Monday, February 6, 2012

Improving the sound of your digital music - Part II: Setting the reference baseline.

  To set our baseline reference, we performed a series of A/B comparisons, first listening to a reference CD on a high-quality full-range loudspeaker system (Mirage M-3s), and then immediately switching to the same track in lossless WAV format on an iPod Touch through standard Apple-supplied earbuds. Rather than use a random selection of music, as in many reviews, we will do a direct comparison to the reference in all of our tests. The reference material for our evaluation is Chesky Records The Ultimate Demonstration Disc, on a standard Compact Disc format.

This test is intended to evaluate how much higher quality earbuds (or in-ear monitors) can improve the sound of your digital music, or conversely, how much you lose by listening through low quality earbuds. This is not a test of the loss from the compressed MP3 format, which would have varying impact depending on the nature of the musical content.

The objective in setting the baseline reference is to first know what you might be missing. The test disc begins with a male narrator who introduces the disc and each test track, guiding the listener on the characteristics and details that should be conveyed in a high quality system.

We gave the results of each test a subjective numeric grade:
  • 10 points: Indistinguishable from the reference.
  • 9 points: High-quality reproduction with all the essential elements of the recording, and only a slight loss of accuracy compared to reference.
  • 8 points: A quality playback, but loses some elements of the reference.
  • 7 points: Listenable, but alters the original or lacks significant characteristics of the reference.
  • 6: Fails to retain many elements of the original, or distorts the reference material.
Introduction - Male vocals
The narrator's voice has a deep chesty resonance in the reference, with a warm, very realistic sound. Each breath as he speaks is audible in great detail, lending a high sense of realism, as if he were there in the room with the listener.
  • iPod earbuds: 7 points. Emphasizes the deep, chesty component of the narrator's voice. Loses some sense of realism.
High Resolution
This is a female vocal of Spanish Harlem, performed by Rebecca Pidgeon. The reference has deep bass in the opening, with an airy, full-range and detailed quality to Rebecca's voice. The shakers in the distance are very detailed, conveying a realistic sense of space, while the violins are reproduced without any sense of excessive brightness. An acoustic guitar sounds very realistic and warm.
  • Earbuds: 6 points. An excessive bass emphasis is evident here. Rebecca Pidgeon's voice is very warm, rather than airy. The studio echo is much more prominent than in the reference, losing the sense of natural ambiance. The soundstage and dynamic range are compressed, and the piano loses realism. Lack of detail in the shakers.
If I Could Sing Your Blues, with female vocalist Sara K. Track opens with a trumpet in the distance, to the right and conveying a sense of a larger space. Very natural and realistic, Sara K with a wide range vocal range. Drums in the rear of the studio on the left, with detailed cymbals.
  • Earbuds: 7 points. Good placement of trumpet in background, but the center stage with vocal and guitar is constrained.  Guitar is up front with singer, losing distinct image and separation. Loses a great amount of high-frequency detail in cymbals. Trumpet more muted.
Maiden Voyage is another female vocal, with Brazilian singer Leny Andrade. The opening has deep bass, conveying the full body of the instrument, combined with detailed and airy cymbals to the right. Realistic piano contributes to a broad and deep soundstage, with excellent imaging of each instrument.
  • Earbuds: 7 points. Opening conveys strumming of the bass strings, but lacks body. The cymbals go soft and recede into the background, almost like white noise. Body of piano lacking, harmonics muted, somewhat bright compared to reference. Soundstage shrinks to a smaller space. Good bass extension, but bass string plucks lack transients and sense of realism.
Midrange Purity
Grandma's Hands is an acapella piece with male vocalist Livingston Taylor. Finger snaps are detailed, voice is full and realistic in the reference.
  • Earbuds: 6 points. Finger snaps lack flesh and bone realism, nearly disappearing at some points in the track.  Livingston Taylor vocal lacks body.
Correnteza, by Brazilian singer and guitarist Ana Caram was recorded in a church, portraying the illusion of a rain forest filled with bird sounds. The reference immerses the listener in another space, with high frequency detail of bird sounds and realistic effects of water dripping. This is a very detailed, high-resolution vocal. The rhythm of of the drum has deep, full-body harmonics. There is a soft triangle detail at the end of the track.
  • Earbuds: 7 points. Much of the sound effect here is on the high end, where the earbud response is lacking. Lacks the sense of envelopment in the reference. Detailed deep harmonics of the drum are lost.  Warm violin, and good reproduction of female vocal. The detail of the triangle at the end of the track is nearly missing, while simulated sound of water dripping loses the illusion.
