Can We Hear Differences Between A/C Power Cords? An ABX Blind Test
On November 13, 2004, Secrets of Home Theater and High Fidelity teamed up with the Bay Area Audiophile Society (BAAS) to conduct a blind AC power cord test. The purpose of the test was to determine if a small group of volunteers could make a statistically significant differentiation of sonic differences between an assortment of generic power cords and Nordost Valhalla power cords.
Here are photos of Manny introducing the experiment to participants in front of the green curtain, the first set of participants, and the setup behind the curtain.
Here is how Manny describes himself:
Editor's Note: The National Research Council, in Canada, conducted research that indicated untrained listeners were just as good as trained listeners at detecting differences in sound quality, so the notion of developing listening skills is not necessarily valid.
1) Do you consider yourself an "audiophile?"
2) Have you ever purchased "premium" or "specialty" power cords for you audio equipment?
3) How strongly do you believe that you you can hear differences between "standard" and "premium power cords in audio equipment?
4) Do you currently play a musical instrument?
5) How often do you hear unamplified musical performances?
1) Do you feel that the test procedure was reasonable in its attempt to answer the question of the audibility of power cords?
2) How large were the differences that you heard? (1 = I heard no differences; 5 = Huge)
3) Do you feel that the length of the musical selections was … (1 = much too short; 5 = much too long)?
Quibbles and Bibbles
Editor's Note: ABX tests are valid and do work. Here is a link to some ABX tests of various types of audio products. In many cases, statistically significant differences could be discerned by participants. In others, no differences could be discerned.
Now, of course, one can dissect an experiment and say, well these 4 people out of 10 participants had good scores, so they could hear the differences. But, no, you have to take all the data together. You can't just pick out the numbers that suit your hypothesis. This would be statistically invalid. Same thing with just looking at one music selection. With statistical random patterns, it is likely that there will be one selection where more participants score correctly than on other selections. If we had enough music selections, there would likely be one where all participants scored perfectly. But, you have to look at all the selections together. That is the purpose of statistics. You may remember the famous monkeys typing randomly concept. If you have enough monkeys, eventually one of them will type all of Shakespeare's works perfectly. To look at only that one monkey might suggest it knew how to type Shakespeare. But, we can't do that and claim good science.