diff --git a/lib/filters.c b/lib/filters.c
index 91cd964..9dc0a32 100644
--- a/lib/filters.c
+++ b/lib/filters.c
@@ -18,23 +18,24 @@ float hard_clip(float sample, float threshold) {
 void init_lpf(FIR *filter, float cutoff, int sample_rate) {
 	float a = tanf(M_PI*cutoff/sample_rate);
 	float a2 = a*a;
-	float r;
+	float r, e;
 
 	for(int i = 0; i < FIR_ORDER; i++) {
 		r = sinf(M_PI*(2.0f*i+1.0f)/(4.0f*FIR_ORDER));
-		sample_rate = a2+2.0f*a*r+1.0f;
-		filter->A[i] = a2 / sample_rate;
-		filter->d1[i] = 2.0f*(1.0f-a2)/sample_rate;
-		filter->d2[i] = -(a2 - 2.0f * a * r + 1.0f) / sample_rate;
+		e = a2+2.0f*a*r+1.0f;
+		filter->A[i] = a2 / e;
+		filter->d1[i] = 2.0f*(1.0f-a2)/e;
+		filter->d2[i] = -(a2 - 2.0f * a * r + 1.0f) / e;
 	}
 }
 
 float process_lpf(FIR *filter, float x) {
+	float output;
 	for(int i = 0; i < FIR_ORDER; i++) {
 		filter->w0[i] = filter->d1[i]*filter->w1[i] + filter->d2[i]*filter->w2[i] + x;
-        x = filter->A[i] * (filter->w0[i] + 2.0f * filter->w1[i] + filter->w2[i]);
+        output = filter->A[i] * (filter->w0[i] + 2.0f * filter->w1[i] + filter->w2[i]);
         filter->w2[i] = filter->w1[i];
         filter->w1[i] = filter->w0[i];
 	}
-	return x;
+	return output;
 }
\ No newline at end of file
diff --git a/lib/filters.h b/lib/filters.h
index 5cd620d..e4e15f5 100644
--- a/lib/filters.h
+++ b/lib/filters.h
@@ -5,7 +5,7 @@
 #include "constants.h"
 #include "oscillator.h"
 
-#define FIR_ORDER 10
+#define FIR_ORDER 21
 
 typedef struct
 {