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pressor on a "frequency-weighted"

basis (see

Figure 4-1). With this arrangement, raising

certain frequencies on the equalizer causes them

to be suppressed in the audio signal. A relatively

high threshold setting can allow normal sounds

t~ be una~fected while solo and very loud sounds

are held back. (Of course, when compression does

occur, the level of the entire program is affected.)

Depen.ding on the threshold setting, lower-level

fundamentals or harmonics will not cause com-

pression, and the program is not subject to the

phase shift normally caused by program

equalization.

NffCTOR

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AUDIO

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Fig. 4•1 - EQ In DetKtor Padl

The converse of the

above

EQ technique may

also be used; dipping the equalizer bands causes

any sound with dominant energy in the affected

detect less need for compression.

During the recording of cymbals and tom-toms,

a compressor with an equalizer in the detector path

can help prevent tape saturation. The equalizer can

adjusted for boost with a

peak

of about 5 kHz.

causing the cymbal to be compressed on a very

loud crash, stopping tape saturation at high

frequencies where there is less headroom. However,

gentle tapping of a drumstick or brushing of the

cymbal will not

held

back. Assuming

the tom-

tom

is a lower-frequency instrument and can be

better

tolerated by the tape, it has less need for

compression. The equalization in the detector

circuit means that the compressor is not

triggered as readily by a loud tom-tom beat as

an equally loud cymbal crash.

In the absence of a more sophisticated de

-esser,

small amounts of high-frequency boost in the

detector

path

can frequently help in the processing

vocals

which have been very brightly equaHzed

which suffer

from a prominent

"ess"

sound.

4. 7 .2

Detector EQ For

Speaker

Protection

If a single compressor is to be used with a multi-

way speaker system (i.e.,before the crossover, after

EQ), the system operator is faced with the problem

of keeping the entire system level down below the

point of destruction of the most sensitive com-

ponent. If. for example, mid-range drivers are

frequently damaged, the whole system must

operated at a lower sound pressure level or

additional mid-range driven must be added. By

inserting an equalizer in the detector path of the

160X, it can

made

more unsitive

frequencies in the range handled by the sensitive

drivers. The system can then be run at higher

average

levels and will only

dropped back when

damaging signals are present.

4.7.3

Detector EQ For Broadcast

By inserting a pre-emphasis filter network in the

detector path of a 160X processing pre-emphasized

audio, higher

average

signal levels can be run within

the headroom limitations of the broadcast chain.

4. 7 .4 Anticipatory Compression

By feeding the program directly to the 160X's

detector input and sending the audio signal through

a delay line before the audio input, the unit can

"anticipate" the need for a gain change; see

Figure

4-2.

With some experimentation,

the effect

can be

that

"zero" attack

time

at a given

frequency. Additional signal delays beyond this

''zero" time will then cause the compressor to

finish reducing the gain before the leading edge of

the loud

passage even enters

the .signal input. This

will suppress the program material preceeding the

loud

passage.

The 160X will then begin to recover

from compression

(release)

before the loud passage

has dropped back down toward the set threshold.

This will cause the output level to surge higher as

the note or passage should be decaying. This special

effect obtained with time delay sounds similar to

the inversion of dynamic envelopes produced

during reverse playback of a tape recording. When

coupled with Infinity+ compression, highly unusual

effects can be achieved.

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Fit- 4-2 - Deley In Sitnal Path