Ultrasonics Matter…I Think

There are plenty of audio engineers and enthusiasts that are happy with the sound of the music they produce and consume. And I really do enjoy listening to Peter Gabriel or Paul Simon recordings played loud once in a while. Music has that special ability to reach beyond the cognitive parts of the human species and get right into your heart and soul. So why have I been spending so much of my life (20 years worth now…and counting) trying to push the envelope with regards to high-resolution audio recording AND playback. It’s simple…because I believe that producing uncompromised new recordings in real HD-Audio makes a perceptible difference. The experience is not subtle…and better than what we’ve been listening to up until now.

But as one of my readers pointed out today, the monitor speakers that I have in my studio don’t have a flat response past the traditional upper limit of 20 kHz. My five trusty old B&W 801 Matrix III spec out to around 20 kHz and then start to drop off. It doesn’t mean that they have a brickwall at 20 kHz but still they aren’t equipped with “super tweeters” and weren’t designed to extend in the ultrasonic region. So if my system isn’t pumping out the octave from 20 – 40 kHz then why am I advocating for recordings that extend to 40 kHz and beyond? The tracks that I’ve highlighted from Qobuz and other sites that lack any meaningful information above 23 kHz will sound the same as a well-done CD, right? So what’s the deal?

Well, because there is ultrasonic acoustic energy in a performance space where musicians are making music. A Harmon muted trumpet or the cymbals of a drum set are capable of producing ultrasonics AND there are plenty of microphones that response to these frequencies. Our high-resolution ADCs and recording DAWs (digital audio workstations) can record ultrasonics AND we have playback equipment that can reproduce them. My old B&Ws are not giving me state-of-the-art reproduction but the prototype Oppo Headphones that they provided and the new SONY 7520 headphones are. I’ll be doing some rigorous testing of over the next few days AND I hope to acquire a set of Harmon M2 speakers that are essentially flat to 40 kHz.

If there’s ultrasonic frequencies in the room where the music was originally played then I want to capture them and reproduce them…just because I can AND because it’s the intellectually appropriate thing to do. While I hope to be able to conduct a research project to firmly establish whether ultrasonics actually matter…at the end of the day, we may never know for certain. But I would rather overreach than accept the established norms. Why not? It’s so simple to move up to high-resolution recording AND distribution for new recordings.

After a lifetime of working with audio and sitting for endless hours in audio studios, I think the best recordings can be produced today. We didn’t reach the ultimate in high fidelity in the 50s, 60s or 70s…we’re there now. Be sure to download the example high-resolution audio files that are on the FTP site and listen for yourself. And then let me know what you think.


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.

6 thoughts on “Ultrasonics Matter…I Think

  • Robert McAdam

    Ultrasonics are critical, since adding a motorola peizo tweeter(with resistor and capacitor) to each of my main speakers which go up to about 40khz I was astounded at the increased bass definition going into the midrange.

    I can’t hear anything coming from these speakers but when removed an immediate lacking in depth of sound is apparent. I’m looking at adding either the Tannoy or Townshend super tweeters which go even further to about 70khz although they are tested to 100khz actual.

    I found a similiar effect when adding subwoofers in that it improved the high frequencies noticeably.

    The influence of harmonic frequencies is critical to the whole sound.

  • Barry Santini

    Ultrasonics may natter, but the mastering matters more. And the power response of the speakers in the room matters equally. I luv your crusade-like enthusiasm for uncovering (unintended?) snakeoilmanship in the burgeoning HRA debate. But sometimes, DR. Mark, I can see why some content suppliers dislike you’re borderline heavy-handed approach to revealing that the emperor has no clothes. Fooling around with a company’s business narrative is not to be undertaken lightly.
    Keep up the great work! I look forward to your blog every day!

    • Admin

      Mastering has been accepted as a necessary final stage in preparing and audio master for commercial release. And there are important steps that are accomplished during mastering. But there has also been a steady march towards over use of digital tools to maximize commercial appeal at the expense of fidelity. I want to be able to hear the mixes as intended by the artist and mixing engineer…at least as an option.

      I’m not sure telling the truth is a “heavy handed” approach, is it? I believe that the whole issue would disappear if the producers and vendors of high-resolution audio would simply be accountable and honest about what they’re creating and selling.

  • Lin Hong Wong

    Dr AIX, your views on super tweeters?

  • Alex S

    1) Fourier says a square wave is an infinite number of odd-order harmonic sine waves. My electronics instructor said that 9 odd order harmonics was enough to approximate a square wave. A square wave at 5,000 Hz would then require a little less than 50,000 Hz in bandwidth to be approximated. This is close to what AIX records provides.

    2) Believe it or not, Dick Burwen says that an uneven rather than a flat upper octave response is what pleases the ear. He even sells software that provides you with such a response. I believe that his ultra high frequency reverberation recreates what one might hear when exposed to the ultrasonic octave from 20,000 to 40,000 Hz: A set of interference patterns in the audible band that are what you hear in nature: a bit of unevenness in the audible band due to addition and cancellation.

    3) I believe that listener fatigue and listening induced tinnitus are a result of the ear-brain attempting to recreate what it expects to hear in nature. When presented with full spectrum of audio extending to 50,000 or 100,000 Hz, the listener fatigue is reduced because the “extra work” the ear-brain has to do is reduced.

    4) I hope that existing or yet to be conducted scientific studies prove or refute my beliefs. But for now my sights are set on experiencing more of what is naturally available by acquiring full spectrum source recordings such as provided by iTrax and eliminating bottlenecks from my playback system so I can experience what is available in nature. I feel fine with dynamic range and quantization distortion (24 bits), but I do feel constrained by waveform and intermodulation distortion induced by limited frequency response in recording and playback.

    • Admin

      I think you’re on to something here.


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