Specifications

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OMNIA
OMNIA
The path to find the next frontier in processing began with a simple, but somewhat frightening, exercise: careful and extremely critical
listening of the status quo. As a developer it requires leaving your own ego at the door and being prepared to face some harsh
realities. Suffice it to say, we were about to embark upon a humbling experience.
Having been around the block a few times with respect to loud competitive processing, our own system was setup to simulate any
one of a number of well-known major market radio stations. Hot Rockin’ Flame Throwin’ applies! Benchmarking was done using
stock processing and cranked up presets, along with the use of processors from other manufacturers. The choice of programming
content was made up of recent recordings as well as many time-tested segments used over the past twenty-plus years for
processing development.
Modern music mastering practices generate content that is noticeably rich in deep bass, presence, and treble. When processed
aggressively, especially for FM-Stereo, the resulting audio appears synthetic in tonality and quality. Treble frequencies appear overly
bright, and sometimes harsh, even with additional application of dynamic high frequency processing. Bass sounds tight and defined,
but depending upon the processor’s spectral limiting system, it can also sound distorted.
Listening to current music, with aggressive processing, produces a distinct annoyance: the appearance of a sizzling or frying sound
to midrange, presence, and treble spectra. This was noticeable on all the processors used for evaluation. Reducing the final limiting,
or clipping, helped ease the pain. This indicated that the problem is harmonic, related to the clipping process. Significant reduction of
clipping removed the annoyance, but the loss of loudness was on the order of 6 dB or more. Not suitable for the needs
of competitive audio.
Was this the age-old issue of too much bass forcing the rest of the spectrum into the limiter? This is known as bass induced
intermod. At first, it would seem so, but the test segments did not have any bass content, and the frying was still present. Was it in
the original source, and the processor was magnifying it via multiband dynamics control? Careful evaluation of the source audio
revealed the answer to be no. Seems a new gremlin hath arrived!
By example, this is easily heard in the song “Because Of You” by Kelly Clarkson. The opening of the selection is a piano solo, and the
vocalist begins to hum along with the piano, a few seconds later. Present day audio processors, set up aggressively, cause the
humming in the vocal to sound as if bacon is being fried! Prior statement not intended for humor, by the way. This was a high rotation
song on CHR (Contemporary Hit Radio) formatted radio stations. Since most of those require aggressive processing, this test case
replicates the real world. This example is just one of many which illustrate the challenges in current processing technique.
Since the aforementioned bacon frying annoyance was affected by the action of the clipping function, a probe into that algorithm was
in order. Most final limiting/clipping systems in modern audio processors employ some form of proprietary means to control
perceived distortion. The methods for these vary. While open for subjective discussion, the end result is still the same: absolute peak
control is performed and a minimal level of harmonic distortion is acceptable within a specified operating range. Basically, some form
of masking method is used to hide the most annoying clipping side effects from the ear. Although, it appears now, we’ve pushed
these methods to the point where modern recordings generate distortion annoyances when aggressive processing is used.
For the processing novice, a clipper – by design – will generate harmonics of the fundamental audio frequency. Using a sinewave for
an example, if the upper and lower peaks of the waveform are chopped off (clipped), harmonics are born out of the clippings and
show up within the spectrum space as harmonic multiples of the original frequency. An example frequency of 1 kHz, with 3 dB of
clipping generates odd-order harmonics at 3 kHz, 5 kHz, 7 kHz, etc, out to infinity. Figures 1 – 2 illustrate examples of this.
Note: Broadcast audio processors band-limit frequency spectra within a specified range, for their respective transmission paths.
FM-Stereo bandwidth is 15 kHz, and AM is between 4.5 kHz and 10 kHz, depending on location. As such, clipping harmonics are
limited via non-overshooting filtering methods in order to properly maintain operating legal bandwidth.
what’s new! /omnia /
FINDING THE ACHILLES HEEL
THE PAIN
THE INVESTIGATION
Figure-1, 1 kHz Square Wave Figure-2, 1 kHz Square Wave Spectra