Quote Originally Posted by RMC View Post
Hi Ian,

"A stereo pair or second loudspeaker 3 metre distance" Is quite a different story and has nothing to do with what is commonly known and used for "mutual coupling" in sound reinforcement for example. That's the only issue raised by me. Other ways of getting "mutual coupling" may exist (e.g. Holland, and described by himself as "perhaps less obvious") however they are far from being widespread, and even talked about in many loudspeaker books...


As I have shown on the figure
re-scaling the frequency axis relative to the distance (here mentioned to 3m, e.g. by reducing the frequency 6 times) it can be seen that such effect called "mutual coupling" would occur for the frequencies LESS then about 50Hz, as in stereo sound reproduction LF speakers are producing almost the same sound program (especially "under 300Hz"). So that is real physics law of the sound. But such effect is "masked by" the sound reflections from the nearby large surfaces where "local" mutual coupling would produce +6dB up to +18dB, but a lot of my words have been 'said' about that in the previous posts here.