What is Phase distortion?

A non-constant group delay in frequency results in phase distortions, it affects the sound signal, and negatively impacts the listening experience.

How does it work?

Music consists of a mix of lower and higher frequencies (among other characteristics we will not cover for the purpose of this article). The lower the frequency, the greater the size of its sound wavelength and the driver (woofer) dedicated to its reproduction. Due to the woofer’s bigger size compared to the tweeter, it is harder for the electrical signal to move the radiating membrane back and forth and reproduce sound. Because of their stronger inertia, low frequencies lag behind higher frequencies. Low and high frequencies that should be heard simultaneously will be heard separately if this delay is not fixed. 

To address the loudspeakers’ phase distortions resulting specifically from X-OVER filters Goldmund developed Leonardo

To help you better understand how phase distortions affect the listening experience, our engineers created an experiment. They modified one track (Castanets) with software to simulate filters having different group delay behaviors (without touching the signal amplitude) that were pushed to extreme levels for easier identification.




Filter implementation
Filter implementation


Flat group delay
Example of a signal with a flat group delay (constant in frequency) presenting, therefore, no phase distortion.
Group Delay shape
A filter with the group delay shape displayed was applied to the original music record. In this example, delay is equal to 1ms in the very low frequencies and decreases along with frequency increase.
The black square curve-shape represents the original undistorted signal; the red curve represents the signal after the implementation of the filter. For each group delay filter experiment below, a distortion example is provided at two frequencies: 300 Hz and 1000 Hz.
300Hz audio signal


Phase distortion 1-1ms
Phase distortion 1-10ms
Group delay 1-100ms
What is Phase distortion? 2-1ms
What is group delay? 2-10ms
What is group delay? 2-100ms
What is group delay? 3-1ms
What is Phase distortion? 3-10ms
Phase distortion filter 3-100ms
Group Delay distortion 4-1ms
Group Delay distortion 4-10ms
Group Delay distortion 4-100ms
Phase distortion 5-1ms
Phase distortion 5-10ms
Group delay 5-100ms
Group delay 6-1ms
Phase distortion filtre 6-10ms
Phase distortion filtre 6-100ms
Phase distortion 7-1ms
group delay filter 7-10ms
group delay filter 7-100ms
Phase distortion 8-1ms
Group Delay distortion 8-10ms
Group Delay distortion 8-100ms