Audiophoolery: Pseudoscience in Consumer Audio Engineering

[Johk]

Do You Hear What I Hear?
Among devoted audiophiles, one of the most hotly debated topics is the notion that ultrasonic frequencies are necessary for high fidelity reproduction. Put aside for a moment that no human can hear much past 20 KHz. Few microphones respond to frequencies beyond that, and even fewer loudspeakers can reproduce that high. If maintaining an extended frequency response were free, I’d have little objection. But in this digital age, storing frequencies higher than necessary waste memory, media space, and bandwidth. Even sillier is the way audio is handled on DVD soundtracks. DVDs accommodate frequencies up to 96 KHz, but then “lossy”data compression— which results in an audible loss in quality—is often needed to make it fit! Record companies and equipment manufacturers just love that millions of people replaced all their old LPs and cassettes with CDs. They’re trying very hard to get us to buy all the same titles, and new gear to play them, yet again with the false promise of fidelity that exceeds CDs.

I think this is being misinterpreted, the 96 kHz for DVDs is the maximum sampling rate for 2ch PCM tracks which are lossless, meaning no compression. The sampling rate is not the same as the frequency range. According to the Nyquist Shannon sampling theorem, "a bandlimited analog signal that has been sampled can be perfectly reconstructed from an infinite sequence of samples if the sampling rate exceeds 2B samples per second, where B is the highest frequency in the original signal". Meaning to reproduce a 20 kHz sound, you need a sampling rate greater than 40 kHz. Therefore the 96 kHz sampling rate would reproduce sounds lower than 48 kHz. Lossy multichannels DVD soundtracks have a maximum sampling rate of 48 kHz (most are at 44.1 kHz) which is slightly above the rate required for a 20 kHz sound. Therefore the lossy compression was required to make soundtracks containing material inside the normal human hearing of 20 Hz - 20 kHz (which varies with people and decreases with age) fit; not because of ultrasonic frequencies. So I don't know why he's calling that "silly".

Also, 2B sampling rate is the minimum required; greater sampling rate means that a greater number of samples are taken from the continuous signal to make a discrete signal. The goal of a greater sampling rate is to reproduce more precisely the original continuous signal. That's why Blu-Ray allows great sampling rate for greater fidelity and not for reproducing ultrasonic frequencies.

The Cable Guy
The earliest audio scam I can recall is fancy wire for connecting loudspeakers, and it’s still going strong. These days vendors claim their wire yields better sound quality when compared to normal wire, and, of course, it’s much more expensive than normal wire. In truth, the most important property of speaker wire is resistance, which is a function of its thickness. The resistance must be low to pass the high-current signals a power amplifier delivers. For short distances— say, up to five feet—16-gauge wire of any type is adequate, though thicker wire is needed for longer runs.

I would just specify that the material has a great impact on resistance and that price/value-wise copper wires would be the best choice

Even sillier than expensive speaker wire is replacement AC power cords and most other power “conditioner” products. The sales claims sound logical: Noise and static can get into your gear through the power line and damage the sound. In severe cases it’s possible for powerrelated clicks and buzzes to get into your system, but those are easily noticed. The suggestion that subtle changes in “clarity and presence” can occur is plain fraud. Indeed, every competent circuit designer knows how to filter out power line noise, and such protection is routinely added to all commercial audio products. Spending hundreds of dollars on a six-foot replacement power cord ignores the other hundred-odd feet of regular wire between the wall outlet and power pole.

Stating that "protection is routinely added to all commercial audio products" is a bit vague. Although I'm not familiar with the means to filter out power line noise I would think that there are more than one way to do it. Selection of components in commercial products is driven by cost and not necessarily by quality. Therefore using power conditioning products can have an impact on audio quality (I'm not saying that every all power conditioning products have an impact or the impact is significant).