Ace Alles: Audio Detective
|Ace Alles: Audio Detective|
Fellow ‘philes, have you ever installed a new component or doohickey in your system and said to yourself, "this is the best my system’s ever sounded, that new ‘doohickey’ is fantastic!"? Or, have you ever substituted audio cables or other gear and surmised that the item in question must be inferior because it made your system sound worse in some way? Let me assure you that in either case it is quite possible that your conclusions may have been erroneous.
As a seasoned reviewer and P.E. (Private Ear) I know all too well that scenarios like those above are almost commonplace in the world of high-end audio. In the case where an obvious synergy is achieved and the system seems to spring to life, it is easy to believe that your new component might be a new performance benchmark and it could well be. But there also exists the possibility that the piece sounds so good simply because it has distinct personality traits that are complimentary to another component in your chain. All of a sudden the sonic portrait appears to be correct because the yin/yang is complete--a marriage has occurred with a partner of inverted profile (Oh Behave!).
It could also be that a particular component was more revealing of flaws elsewhere in your system and that the unit that sounded better, was actually masking or minimizing these flaws. It is all too easy to let ourselves be fooled by these phenomena. From a music lover’s perspective, the reasons for sonic improvements may not need to be put under a microscope to isolate the specific benefactor(s). Many of us are content just to hear an improvement. But a reviewer needs to be a good detective.
For this reason many reviewers, including myself, utilize and maintain multiple reference systems, to learn how a component will sound with a variety of associated gear. This can help clue you in to whether the component under test is truly outstanding--or if it is merely a fortunate synergism.
Many other factors add to the puzzle the reviewer must resolve. Simple procedures such as matching volume levels during A/B comparisons are not always easily achieved, especially when the components being tested differ in their respective sensitivities. Since it is widely held that "louder sounds better," from a psycho-acoustic perspective, this is a crucial variable in any subjective evaluation. Unfortunately, at times, matching levels comes down to our best guess--approximated by ear.
Absolute polarity is another avenue for error. According to Clark Johnsen, author of the book, The Wood Effect*, it has been established that we humans are able to perceive the sonic effects of polarity inversion. If the polarity of your system is inverted your speakers will be presenting you with rarefactions when they should be presenting compressions and vice-versa. A recording reproduced with correct acoustic polarity often sounds more immediate and more natural than one that’s been inverted. Since some preamplifiers and other electronic components can invert polarity, it is important to note whether or not absolute polarity has been maintained to the final link in the reproductive chain, the speakers. If you find that you have a piece of gear that inverts, you can compensate for this by transposing the positive and negative loudspeaker leads. Manufacturers will sometimes indicate that their product inverts in the owner’s manual. When in doubt regarding a particular piece of gear, it is best to contact its maker.
This has thrown me a curve on a couple of occasions. I normally use a tube preamplifier that inverts polarity and I have the speaker wires reversed at the amplifier to compensate. Once when I was reviewing a particular non-inverting solid-state preamp I neglected to change the speaker wires back to their normal positive and negative terminals. I listened awhile before I caught my mistake and I can assure you that it did alter my impression of the preamp. Luckily for all you readers and the manufacturer, this happened early-on, before I’d written the review.
Additionally, many of the recordings that are routinely used for reference contain polarity inversions and phase inconsistencies that can affect our impressions if we are unaware of them. My best advice is to play your recordings both ways and to note and catalogue the CDs or particular tracks that sound more natural when reproduced with the polarity reversed. If your digital source or preamp has a polarity invert switch this is easily accomplished; but if you need to reverse your system’s wiring to make the comparison it can become a tedious and frustrating exercise. One caveat though--if your speakers aren’t phase coherent (and many are not) the effects of absolute polarity reversal will be more difficult if not impossible to detect.
[* Clark Johnsen’s book The Wood Effect, is available from: The Modern Audio Association, 23 Stillings Street, Boston, MA 02210; Tel: 617/357-8040. It normally sells for $12.95 plus shipping; Stereo Times readers can buy it for $10.00, shipping included, by mentioning this article.]
Another pitfall to watch out for is correct AC plug orientation. Since polarized AC plugs are now the norm, you may need to use a three to two prong adapter, or"cheater-plug" to reverse the "hot" and "cold" legs of the AC plug. Use a decent quality cheater plug, don’t opt for the least expensive; both Eagle and GE make good ones. Also you will need to file or clip the ears off the larger "cold" prong in order for it to fit into your AC outlet when reversed.
In one position there will be less voltage potential between the component’s chassis and ground, and that is the correct orientation. Oft times audible sonic improvements will result. The sound can be less edgy, smoother and more engaging with the correct orientation. If you don’t trust your ears (and don’t own a voltmeter) a company named Elfix manufactures a low cost ($29.95 at Audio Advisor) polarity checker for this purpose, that is very easy to use. With some equipment you may need to remake the ground connection as a safety precaution. When in doubt, always consult the manufacturer.
Directionality in wiring is yet another cause for concern. Many audiophiles contend that all wiring is directional. Simply stated this means that each piece of wire in your system will sound better connected one way than the other. Most manufacturers put arrows or writing on the cable’s insulation jacket to indicate the intended direction of hook-up which makes this an easy task. However some purists insist that you still need to listen to the cable both ways, to confirm that the manufacturer was correct in the labeling.
I know of at least one gentlemen (Lloyd Walker of Walker Audio) who has taken this one step further, by insisting that he can hear worthwhile improvements in sound by checking the orientation of each and every fuse, in each and every piece of gear in his system. He removes and inverts each fuse, one at a time, listening to each change before proceeding to the next fuse. Don’t laugh too hard because you may catch yourself doing the same thing now that you’ve been informed!
Above all, when auditioning new gear you need to keep track of the constants, inserting only ONE variable at a time. Use the same wiring (including the AC cord if possible) isolation systems, mechanical dampening devices, and whatever other transferable tweaks you had in place for the component that you’re comparing. It’s tough enough to make a fair and unbiased subjective comparison even when you’ve paid careful attention to detail and have done everything possible to preserve impartiality in your testing protocols.
Reviewers agonize over these minutiae to make their evaluations more complete, fair and repeatable. Despite our best efforts and good intentions, due in part to practical considerations and time constraints, we can not always be as thorough as we ought to be. Personal tastes will vary just as errors will continue to be made....
Still, there are credible reviewers who consistently manage to achieve results that are both fair and representative of the objects of their scrutiny. Read ALL reviews with these things in mind and above all, let your own ears be the final arbiters. Happy listening!
Ace Alles, P.E.
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