Where do I position 4 speakers for 3D stereo sound

Some kind of processing is needed or else what you will wind up with is sitting between two stereo pairs playing the same thing. To get any kind of ambiance, the rear speakers have to be fed a different signal than the front ones, or else they would have to be placed somewhere across the street (maybe across town) from your front speakers. Running the same signal, you will wind up with bass cancellation problems and, like Sean said, good luck. The simplest approach would be to use a Dynaco type set-up. The best way is an ambiance synthesizer. No one really makes these anymore for various reasons, none of which have to do with how effective the better ones were. Yamaha, Sony, JVC are the most memorable makes. I have owned a JVC XP 1010 for many years. It is not presently in my system, since I decided to be more of a two channel purist a while back. I am seriously thinking about getting it back into operation though, as it does provide an added degree of realism, especially to dry recordings. If you believe that one should not be limited to two channels, you should consider multi channel SACD. The problem there is that unlike synthesizing additional channels from stereo program material, you need a brand new collection of software. SACD recordings are still not very numerous. The manner in which they are going about multi channel is also quite perplexing. Just a quick explanation of the ITU standard for the speaker array they recommend and its placement gives one pause. You are right on one score though: less is more does not apply too well when it comes to channels in an audio system, purist be damned. Good day.

You will have a rough time with the people here on the 'Gon with almost anything but two channel, analogue/vinyl tweaked out systems, being fed reconstituted power through special ac cords. So there I said it, again. Do I fell any better? No, not really. Briefly, just looked at the current issue of the British magazine "Hi-Fi +" on the newsstand today and, lo and behold, a new multi-channel decoder or enhancer or whatever ( I didn't actually read the article and was too cheap to buy the mag, preferring to spend my limited money on records instead) made by Dynavector. Interestingly, the ambiance channels seem to be on the sides of the room, somewhat next to the listening position, but, it seems, pointing forward, towards the main speakers. So, you see, your notion that, somehow, the sound would have more depth with four rather than two speakers, positioned fore and aft, actually makes so much sense that one of the most respected cartridge manufacturers has decided to come out with this type of product. I don't know what to tell you as to what may be available between what I have (and may put back in the system soon enough) which is no longer made and going the multi-channel SACD route, which may very well be premature. Since I have never been into 5.1 home theatre, the Dolby decoder, whatever it is thing, is a total unknown to me. Yes, I have lived through some kind of audiophile eclipse. So now, maybe, you can look up what Dynavector proposes, it might be the ticket for you, and don't let the buzzards get you down, it's your system to set up the way you enjoy it. The same nay Sayers would be saying nay about stereo if we set the clock back to mono days.

Just took a look at the Dynavector site and, indeed , the additional channels face forward towards the main speakers. The system is called Super-Stereo. I don't know much more about it, but look it up. Seems you need propriatery speakers though. Cheers.