Friday, December 18, 2015

Bullshit Audio Terms

I’m not even close to being the first guy to gag on the bullshit marketing terms applied to non-existent audio equipment qualities.

Immersive: As in “I felt the music was all around me. . .” (Other bullshit terms used for this generally non-existent quality are “open,” and “air.”) Bob Carver made a nasty audiophile device called the “Time Lens,” back in the 80’s. If you like “immersive,” you’d love this thing. This awful device screwed with mid and upper-mids L/R phase relationships so severely it was hard to locate any sound sources in some rooms. Carver had some really fancy explanations for why sound seemed to be originating everywhere but from the speakers, but simple test equipment (an oscilloscope) demonstrated the fact that frequency-dependent phase relationships were being messed with and the result was semi-entertaining until it gave you a headache. A surround sound mix can be “immersive,” if the speakers and listener are properly placed. Otherwise, stereo means “solid” which will always put the listener in a position facing the sound sources and, at best, a good mix and proper playback system will provide left, right, close and distant perspective. And that’s it. If you hear signals behind you, your system or room acoustics are screwed up.

Warm: (aka “creamy,” silkiness,” and “natural”) Ideally, you might hope this means some mild addition of even harmonics—mostly 2nd—distortion contribution that might seem pleasant. Usually, what most people call “warm” is the result of slew or crossover distortion and is in no way pleasant if you are used to listening to low distortion reasonably accurate sound reproduction. Distortion-wise, we tend to “like” what we’re used to hearing and if we spend enough time with low fidelity equipment and recordings we’ll learn to love that. That is not, however, a good thing.

Presence: Three decades ago, I had the pleasure of getting to mess with a Mark Levinson stereo power amplifier when I was a design and test engineer at QSC Audio Products. The Levinson claim to fame from advertising and reviewer hype was “presence.” hen I put a Mark Levinson amp on the bench, what I found was a slowly rising upper-midrange shelf that peaked at about 3dB at 3kHz (along with the associated phase distortion created by this built-in EQ). Otherwise, there was nothing special about this overpriced equipment in any regard. It wasn’t quick, it wasn’t particularly stable when super-sonic signals or reactive loads were introduced, and it wasn’t particularly low distortion (IMD or THD wise). A few moments with some simple electronic test tools would have dispelled the magical claims from a power amplifier with a silly built-in EQ, but audiophile magazines shy away from test equipment and objective listening tests.

Wide Dynamic Range: Dynamic range is a fairly straight-forward specification in audio equipment: “the ratio between the largest and smallest values of a changeable quantity.” At the most impractical theoretical extreme, the human ear is capable of detecting 140dB of aural signals. That assumes 0dBSPL as the threshold of hearing, which quickly deteriorates from infanthood to adolescence with age and noise exposure to more practical values of 15 to 30dBSPL. This also assumes the maximum sound pressure a human can tolerate and discern is 140dBSPL; a dubious claim at best. 140dBSPL is, for example, typically described as a full-throttle jet engine at 50 meters. A typical gun muzzle blast generates an impulse sound pressure level of 140dbSPL or more and that exposure is commonly known to cause permanent hearing damage. Relative to 1V (0dbV), the theoretical perfect (but practical) unity gain amplifier will produce 123dB of dynamic range. This can be bumped up to about 129dB if the relative maximum is 10VRMS. So, regardless of the unrealizable human hearing maximums, 123-128dB of dynamic range is pretty much as good as it gets in the real world. This relatively straight-forward specification and its associated practical limits are regularly ignored in the bullshit marketing world where numbers as insanely silly as “200dB” are quoted regularly and stupidly. Keeping in mind the analog thermal noise threshold, it’s useful to remember that every combination of amplifiers that produces an exponent of 2 (2, 4, 8, 16, 32, etc.) will reduce the combined dynamic range by 6dB. “Floating-point audio” or 64-bit or any other bullshit aside, physics and biology put an end to the realistic gains we’re going to get from playing with numbers.

This list of bullshit words is not by any means complete. I’ve left out color and taste sensory analogs, for example. A good rule to apply to modern ad-driven reviews and marketing claims is “any asshole can write marketing bullshit.” There is no one checking these claims with test equipment or even half-decent ears. So, if it sounds too good to be true, it is.

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Wirebender Audio Rants

Over the dozen years I taught audio engineering at Musictech College and McNally Smith College of Music, I accumulated a lot of material that might be useful to all sorts of budding audio techs and musicians. This site will include comments and questions about professional audio standards, practices, and equipment. I will add occasional product reviews with as many objective and irrational opinions as possible.