I was reading an old thread on spaced omnis with center card (https://taperssection.com/index.php?topic=163840.0) and was curious if anybody has been trying this three-mic configuration out lately. I'm thinking about trying this out with a pair of Line Audio OM1s (omnis) and a single center CM4 (somewhere between a subcardioid and cardioid) into the three-channel MixPre-3.
Yes. It may help to conceptually think of this as spaced omnis +. In other words, mostly spaced AB omnis plus additional help from the mic in the center.
The thread heathen linked above is a good read on that, being more concise than these OMT threads which also cover it. I just added a comment and edited my previous last post there.
Things to keep in mind:
The most appropriate choice of center pattern in such a 3-microphone setup boils down to the question:
In what ways should center microphone pickup differ from AB pickup? ..which relates to at least two different, sometimes contradictory aspects. The center microphone mostly contributes forward presence and direct focus, yet needs to do that in such a way that it blends in seamlessly.
If you can't space the omnis much, a more directional center microphone can help to avoid problematic interaction between the omnis and center (there is no available spatial hole to fill). In this case the center microphone is primarily providing increased direct-sound pickup and clarity which gets overlaid on the already seamless spatial stereo "bed" provided by the omnis.
As AB-omni spacing is increased it can help to shift to a wider pickup pattern for a single center mic. That helps blend the center channel contribution seamlessly into the stereo mix so that when brought up to a desirable level it is not perceived as being separate from what the omnis are providing - separate both in terms of Left/Center/Right energy-balance (hole-in-the-middleness)
and in terms of timbre. You don't want the contribution from the center mic to be perceived as a sort of separate narrow pool of sound tightly centered the middle of the playback image (more likely when the timbre in that channel differs greatly from that of the omnis) because if that happens you can't raise the level of the center channel enough in the mix to make a useful contribution without calling too much attention to it. In that case we need more overlap / interaction between the center and AB omnis rather than less.
Yet at the same time, use of a more directional center microphone is desirable to achieve enhanced clarity and presence of the direct-sound pickup. This is why going to a coincident stereo pair in the center works so well. We can get both that clarity as well as a bit of increased spatial width in the center which helps it blends in with the omnis. Plus we get the ability to adjust that center width in the mix. A single center mic works too, you just need to home in on the optimal pattern/spacing arrangement with a bit less flexibility afterwards in the mixing stage.
To really get a good handle on what's going on, try it both ways- A pair of spaced OM1s with a single center OM4, versus a pair of OM4s with a center OM1. Without any EQ filtering applied there will be limits to how narrow and how wide the pair should be spaced for all three to work best in combination, but either way should have the pair spaced somewhat wider than if that pair was in use alone without the center microphone channel.