User manual

User Manual • System Gain, Sub Offset and Level Etc. • Power Up Sequence • Page 7
6. System Gain, Sub Offset &
Level Overview
System Electrical Gain: The input stage of BMC MK III is designed for a
maximum input level of +24dBu (balanced or unbalanced) before clipping.
The output stage will also drive a balanced 10K Ohm load to a maximum
of +24dBu. However, because the BMC can add up to +6dB of gain to a
channel to balance the system, there are situations where the BMC MK
III will clip. For example you cannot take a +24dBu input, set the system
gain at 0dB, add +6dB of calibration gain to the signal and get +30dBu
on the output. The output amplifiers in the BMC MK III will clip under these
conditions.
In order to reduce the possibility of clipping the bass / LFE summation buss
with +4dBu nominal sources, the BMC MK III offers a 0dB / -10dB “SUB
OFFSET” pad feature. Controlled via the remote, and located in the “CAL
CHANNELS” menu (pictured below - for more information, see the “Software
Features” section on page 8 and 9), this feature allows the user to add a
-10dB “pad” on the SUB summation / output buss.
Although this may seem to be a limitation, in practice it is not. The Blue
Sky monitors, like most amplified monitors, have relatively high voltage
sensitivity. Therefore, there is quite a bit of flexibility in setting gains.
For the best signal to noise ratio and to minimize noise and hum pickup,
the BMC MK III should be driven with as high a signal level as possible. The
output signal going to the monitors should be kept relatively high and if
necessary signals should be attenuated at the monitors.
Calibration, Level Trims, -3dB Surround Setting: The individual channel
level trims (+/- 6dB, in .5 dB increments) in the BMC MK III, are “OUTPUT”
channel level trims and are used to adjust the relative level between the
subwoofer and satellite speakers, so as to achieve proper summation and
provide smooth full range response for each channel. The reason this fact
is important is because in certain applications, such as in a 5.1 theatrical
film setup, the surround channels may need to be calibrated -3dB lower than
the front channels. In order to still achieve proper summation between the
surround SATs and the SUB, there needs to be an additional complementary
-3dB offset for the bass-managed portion of just the surround channel
signals. The BMC MK III now makes this possible, by adding a ‘surround
& subwoofer gain offset’, which is listed under the ‘CAL CHANNELS’ setup
menu as ‘SUR SUB MAIN (or AUX) GAIN’ (see picture below).
This toggle lowers the subwoofer level, just for the surround channels, by
-3dB and also lowers the left and right surround calibration settings by -3 dB.
When this toggle is set to the -3dB setting the -3dB LED will also turn on. For
more information, see the “Software Features” section on page 8 & 9, along
with “5.1 System Calibration” on page 12.
“LFE TRIM”: This new “CAL CHANNELS” menu feature allows you to make
small tweaks to just the LFE channel level. For most applications, the +10
LFE level (without any trim) is the correct setting. However, sometimes the
LFE level used in a small room, may not translate when the mix is played
back in a larger dubbing stage or movie theatre. In this case, the LFE level
can be trimmed up or down. This adjustment does not impact the bass-
managed subwoofer level. The range of the adjustments is +/- 2dB, in .5dB
increments and is relative to the LFE GAIN setting (0 or +10 dB). For more
information, see “5.1 System Calibration” on page 12 to 14, and “Additional
Surround & Setup Information” on page 15.
GAIN = -10.0 dB
SUB OFFSET MAIN
GAIN = - 3.0 dB
SUR SUB MAIN
7. BMC Power Up Sequence
1. Although the system will startup without the BMC remote being connected,
in order to calibrate the system and gain full access to all of the BMC MK III’s
features, the BMC remote must be connected to the I/O unit(s). Once the
system has been calibrated, the remote can be disconnected and the main
I/O unit will retain all the setup information. Once the systems’ power is
cycled, the main I/O unit will power up fully calibrated and at the “reference”
position. See the “Software Features” section on page 8 and the “5.1
System Calibration” section on page 12 for more information.
2. The startup sequence is activated when ever a remote is connected to
the I/O unit or when the power is cycled with the remote connected. The
power up sequence is as follows -
A: The LEDs may flash momentarily as the remote receives power
from the main I/O unit. The power LED on the front of the I/O unit(s)
should be lit.
B: Within the I/O unit(s) the output relays will click on.
C: The LCD will display the current software version for 5 seconds.
D: After the BMC has fully activated the system will go into the mute
mode and the display will show the following message.
BMC MK II Power Up Sequence
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BMC MK I I I V3.00
SYSTEM MUTED
USER MANUAL • SYSTEM GAIN, SUB OFFSET & LEVEL OVERVIEW. • POWER UP SEQUENCE
BMC MK III