How to Judge Audio Accuracy

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What do we really mean when we talk about sound coming out of a pair of speaker? We have talked about it before and we have heard it but what should a good loudspeaker sound like?

An accurate speaker’s role is to reproduce accurately the sounds of acoustic musical instruments and human voices exactly as they were present in the original source recording. An audio speaker should not add any sound of its own, it should not make Violins, Cello and Violas sound screechy or edgy, Double-Bass should be free of strident or harsh accents nor should it artificially add Bass emphasis to Male singers’ voice. (This is a common crisis of many cheap audio speakers).

So what sonic indication should immediately become evident? What Characteristic do we listen for, and what weaknesses should we be mindful of? Let’s start with the midrange, which is where most musical content resides, and where our hearing is by far the most sensitive. (Yes, we all love Bass, but a speaker must reproduce the midrange smoothly if we are in due course going to like it.) If an audio speaker nails the midrange precisely, without harsh-sounding peaks, or dips that make the mid- frequency sound muffled and distant, it will tell your ears immediately whether you will accept it as natural and “musical.” If not, you will reject it as tonally “false” or “colored,” and music will not sound realistic. It’s important to place your trust in accurate sound production of possibly nature’s greatest instrument, “Male and Female singing voice”. From my experience, if you get it right with the vocals other musical instruments will sound accurate as well; this is because much of the harmonic content of musical instruments resides in the midrange.

We have all heard great “Singers” and we are accustomed to the quality sound and fine distinction of male and female voices. And we have all grown up hearing pop music, which mostly features vocalists or groups of singers, as well as live choruses.

Therefore, a good place to start is with a good quality CD of an Individual singer or a group. If it’s a female vocalist, does the voice sound smooth and clear? On the other hand, the vocal may sound toppy clear, with exaggerated “s’s” and “t” sounds (that’s called sibilance), which can tip you off to a speaker with a midrange peak that makes female voices sound sharp or shrill. Make sure you choose a recording that’s smooth and natural to begin with many are not in order to properly judge whether a loudspeaker can accurately reproduce that voice. An older CD with a natural female vocal is Jennifer Warne’s Famous Blue Raincoat. Norah Jones’s voice on the DVD Live in New Orleans is a current recording that very naturally captures her vocals, without excessive sibilance or brightness.

Likewise, Diana Krall Live in Paris is well engineered. If you are listening in stereo, the vocal should be naturally placed with the other instruments; it should not sound dull or muffled or sound farther back. The latter is a sure sign of a speaker’s reduced or recessed midrange (sometimes termed “laid-back”), which will place midrange sounds farther away and make them less distinct.

A choral recording of men’s and women’s voices is an excellent test of midrange clarity and detail: Can you separate the four parts of a Chorus the male Basses and Tenors, and the female Altos and Sopranos? The Sopranos are the highest-pitched female vocals; the Altos are lower. You should be able to hear each section of a choir clearly. Speakers with depressed midrange response make all choirs sound somewhat muffled and blurred sounding. Almost any modern CD of Handel’s Hallelujah chorus from “The Messiah” will do. Listen for each section of the chorus. This disc also features a very spacious and open sound with great Brass, Strings and Percussion (try playing it back in multichannel through Dolby Pro Logic II or Logic 7 processors; it decodes wonderfully) and very convincing hall sound and depth. And there are loud, exciting musical climaxes, with plenty of cymbals and drums. Good quality speakers should remain clear and not get muddy during the loudest peaks in the music. This CD is a great choice for anyone who finds some older classical works boring and ponderous.

A well-recorded male vocal such as Harry Connick’s voice on the soundtrack CD from When Harry Met Sally (any track except track 1, which has harsh trumpets), or James Taylor’s concert DVD Live at the Beacon Theater, should be smooth and natural, with no fuzzy or low Bass emphasis. Speakers with an elevated upper Bass hump will make most male voices sound thick or fat, rather than natural and real. These recordings also have excellent acoustic and electric Bass lines, respectively, with crisp sounding Cymbals and good Acoustic Drums. On loudspeakers with good Bass response (even some bookshelf models like JBL’s have clear, smooth Bass to about 80 Hz) you will be able to follow each individual Bass note very clearly. A speaker with poor or uneven Bass output will make Electric or Acoustic Bass sound like a dull thump, with individual notes hard to distinguish.

