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Negative ratios can also be used to prevent musicians from continually increasing the volume of their instrument (e.g.,

in live applications where there is no sound engineer to control the house levels). With their signal compressed by a neg-

ative COMPRESSION RATIO, each volume increase initiated at the instrument or amp would actually decrease the

volume level at the final mix.

Fattening Kick Drums and Compressing Other Drums

Weak, flabby kick drums often have too much boom, and not enough slap. To tighten them up, start with the 160A

adjusted for a medium to high COMPRESSION RATIO (e.g., 6:1), adjust the THRESHOLD control so that the GAIN

REDUCTION meters show 15dB of gain reduction, then increase the COMPRESSION RATIO if necessary. In

OverEasy mode, the 160A takes slightly longer to react than in Hard Knee mode, and will therefore emphasize the slap

at the beginning of the note and reduce the boominess of its body. The 160A also works well for tightening snare drums

and tom toms and can be used with drum machines to effectively alter the character of any electronic drum sound.

For drum kit submixes (e.g., mixing multiple drum tracks to two tracks while using two 160As for compression), con-

sider backing off the COMPRESSION RATIO on each 160A (down to 2:1) to avoid an excess of cymbal "splattering."

In larger multitracking systems, compress the kick and snare separately. A further possibility (if you have two more

compressors) is to heavily compress a stereo submix of toms and leave the remaining percussives unaffected.

Raising a Signal Out of a Mix

Since reducing dynamic range increases the average signal level by a small amount, a single track can be raised out of a

mix by boosting its level slightly and applying compression. Start with a 2:1 COMPRESSION RATIO and a relatively

low THRESHOLD setting (-20dB). Adjust both controls as necessary.

Compressors have also been used to bring vocals to the forefront of a mix in volume-restricted studios (e.g. home stu-

dios). Start by adding a foam windscreen to the mic (if it doesn't have one). Set the COMPRESSION RATIO to 10:1 and

the THRESHOLD to -10dB. With your mouth approximately 2 inches from the mic, sing the vocal part, but with less

volume than normal. Use phrasing to give the part some intensity. An equalizer (e.g., a dbx 20 or 30 Series Graphic

Equalizer) or a vocal effects device (e.g., reverb, delay, distortion) can be added to further toughen the performance.

It is also possible to separate certain vocals or instruments from a mono program already mixed: refer to frequency-

weighted compression on page 8.

Note: When compressing a stereo program with a pair of 160As, the factors affecting a compression curve and the actual COMPRESSION RATIO and

THRESHOLD settings, are like those previously covered with reference to single channels of program material. However, it will generally be found that

large amounts of compression are more audible in a mixed stereo program than they might be on the separate tracks that were mixed to create the pro-

gram.

Preventing Analog Tape Saturation

With programs of widely varying levels, compression can prevent recording levels (e.g., cymbal tracks in a final mix or

drum kit submix) from saturating tape tracks (see frequency-weighted compression, below).

Preventing Digital Overload

Some digital recorders and samplers produce audible distortion when they exceed their headroom (i.e., the range above

their normal operating level). The 160A effectively ensures that audio input does not overload a digital recorder's D/A

(digital-to-analog) converters. The 160A can perform this compression quietly enough for all digital media. Set the

160A for limiting with Hard Knee mode On, the COMPRESSION RATIO to ∞:1, and set the THRESHOLD 2 to 3dB

below the overload point of the recorder.

Speaker Protection (Auditoriums, Churches, Mobile DJs and Sound Systems)

Compressors are frequently used to prevent excessive program levels from damaging drivers in a sound-reinforcement

system (whether you're doing auditorium, church, or club sound engineering, or are a mobile DJ for small dances, or

like to push the limits your home's audio entertainment center). Set the 160A for limiting (Hard Knee mode On, with a

COMPRESSION RATIO of 10:1 or greater) and adjust the THRESHOLD to provide 15dB or more of compression (just

a few dB below the input clip). For low-level signals, the 160A won't change gain, but if large signals come along, the

gain will be reduced to prevent clipping and save sensitive system components from excessive heat buildup or other

type of damage .

In circumstances where the 160A is expected to cause no change in gain unless an emergency arises (wildly excessive

levels), some operators set Hard Knee mode On, the COMPRESSION RATIO to ∞:1, and the THRESHOLD to the

highest permissible level.

dbx 160A COMPRESSOR / LIMITER