CEO, explained their new DIRAC VR system in quite some detail. Outwardly, it was just a laptop and some electronics connected to a Sennheiser HD 650 with a head tracker mounted in the headband. Inwardly, meaning all that software running on the laptop, abundant numbers were being crunched. Room acoustics, head movements, and HRTFs were continually being combined to filter the incoming audio signal with intent to fool you.
What sets DIRAC apart is not the number crunching itself, but the HRTF database they start with. Very simply, most HRTFs are acquired with sound coming at various angles towards a standing person who is facing forward. The problem, DIRAC claims, is that in a VR goggle application the person is moving their head in all different directions relative to their torso. HTRFs with your head in its normal position are quite different than HRTFs with your head tilted and turned in various directions. Holy smoke, that makes so much sense. Johnsson sent me some proprietary internal studies showing the changes to HRTF with oddly angled headpositions and it was quite apparent they have a lot of effect.
How good was the demo? I'd say quite good. Very often I hear what I can only call a squeaky character in the treble. I chalk it up to the fact that a lot of the HRTF cues are in the 4kHz-10kHz range, and there are probably a lot of DSP artifacts showing up there. I didn't hear that as much in this case, I felt the DIRAC system was just more natural sounding than many I've heard. Maybe it was due to the fact that they chose a good headphone to start with, but I liked what I heard.
On the down side, I still didn't get tight forward localizationwhich is the hardest thing to do. As is usually the case, when I turned my head from left to right, the image rose when directly in front of me. But I have to say, I've never heard a generic HRTF system get frontal localization right, and I felt the sense of space otherwise with the DIRAC VR pretty good. Off axis sound sources were stable in seemed well placed in space.
Don't know if DIRAC will be one of the lucky, or just damned good, companies to make it from the bleeding edge to the leading edge in virtual audio, but I'm going to keep me ear on them.