Denon AVR-2807CI, AVR-3806, AVR-4806, AVR-4306 User Manual

Denon has chosen, for many of its acclaimed A/V receivers, with what we feel to be the most
advanced and sonically beneficial Auto Setup and Room Eq system currently available, the
MultEQxt system from Audyssey. Introduced first on the AVR-5805, MultEQxt is now available
on the AVRs-4806, 4306, 3806 and the upcoming AVR-2807CI (March ’06). Due to its
complexity and differentiation from competitors systems, there have been many questions to
what MultEQxt actually does, and with that, quite a lot of misinformation has been generated.
With the assistance of Audyssey, Denon would like to provide you with an informative insight
into this technology.

1. What is MultEQxt?

Audyssey MultEQxt is an acoustical correction technology that calibrates a Denon A/V Receiver
so that it can achieve optimum performance for every listener within a large listening area.
There are two components to MultEQxt:

(i) Automatic Setup (Auto Setup)

(ii) Multi-listener equalization.

During Auto Setup, MultEQxt first finds how many loudspeakers are connected in the system,
then determines the loudspeaker type (satellite or subwoofer), checks the absolute polarity
(phase) of each channel, and identifies the optimum crossover frequency for each loudspeaker
and the subwoofer(s). After that it calculates the distance between each loudspeaker and the
first microphone position in order to automatically set the appropriate delays. Finally, it identifies
any level differences among the loudspeakers and automatically sets the trims.

The multi-listener equalization process combines measurements from several locations within
the listening area to create filters that address the acoustical problems arising from the
interaction of sound with the environment.

2. How is MultEQxt different from other equalization methods?

There are two fundamental differences from every other Room Eq method available in AV
receivers today. The first is that MultEQxt is not based on parametric equalization. Parametric
equalization relies on a few bands that are centered at certain frequencies. These bands do not
provide sufficient resolution to address many room acoustical problems. Also, parametric bands
tend to interact so that changes at one frequency have undesirable results at nearby
frequencies. Moreover, parametric equalization methods use a particular type of digital filter
called Infinite Impulse Response (IIR) that only attempts to correct the magnitude response in
the frequency domain. These filters can cause unwanted effects, such as ringing or smearing,
in the time domain particularly as the bands get narrower. MultEQxt uses Finite Impulse

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Response (FIR) filters for equalization that use sevral hundred coefficients to achieve much
higher resolution in the frequency domain than parametric bands. Furthermore, by their nature,
FIR filters simulatneously provide correction in the frequency and time domains.

The second major difference is that MultEQxt combines multiple measurements to create
equalization filters that better represent the acoustical problems in the room. Most other
methods only perform a single point measurement and this can result in making other locations
in the room sound worse than before equalization. There are some methods that use spatial
averaging to combine multiple room measurements. Although this is a step above single-point
correction, it does not always provide optimum correction. For example, it is common to find a
peak at a certain frequency in one location and a dip at the same frequency at another nearby
location. The averaging methods will add the peak and the dip and this will result in an apparent
flat response at that frequency, thus causing the equalization filter to take no action. MultEQxt
uses a clustering method to combine measurements so that acoustical problems are better
represented, thus allowing the equalization filter to perform the appropriate correction at each
location.

3. What is a target curve?

Once the room measurements are completed, MultEQxt calculates a filter for each loudspeaker
channel including the subwoofer. The role of these filters is to achieve a particular frequency
response within the entire listening area for each loudspeaker. This curve is determined based
on several acoustical and program materiial considerations and is called a “target” or
“calibration” curve.

4. What target curves does MultEQxt use?

Contrary to popular belief, a target curve that is flat from 20 Hz to 20 kHz is not always the one
that will produce the correct sound. There are several reasons for this including the fact that
loudspeakers are much more directional at high frequencies than they are at low frequencies.
This means that the balance of direct and room sound is very different at the high and low ends
of the frequency spectrum. In Denon A/V receivers equipped with MultEQxt, you have a choice
of (4) listening target curves, or ‘modes’; please note for different source inputs, your prefered
listening mode is remembered in Personal Memory Plus. These are:

The ‘Audyssey’
alleviate this problem. A slight roll-off is introduced that restores the balance between direct and
reflected sound.

The ‘Flat’
not apply a high frequency roll-off. This setting is appropriate for very small or highly treated
rooms in which the listener is seated quite close to the loudspeakers. It is also recommended
for all rooms when the receiver is in THX processing mode. This allows THX re-equalization to
operate exactly as it was intended.

The ‘Front’
it does not apply any filtering to the front left and right loudspeakers. The average measured
response from the front left and right loudspeakers is used as the target curve for the remaining

setting uses the MultEQxt filters in the same way as the Audyssey curve, but it does

target curve setting makes the appropriate correction at high frequencies to

setting uses the MultEQxt filters that were calculated for the entire listening area, but

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