Re: Why does Soundstage Depth and Width Change with Toe-in?
I think that it is not possible to give you a completely factual reason for this and your experience may be different to others - or the same.
The key point to remember is that stereophonic reproduction at home is an illusion. It is a trick played on the mind by the ears. It is entirely in your brain that the magic of width and depth is created from two loudspeakers. How this precisely works I don't know, but I do know that the notches, cavities and protrusions that define the shape of your outer ear all have an important part to play in directional location.
Occasionally my wife asks me to peg out the washing on the washing line in the garden. It is over a hard pathway. Quite often there are aircraft at about 5000 feet making a circuitous approach to a nearby airport. It always interests me that when they are passing overhead, if I bend down to the washing basket that there is a audible phasiness to the sound of their engines - a swooshing in the tone. If you bob up and down you can clearly hear how the ear uses the reflection from the ground to tell your brain that the noise (of the plane) is up high above in the same way that the shape of your outer ear tells you that birdsong is (generally) associated with birds in trees. Try it yourself but you must be on a hard reflective surface, not grass.
We are not conscious of these reflections but they form a critical part of our 3D location system. And if we did not have this inbuilt audio location capability we would not be here today discussing this point: our ancestors would have been eaten by predators.
Alan A. Shaw
Harbeth Audio UK