Some classic rock recordings like Dire Straits’ Brothers in Arms are very well recorded, with natural sounding vocals, deep Bass, and guitar lines that is not harsh. Likewise Eric Clapton’s Unplugged DVD is an engineering stand-out. You will likely have your own favorites that you have heard so often your “Ears” will tell you when they sound “right” on good quality HI-Fi speakers.

If you are considering speakers for mostly home theater use, the same standards apply. A speaker that is smooth and accurate on music alone will be just as neutral and transparent with movie

soundtracks. I do not believe that there is a separate category of speakers which are “good for home theater” or “good for music only.” The same standards of fidelity apply. Center-channel speakers pose a particular challenge to any manufacturer, because the tonal (timbre) match between the center and the front left and right main speakers are very important. If there is no reasonably smooth tonal match, character’s voices will shift its tonality as they move across the stereo soundstage and the seamless blend of dialog with music and sound effects will be broken. So listen to center speakers for any “boxy” effects. Speaking voices heard through a good center should not sound like a disembodied voice inside a box (compressed). It should seem natural and not change tonal quality as the actor moves across the stereo stage from left to right, or vice-versa.

I asked Tom Cumberland, an “B&W Speakers colleague and an experienced engineer involved in the audio business for many years in the UK, how he judges loudspeaker sound: His answer was: “As an electronics guy, I always listen for listening fatigue, which shows up as non- linearity’s in a loudspeaker’s sound. With amplifiers, listening fatigue can result distortion and other artifacts. With speakers, non-linearity’s show up as peaks “You cannot just listen for a few minutes,” notes Tom Cumberland. “You have to listen for at least an hour to music or watch a whole movie in your home theater. If the speakers cause listening fatigue, it will show up with longer-term exposure.”

I also queried Michael Barnes, the founder of “Norh” speakers, on what he listens for when assessing prototype speakers:

“As the designer of “Norh” loudspeakers, I in actual fact analyze and compare the connections between the data from double-blind listening tests to laboratory acoustical measurements.

For those of us who do extensive listening, we become adept at picking out fairly quickly when the loudspeaker is coloring the sound. For most people who do not listen to loudspeakers for a living, this process can take some time. Regardless of the experience level, however, the individual results are shockingly consistent from double-blind listening tests. An inexperienced listener and even listeners who claim they are tone-deaf, eventually in a matter of time will have the same conclusion as the experienced listener. This process lends itself to listeners becoming more and more satisfied with the sound of a good speaker over time and more and more frustrated with a bad one.

“An analysis of why this happens shows that it is related to amplitude and balance in relation to the source material. Even using source material that is colored on the original recording and there are lots of recordings like that it will still sound as good as it is ever likely to sound when reproduced on properly designed loudspeakers. This is because the odds of a colored loudspeaker lining up in exactly the inverse coloration of a bad recording are simply impossible in the long run. The amplitude, or volume level, has a dramatic effect on the blind listening test. Two identical loudspeakers with one set just slightly higher in amplitude will consistently result in the louder one winning the listening test.

Since a colored loudspeaker will have broad variations in amplitude response throughout the audible frequency range there will inevitably be certain sections of the performance that are unnaturally louder than they should be. The inexperienced listener may conclude early on in the listening session that this is a good thing because it is a louder thing, but as various source materials are used and as various instruments or vocals on the same source material coincide with this unnaturally loud frequency region, the fatigue and the imbalance begin to become apparent and undesirable.” On the other hand, if a speaker has little or no Bass output, its midrange becomes more noticeable and we can describe its sound as “Frontwards or Too-harsh”, this is because the midrange and treble seems more outstanding. You must keep this idea of “Overall Frequency Balance” in mind when you ever come up with a conclusion of speakers for yourself. A “well-balanced” is the one of the foremost compliments you can ever honor a pair of speakers, because it confirms that the pair of speaker reproduces deep Bass, midrange and treble frequencies equally balanced, that is without any attenuation or beautification involved. Great sounding audio speakers should define the term “High Fidelity” by achieving a kind of musical truth through keeping all sounds in correct relative balance, exactly as they were recorded. There you are, I hope you did get some basic knowledge on understanding of Audio speaker’s accuracy.

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