JBL SP MKII User Manual page 24

SURROUND POLARITY: Using the Pro Logic mode (not the THX mode) stand by the
screen and face the surround speakers. With strong surround program materials (such
as Chapter 11 on WOW!), you should hear a solid center image between the surround
speakers and your standing position.
ADDITIONAL HINT: After system polarity checks are completed, use the internal noise
generator in the SP MK II to verify proper hookup. The burst of noise should start at left
front and move clockwise around the room. The Noise Sequence switch on the rear
panel of the SP MK II should be set to turn off the L and R Side outputs.
INPUT LEVEL CALIBRATION
It is necessary to adjust the input level of sources in order to get the best results from
your SP MK II. This adjustment yields the best dynamic range from the surround
decoder circuitry, preventing overload distortion or excessive background hiss.
Correct calibration also ensures accurate tracking of the steering logic and the modi-
fied Dolby B noise reduction system in the Dolby Pro Logic circuitry.
A test tone (Chapter 5 on WOW!) can be used in conjunction with the front panel LED
level display to calibrate the system. Feed in the test tone and adjust the input level so
that the 0 dB LED just reaches full intensity. Under normal operating conditions, the
red LED should never do more than flicker occasionally (which indicates input over-
load).
If no test tone is available, you can still calibrate the system with reasonable accuracy
by turning up the input level control until the 0 dB LED glows brightly during medium
level passages in movies, but not high enough to illuminate the red LED. Movies are
duplicated at slightly different audio levels, so you may need to touch up this adjust-
ment occasionally. You may expect a 1 to 3 dB variation among various film transfers.
AUTO BALANCE/INPUT BALANCE
The Automatic Input Balance circuit corrects improperly balanced software, which
tends to pull the dialog off center. These channel errors occur in the multiple copying
stages between the original master and your source. In most cases the autobalance
circuitry within your SP MK II will provide extremely accurate correction. Occasionally,
some software may have errors beyond the correction ability of the internal circuitry. To
manually correct for such imbalances, press the left or right button located on the right
side of the front panel of the SP MK II to turn off the autobalance circuit. With the
Center output on but with the the Center Speaker amplifier turned off, push the left or
right channel button to minimize leakage of center channel dialog to left or right speak-
ers. The liquid crystal display will indicate the amount of level change. Turn the center
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