This track features the Fred Hirsch trio, piano, drum and bass, on Played Twice. Opens with soft drum hits to the right rear, followed by piano and deep bass plucks. A great amount of detail is reproduced in the cymbals, with full harmonics, air and transients. Realistic, full piano sound.
  • Earbuds: 8 points. Bass response is good, can hear individual string plucks, but lacking in full body. Good reproduction of piano, but it should be more upfront and clearly delineated. Decent reproduction of drum and cymbals, but the overall soundstage is compressed and lacks depth compared to the reference.
Ask Me Now is a tenor saxophone solo, performed by Joe Henderson in a large recording studio. The reference blasts from the speakers to the right of center, with a full, realistic, three-dimensional body resonance. The echo in the recording studio comes through in playback, giving a sense of the size of the space. Each keystroke and breath is clearly detailed.
  • Earbuds: 6.5 points. Lacks a sense of the full body of the instrument. Loss of details on key strokes. Good on low notes, but lack of harmonics. The echo from back wall is distorted, losing a sense of the space. 
Visceral Impact
Sweet Georgia Brown by Monty Alexander, with two drum sets, and both an acoustic and electric bass. Opens with piano on left, audible mutterings of Monty Alexander, realistic full drum set to the right rear. Airy cymbals from second drum set to left rear. Clear sounds of both acoustic and electric bass. Dynamic soundstage filled with horn blasts.
  • Earbuds: 7.5 points. Very good energy, can identify individual instruments, distinguish electric and acoustic bass. Piano lacks body. Excellent low bass. Some loss of details and soundstage.
Rhythm and Pace
Johnny Frigo on jazz violin performing I Love Paris. Opens with electric guitar to the right. Airy cymbals and sweet sound of violin. Deep notes of electric bass keeps rhythm to the left. Excellent imaging of high-hat cymbal. Very deep kick drum with visceral impact. Saxophone on left fills soundstage while cymbals and guitar keep pace on right. Very dynamic!
  • Earbuds: 7.5 points. Good soundstage. Good detail on cymbal hits, but lacks air compared to reference. Very good bass and electric guitar. Some loss of transients on violin. Smearing of image on violin from center to left. High-hat imaged more upfront. Drum kicks lack depth. Good dynamics.
Vivaldi Flute Concerto in D. Wide dynamic range with deep bass notes along with high fluttering notes from the flute. Can hear detail of the musician's breaths. Excellent sense of space and realistic ambience.
  • Earbuds: 8 points. Maintains focus of flute against background instruments, but loss of ambient detail that conveys a sense of realism in the reference. Reduced dynamic range.
Holographic Imaging
Festival Te Deum is a performance by the Westminster Choir in a large cathedral (60' W, 225' L, 90'H) with pipe organ, recorded with a single microphone elevated 35 feet high. This track is challenging for a full-range loudspeaker to image the large space, and presentation of the wide, yet detailed dynamics. The reference system has excellent depth, and fills the room with images of the choir as a whole, while retaining the individual voices.
  • Earbuds: 8 points. Very good sense of the expanse of the cathedral, and detailing of individual voices in the choir. Loss of harmonics and depth in organ alters the visceral impact and sense of realism. 
Stravinsky's The Royal March. This is a very dynamic track, with very deep notes from the kettle drums to the high frequency transients from violins, flutes, and trumpets.
  • Earbuds: 8 points. Very good in lower frequencies, excellent trombone transients, but high-end loses accuracy, especially on strings. Good depth of soundstage. 
Bass Resonance
This is a single standup bass recorded 3' from the microphone. The reference system produces a full, realistic sound of the body of the instrument, along with the string plucks, that never fails to shake something in the room before finally trailing off in a gentle fade out.
  • Earbuds: 7 points. The earbuds emphasize low frequencies, and do very well with this track. There is detail of the standup bass string plucks, but an inevitable loss of the full body harmonics that earbuds can't convey.
Dynamic Test
This is a wide dynamic range solo drum recording. The snare and kick drum open relatively low in volume, with detailed cymbal hits and clear, deep drum kicks. Excellent holographic imaging of the complete drum kit, along with height of the cymbals. Incredibly realistic!
  • Earbuds:  7.5 points. The initially quiet cymbal hit dynamics roll off too quickly. Muted kick drum.  Some blurring on dynamics. Good imaging of cymbals, and follows peak dynamics well.
For the wide ranging set of 15 different tests, the standard iPod earbuds averaged a score of 7.2 points compared to the reference material.This indicates that the earbuds may be adequate for casual listening, but the loss of many characteristics of the recorded music make them inadequate for anything close to an audiophile experience, or for listening to high-quality uncompressed recordings. By comparing directly to the reference in a series of A/B tests, we can discern what is lacking - most significantly: depth of soundstage, resolution and accurate soundstage imaging.

Next up: iFrogz Audio Spectra earbuds

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