i wrote "phase coherence between overheads is not a necessity UNDER ANY CIRCUMSTANCE", refering to a situation (without explicitly mentioning it - me bad) where a room is small yet one wants to picture the drums very wide: to get this, you'll need an a/b setup, phase coherence of overheads then becomes much less important (than for instance level balance) or actually impossible to achieve - whether such a scenario and approach is very likely, sensibel or stupid is another discussion.

the thing to notice though is that the method of how/where one puts up the overheads does not need to be dictated/is not much depending on the room size, stage setup or pa system but much more on the drum/cymbal setup (think of highly asymmetric setups with a couple of crashes/chinas high up on one side but not much on the other side) and the soundfield one is trying to achieve (coincident overheads allow for an accurate 'picture' of the drumset with correct directional information, a/b doesn't) and how signals shall get processed (one cannot align close mics to a/b overheads) and how an engineer values different aspects.

if you ever precisely aligned a snare to a single overhead or coincident stereo pair (going full tilt and measure and analyze with the appropriate tools and then correct using a speaker processor including all its options such as allpass filters), i'm sure you noticed how much of a difference this can make - now this is not always wanted or needed (or just impossible to achieve due to time restraints or the lack of gear) and there are probably as many good sonic reasons to go with another approach such as a/b (or much more rarely l/c/r) than with a coincident pair.

btw: the reason you mostly get to see a/b on large stages/festivals is quite simple: if you're mixing foh and you're not with the headliner and don't have a drum tech on the travel party who you can instruct on how you precisely want the oh's positioned, you end up getting whatever the folks from the local pa rental company think makes sense: you often don't have the time during change over to verify all details and need to trust the local crew to a high degree that they proceed as instructed and that they are not messing up things: they usually don't, certainly not on purpose! but at times, you're already happy if the monitor tech does not forget to switch on phantom power... - for these reasons alone, i switched to using a single overhead mostly (even on very large drum kits) and/or close mics on the cymbals.

I believe that this gets to the crux of the matter . . . the question of whether the uppermost mics are indeed “overheads”, or whether they’re actually cymbal mics. If they’re used as cymbal mics, the mic choice and placement will generally be such that there’s sufficient level difference for any single instrument covered by multiple mics . . . allowing mix decisions to be made that sidestep artifacts with multi-mic coherency issues. This is no different than any combination of multiple mics anywhere on the stage mixed together.

Put another way, what at a glance might look like an “A-B pair” used as “overheads” might not be functioning as such in the mix, and thus the comparisons to classical two-mic stereo techniques might not be very relevant.

As far as X/Y goes . . . if you look at the polar response of the combined pair, there’s just not much rejection until sound sources are pretty much behind the mics. So to function as overheads (coherently covering the bulk of the kit) . . . there’s a drummer in the way for where the X/Y really would work the best. I do use X/Y with success in percussion applications where the wide combined polar pattern is a good fit, and it can work very well.

I've used X/Y for drum overheads live many, many times. And phase coherence is always a consideration. Front fills, delays, etc. are all still mono.

The biggest reason it isn't used more often is aesthetic appearance and a lack of a decent mic stand that is substantial enough to provide placement without interfering with anything else. Much easier to position less substantial stands for spaced pair and visually it is what people expect.

All things being equal, the placement I like best is putting the stand over the drummer’s head, as low as possible with the mics aimed generally at the snare and somewhere between the toms with a single mic on the kick....it goes without saying that the drummer must be consistent and play with control. This works well even with drummers who hit hard, as long as they are consistent.

I’ve tried this with the new Austrian Audio OC818 in stereo mode and had great success but just haven’t had the chance to use it on the road because the type of stand I’d feel comfortable using are rarely (if ever) seen on a festival stage.

easy to do with the schoeps cmxy4v... :-)

have been using these for jazz quite often - i'm adding a snare mic (for brushes) though.

Hi TJ99, the main reason is that a coincident xy stereo pair has a pickup pattern of 180 so in a small or noisy stage you risk to turn your overheads into room mics.

To get polished XY ohs in a live situation (minimal room and minimal bleed) you have to set them down and close to the kit but you will risk to get them smashed by the drummer sticks.

Sometimes in a live situation your ohs are simply cymbals mics so placing a good A-B pair you will get a more focused sound and reduce the spill (from the other intruments, from the wedges and from the drums, too).

As a plus, an A-B stereo pair is simpler to place in a busy stage.
A good habit is to place them at least equidistant from the snare drum 'cause these mics will contribute a lot on the overall sn sound.

In a live context kick bleed in the ohs is a negligible problem because is common to cut a great lo end amount on the oh mics to eliminate rumble and mud.

Another good reason to use A-B configuration in a live show is stereo width: usually we all tend to get a very mono mix so panning your ohs hard left and hard right gives the audience the impression of a wider-exciting mix.

That said, in some situations, a good XY is just what you need if all the other elements are under control so it's worth a try.

If you like coincident (or semi-coincident) stereo setup I suggest you to try ORTF or, even better, NOS.
They have a narrower pickup pattern and minimal angular distortion than the A-B technique.

Experiment and let us know which technique you prefer!

Wanted to report back, mixed at different shows the last 2 years (before the lockdown obviously) and tried different approaches. I have to say that ORTF/XY was one of my favourites for outdoor concerts/festivals.
And couldn't be easier to set up: 1 mic stand with both mics on a ORTF/XY clip.
On small stages indoors I preferred spaced pair aimed slightly at the center.

FWIW if I can only use 3 mics on the drums, XY is my go-to setup.
When using a simple stereo bar, it can be a bit dificult to position the mic stand in such way that it isn't directly infront of the drummer, though.

Who uses overheads anymore? Underheads are all the rage lately.

I am partially joking.

Underheads are actually something I see used quite often, usually individual cymbals being under-mic'd. Close under-mics on cymbals are useful for isolation where the objective of the drum reinforcement is larger than life or for problem correction, rather than a natural picture. You do have to be careful of your placement as you can get a low frequency warble sort of effect if you do it wrong.