The stereo phantom center image suffers an audible 2kHz timbre dip affecting speech intelligibility

Evidence

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

Categorization

• QUESTION: Choisel and Wickelmaier (2007) and Shirley et al. (2007) are worth tracking down as primary citations for the phantom-center timbre dip.
• XREF: connects to: Stereo phantom center images have a spectrum dip near 2 kHz from interaural crosstalk — Toole, Floyd E, Sound reproduction- the acoustics and…, 415; Phantom center image sound quality is inherently compromised even in the sweet spot; Center channel carries most dialog but stereo mixing habits undermine TV use (+6 more)

Broader Connections

• Speaker drivers’ directivity at high frequencies causes spectral dips in the reverberant field #expands (0.80)
• Excess uncorrelated rear-wall sound can destroy the phantom center image #complicates (0.75) — , Toole, Floyd E - Sound reproduction-…, 702