First Impressions of DTS Headphone:X
The Hardest Thing to do on Headphones
Mother Nature has given us ears exquisitely designed to make your head turn to face exactly where that twig snap was heard. When our eyes and thoughtfulness are narrowly focussed, our ears are wide open and capable of establishing a spherical awareness of our surroundings aurally...with nary a thought. It works damn good, and fooling it is no easy task.
I've heard a whole lot of headphone imaging schemes: simple cross-feeds from HeadRoom and Meier; digital headphone amp units like the Sennheiser Lucas, AKG Hearo999, Beyerdynamic Headzone; wireless headphones with Dolby Headphone and various SRS implementations; and one-off attempts like that in the sweet, but now long-discontinued, Sony D-555 portable CD player, and many in various portable DVD players. With one singular exception, they've been convincingly unconvincingthey never really get the sound out of my head. The one exception is the Smyth Realizer; a piece of gear that requires you to have your ears measured in a reference surround system and room, and which includes the ability to track your head movements. It's complicated and expensive, but it works, and it works mostly because it measures your ear's response to a particular model of headphones, and your ear's response to real speakers in a room. It's got your Head Related Transfer Function (HRTF) down pat...and it creates changing HRTF cues with your head movements.
Monitoring head movement is incredibly important for out-of-head localization. You brain can hear the various acoustic cues developed by reflections and time differences in and between your ears, but what it's best at hearing is how those cues change when you move your head. When people search for sound sources in a dark room, they gently wiggle their head back and forth about +/- 3-5 degrees to hear the way the cues change as they hunt for the sound source. When you can't move your head relative to the source of the sound, localization acuity drops dramatically. It's like staring at one thing for a long time, eventually you can't see what your looking at any more unless you move your gaze.
Making you believe you're hearing speakers outside your head when wearing headphones is incredibly hard. You need to account for the direction of the source of the sound; the sound of an acoustic environment (the room); reflections off the pinna (outer ear)which is somewhat individual; the acoustic corrections needed for the headphones; and, if you can, how all these signals change with head movement. It's a daunting computational task.
Daunting computational tasks are something with which DTS is intimately familiar. DTS (Digital Theater Systems) is all about recording, transporting, and decoding multi-channel audio. They have a bevy of codecs and audio processing software for equipment used in everything from recording studios and sound stages, to consumer equipment in home theater systems, TVs, sound bars, computers, automobiles, and mobile devices. With Headphone:X, they're adding a systen for reproducing multi-channel audio on headphones.
My first thought when I heard of the projects was, "Good luck with that."
Like I said, I've heard most of what's been available, and to set out to make a generic version of surround for headphones on tablets and smart-phones is close to a fools errand. But here's the thing: if you can pull it off, you'll rule the world...of headphones, anyway. So, it was with great interest that I took the opportunity to visit DTS's Calabasas, CA facility to get a personal demo of Headphone:X and chat with some of their product management and engineering team.
Flip the page for my impressions.