Dr. AIX's POSTS — 21 June 2014


Lately, I’ve been working with Scott Wilkinson over at AVS Forum to create a quasi-meaningful test to determine whether people with very good playback systems can “perceive” the difference between a bona fide 96 kHz/24-bit track and the downconverted 44.1 kHz/16-bit version of the same track. We’ve just about ready to launch the thing as soon as the technical people at AVS Forum figure out the right place to put the test files. This is certainly not going to be the rigorous test that I’m planning but we thought it would be interesting to let readers participate in a survey that actually could provide some useful feedback.

I’ve seen a number of surveys lately the attempt to determine whether people can “hear” the difference between high-resolution audio and standard compressed files or the difference between 16 and 24-bit audio. But just as the Boston Audio Society study failed because none of the content evaluated during their study were real high-resolution audio, the current surveys are using content downloaded from the web that says that it is high-resolution but in reality isn’t. So Scott and I decided to try a similar test using a few of my recordings that actually do have ultrasonics and dynamic range in excess of standard CDs.

I pulled three tracks from my catalog. There’s the “Mosaic” track that I’ve shared repeatedly with readers, a track from Steve March Torme and a big band that has a dynamic range above 100 dB as well as ultrasonics AND a track by trumpeter Wallace Roney and his band playing with a Harmon mute, which produces lots of energy above 20 kHz.

The plan is to provide these tracks at 96/24 and 44.1/16 and let users compare them using the ABX methods provided by Foobar (PC) and ABX Tester (Mac). He’s written up the whole thing and will launch it on AVS Forum very shortly. I have the spectrograms and audio as well and will make them available as soon as the thing goes live on AVS.

But in the midst of preparing the files, I downloaded the ABX Test app for my Mac to check out how it works. The program allows you to associate “A” and “B” audio tracks with the program and then randomly builds 5 “X” items. You can listen to “A” or “B” as many times as you want from anywhere in the track and then listen to the “X” item. Based on what you hear, you choose whether you believe the track is the “A” or “B” version.

So I took the test myself yesterday. The first track that I plugged in to the ABX Tester was the “On the Street Where You Live” by Steve March Torme. This track has a tremendous dynamic range and lots of ultrasonics. I know that the last 40 seconds contains the highest dynamic range so I concentrated on that section as I did the test. I listened to all 5 “X” items and made my choices.

The system I used consisted of my tower Mac connected via USB to a Benchmark DAC1 to a set of Oppo PM-1 headphones. I didn’t really go to any effort to maximize my situation…after all I just wanted to check out the ABX Tester app. But this equipment is more than capable of delivering great reproduction.

To my utter disappointment and complete surprise, I failed miserably to correctly identify the high-resolution version. When I clicked on the “Check Answers” button, the window popped up and told me that I got 0% right. My instantaneous reaction was complete shock. I could see my life’s work going down the toilet.

Then I thought a moment. The fact that I got them ALL wrong, merely indicated that I swapped the high-resolution and standard resolution files during the test. Getting 0% is the same as getting 100%! I was able to distinguish the difference between the two files every time…I simply reversed the “A” and “B” source files.

Even after this realization, I was genuinely surprised that I scored a perfect 0%. It’s true that I know what to listen for and clearly heard the difference in my tracks…but I didn’t think I would get this results the first time out.

You can do this today with the “Mosaic” track that is on the FTP site. Download ABX Tester and try it yourself. Can you get 5 out of 5? I did…and I’m an old man with aging ears.

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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.

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