The two fundamental stereo techniques

There are two fundamentally distinguishable stereo recording, playback and mix processes:

1. Headphone stereophony [Head-related stereophony]

Binaural recording with two microphones in a dummy head [head-related signals]. The signals are called "interaural" signal differences. This sound field process is approximately equivalent to the natural hearing.

Head-related signals are mixed and played back with headphones only. Listern to interaural tracks on loudspeakers, the whole effect can't be heard.

2. Speaker stereophony [spatial stereophony]

Stereo recording with various microphone systems, including support microphones, polymicophone and so on. The speaker signals generated are called "inter-channel" signal differences. This is an "artificial" transfer.

Spatial signals are mixed and played back through stereo speakers only. Listern to spatial tracks on headphones, the whole spatial effect and inter-channel does not work.

I dunno, I am such a fan of the 3D/HTRF pluggies of recent years. That effect just fascinates me (put a sound behind your head!!) and it's only truly appreciable with headphones. That said, I developed a mild (thank god) tinnitus last year, and do not wish to exacerbate it.

Yup, and HRTF is way cool the way it can also make sounds appear above and below the plane of the speakers, too.

I disagree that "Listern to spatial tracks on headphones, the whole spatial effect and inter-channel does not work." True, it doesn't work *the same*, but a good speaker stereo mix sounds good in headphones too. After all, we listen to the same CDs with speakers and headphones, and enjoy both.

Going the other way is more problematic. As you said, the whole effect can't be heard. What's more, a perfectly good binaural recording can have phase cancellation issues with speakers, causing the image to shift significantly if you move small amounts left or right from dead center between the speakers, and causing phase shift coloration when summed to mono.

BTW, there's another dichotomy in stereo imagery: realistic vs. unrealistic. The first is like a soundstage, recreating a real or imagined performance. The latter can be anything. Both can be great or terrible. Unrealistic ones suffer less when you cross the binarual/spatial boundary (record one way, listen another). Actually, it's more of a spectrum than a dichotomy, because you can compromise between the two, and that's what I tend to do, as do many commercial CDs. Take Dark Side of the Moon, for example. There are a number of songs where the rhythm section is spatially placed but the guitar is everywhere, and sometimes the guitar is spatial but the keyboards are spread. Our good friend the Leslie creates an unrealistic image despite being real!

Realistic is called "a natural recording", for example a grand piano in a concert hall with a Blumlein pair.

Unrealistic is called "Kn

"Natural recording" is not what I mean by "realistic image". As I understand it, "natural recording" means actually recording a performance and capturing the image and ambience as faithfully as possible (as in the example you mentioned). Of course, a natural recording would have a realistic image, but you can build (or try to build) a realistic image entirely in the studio, with or without stereo miking techniques, and without ever arranging instruments as they would be in a natural recording. So, I make a distinction between "realistic image" and "natural recording".

Of course, there are a lot more tools in the stereo imaging kit than the few you listed, as I'm sure you know.

40 theatre mics

Mixer