Madrigal Imaging Audio/Video Preamplifier guide

1ENTER THE SET LEVELS MENU

Output Level Calibration

LEFT FRONT

CENTER

RIGHT

FRONT

INTERNAL

LEFT REAR

SUBWOOFER

EXTERNAL

set levels menu

ing differences in level between various sources (some of which may seem “louder” than others without such a correction).

The PAV also incorporates level controls for each output. These allow you to compensate for differences in amplifier and speaker sensitivities and for place- ment variations in different rooms. These adjustments are essential for re- producing proper soundstaging and image localization. Fortunately, they are normally a one-time adjustment during setup, and only need to be revisited if amplifiers or speakers change.

The simplest and best way to adjust the output level controls is by using a dB Sound Pressure Level (SPL) meter and the internal test tone generator. The goal is to set the volume at the primary listening position to read 75 dB SPL (C-weight- ing, slow mode) from each speaker in sequence, using the individual output level controls. You should point the meter at the ceiling so as to avoid inadvertently favoring one speaker over another. (Note that if the tones in Chapters 8-11 of the WOW! test disc are used, the meter should read 85 dB SPL, since these tones are recorded at a level 10 dB higher than those generated by the internal generator. If external tones such as these are used, you must also be certain that the input level calibration has been done accurately prior to calibrating the output levels.)

In the absence of a dB SPL meter, it is possible to set the output level controls by ear. Use the built-in pink noise generator in the PAV to adjust all volumes to sound the same as they cycle around the various speakers. (This signal is band- width-limited pink noise to minimize the problem of timbre shifts influencing the setting of levels.) The system will then be reasonably well balanced, although of course it is not “calibrated.”

SET LEVELS

RIGHT REAR

Select set levels in the setup menu and press volume +/–. Then select inter- nal (to use the internal noise generator) and press volume +/–. You will then see a screen which should look something like the following:

NOISE SETUP MODE
LEFT FRONT	83
CENTER	83
RIGHT FRONT	83
RIGHT REAR	83
LEFT REAR	83
SUBWOOFER	83

2RAISE OR LOWER THE LEFT FRONT SPEAKER’S VOLUME TO 75 DB SPL AS MEASURED AT THE PRIMARY LISTENING POSITION

Remember that you should be using the “C” weighting curve and the “Slow” ballistics of the SPL meter in order to get an accurate reading.