Antares MDT user manual

							 
MDT UserÕs Manual
 
11
 
Owner Registration
 
Owner Registration 
Your purchase of MDT entitles you to technical support, special introduc-
tory offers on new products from Antares Audio Technologies, and notiÞca-
tion of software updates. Software updates will be published as the
program evolves.
Please Þll out and return the Owner Registration Card. The information on
the card will allow us to communicate more effectively with you and will
enable us to serve you better in the future. 
 
Installing MDT 
To install MDT, double click the installer icon. Information about the autho-
rization process call be found in the installed read-me Þle.
 
Technical Support  
If you have some problem using MDT that canÕt be solved by reading the
manual, call technical support at (888) 332-2636, or (408) 399-0008 Monday
through Friday between 9 AM to 5 PM PaciÞc Standard Time.
Also, you might Þnd what you want at our web page:
www.antaresTech.com
You can also e-mail:
[email protected] 
						

							 
Getting Started
 
12
 
MDT UserÕs Manual 
						

							 
MDT UserÕs Manual
 
13
 
CHAPTER 2
 
Introducing MDT
 
MDT is a breakthrough among with dynamics processors. It puts your
hands on the dials and levers of the DSP process itself, letting you shape the
results in ways never available before. Access to this new level of ßexibility
and control is achieved by shifting the way you think about how compres-
sion and expansion work. This chapter introduces MDTÕs operating para-
digm and gives the information needed to use it effectively.
 
Understanding Compression 
Next to reverb, compression is probably the most important signal process
used in todayÕs studios. Simply put, compression reduces the 
 
dynamic range
 
of a signal. That is, it reduces the difference in loudness between the loudest
and quietest parts of a piece of music. Another way to think about this is
that the compressor is acting as an automatic fader which fades down when
the music gets loud and fades back up when the music gets soft.
Why reduce the dynamic range? Consider mixing a vocal into a pop music
bed. Typically, pop music has a relatively consistent level of loudness. If an
uncompressed vocal track is added to a typical pop mix, certain loudly sung
words or syllables would be very obtrusive, while quieter phrases would be
buried underneath the instrumental texture. This is because the difference
between the loudest and softest sounds in the vocal, its dynamic range, is
very large. This same problem occurs for any instrument which had a
dynamic range larger than the music bed into which it is being mixed. 
By using a compressor to decrease the dynamic range of the vocal, the softer
sounds are increased in loudness and the loudest sounds are reduced in
loudness, tending to even out the overall level of the track. This makes the 
						

							 
Introducing MDT
 
14
 
MDT UserÕs Manual
 
vocal track sound generally louder and more distinct, and therefore, easier
to hear in the mix.
 
Ratio And Threshold
 
How is compression measured? What is a little compression and what is a
lot of compression? The concept called 
 
compression ratio 
 
is
 
 
 
the measure of
how much the dynamic range is compressed. Look at the illustration below.
This graph represents the relationship between the input level of the signal
and the output level of the signal after compression. Notice that the curve
has a breakpoint called a 
 
threshold
 
. All standard compressors use a thresh-
old. Signals that are louder than the threshold are processed (reduced in
level) while those softer than the threshold are unchanged.
As the input signal exceeds the threshold, 
 
gain reduction
 
 (reduction in loud-
ness) is applied. The amount of gain reduction that is applied depends on
the compression ratio. The higher the compression ratio, the more gain
reduction is applied to the signal.
The graph shows the relationship between compression ratio and gain
reduction. Examine the 2 to 1 ratio curve. For signals above the threshold,
INPUT LEVEL OUTPUT LEVEL1 to 1 r atio
2 to 1 r atio
4 to 1 r atio
8 to 1 r atio
¥ to 1 r atio THRESHOLD
Louder
I/O Cur ve
Louder 
						

							 
MDT UserÕs Manual
 
15
 
Understanding Compression
 
this curve transforms a range of loudness 2 units large into a range of loud-
ness one unit large. Examine the  
¥
 
 to 1 curve. This curve transforms all
sounds above the threshold to the same loudness. Dynamics processors
which have this sort of curve are called limiters.
 
MDT As A Compressor
 
The graph described above appears in MDTÕs user interface. The following
illustration is a screen shot of MDTÕs In/Out Grid.
Like the Þrst graph, this is a graph of the Input Level versus the Output
Level. The curve on the graph has a threshold and the curve segment above
the threshold has a 4 to 1 compression ratio. 
The gray bar at the bottom of the graph is an input level meter. It shows
how loud the input signal is so that you can see where on the curve it falls.
In the illustration below, the input level is at -18 dB. The threshold is at
THRESHOLD
4 to1 Ratio
Input Level
I/O Curve 
						

							 
Introducing MDT
 
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MDT UserÕs Manual
 
-48 dB. The input is above the threshold so it is getting a gain reduction of
-21 dB. This puts the output at -39 dB.
 
