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Thursday, December 22, 2011

Twenty Questions: Dynamic Details

Test your knowledge of compression in various applications in our latest pop quiz.

Go ahead and see how much you really know or don’t know about Compression.

This mini-test gets progressively more difficult and is a good indicator of where you stand in this area of pro audio science.

Rick Kreifeldt, Harman Professional SDIG Vice President, has graciously guest authored a dynamics processing inspired Twenty Questions.

There is one correct answer for each question. Good luck!

 
1.) What does a Compression Ratio of 4:1 mean?

A.) Once past the threshold, the input signal must increase by 4 dB for the output to increase by one dB.
B.) Once past the threshold, the output signal will be 4 dB less than the input signal.
C.) Once past the threshold, the compressor will have 4 dB of gain reduction.

 
2.) Compressor attack time is defined as:

A.) The time it takes for the compressor to come out of gain reduction.
B.) The time it takes before the compressor starts gain reduction.
C.) The time it takes for the compressor to enter full gain reduction.
D.) None of the above.

 
3.) Signals below the compressor threshold pass through without being compressed:

A.) True
B.) False

 
4.) If a compressor is showing 10 dB of gain reduction and you add 10 dB of makeup gain, lower level signals below the threshold will be:

A.) Reduced by 10 dB.
B.) 10 dB louder.
C.) 20 dB louder.

 
5.) Signals below the threshold of a downward expander are:

A.) Passed through without any gain reduction.
B.) Reduced by the downward expander ratio.
C.) Made louder by the expansion ratio.

6.) A soft knee compressor:

A.) Starts compression before the threshold.
B.) The compressor will not be at the full compression ratio until after the threshold.
C.) Has a lower output level at the threshold than a hard knee compressor.
D.) All of the above.

 
7.) Gate attack time is defined as:

A.) The time it takes for the gate to enter gain reduction.
B.) The time it takes for the gate to close.
C.) The time it takes for the gate to come out of gain reduction.
D.) None of the above..

 
8.) A parametric EQ with a bandwidth of 1/4 octave inserted into the side chain of a compressor with a boost of 6 dB at 1 kHz will cause the compressor to compress a signal at1 kHz more than a signal at 100 Hz.

A.) True
B.) False

 
9.) An optical compressor uses what for the gain element:

A.) Photo cell and LED.
B.) Photo diode and LED.
C.) Fiber optic VCA.
D.) Flux Capacitor.

 
10.) A compressor is set to a 3:1 ratio. The threshold is set at +3dBu. If the input signal is at +12dBu, what is the level of the output signal?

A.) +4 dBu.
B.) +5 dBu.
C.) +6 dBu.
D.) +7 dBu.

 
11.) A gate has a look-ahead time of 600uSec. Which of the following is true:

A.) The gate will open 600uSec faster if this feature is turned on.
B.) The gate looks 600uSec ahead in time to see if it will need to open.
C.) The gate will open in 600uSec plus the attack time.
D.) The main signal will be delayed by 600uSec so that the gate will have time to open before the signal passes through the gain element.

12.) What will be the result of running the kick drum into the key input of the bassist’s gate?

A.) When the kick drum is played, the bassist’s sound will be compressed.
B.) The bass will only be heard when the kick is played.
C.) The bassist will finally be in time.
D.) The drummer will finally be on time.

 
13.) An acoustic guitar player switches between strumming and finger picking in the same song. Which of the following compressor settings will make his finger picking 8 dB louder if his strumming peaks at 8 dBu?

A.) Adjust the threshold to ­8 dBu and the ratio to 2:1.
B.) Adjust the threshold to 0 dBu with a ratio of Infinity:1.
C.) Adjust the threshold and ratio until you have 8 dB on the gain reduction meter when he is strumming and no gain reduction when he is finger picking. Add 8 dB of make-up gain.
D.) Adjust the threshold 0 dBu and the ratio to 8:1; add 8 dB of make-up gain.

 
14.) You are using a digital limiter. The A/D of the digital compressor reaches it’s maximum output when the input signal is at +22dBu, and the box is unity gain.

Assuming no other gain through the unit, at what threshold must you set the digital limiter so that the output signal will not exceed +10dBu?

A.) ­0 dBFS
B.) +10 dBFS
C.) +12 dBFS
D.) ­10 dBFS

 
15.) If a downward expander is set at a ratio of 1:1.5, a threshold of ­40dBu, and a maximum attenuation or depth of 20dB, how much gain reduction will there be if the input signal is at ­50dBu?

A.) 10
B.) 12.5
C.) 15
D.) 20

 
16.) Compression ratio of 2:1. Compressor threshold of ­10dBu. Limiter threshold of 0dBu. If the input signal is at +10dBu, how much gain reduction is being contributed by the limiter:

A.) 10 dB
B.) 5 dB
C.) 20 dB
D.) None
E.) 15 dB

17.) If you want to duck music when someone talks into a mic, you should:

A.) Use a gate with the music going through the gate and the mic plugged into the key input.
B.) Use a mixer to add the two signals, and then use mixed signal into a key input of a gate.
C.) Use a gate set to duck and have the voice in the sidechain, music in the program pathway.
D.) None of the above.

 
18.) A Hi-Shelf EQ is inserted into the side chain of a compressor. The EQ is set to cut 10dB at 5kHz with a slope of 18 dB/octave. The compressor is set to 2:1 at a threshold of -10dBu. If the input signal is +10dBu at a frequency of 10kHz, what is the level of the output signal?

A.) ­5 dBu
B.) 0 dBu
C.) +5 dBu
D.) +10 dBu

 
19.) Which compressor settings will most accentuate the transient attack of a snare drum?

A.) Fast attack and slower release.
B.) Fast release and slower attack.
C.) Fast attack, fast release, long hold time.
C.) 15 dB
D.) Slow attack, slow release, short hold time.

 
20.) Assuming you have a unit which is a multi-band compressor / limiter, which of the following statements is NOT true:

A.) A multi-way crossover is used to divide up the frequency bands.
B.) This unit can be used to de-ess full program material.
C.) For each band you have a separate VCA and RMS detector.
D.) Setting the threshold of each band’s limiter to 0 dBu will ensure that the output will not be above 0 dBu.

Be sure to let us know how you scored in the comments!

More Fun Quizzes on PSW:
Take Our “Real World” Stage Monitoring Quiz
Test Your Knowledge Of Power As It Relates To Sound Systems
Quiz To Rate Your Audio Skills, Knowledge & Personality Type

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