Dr. AIX's POSTS TECH TALK — 24 March 2014


The posts over the weekend described what high-resolution audio isn’t and what it is. Today, I guess I’m going to offer my definition of high-resolution. For those that have been reading these posts since the beginning (which started on April 2, 2013), might remember a post from April 4th. I launched this site with a definition. I think it’s still pretty accurate…which is pretty good considering all of the months that have gone by…but it might need a little tweaking to make it to the masses. The only thing that I’ve changed is the name. I was (and still am…) in favor of HD-Audio but I have moved over to High-Resolution Audio because it seems others believe that’s a better name. Don’t ever say that I’m not flexible.

Here’s what I wrote last year:

HD-Audio is a recording that has been captured during an original session using equipment capable of matching or exceeding the capabilities of human hearing. If the generally accepted measure of the human auditory system includes a frequency span of roughly 20 Hz to 20 kHz and a dynamic range that tops out at around 135 dB, then a recording system would need to be able reach these specifications to be considered HD. In the world of PCM digital recording, this would translate to at least 48 kHz and 24-bits. Given there is some evidence that higher frequencies may impact our listening experience and that moving to 96 kHz has advantages for equipment designers, it’s seems reasonable to adopt 96 kHz as the minimal HD sampling rate (I would accept 88.2). As an engineer/producer creating new HD tracks, I choose 96 kHz/24-bits as the minimal specifications to achieve HD-Audio.

This applies to the source recording…when the musicians are (or were) actually in the studio laying down their parts. It does NOT mean that all files called “high-resolution” tracks are actually qualify Sadly, most of what is being sold through the different HD download sites are no better than the CDs that you already have and they may be worse if the wrong masters are used. The sound may be different but the actual fidelity is no better than before.

Here’s a mass-market version of the definition:

High-resolution audio (or HRA) means a source recording was made that meets or exceeds the full capabilities of human hearing, which means a frequency range of 20 Hz to 20,000 Hz and a dynamic range of 135 dB.

Let’s parse this statement and see if it really makes sense in the context of the last couple of days of posts.

1. We’re talking about original recordings that can take advantage of the fidelity (regardless of format) of our ears. I don’t honestly care if the tracks were made on analog tape, DSD, vinyl LPs, wire recorders or PCM…but they must be capable or have the potential of delivering 20-20,000 Hz AND a dynamic range of 130 dB.

2. How does this definition do with regards to sources and delivery formats and specs? If the source is made with fidelity in mind, say at 96 kHz/24-bits PCM then audiophiles can get the benefits AND lesser fidelity files can be derived from it for iTunes or CDs or anything else. If the delivery container has “Hi-Res” specs but the source doesn’t, then the delivery is not HRA. This is where proper provenance information will be needed…which may be a real challenge.

Give me your feedback. I feel pretty good about this as a simple metric for HRA

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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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