Hi-Fi Hokum

January 11, 2010

I have been meaning to write this post for a few days now, since I saw a product advertisement (discussed below) that really left me shaking my head at the apparent gullibility of some consumers.  Then my friend Phil sent me a link to an article at the Skeptic Web site, dealing with more cases of the same thing: audio products that are sold on the basis of claims that frequently defy not only science but any sort of sense.   This is not a new phenomenon.  I’ve been interested in sound reproduction systems since I was in high school.   I enjoy listening and also have been a fairly serious amateur musician.  I’ve played the trumpet in orchestra and jazz band, and have done a fair amount of singing, so I do know what live music sounds like.

That actually brings me to the first important point I want to make.  I am interested in the quality of sound reproduction: how accurately does the equipment in question replicate the sound as originally recorded?  Some people express a preference for the sound produced by particular types of components, saying that they sound “warmer” or “smoother”, for example.  If that quality was not in the original, it is a distortion.  It is perfectly OK to like the sound, but one is then talking more about something like a musical instrument, rather than a system for sound reproduction.

There is an enormous amount of misinformation pumped out on this topic, despite the fact that the key principles involved have been well understood for decades.

In my 35 years as a professional audio engineer and musician, I’ve seen some of the most outrageous pseudoscience sold to consumers, and even to other audio pros who should know better. Not unlike claims for alternative medicine, nonsense is shrouded in scientific-sounding jargon to confuse the uneducated, or a sales pitch will cite science that is legitimate but irrelevant. The result is endless arguments among audiophiles over basic scientific principles that have been fully understood for fifty years or more.

As the author of the article, Ethan Winer, points out, there are just four basic things that affect the quality of sound reproduction:

  • Noise (e.g., hiss on analog magnetic tapes)
  • Frequency Response (the notional range of human hearing is 20 Hz –  20 kHz)
  • Distortion (essentially, non-linearities in the reproduced signal)
  • Time-based errors (more common with electro-mechanical devices, like turntables)

Room acoustics also have an enormous effect on the sound that reaches your ears, but these of course are independent of the equipment used.

One of the oldest products of very dubious value is special, allegedly super-duper wire for connecting loudspeakers to a power amplifier.  Here we are talking about transmitting a relatively low voltage, low frequency (compared to RF signals, for example), and high current signal over a distance that is typically a few feet.  There is no reason to believe that fancy, expensive speaker cables can do this job any better than the stranded lamp cord that you can buy at the hardware store for a few cents a foot.  Even sillier (and this was a new one to me) is the idea that the sound can be improved by using a special AC power cord between the wall socket and the amplifier.  As Mr. Winer correctly points out, the techniques for keeping AC line noise and 60 Hz hum out of the electronics are effective and very well known.  Even if they weren’t, the wiring inside the walls of the user’s house is not going to be replaced.

An advertisement for another very questionable product first renewed my interest in these issues.  It is an integrated amplifier that, according to the advertisement,

… teams up a vacuum tube preamp stage with a state-of-the-art digital-to-analog converter (DAC) and high-current, solid-state power amplifier to deliver rich, satisfying sound. The tube preamp lends smoothness and warmth to your music’s high and mid-range frequencies, while solid-state amplification delivers tight, punchy bass. Sophisticated digital-to-analog conversion means better sound for your digital music library.

Although the supposed superior qualities of vacuum tube amplifiers have been a staple of audio magazine discussions for at least 40 years, I am aware of no evidence from a controlled experiment that, assuming the amplifier is not over-driven to the point of distortion, anyone is able to hear the difference between tube and solid-state amplifiers of equal specs.  And the idea that different devices have some sort of affinity for particular audio frequency ranges is just moonshine.

The best thing about this product, though, is that it is sold as a way to play back music in MP3 format with better sound.   Even if the claims made for “smoothness”  and “warmth” had some validity, the reality is that MP3 files are compressed using a lossy compression technique; among other things, this involves a dramatic cut-off (> 30 dB down) of frequency response above about 15 kHz.   For example, here is a frequency graph of a snippet of musical content in the original:

And here is the corresponding frequency graph for the snippet recorded in MP3 format:

It should be reasonably apparent that having better high frequency response in the amplifier is not going to buy you much.  Oh, and I forgot to mention, the price of this amplifier is $ 1,219.99.

But even this is not the most egregious example.  The Skeptic article mentions a replacement knob for your volume control, which is claimed to have near-miraculous properties:

“The new knobs are custom made with beech wood and bronze … How can this make a difference??? Well, hearing is believing as we always say. The sound becomes much more open and free flowing with a nice improvement in resolution. Dynamics are better and overall naturalness is improved.”

And this amazing knob can be yours for only $485!  I am at somewhat of a loss to explain how anyone can be taken in by this nonsense.  I suppose, if we needed it, it is one more piece of evidence that P.T. Barnum’s Law of Applied Economics is still very much in force.


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