TC Electronic SYSTEM 6000 MKII Algorithm Manual - Unwrap Hd
76
unwrAP HD
Basic conversion options
Some conversion options are of a profound nature, e.g. if
the process is thought of as purely additive, if the ability to
collapse to mono or stereo again is important, or if an LFE
channel or Center channel should be derived at all.
Using the additive approach, UnWrap HD preserves the
Left and Right channels bit transparent all the way down
to the LSB of a 24 bit input. If the original stereo-mix is
later requested, it can be obtained using only these two
channels. If subsequent down-mix capability using all the
channels is essential, this option is available too. In both
cases, the LFE channel can be fully exploited, omitted or
anything in between, as can the Center.
Program related conversion options
It has been the goal to provide presets that can make most
kind of program material present itself better and more
engaging in 5.1 than in stereo. From old to recent pop
and rock music, sound effects, drama, unique classical
recordings to highly ambient modern tracks, from ultra dry
to wet source material, UnWrap HD comes with settings to
complement most situations.
Add to the default presets the capability to time-align all
channels at sample precision, widen or narrow the image,
control the amount of Center and LFE channel to be used,
change filters and envelopes, and you begin to get an idea
of the power behind this algorithm.
Time alignment
When all Delays are set at “0”, all Outputs from UnWrap
HD are aligned with sample precision. The basic Delay
through the algorithm in this case is 3.6 ms at 44.1 and
48kHz. Try offsetting the Delays in samples and ms, and
note the shift in image.
Delays may be used...
- on the Surround channels to ensure that sounds appear
to originate from the front speakers.
- on the Center channel to compensate for its position.
- on the LFE channel to compensate for speaker position
or to advance/delay it for artistic reasons.
When the front channels are not assigned the same Delay,
please note that a subsequent stereo down-mix may not
work so well.
Bit Transparency
When 0% L/R Processing is selected, Input Trims and
Output Levels are at 0dB, the inputs are bit transparently
cloned to the L Front and R Front Outputs.
Main Page
Input trims are provided to carefully match the L/R balance.
If working from analog tape, adjust balance with a 1kHz
calibration tone. If working from a digital master with stereo
levels at full scale, it may be necessary to adjust down
Input levels a little bit to avoid UnWrap HD overloads.
The L/R Processing parameter determines how much the
L and R front channels are processed. At 0% UnWrap HD
only adds sound to the 4 other channels preserving the
original L and R as they were. Somewhere between 60
and 70% the width of the original mix is typically preserved
even though a Center channel is added. Tip: A/B the width
soloing the three front channels and toggle by-pass.
UnWrap HD may derive an LFE signal from the Input. It is
recommended to low-pass it between 40 and 120Hz using
a 2nd or 4th order filter.
Center Page
To better separate and optimize the Center Output, EQ and
contour controls are provided.
First set the Ref. Level control at the approximate reference
level of the Input signal. For a typical level, set Ref. Level
at -10 to -18dB. With a full scale digital Input, Ref. Level
would be set high, typically 0 to -12dB. With a quiet or
highly dynamic Input, set it between -15 and -25dB.
Then choose between the four Contour Styles, and finally
apply EQ to the center channel if desired.
UnWrap HD’s 48 bit EQ can work wonders on most signals
and be used to selectively suppress spectral ranges where
the L/R width could otherwise get compromised, or to
boost selected frequencies to strengthen the center anchor
function.
Surround Page
To control the surround channels, de-correlation, EQ and
contour controls are provided.
First set the Ref. Level control at the approximate
reference level of the Input signal. For a typical level, set
Ref. Level at -10 to -18dB. With a full scale digital Input,
Ref. Level would be set high, typically 0 to -12dB. With
a quiet or highly dynamic Input, set it between -15 and
-25dB. Choose between the four Contour Styles to zoom
in on particular elements of the source, and finally select
a de-correlation style also complementing the program
material.
The different de-correlation styles should always be
tried. They are highly subjective and best evaluated with
the Focus control set at “0”. When a style is found, try
changing the Focus control to check if further optimization
is possible. It may prove convenient to solo the surround
channels while doing so.
Now adjust the de-correlation Tone and EQ parameters.