Classe Audio VSX-81TXV-S manual How to use Professional Acoustic Calibration EQ

The System Setup menu 07

How to use Professional Acoustic Calibration EQ

If you find that lower frequencies seem overly reverberant in your listening room (i.e. it sounds `boomy'), or that different channels seem to exhibit different reverb characteristics, select Aco Cal EQ Pro. (or ALL) for the Auto Mode setting in Automatic MCACC (Expert) on page 33 to calibrate the room automatically. This should provide a balanced calibration that suits the characteristics of your listening room.

If you still aren't satisfied with the results, the manual Advanced EQ setup (below) provides a more customized calibration of your system using the direct sound of the speakers. This is done with the help of a graphical output that can be displayed on-screen, or using a computer (with software available from Pioneer — see Connecting a PC for Advanced MCACC output on page 57).

How to interpret the graphical output

The graph shows decibels on the vertical axis and time (in milliseconds) on the horizontal axis. A straight line indicates a flat-response room (no reverb), whereas a sloping line indicates the presence of reverberation when outputting test tones. The sloping line will eventually flatten out when the reverberant sound stabilizes (this usually takes about 100 ms or so).

By analyzing the graph, you should be able to see how your room is responding to certain frequencies. Differences in channel level and speaker distance are taken into account automatically (compensation is provided for comparison purposes), and the frequency measurements can be examined both with and without

the equalization performed by this receiver.1

Setting Professional Acoustic Calibration EQ according to your room characteristics

Using the manual setup, you can set the time period at which the frequency response is analyzed, pinpointing the time that is best for system calibration with your particular room characteristics.

The graph below shows the difference between standard acoustic calibration and professional calibration (the gray circles represent the point at which the microphone captures the sound for frequency analysis).

Level
			Test tone
	Acoustic Cal. EQ Pro	Standard Acoustic Cal.
	calibration range	EQ calibration range
			Time
0	80	160	(in msec.)

As soon as audio is output from your speaker system, it is influenced by room characteristics, such as walls, furniture, and the dimensions of the room. The sooner the frequency analysis, the less it is influenced by the room. We recommend an earlier time setting of 20 ms to 40 ms to compensate for two major factors that will influence the sound of most rooms:

•Reverberance of high vs. low frequencies – Depending on your room, you may find that lower frequencies seem overly reverberant compared to higher frequencies (i.e. your room sounds ‘boomy’). This may result in a skewed frequency analysis if the measurement is done too late.

Level			Low
			frequencies
			High
			frequencies
	Acoustic Cal. EQ Pro	Standard Acoustic Cal.
	calibration range	EQ calibration range
				Time
0	80	160		(in msec.)

•Reverb characteristics for different channels – Reverb characteristics can be somewhat different for each channel. Since this difference increases as the sound is influenced by the various room characteristics, it is often better to capture a frequency analysis early on for smoother mixing of channel frequencies/sounds.

Level			Left
			surround
			Right
			Surround
	Acoustic Cal. EQ Pro	Standard Acoustic Cal.
	calibration range	EQ calibration range
				Time
0	80	160		(in msec.)

If your room isn’t affected by the factors above, it is often not necessary to make a 20 ms to 40 ms setting. Later time settings may provide a more detailed sound experience with your speaker system. It is best to try and see what works best for your particular room.

Note that changing the room (for example, moving furniture or paintings) will affect the calibration results. In such cases, you should recalibrate your system.

Note

1Note that due to an effect known as ‘group delay’, lower frequencies will take longer to be generated than higher frequencies (this is most obvious when comparing the frequencies at 0 ms). This initial slope is not a problem (i.e. excessive reverb) with your listening room.

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