Dr. AIX's POSTS TECH TALK — 10 April 2014


Lorr Kramer, the local representative of the Smyth Research “Room Realizer”, came by the studio yesterday to assist with yet another measurement for a client that was in Los Angeles. A measurement in this case means that he sat in my surround sound studio with tiny microphones in his ears while Lorr ran a series of sweep tones from the various speaker configurations (5.1 B&Ws and the THX certified theatrical JBL system) we have. The result is a set of filter parameters that can be loaded into the client’s Smyth “Room Realizer” that will emulate the sound of the physical space in a set of headphones. It’s a very cost effective and extremely convincing way to hear a “virtualized” room using headphones as opposed to the “inside your head” sound typically experienced in headphones listening.

It turns out that the AIX Studio is a prime target for Smyth owners to get measured in. The discussion forum over at Head-Fi.org recommends my studio quite highly and we had a large number of Smyth owners schedule a measurement session in the room. Why is this room so special? We chatted about it yesterday following the session.


Figure 1 – A photo of the AIX mixing room before the theatrical system was installed.

The AIX Studios main mixing room is unusually large as audio recording studio go. It’s actually more similar to a great home theater than a typical mixing room. We have 5 B&W 801 Series III speakers on anchor stands in a large circle around the central mixing location. In addition, I can reconfigure the room into a 7.1 listening environment by shifting the location of the left and right surround speakers and adding two more B&W 805 speakers in the rear. Finally, the client can have a measurement done through the THX certified theatrical system with the 146″ Stewart Film screen lowered.

There are other surround headphones available. DTS makes Headphones X, Darin Fong has a system, Beyer Dynamic, Beats, Astound Sound and the Headphones 3D app are all options in addition to my own Headphones[xi] version.

I did research into binaural audio as part of my dissertation many years ago and can tell you without hesitation that the Smyth Research methodology is by far the best. It’s customized to your particular head and ears. The goal is to recreate the acoustic properties of specific room AND a set of speakers. And the coolest thing that is unique to the Smyth Research unit is the IR head tracker that “locks” the virtual speakers directly in front of you even if you turn your head from side to side.


Figure 2 – The Smyth Realizer

The unit is not cheap. With the lowest cost Stax headphones, the package is just over $3000. So what is a surround headphone fan on a budget to do? Well, if you enjoy the recordings that I produce on AIX Records, you can access the Headphones[xi] version of the surround mixes. Yep, I take the Smyth process and my own set of filters and capture the 2-channel output. I make those files available on iTrax.com and iTunes…and on some of the latest Blue-ray titles; I place the Headphones[xi] files on the ROM section of the disc. The new iTrax.com will have an option to download these files.

These files can also be loaded onto portable music players. They are just like any other stereo file except they produce a processed “surround” or “outside your head” listening experience.

I’ve prepared a number of example tracks and will put them on the FTP site later today for anyone interested in hearing how Headphones[xi] sounds. You can also listen to The Beatles “Eleanor Rigby” in Headphones[xi] on YouTube. See below:

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About Author


Mark Waldrep, aka Dr. AIX, has been producing and engineering music for over 40 years. He learned electronics as a teenager from his HAM radio father while learning to play the guitar. Mark received the first doctorate in music composition from UCLA in 1986 for a "binaural" electronic music composition. Other advanced degrees include an MS in computer science, an MFA/MA in music, BM in music and a BA in art. As an engineer and producer, Mark has worked on projects for the Rolling Stones, 311, Tool, KISS, Blink 182, Blues Traveler, Britney Spears, the San Francisco Symphony, The Dover Quartet, Willie Nelson, Paul Williams, The Allman Brothers, Bad Company and many more. Dr. Waldrep has been an innovator when it comes to multimedia and music. He created the first enhanced CDs in the 90s, the first DVD-Videos released in the U.S., the first web-connected DVD, the first DVD-Audio title, the first music Blu-ray disc and the first 3D Music Album. Additionally, he launched the first High Definition Music Download site in 2007 called iTrax.com. A frequency speaker at audio events, author of numerous articles, Dr. Waldrep is currently writing a book on the production and reproduction of high-end music called, "High-End Audio: A Practical Guide to Production and Playback". The book should be completed in the fall of 2013.

(14) Readers Comments

  1. Unbelievable! I Sennheiser HD598 and a Melos SHA1 tube headphone pre-amp. When the clip started, I literally lunged for the pre-amp thinking that the headphones weren’t plugged in because I was convinced that I was hearing the sound of my Wharfedale 10.2 desktop speakers. Totally awesome 5 channel sound. WOW!

  2. I agree that the Smyth Realiser is the best. I heard it years ago at CES when they had it in prototype form. It’s my guess that the measurement to your particular HRTF (head related transfer function) is cruicial, as well as the head-tracker.

    I have your Mark Chesnutt Blu-ray and would love to listen to your Smyth-encoded tracks but I don’t have a Blu-ray ROM drive. Is there any chance you could download them if you’ve already purchased the disc?

    Thanks……… I always enjoy your posts.

  3. I enjoyed your comments in yesterday’s, 4-10-2014, post. I have been following the developments in the field of headphone processed surround technology. I am wondering if you could discuss, in a future post, the differences, and/or, your thoughts regarding the headphone technology of DTS Headphone X, your Headphone Xi, and Smyth Realizer, as I understand they are variations of the Smyth approach.

    Thank You for the education I am receiving by the wealth of information you provide through your columns.

    Best Regards
    Wayne Lacina
    San Diego

    • I can expand more on these technologies and those of several other research projects. Stay tuned.

      • Thank You!
        I look forward to the articles with eager anticipation.

  4. That youtube sample sounds great with Sennheiser HD-600 and Stax SR-507, but interestingly the difference is not huge, when comparing to well made conventional recording listened with Stax SR-009, IMHO.

    • It’s an optional way to process and can be customized through careful measurement in my room (of others).

  5. Interesting. Listening through Planars the sound is projected slightly forward, although I still doesn’t sound “out of the head”. However, I preferred the headphone mixes because they lacked the dryness of the original. I’m not sure what was going on with Mel Torme’s voice though, it had a distinctive processed sound to it, which wasn’t on the original.

    • I’ll have to check out the Steve March Torme, it sounded OK in the new Oppo phones as I was doing the transfers yesterday.

  6. I heard the dts 11 channel headphone system in comparison to an 11 channel speaker system at CES 2014.
    And I just listened to your xi headphone Eleanor Rigby mix. I find all the channel locations are quite accurate, except the center channel – it still comes from the center of my head, not from in front of me. I have not heard the Smyth Realizer – does it have that characteristic as well?

    • The center is the toughest one to recreate. It helps if there’s a picture (of an actual speaker) in front of you. The Symth system is customized to your specific ears and does the best job I’ve heard for all of the speaker locations.

  7. Hello Mark
    For those of us on very modest budgets is there an app that can emulate the effect of the Smyth processor? Having heard your demo tracks I would like to explore the “headphone surround” with my recorded music collection.

    • Yes, there are several. I will write a post very soon about some options.

  8. I took cut samples from 13-15 seconds (Right front) and 22.5-24.5 seconds (Right surround) and looped them together and kept listening to them. Both sound exactly the same to me and both just sound like RIGHT to me!

    So no I don’t hear the surround effect at all.

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