The general thing, as usual, is to space the microphones apart more and use less angle between them the farther back the recording position is, or the crappier the room sound is, or the more annoying the audience is. The closer you are, or the better sounding the room is, you can go with a narrower spread combined with a wider angle between the microphones. That basic relationship is no different using cardioids.
One extreme of that is coincident X/Y, using a wide angle between microphones, and the other extreme is a spaced A-B setup with both microphones pointing directly ahead. All stereo imaging in coincident arrangements will be entirely from signal level differences with no phase information, nearly all stereo imaging in parallel A-B setup will be phase differences with minimal level differences. Arrangements in between those extremes will leverage some of both types of imaging. That relationship is generally the first aspect of stereo recording that people learn about. Most here understand it. Typical articles on recording cover it.
But there is more going on than those differences in stereo imaging. By arranging the microphones with less angle between them, the sensitivity to sound arriving from in front is maximized as much as possible, so you get somewhat less room and audience contribution from the sides and rear and maximize the sound arriving from in front as much as possible. Think of the combined pickup pattern in the room of both microphones if they were mixed together in mono. With less angle between microphones, you'll still get ambient pickup from the sides and rear, just less of it in proportion to sound from the front. By using a wider angle between microphones the pickup becomes less biased towards the front and more even across the horizontal plane. Optimizing this balance of "front verses all other directions" is more important to making a good sounding recording than optimizing the stereo imaging of the sound arriving from in front, and since you can (and most definitely should) trade one type of imaging for the other while changing this bias of "front verses all other directions", it makes sense to think primarily in terms of this aspect when deciding what stereo setup to use.
Another thing going on besides the nature of the stereo imaging of sounds in front and the overall sensitivity to the sound from in front verses sound from the sides and rear, is the nature of the ambient pickup. The quality and 'feel' of the ambient sound is dependent on how much difference there is between the two microphone signals for sounds arriving from all directions other than the front. With a spaced arrangement, the ambient pickup of reverberant sound and audience reaction becomes decorrelated above a certain frequency determined by the distance between capsules. The spacing creates a phase difference between signals for any sounds which arrive from either side of the center-line plane (front center, directly up/down, directly to the center rear). With more widely spaced microphones, the frequency down to which this happens grows lower. The farther off to either side of center that the sound arrives, the greater the phase difference between the resulting signals in each channel. This happens regardless of the microphone pattern used. It's all about the spacing.
With coincident cardioids, there are no phase differences regardless of the angle of arrival. The differences are entirely signal level differences, which are relatively minimal unless the angle between microphones is super wide, which causes other problems. The reverse-polarity lobes of supercardioids, hypercardioids, and figure-8's introduces the equivalent of 180 degree phase difference information, and if the front and back lobes of the pattern of one microphone are more or less aligned with the null-zone of the other microphone, that increased signals difference between channels causes the ambient sound arriving from the sides and back sound less mono, more open and wide. More 'stereo-like'.
Supers and hypers have broad application because they are the most directional patterns we have (other than shotguns), and can be setup in various ways to offer the most control we can get over the balance between sound from the front verses sound from all other directions (other than physically moving the recording position closer or farther, which offers far more control). That's all about the angle between the two microphones. Choosing an appropriate arrangement subsequent to that can improve the less important aspects such as the nature of the stereo imaging in front and the nature of the ambient pickup from the sides and rear, and that's all about choosing the most appropriate spacing between microphones to suit the angle between them.
All that doesn't directly answer your question, but provides the basic principles to work from in any recording situation.
Topic: Hyper Caps (Read 7966 times)