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I think I saw the future of headphone technology at the recent 2019 Audio Engineering Society International Conference on Headphone Technology, held in San Francisco from August 27 to 29. My vision came during a presentation by Ramani Duraiswami, a professor at the University of Maryland and also president and founder of VisiSonics, a company dedicated to 3D audio reproduction, mostly for gaming applications. Duraiswami’s presentation didn’t awaken me to any concepts I hadn’t heard of before -- but it did give me the faith that the processing needed to make headphones sound as good and natural as a high-quality set of stereo (or surround) speakers is within our grasp.

Convention crowd

Duraiswami’s presentation explored methods for getting 3D sound reproduction from headphones. As he explained, the crux of the problem lies in the fact that we localize sounds based on a number of physical factors, including the shape of the pinnae, as well as the size and shapes of the head and shoulders. Our brains evaluate the way the reflections and frequency-response alterations caused by these physical factors differ from the direct sound. It’s a process called head-related transfer function, or HRTF. Headphones and earphones bypass our HRTFs, which is why center images from headphones seem to come from inside our heads. By precisely replicating a person’s HRTF using digital processing, it’s possible to restore a natural sense of spatiality and directionality when listening through headphones or earphones.

The problem is that just as everyone’s physical characteristics are different, so are their HRTFs. I tackled this topic in my June 2016 column that described the Smyth Realiser A8 headphone processor, which uses tiny microphones inserted into the ears to measure the listener’s HRTF. The result was the most realistic sound I’ve heard from headphones since the late 1990s, when I’d had my HRTF measured by a company named Virtual Listening Systems.

HRTF

We’re talking a huge leap in realism here -- even more dramatic than you’d get by going from a good set of $100 headphones to the multi-thousand-dollar models from Focal, HiFiMan, and Meze. Basically, headphones with accurate, personalized HRTF processing don’t sound like headphones at all. That impression of having the audio emerging from the center of your head disappears -- and the effect is far more natural and powerful than any “one size fits all” technology such as crossfeed circuits or Dolby Headphone can deliver.

Obviously, it’s wildly optimistic to assume that consumers will be willing to spend thousands for a Smyth Realiser, or to insert microphones into their ears and run a bunch of test tones through a set of speakers to calibrate the processor. And as Duraiswami pointed out, directly measuring HRTF -- a process that typically requires an anechoic chamber, a complicated array of speakers and/or microphones, and about an hour of time -- isn’t practical, either.

HRTF

At CES in January, Creative Labs presented a potentially more practical solution: a smartphone app that lets you take pictures of your earlobes and your face, then calculates your HRTF and creates a processing algorithm that can fool you into thinking you’re hearing real speakers. The technology is called Super X-Fi, and it’s available in Creative’s Super X-Fi Amp. The CES demo was buggy to say the least, and they used insert microphones to create HRTF profiles for the listeners -- which led me to believe the photo-based Super X-Fi technology wasn’t reliable enough for a tradeshow demo. My post-CES attempts to shoot pictures of my ears and face and use the app to calculate my HRTF have all failed because the app is buggy and it refused to upload the data. The app also requires use of its embedded music player -- and few people will tolerate a second-rate interface for the sake of better sound, especially after they’ve been spoiled by the user-friendly interfaces of Spotify, Tidal, and Qobuz. So despite the fact that the Super X-Fi demo worked amazingly well for me for, literally, about ten seconds, I’m not sure if there’s a viable product here.

Super X-Fi

Duraiswami’s presentation convinced me that this technology has legs. He went deep into the details of how HRTFs are calculated -- an unbelievably complex process that demands a great deal of computer power -- and discussed how it was possible to do this through photos that show the user’s physical characteristics. Even though the processing would likely demand an impractical amount of time with a smartphone, Duraiswami said the calculations take only about four minutes on the Amazon cloud.

I think that if this technology can be made to work reliably, on a wide selection of affordable devices, it’ll be the most important development in the history of headphone sound since 1958, when John Koss invented stereo headphones. Active headphones, with built-in amps, wireless receivers, and digital signal processing (DSP), have taken over the market, and the best of these headphones may already have enough DSP power to do effective HRTF processing -- and even if they don’t, they probably will in a year or two. And then we’ll have sound quality and spatial realism that no traditional passive headphones and analog electronics can even approach, at prices that average people can afford. If we can get effective HRTF processing plus higher-quality noise canceling, we’ll be in for an exciting new generation of headphones.

. . . Brent Butterworth
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  • This commment is unpublished.
    Mauro · 5 days ago
    I've tried the Sound Blaster X3 USB DAC/Amp, the bigger brother of the small dongle in the picture above. It is a very smart device with very nice smartphone and PC apps to extend PCs with headphone, mic, active speakers via jacks and amplifiers via optical output.

    I can't judge the DAC, I am no expert, but I wanted to share my impression on SuperX-fi technology.

    Unluckily it is still not a mature technology to reproduce speakers in a room. I've tested it with two compatible headphones, any song felt like I was in a bathroom with the singer singing in a bad microphone placed just in front of my nose.

    It would be interesting to know if Brent tried a different setup at CES, but the current commercial product, for the time being, it is not a technology for audiophiles..or maybe it does not work with compatible headphones, but just with Creative headphones. Dunno.

    You trade tonal balance and details in a very bad bad way,... for spatial awareness.
    To me it seems a product well suited for gamers. It has little to do with speakers in a room.

    If anyone at Creative is reading, if the audiophile audience is of interest, I would love to see in the same package a bluetooth/airplay receiver for audio streaming (and BT transmitter why not), keep just two RCA analog outs and the very nice software..and more watts out..
    • This commment is unpublished.
      Brent Butterworth · 4 days ago
      Great comment, thanks for the detailed info! The CES demo I got used insert mics, so they basically cheated -- what they did was basically their version of a Smyth Realiser, which is a fantastic product but anything that relies on insert mics is not a viable consumer product IMO. That demo was a disaster, it did seem to work for a couple of people but not for most, and of course, they weren't actually demoing the technology they were saying they have. But it does seem possible that it could work down the line.
      • This commment is unpublished.
        Mauro · 4 days ago
        It was a nice opportunity anyway to remind me that headphones are not speaker replacements, when you can’t use them or when you want hear all the details in the recording.

        They are also better in create intimacy with the singer. The singer is not in the room with you...

        the singer is inside you!!!
        • This commment is unpublished.
          Brent Butterworth · 4 days ago
          Have you heard the Smyth Realiser? I'd be curious to get your take.
          • This commment is unpublished.
            Mauro · 4 days ago
            No, unluckily. Reviews are enthusiastic!

            I cannot find a dealer page on their website. I should visit the Munich show. I doubt that in Italy anyone is selling it anyway ? It could have been a nice topic for an article: a newbie faces an extremely expensive audio equipment!
            • This commment is unpublished.
              Brent Butterworth · 3 days ago
              It's hard to get a demo, apparently. I got one because a consultant friend of mine knew someone who had one, and he really wanted me to hear it, so he made arrangements. Not a consumer product but I think for a headphone enthusiast it would be $4K well spent.
  • This commment is unpublished.

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