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Linear Acoustic UPMAX v4 User Guide
power amplifiers or powered speakers. To maintain the lowest noise and widest dynamic
range, it is important to manage analog gain stages properly and in order.
It is strongly recommended that gains be adjusted in the following order:
•
Gains of power amplifiers or powered speakers
•
UPMAX v4 channel trims
•
UPMAX v4 volume control
With an input level of -20dBFS, the analog outputs will be at +4dBu. While appropriate
for most every power amplifier/speaker combination, many powered loudspeakers will
produce excessive output SPL when driven at this level and thus will usually contain con-
tinuously adjustable input gain controls for trimming. In some cases, these might not have
enough range or the gain controls may just be coarse adjustments. In this case, it will be
necessary to use an external attenuator to match the reference levels of the UPMAX v4
and the powered speaker or amplifier. Contact the factory for more information.
4.10.1
Main Channel SPL Adjustment
Monitor calibration is the single most important part of calibrating an UPMAX v4 and a
proper mix environment. Take the time to get this right and check it regularly.
With the UPMAX v4 properly referenced, set to NOT upmix (pass through), and volume
and channel trims at 0dB, apply pink noise at plant reference (such as -20dBFS) to one
channel at a time starting with the Center channel. This is best accomplished via a console
where the pink noise can be "eyeball averaged" at 0VU and routed to one channel at a time.
If the pink noise can only be supplied as a two-channel signal, this will also work by either
disconnecting the speaker that is not being adjusted, or setting its Output Trim setting to
"Mute".
Using a sound pressure level (SPL) meter set to "C-weighted" and "Slow Response" adjust
the Center channel power amplifier to the desired SPL. Typical industry levels range from
78-79dB/C/Slow for near field television mixing to 85dB/C/Slow for far-field film mix-
ing. It is important to note that while an overall reference level is very important, it is more
important to ensure that all main channels are set to the same SPL.
If the power amplifier or powered speaker is adjusted as low as possible and the desired
target SPL cannot be reached, use the Center channel output trim on the UPMAX v4 to
adjust to the desired SPL.
Repeat this procedure for all of the main audio channels, again making sure that the UP-
MAX v4 volume control remains at 0dB. This allows the "return to reference" function to
support any desired volume setting while mixing, and a simple return to the calibrated SPL
during final mixing or mastering.
25
Detailed Operation
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