تست دستگاه با روش Contrast

تست دستگاه با روش Contrast

چهارشنبه 28 مارس 2018
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The old method: comparison by reference

We should begin by examining the method in current favour: The usual procedure is to use one or more favoured recordings and, playing slices of them on two different systems (or the same system alternating two components, which amounts to the same thing); and then deciding which system (or component) you like better, or which one more closely matches your belief about some internalized reference, or which one “tells you more” about the music on the recording. It won’t work! … not event if you use a dozen recordings of presumed pedigree … not even if you compare the stage size frequency range, transient response, tonal correctness, instrument placement, clarity of test, etc. – not even if you compare your memory of your emotional response with one system to that of another – it makes little difference. The practical result will be the same: What you will learn is which system (or component) more closely matches your prejudice about the way a given recording ought to sound. And since neither the recordings nor the components we use are accurate to begin with, then this method cannot tell us which system is more accurate! It is methodological treason to evaluate something for accuracy against a reference with tools which are inaccurate – not least of which is our memory of acoustical data. Therefore, it is very likely to the point of certainty that a positive response to a system using this method is the result of a pleasing complementarity between recording, playback system, experience, memory, and expectation; all of which is very unlikely to be duplicated due to the extraordinarily wide variation which exists in recording method and manufacture. (Ask yourself, when you come across a component or system which plays many of your “reference” recordings well, if it also plays all your recordings well. The answer is probably “no;” and the explanation we usually offer puts the blame on the other recordings, not the playback system. And, no, we’re not going to argue that all recordings are good; but that all recordings are much better than you have let yourself believe).

Recognising that many will consider these statements as audiophile heresy; we urge you to keep in mind our mutual objective: to prevent boredom and frustration, and to keep our interest in upgrading our playback system enjoyable and on track. To this end it becomes necessary that we lay aside our need to have verified in our methodology beliefs about the way our recordings and playback systems ought to sound. As we shall see, marriage to such beliefs practically guarantees us passage to AUDIO HELL. It is our contention that, while nothing in the recording or playback chain is accurate, accuracy is the only worthwhile objective; for when playback is as accurate as possible, the chances for maximum recovery of the recorded program is greatest; and when we have as much of that recording to hand – or to ear – then we have the greatest chance for an intimate experience with the recorded performance. It only remains to describe a methodology which improves that likelihood. (This follows shortly).

Listeners claiming an inside track by virtue of having attended the recording session are really responding to other, perhaps unconscious, clues when they report significant similarities between recording session and playback. As previously asserted, no-one can possibly know in any meaningful way what is on the master tape or the resulting software, even if they auditioned the playback through the engineer’s “reference” monitoring system. Anyone who thinks that there exists some “reference” playback system that sounds just like the live event simply isn’t paying attention; or at best doesn’t understand how magic works. After all, if it weren’t for the power of suggestion, hi-fi would have been denounced decades ago as a fraud. Remember those experiments put on by various hi-fi promoters in the fifties in which most of the audience “thought” they were listening to a live performance until the drawing of the curtain revealed the Wizard up to his usual tricks. The truth is the audience “thought” no such thing; they merely went along for the ride without giving what they were hearing any critical thought at all. It is the nature of our psychology to believe what we see and to “hear” what we expect to hear. Only cynics and paranoids point out fallibility when everyone else is having a good time.

Another relevant misunderstanding involves the correct function of “monitoring equipment”. The purpose of such equipment is to get an idea of how whatever is being recorded will play back on a known system and then to make adjustments in recording procedure. It should never be understood by either the recording producer or the buyer that the monitoring system is either definitive or accurate, even though the engineer makes all sorts of placement and equipment decisions based on what their monitoring playback reveals. They have to use something, after all; and the best recording companies go to great lengths to make use of monitoring equipment that tells them as much as possible about what they are doing. But no matter what monitoring components are used, they can never be the last word on the subject; and it is entirely possible to achieve more realistic results with a totally different playback system, for example, a more accurate one. Notice “more accurate,” not “accurate.” It bears repeating that there is no such thing as an accurate system, nor an accurate component, nor an accurate recording. Yet as axiomatic as any audiophile believes these assertions to be, they are instantly forgotten the moment we begin a critical audition.

