diff --git a/AudioFilterFIR_F32.h b/AudioFilterFIR_F32.h
index 90d60fc..966195a 100644
--- a/AudioFilterFIR_F32.h
+++ b/AudioFilterFIR_F32.h
@@ -22,38 +22,38 @@
 class AudioFilterFIR_F32 : public AudioStream_F32
 {
 //GUI: inputs:1, outputs:1  //this line used for automatic generation of GUI node  
-public:
-  AudioFilterFIR_F32(void): AudioStream_F32(1,inputQueueArray), coeff_p(FIR_F32_PASSTHRU) {
-  }
-  void begin(const float32_t *cp, int n_coeffs) {
-    coeff_p = cp;
-    // Initialize FIR instance (ARM DSP Math Library)
-    if (coeff_p && (coeff_p != FIR_F32_PASSTHRU) && n_coeffs <= FIR_MAX_COEFFS) {
-      arm_fir_init_f32(&fir_inst, n_coeffs, (float32_t *)coeff_p,  &StateF32[0], AUDIO_BLOCK_SAMPLES);
-      //if (arm_fir_init_f32(&fir_inst, n_coeffs, (float32_t *)coeff_p,  &StateF32[0], AUDIO_BLOCK_SAMPLES) != ARM_MATH_SUCCESS) {
-        // n_coeffs must be an even number, 4 or larger
-        //coeff_p = NULL;
-      //}
-    }
-  }
-  void end(void) {
-    coeff_p = NULL;
-  }
-  virtual void update(void);
-
-  void setBlockDC(void) {
-    //helper function that sets this up for a first-order HP filter at 20Hz
-    
-  }
-private:
-  audio_block_f32_t *inputQueueArray[1];
-
-  // pointer to current coefficients or NULL or FIR_PASSTHRU
-  const float32_t *coeff_p;
-
-  // ARM DSP Math library filter instance
-  arm_fir_instance_f32 fir_inst;
-  float32_t StateF32[AUDIO_BLOCK_SAMPLES + FIR_MAX_COEFFS];
+	public:
+		AudioFilterFIR_F32(void): AudioStream_F32(1,inputQueueArray), 
+			coeff_p(FIR_F32_PASSTHRU), n_coeffs(1), configured_block_size(0) {	}
+
+		//initialize the FIR filter by giving it the filter coefficients
+		void begin(const float32_t *cp, const int _n_coeffs) { begin(cp, _n_coeffs, AUDIO_BLOCK_SAMPLES); } //assume that the block size is the maximum
+		void begin(const float32_t *cp, const int _n_coeffs, const int block_size) {  //or, you can provide it with the block size
+			coeff_p = cp;
+			n_coeffs = _n_coeffs;
+
+			// Initialize FIR instance (ARM DSP Math Library)
+			if (coeff_p && (coeff_p != FIR_F32_PASSTHRU) && n_coeffs <= FIR_MAX_COEFFS) {
+				arm_fir_init_f32(&fir_inst, n_coeffs, (float32_t *)coeff_p,  &StateF32[0], block_size);
+				configured_block_size = block_size;
+			}
+		}
+		void end(void) {  coeff_p = NULL; }
+		virtual void update(void);
+
+		//void setBlockDC(void) {}	//helper function that sets this up for a first-order HP filter at 20Hz
+		
+	private:
+		audio_block_f32_t *inputQueueArray[1];
+
+		// pointer to current coefficients or NULL or FIR_PASSTHRU
+		const float32_t *coeff_p;
+		int n_coeffs;
+		int configured_block_size;
+
+		// ARM DSP Math library filter instance
+		arm_fir_instance_f32 fir_inst;
+		float32_t StateF32[AUDIO_BLOCK_SAMPLES + FIR_MAX_COEFFS];
 };
 
 
@@ -78,14 +78,21 @@ void AudioFilterFIR_F32::update(void)
     return;
   }
 
-  // get a block for the FIR output
-  b_new = AudioStream_F32::allocate_f32();
-  if (b_new) {
-    arm_fir_f32(&fir_inst, (float32_t *)block->data, (float32_t *)b_new->data, block->length);
-    AudioStream_F32::transmit(b_new); // send the FIR output
-    AudioStream_F32::release(b_new);
-  }
-  AudioStream_F32::release(block);
+	// get a block for the FIR output
+	b_new = AudioStream_F32::allocate_f32();
+	if (b_new) {
+		//check to make sure our FIR instance has the right size
+		if (block->length != configured_block_size) {
+			//doesn't match.  re-initialize
+			Serial.println("AudioFilterFIR_F32: block size doesn't match.  Re-initializing FIR.");
+			begin(coeff_p, n_coeffs, block->length);
+		}
+		//apply the FIR
+		arm_fir_f32(&fir_inst, (float32_t *)block->data, (float32_t *)b_new->data, block->length);
+		AudioStream_F32::transmit(b_new); // send the FIR output
+		AudioStream_F32::release(b_new);
+	}
+	AudioStream_F32::release(block);
 }
 
 #endif