A buddy of mine was reading one of Steve's papers talking about speakers drivers and cabinets and the potential problems with phase distortion. This posed the question of how the 360 degrees of phase relate to driver movement and the sine wave.

Well I got lucky and found this gif which was used to basically sum up calculus.



So correct me if I'm wrong, but doesn't the vertical line which connects the sine wave to the compass accurately represent the ideal movement of the speaker driver?

So phase distortion would be any deviation in the speaker driver's movement from this ideal? Or phase deviation introduced through distortions caused by the cabinet?

Based on this image I can see how easy it would be to have phase distortion anywhere along the chain.

Good visual explanation. Years ago, someone described a sine wave as viewed from end to end rather than how it appears on a scope, i.e., from the side. End to end, it is a spiral. Makes you think a little differently about these things.....

good thing speakers dont spin while they are playing

That would sound like the spinning speakers in the Leslie speaker cabinets made for Hammond organs (and also used by guitarists like Jimi Hendrix and Willie Oteri).

Sounds interesting, but not for a steady diet!

Hmm, true indeed.  Hell, I've had so many drinks I'm going to try to explain it!

Good illustration for sure...

The speed of the circle is determining the frequency.  You could look at the circle as the microphone and the wave as the speaker cone.  Often there is a delay between the speaker cone and the microphone.  To make matters more complicated, this delay is frequency dependent.  It can go up and down at different frequency ranges, but tends to increase as frequency rises.

Now imagine this single frequency of the circle superimposed with 20,000 additional frequencies and the harmonics of those frequencies all happening at the same time.  

Since the speaker has a phase angle (that can be plotted) which deviates from perfect throughout the frequency range at a single frequency, you have to wonder what happens when the speaker is asked to play a bass note with a phase angle delay of say 70 degrees, and a midrange note with a phase angle delay of 10 degrees and a treble note with a phase angle delay of 150 degrees....  which phase angle does it choose at any given second in time?  

Now imagine those three simultaneous frequencies multiplied by 1000's to make up a complex transmission called music.


When we look at a phase angle plot such as the one below -



All we can really conclude is that 100 cycle notes (in this graph) are delayed in time by about 50 degrees... making instruments that fall into that tuning sound like they are farther back in the sound stage than actually intended by the recording.

So phase angle is all about imaging, and sound stage front to back placement.  I can remember studies being done where blind listening tests concluded the average person couldn't tell a speaker had been moved until the distance was almost 10 feet, and my guess is it had to do more with loudness than timing.  

You can calculate the degrees of delay to inches based on the speed of sound and I have found it is generally better to have an overall phase angle that decays so that as you move into higher frequencies the decay is longer.  This gives a nice illusion of depth.



Steve