The proposed method: Comparison by contrast.

When auditioning only two playback systems using the usual method, we will have at least a 50% chance of choosing the one which is more accurate. However, evaluations of single components willy-nilly test the entire playback chain; therefore efforts to choose the more accurate component are compounded by the likelihood that we will be equally uncertain as to the accuracy of each of the system’s associated components if for no other reason than that they were chosen by a method which only guarantees prejudice. How can we have any confidence that having chosen one component by such a method that its presence in the system won’t mislead us when evaluating other components in the playback chain, present or future?

The way to sort out which system or component is more accurate is to invert the test. Instead of comparing a handful of recordings – presumed to be definitive – on two different systems to determine which one coincides with our present feeling about the way that music ought to sound, play a larger number of recordings of vastly different styles and recording technique on two different systems to hear which system reveals more differences between the recordings. This is a procedure which anyone with ears can make use of, but requires letting go of some of our favoured practices and prejudices.

In more detail, it would go something like this: Line up about two dozen recordings of different kinds of music – pop vocal, orchestral, jazz, chamber music, folk, rock, opera, piano – music you like, but recordings of which you are unfamiliar. (It is very important to avoid your favourite “test” recordings, presuming that they will tell you what you need to know about some performance parameter or other, because doing so will likely only serve to confirm or deny an expectation based on prior “performances” you have heard on other systems or components. More later.) First with one system and then the other, play through complete numbers from all of these in one sitting. (The two systems may be entirely different or have only one variable such as cables, amplifier, or speaker).

The more accurate system is the one which reproduces more differences – more contrast between the various program sources.

To suggest a simplified example, imagine a 1940’s wind-up phonograph playing recordings of Al Jolson singing “Swanee” and The Philadelphia Orchestra playing Beethoven. The playback from these recordings will sound more alike than LP versions of these very recordings played back through a reasonably good modern audio system. Correct? What we’re after is a playback system which maximizes those differences. Some orchestral recordings, for example, will present stages beyond the confines of the speaker borders, others tend to gather between the speakers; some will seem to articulate instruments in space; others present them in a mass as if perceived from a balcony; some will present the winds recessed deep into the orchestra; others up front; some will overwhelm us with a bass drum of tremendous power; others barely distinguish between the character of timpani and bass drum. In respect to our critical evaluation process, it is of absolutely no consequence that these differences may have resulted from performing style or recording methodology and manufacture, or that they may have completely misrepresented the actual live event. Therefore, when comparing two speaker systems, it would be a mistake to assume that the one which always presents a gigantic stage well beyond the confines of the speakers, for example, is more accurate. You might like – even prefer – what the system does to staging, but the other speaker, because it is realizing differences between recordings, is very likely more accurate; and in respect to all the other variables from recording to recording, may turn out to be more revealing of the performance.

Some pop vocal recordings present us with resonant voices, others dry; some as part of the instrumental texture, others envelope us leaving the accompanying instruments and vocals well in the background; some are nasal, some gravelly, some metallic, others warm. The “Comparison by Reference” method would have us respond positively to that playback system, together with the associated “reference” recording, that achieves a pre-conceived notion of how the vocal is presented and how it sounds in relation to the instruments in regard to such parameters as relative size, shape, level, weight, definition, et al. Over time, we find ourselves preferring a particular presentation of pop vocal (or orchestral balance, or rock thwack, or jazz intimacy, or piano percussiveness – you name it) and infer a correctness when approximated by certain recordings. We then compound our mistake by raising these recordings to reference status (pace Prof. Johnson), and then seek this “correct” presentation from every system we later evaluate; and if it isn’t there, we are likely to dismiss that system as incorrect. The problem is that since neither recording nor playback system was accurate to begin with, the expectation that later systems should comply is dangerous. In fact, if their presentations are consistently similar, then they must be inaccurate by definition simply because either by default or intention no two recordings are exactly similar. And while there are other important criteria which any satisfactory audio component or system must satisfy – absence of fatigue being one of the most essential – very little is not subsumed by the new method of comparison offered here.

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