# The Effect of Threshold and Ratio on Compressor's Output Level

The Music Telegraph | Text 2023/08/15 [18:23]

# The Effect of Threshold and Ratio on Compressor's Output Level

The Music Telegraph| 입력 : 2023/08/15 [18:23]

The Effect of Threshold and Ratio on Compressor's Output Level

In this article, I will suggest you an operation from which you will gather data that will aid you in understanding how the threshold and ratio parameters effect the operation of a compressor. You will be setting 2 different threshold levels (one high and one low) and measuring the output response to these levels at compression ratios of 2:1 (gentle) and ∞:1 (limiting). It is important for a sound engineer to know how much gain reduction (attenuation) is being used on a signal becuase it will determine the quality of the sound.

1) Turn the Threshold control to -20 dBu.

2) Observe the amount of gain reduction indicated on your compressor's meter.

Gain Reduction: _______ dB

<Effect of ratio on signals: Compressor at a low threshold level>

3) Adjust the signal generator for -50 dBv output (at 1,000 Hz).

To do this, put the compressor in bypass mode to read the generator's output on the ACVM.

4) Read the compressor's output level and record this value in the appropriate section of Table 1 (below), Column A.

To do this, put the compressor in the circuit (bypass button up) and read the output on the ACVM.

5) Read the amount of gain reduction from the compressor's meter and enter this value in the appropriate section of Table 1, Column A.

6) Repeat the previous 3 steps (steps 3, 4, 5) for each input level listed in Table 1.

When you have finished with this step, you will have generated enough data points to draw a graph showing the relationship between the input and output of a compressor whose threshold is set at a relatively low level (-20 dBv) and whose ratio is 2:1.

To see if you have done your data gathering accurately, you should find that the output level would be (approximately) the difference between the input level minus any gain reduction. Also, the greater the input level is above threshold, the more gain reduction you will measure.

7) Change the compression ratio to ∞:1 (infinity to one).

This ratio is an extreme case of compression. No amount of increase in input level above threshold will result in any increase in the output level. This type of compressor is called a limiter

8) Repeat steps 3, 4, 5 for each input level listed in Table 1. Enter data in Column B.

You will be generating input/output (I/O) data as before, but this time the ratio has been changed so that the gain reduction will be even more drastic than the previous ratio.

Table 1

 Column A Column B Parameter Settings Threshold: -20 dBu Ratio 2:1 Threshold: -20 dBu Ratio ∞:1 Input Level (dBv) Gain Reduction (dB) Output (dBv) Gain Reduction (dB) Output (dBv) -50 0 -50 0 -50 -45 0 -45 0 -45 -40 0 -40 0 -40 -35 0 -35 0 -35 -30 0 -30 0 -30 -25 0 -25 0 -25 -20 0 -20 1.5 -21.5 -15 2 -17 6.5 -21.5 -10 4.5 -14.5 11.5 -21.5 -5 7 -12 16.5 -21.5 0 9.5 -9.5 22 -22 +5 12.25 -7.25 27 -22 +10 15 -5 32.5 -22.5

Comment