diff --git a/include/RmsHelper.h b/include/RmsHelper.h
new file mode 100644
index 0000000000..784a5fd3c7
--- /dev/null
+++ b/include/RmsHelper.h
@@ -0,0 +1,94 @@
+/*
+ * RmsHelper.h - helper class for calculating RMS
+ *
+ * Copyright (c) 2014 Vesa Kivimäki <contact/dot/diizy/at/nbl/dot/fi>
+ * Copyright (c) 2008 Tobias Doerffel <tobydox/at/users.sourceforge.net>
+ *
+ * This file is part of LMMS - http://lmms.io
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef RMS_HELPER_H
+#define RMS_HELPER_H
+
+#include "lmms_math.h"
+
+class RmsHelper
+{
+public:
+	RmsHelper( int size ) :
+		m_buffer( NULL )
+	{
+		setSize( size );
+	}
+	virtual ~RmsHelper() 
+	{
+		if( m_buffer ) delete m_buffer;
+	}
+
+	inline void setSize( int size )
+	{
+		if( m_buffer )
+		{
+			if( m_size < size )
+			{
+				delete m_buffer;
+				m_buffer = new float[ size ];
+				m_size = size;
+				reset();
+			}
+			else
+			{
+				m_size = size;
+				reset();
+			}
+		}
+		else
+		{
+			m_buffer = new float[ size ];
+			m_size = size;
+			reset();
+		}
+	}
+
+	inline void reset()
+	{
+		m_sizef = 1.0f / (float) m_size;
+		m_pos = 0;
+		m_sum = 0.0f;
+		memset( m_buffer, 0, m_size * sizeof( float ) );
+	}
+
+	inline float update( const float in )
+	{
+		m_sum -= m_buffer[ m_pos ];
+		m_sum += m_buffer[ m_pos ] = in * in;
+		++m_pos %= m_size;
+		return sqrtf( m_sum * m_sizef );
+	}
+
+private:
+	float * m_buffer;
+	float m_sum;
+	unsigned int m_pos;
+	unsigned int m_size;
+	float m_sizef;
+};
+
+
+#endif
diff --git a/plugins/dynamics_processor/dynamics_processor.cpp b/plugins/dynamics_processor/dynamics_processor.cpp
index 24e421deb3..cd18e0f13e 100644
--- a/plugins/dynamics_processor/dynamics_processor.cpp
+++ b/plugins/dynamics_processor/dynamics_processor.cpp
@@ -58,7 +58,10 @@ dynProcEffect::dynProcEffect( Model * _parent,
 	m_dpControls( this )
 {
 	m_currentPeak[0] = m_currentPeak[1] = DYN_NOISE_FLOOR;
-	m_needsUpdate = true;
+	m_rms[0] = new RmsHelper( 64 * engine::mixer()->processingSampleRate() / 44100 );
+	m_rms[1] = new RmsHelper( 64 * engine::mixer()->processingSampleRate() / 44100 );
+	calcAttack();
+	calcRelease();
 }
 
 
@@ -66,6 +69,7 @@ dynProcEffect::dynProcEffect( Model * _parent,
 
 dynProcEffect::~dynProcEffect()
 {
+	delete[] m_rms;
 }
 
 
@@ -110,15 +114,25 @@ bool dynProcEffect::processAudioBuffer( sampleFrame * _buf,
 // debug code
 //	qDebug( "peaks %f %f", m_currentPeak[0], m_currentPeak[1] );
 
-	if( m_dpControls.m_attackModel.isValueChanged() || m_needsUpdate )
+	if( m_needsUpdate )
 	{
+		m_rms[0]->setSize( 64 * engine::mixer()->processingSampleRate() / 44100 );
+		m_rms[1]->setSize( 64 * engine::mixer()->processingSampleRate() / 44100 );
 		calcAttack();
-	}
-	if( m_dpControls.m_releaseModel.isValueChanged() || m_needsUpdate )
-	{
 		calcRelease();
+		m_needsUpdate = false;
+	}
+	else
+	{
+		if( m_dpControls.m_attackModel.isValueChanged() )
+		{
+			calcAttack();
+		}
+		if( m_dpControls.m_releaseModel.isValueChanged() )
+		{
+			calcRelease();
+		}
 	}
-	m_needsUpdate = false;
 
 	for( fpp_t f = 0; f < _frames; ++f )
 	{
@@ -131,14 +145,15 @@ bool dynProcEffect::processAudioBuffer( sampleFrame * _buf,
 // update peak values
 		for ( i=0; i <= 1; i++ )
 		{
-			if( qAbs( s[i] ) > m_currentPeak[i] )
+			const double t = m_rms[i]->update( s[i] );
+			if( t > m_currentPeak[i] )
 			{
-				m_currentPeak[i] = qMin( m_currentPeak[i] * m_attCoeff, qAbs( s[i] ) );
+				m_currentPeak[i] = qMin( m_currentPeak[i] * m_attCoeff, t );
 			}
 			else
-			if( qAbs( s[i] ) < m_currentPeak[i] )
+			if( t < m_currentPeak[i] )
 			{
-				m_currentPeak[i] = qMax( m_currentPeak[i] * m_relCoeff, qAbs( s[i] ) );
+				m_currentPeak[i] = qMax( m_currentPeak[i] * m_relCoeff, t );
 			}
 
 			m_currentPeak[i] = qBound( DYN_NOISE_FLOOR, m_currentPeak[i], 10.0f );
diff --git a/plugins/dynamics_processor/dynamics_processor.h b/plugins/dynamics_processor/dynamics_processor.h
index 004146eb27..cf9d585866 100644
--- a/plugins/dynamics_processor/dynamics_processor.h
+++ b/plugins/dynamics_processor/dynamics_processor.h
@@ -29,7 +29,7 @@
 
 #include "Effect.h"
 #include "dynamics_processor_controls.h"
-
+#include "RmsHelper.h"
 
 
 class dynProcEffect : public Effect
@@ -59,6 +59,8 @@ private:
 	double m_relCoeff;
 	
 	bool m_needsUpdate;
+	
+	RmsHelper * m_rms [2];
 
 	friend class dynProcControls;