feat: add behaviour to hp/lp filters

src/features/dsp408/constants.ts

@@ -93,6 +93,11 @@ export const GEQ_GAIN_MIN = -12;
 export const GEQ_GAIN_MAX = 12;
 export const GEQ_GAIN_STEP = 0.1;
 
+// ------ Filter constants ------
+export const FREQUENCY_MIN = 19.7;
+export const FREQUENCY_MAX = 20160;
+export const FREQUENCY_QUANTIZATION = 300;
+
 // ------ Matrix constants ------
 export const MATRIX_GAIN_MIN = -60;
 export const MATRIX_GAIN_MAX = 0;