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Audyssey MultEQ XT
There are several factors that can degrade the sound from even the best loudspeakers in a listening room. One of the most important is the
interaction of sound from the loudspeakers with large surfaces such as walls, the floor, and the ceiling in the room. Even with careful loudspeaker
placement and acoustical treatments, there are significant problems that are caused by room acoustics. These include reflections from nearby
surfaces and standing waves that are created between large parallel surfaces in the room.
In a home theater the situation is further complicated because there are several listening locations. The effects of room acoustics on the sound
arriving at each person’s ears are very different and the result is a listening experience that is degraded in a different way for every person in the
room. It is not uncommon to have variations in two adjacent seats that are as large as 10 dB, particularly in the frequency range below 250 Hz.
The solution to this problem is to apply room correction after precisely measuring how each loudspeaker interacts with the room. Because the
room causes variations in the frequency response of the loudspeakers that are so large from seat to seat, it is important to measure each
loudspeaker at several locations in the listening room. This should be done even if there is only one listener. Measurement at a single location is
not representative of the acoustical problems in the room and will, in most cases, degrade overall performance.
Audyssey MultEQ XT is the only technology that can achieve room correction for multiple listeners in a large listening area. It does so by
combining the data collected at several points in the room from each loudspeaker and then applying correction that minimizes the acoustical
effects of the room and is matched to the frequency resolution of human perception (known as psychoacoustics). Furthermore, MultEQ XT
correction is applied both in frequency and time domains and so there are no artifacts (such as smearing of sound or modal ringing) that are
sometimes associated with traditional methods of room equalization.
In addition to correcting frequency response problems over a wide listening area, Audyssey MultEQ XT provides a completely automated sound
system set-up process. It identifies how many loudspeakers are connected to the amplifiers and whether they are full-range, satellites, or
subwoofers. If there is a least one subwoofer connected, Audyssey MultEQ XT determines the optimum crossover frequency between each
satellite and the subwoofer(s). It automatically checks the polarity of each loudspeaker and alerts the user if there are any that may be wired out-
of-phase relative to the others. It measures the distance to each loudspeaker from the main listening position and adjusts the delays so that sound
from each loudspeaker arrives at the same time. Finally, Audyssey MultEQ XT determines the playback level of each loudspeaker and adjusts the
volume trims so that all levels are equal.
The two diagrams below illustrate two examples of microphone placement for two types of seating arrangements. There are six measuring
positions shown in each case. Increasing the number of measuring points will provide a better sampling of the listening area and produce better
results. The dotted line represents the area in which the room correction provided by Audyssey MultEQ XT is optimal. The microphone must be
placed at ear height at each location.
HDCD®(High Definition Compatible Digital®)
HDCD is an encoding/decoding technology that greatly reduces the distortion that occurs upon digital recording while maintaining compatibility
with the conventional CD format, thus expanding the dynamic range and achieving a high resolution.
Conventional CDs and HDCD compatible CDs are identified automatically to select the optimum digital processing.
•Audyssey MultEQ XT is a trademark of Audyssey Laboratories. It is licensed under US and National Patent
Applications 20030235318 and 10/700,220. Additional U.S. and Foreign Patents pending. MultEQ and the
Audyssey MultEQ logo are trademarks of Audyssey Laboratories, Inc.. All rights reserved.
•®, HDCD®, High Definition Compatible Digital®and Microsoft®are either registered trademarks
or trademarks of Microsoft Corporation, Inc. in the United States and/or other countries. HDCD system
manufactured under license from Microsoft Corporation, Inc. This product is covered by one or more of
the following: In the USA: 5,479,168, 5,638,074, 5,640,161, 5,808,574, 5,838,274, 5,854,600, 5,864,311,
5,872,531, and in Australia: 669114. Other patents pending.