The In/Out Grid
 
In conventional dynamics processors, there are knobs or sliders that control
the threshold and ratio parameters. MDT uses a graphic interface called the
In/Out Grid for these adjustments. The In/Out Grid provides visual feed-
back of the effect the tool is having on the sound. The complexity of the pro-
cessor Õs conÞguration is easily controlled using multiple thresholds and
their associated compression ratios.
The details of how to use MDTÕs graphic interface are explained in Lesson 1
of the MDT Tutorial.
MDTÕs I/O Curve can be arranged to create many different kinds of
dynamic processing devices in addition to compressors. Many esoteric and
expensive outboard dynamics processors can also be emulated. The Setting
menu contains many settings which you will Þnd useful in creating ÒsweetÓ
sounding digital expanders, spectral enhancers, companders, and other
tools useful in mastering, tracking, and sound design. The examples below
THRESHOLD = -48 dB4 to 1 Ratio
Input Level: -18 dB Output Level: -39 dB
Gain Reduction = 21 dB 
						

							 
MDT UserÕs Manual17 Understanding Compression
explain some of the conÞgurations that are possible using MDTÕs unique
graphic interface.
ÒSoft KneeÓ Compressor
ÒSoft kneeÓ compressors sound less obvious than regular Òhard kneeÓ com-
pressors because the compression ratio near the threshold changes gradu-
ally. In the example above, as the signal gets louder than the threshold, it is
Þrst compressed at 2 to1. As it gets louder still, the ratio goes to 3 to1, until,
Þnally, it reaches its maximum ratio of 4 to 1. This setting sounds less
ÒsquashedÓ than a plain 4 to 1 hard knee compressor because only the
peaks in the signal get the full 4 to 1 compression.
The Òsoftest kneeÓ dynamics processors available are the tube-type com-
pressors, especially the vintage variety. The following example shows how
MDT can be conÞgured to emulate a tube compander.
Ratio = 2 to 1 Ratio = 3 to 1 Ratio = 4 to 1
Ratio = 1 to 1 
						

							Introducing MDT
18MDT UserÕs Manual
ÒTubeÓ Compander
The curve shown above has no clear threshold point where the signal starts
to get processed. Instead, the compression or expansion ratios change grad-
ually. It is called a compander because it both compresses and expands the
dynamic range, depending on the level of the input. The top half of the
curve compresses the dynamic range. The bottom half of the curve expands
the dynamic range.
The sonic effect of processing through this kind of setting is very natural.
Only the peaks of the sound get compressed heavily, while most of the sig-
nal passes through at a 1 to 1 ratio. This assumes that the average input
level is around -40 dB. (See ÒThe Input Offset ArrowsÓ on page 27 for an
explanation of how to ÒplaceÓ an input on the curve without actually
changing its level.)
Sounds quieter than -48 dB get expanded downward, that is, they are faded
down as they get softer. Because the curve increases in slope gradually, this
subtle gating effect sounds very natural. It is useful for eliminating noise
and maintaining a sense of wide dynamic range while still compressing the
hot peaks in the signal.
Compression Ratios
3 to 1
2.2 to 1
1.5 to 1
1 to 1
Expansion Ratios
1 to 1.5
1 to 2.2
1 to 3.0
1 to 4.0 
						

							MDT UserÕs Manual19 Understanding Compression
Attack And Release Times
The attack time of a compressor is simply how long it takes for the compres-
sor to react once the input level has met or exceeded the threshold level.
With a fast attack time, the signal is brought under control almost immedi-
ately, whereas a slower attack time will allow the start of a transient or a
percussive sound to pass through uncompressed before the processor has
time to react. Creating a deliberate overshoot by setting an attack time of
several milliseconds is an effective way to emphasize the percussive nature
of instruments. The illustration below shows the effect of changing the
attack time.
The release time of a compressor is the time it takes for the gain to return to
normal after the input level drops below the threshold. Setting too quick a
release time can cause a pumping effect in the output. If the release time is
too long, the compressor will not accurately track level changes in the
input. The illustration below shows the effect of changing the release time.
Uncompressed Input CompressedCompressed
1 mSec attack 10 mSec attack
Uncompressed InputCompressed
1 mSec releaseCompressed
50 mSec release 
						

							Introducing MDT
20MDT UserÕs Manual
MDT In The TDM Environment
The TDM software environment is supported by hardware from Digidesign
called the DSP Farm. Each DSP Farm card contains DSP chips on which
MDT and other DSP plug-ins run. The TDM system requires that one chip
on the DSP Farm be used for the Mixer plug-in which comes with ProTools.
Assigning a large number of ProTools voices will sometimes require the use
of two DSP chips on the DSP Farm. 
MDT processes two audio channels per DSP chip. The table below shows
how many DSP chips are used as more MDT channels are allocated.
Number of MDTs used Number of DSP chips allocated
2 mono to mono MDTs 1
1 stereo to stereo MDT 1
1 mono to mono plus 1 stereo to stereo MDT 2
NOTE: Sometimes TDM will post a warning dialog saying that there are an
insufÞcient number of DSP chips available when you have added a nor-
mally legal number of MDTs. This is because of the order in which TDM
allocates the DSP chips as you add more inserts. If this occurs, de-assign a
MDT or two and then re-assign them. This allows TDM to sort out its DSP
allocation, allowing the greatest use of the available DSP chips.