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

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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’ target curve setting makes the appropriate correction at high frequencies to alleviate this problem. A slight roll-off is introduced that restores the balance between direct and reflected sound.

The ‘Flat’ setting uses the MultEQxt filters in the same way as the Audyssey curve, but it does 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’ setting uses the MultEQxt filters that were calculated for the entire listening area, but 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

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