EQ second order filters: Q factor and gain at Fc

The quality factor Q of a second order filter represents the peakiness of its frequency reponse curve, its height and narrowness around the corner frequency.
The following table shows some amplitude levels at the filter frequency and the related Q.

dB gain at Fc Q
-9.0 0.3536
-8.5 0.3746
-8.0 0.3969
-7.5 0.4204
-7.0 0.4454
-6.5 0.4719
-6.0 0.5
-5.5 0.5297
-5.0 0.5612
-4.5 0.5946
-4.0 0.6300
-3.5 0.6674
-3.0 0.7071
-2.5 0.7492
-2.0 0.7937
-1.5 0.8409
-1.0 0.8909
-0.5 0.9439
0 1
+0.5 1.0595
+1.0 1.1225
+1.5 1.1892
+2.0 1.2599
+2.5 1.3348
+3.0 1.4142
+3.5 1.4983
+4.0 1.5874
+4.5 1.6818
+5.0 1.7818
+5.5 1.8877
+6.0 2
+6.5 2.1189
+7.0 2.2449
+7.5 2.3784
+8.0 2.5198
+8.5 2.6697
+9.0 2.8284

dB = 20*LOG(Q)
Q  = POWER(10;dB/20)



November 2016