Headphones lack the phantom-center 2 kHz comb notch present in loudspeaker stereo

Evidence

The stereo phantom center image will suffer from a significant dip in the spectrum around 2 kHz because the sound from both loudspeakers reaches both ears at different times. This interaural crosstalk cancellation is the first dip in an acoustical interference comb filter as explained in Figure 4.4. — Toole, Floyd E, Sound reproduction- the acoustics and…, 415 (#corroborates, via linked claim)

Comb filtering is apparent in measurements when direct and delayed sounds acoustically interfere with each other, so technically there is a problem. However, in perceptions by two ears and a brain, delayed sounds arriving from different horizontal angles than the direct sound are generally perceived as contributing to spatial effects—see Figure 1.5. Reflections deliver information about the room, confirming what the eyes see, and also do more. Figure 4.4 shows that for the phantom center image, stereo introduces a problem: a massive 2 kHz dip in the direct sound. Reflected sounds in the room reduce the dip: Figure 4.4(e), improving not only sound quality but speech intelligibility. This is a parallel with the seat-dip effect in concert halls, where reflected sounds reduce the audibility of the measured direct-sound effect. — Toole, Floyd E, Sound reproduction- the acoustics and…, 445 (#corroborates, via linked claim)

It is a clearly audible effect. Plenge (1987) explains it, as done here, and goes on to relate it to some theories of timbre perception, pointing out along the way that most listeners do not sit still, and are obviously not bothered by the consequent changes in sound image location and timbre. However, dedicated audiophiles and recording engineers who gravitate to the stereo seat are exceptions. Augspurger (1990) describes how easy it is to hear the effect using 1/3-octave bands of pink noise, observing a “distinct null at 2 kHz” (p. 177). Pulkki (2001) confirmed that the comb filter was the dominant audible coloration in anechoic listening to amplitude-panned virtual images, but that it was lessened by room reflections. Listeners in experiments by Choisel and Wickelmaier (2007) reported a reduction in brightness when a mono center loudspeaker was replaced by a stereo phantom image (their figure 4). Listeners in the Shirley et al. (2007) experiments not only heard the dip seen in Figure 7.2e but demonstrated that it had a significant negative effect on speech intelligibility. This is hardly the epitome of sound reproduction technology. — , Toole, Floyd E - Sound reproduction-…, 673 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Room reflections mitigate the phantom-center comb-filter dip near 2 kHz. — Toole, Floyd E, Sound reproduction- the acoustics and…, 445; The stereo phantom center image suffers an audible 2kHz timbre dip affecting speech intelligibility — , Toole, Floyd E - Sound reproduction-…, 673; The null of the phantom-center comb filter makes the sweet spot findable by ear — , Toole, Floyd E - Sound reproduction-…, 667 (+2 more)

Related

• Stereo phantom center images have a spectrum dip near 2 kHz from interaural crosstalk (similarity 0.92)
• The stereo phantom center image suffers an audible 2kHz timbre dip affecting speech intelligibility (similarity 0.91)
• Phantom center image sound quality is inherently compromised even in the sweet spot (similarity 0.91)
• Phantom center images reduce speech intelligibility due to interaural crosstalk (similarity 0.91)
• Stereo presentation masks audible differences between loudspeakers found in mono. (similarity 0.85)
• Room reflections mitigate the phantom-center comb-filter dip near 2 kHz. (similarity 0.84)
• Phantom center dullness stems from destructive acoustical interference, not loudspeaker inadequacy (similarity 0.84)
• A speaker near hard surfaces produces phantom image sources that color its sound (similarity 0.84)
• The null of the phantom-center comb filter makes the sweet spot findable by ear (similarity 0.84)
• Loudspeaker level differences become inter-ear phase differences via cross talk (similarity 0.83)
• Stereo hearing exploits only one directional cue and the ear fills in the rest (similarity 0.83)
• The phantom center image in stereo is always corrupted at the symmetrical sweet spot (similarity 0.82)
• Headphones lack the phantom-center timbre notch because no interaural crosstalk exists. (similarity 0.82)
• A real center speaker improves dialogue clarity over a phantom center (similarity 0.81)
• Excessive rear-wall diffusion can destroy the stereo center image (similarity 0.81)

Broader Connections

• Room reflections mitigate the phantom-center comb-filter dip near 2 kHz. #corroborates (0.95) — Toole, Floyd E, Sound reproduction- the acoustics and…, 445
• Stereo phantom center images have a spectrum dip near 2 kHz from interaural crosstalk #corroborates (0.95) — Toole, Floyd E, Sound reproduction- the acoustics and…, 415
• The stereo phantom center image suffers an audible 2kHz timbre dip affecting speech intelligibility #corroborates (0.90) — , Toole, Floyd E - Sound reproduction-…, 673
• Phantom center dullness stems from destructive acoustical interference, not loudspeaker inadequacy #expands (0.85)
• The null of the phantom-center comb filter makes the sweet spot findable by ear #expands (0.80) — , Toole, Floyd E - Sound reproduction-…, 667