fwiw I was picking Doug's brain about the R4 and 4-mic mixes a couple months ago and below is his response, which is very much along the same line of thinking as items previously mentioned by Wayne, Shawn, easyjim, 'sauce, etc:
Yes, it can be done with a few techniques and a lot of effort in setup and mixing. 90° hypers X-Y with 8 foot spread omnis, about 20dB down is one of a very few good techniques, but only if you can get good alignment. That is the trouble. Almost all 4 mic mixes destroy transient response, sounding somehow dull or lifeless at their very best. It also causes massive image smear in most cases. Selecting the right set of polar patterns, spacing and angles can make it possible to mix an omni or pair of omnis without severe degradation. I have never heard 4 directional mics mixed that was anything other than bad. It must be a main pair with omni flanking mics to open up the sound and flesh out the low end. I can do a TMOD Concert that will max out the R4 for use as a 4 mic unit (i.e no int mics and no pad but it will take a +14dB signal via the XLRs) if the demand is there or even by special request. These folks probably have low end to mid range systems that cannot recreate the recorded space accurately and hence listen only for flavors which does change with more mics but accurate 3D space reproduction suffers dramatically....peace...Doug
