Rules of thumb for mic distance vs hall reverb?

[jnorman]

hey now - i am starting to do more work with chamber groups (2-6 performers, piano duos, string quartets, etc) at remote venues, which range from smaller halls with almost no natural reverb to very large cathedral type venues which have enormous reverb. i never have the opportunity to do sound and level checks prior to the preformance, and sometimes do not even have the ability to set up where i might want to, but...

what are your general rules of thumb for deciding where to place your main mics (generally i am using a single ORTF pair of cards)?

in a very live hall, do you tend to place your main mics closer (maybe 10 feet?) or further away (15-25 feet?).

in a relatively dead sounding space (even fairly reverby spaces can be rather dead when filled with people), do you tend to mic closer or further out? what types of distances seem to work best?

or, do you tend to try to use about the same mic distance no matter what the venue? ie, is there some optimal mic-to-performer distance which you try to maintain, and deal with reverb issues in post?

i recently did a flute/harp duo in a cathedral (maybe 6 seconds reverb time) with the mics at about 20-25 feet (i had no choice on placement, due to restrictions to accommodate the audience) and, while pretty nice (performers liked it), i found it to be too distant for my taste. in a rahter large but dead space, i did a flute and piano duo with mics at about 8 feet out, and found it sounded too close - i had just recorded that same duo in the studio (very dry) with mics at about 12 feet and it sounded too distant for me...

thanks for any suggestions.

[7rojo7]

Critical distance changes in every space. There's little to do about the nature of the reverb, but distance from the source is your 'mixer'. I walk around like an idiot making strange noises, it's better if somone else can do it while you listen.
Get there before the musicians and director and suss this out before they even show up so you can say "this is the best place to put the microphones"
Don't forget that a low mic placement will work similarly to a high one except that there will be more bass due to the boundary effect.
In very live spaces, the closer the better. Don't be afraid to change the angles on the 'ORTF' if you have to move in close. Just do what sounds good. Close, I would use an xy in conjunction with an omni, omni between -6 and -10 Db.
Close one ear while checking critical distance.

[MichaelPatrick]

My habit is to place the mics to capture a good image of the ensemble regardless of the space; i.e., about the same distance no matter what.

In nice spaces the room is then present but not overwhelming. If more hall is needed I mix in more of the room mics (pattern and placement is an issue! even in nice rooms cardioids may be better than omnis.). If the room isn't good and the customer wants artificial reverb, I add it later with a Bricasti M7. On rare occasions I'll move mics back a bit, but that decision is made only when I'm confident that the room sounds really good and the recording will improve by having more of it.

[joelpatterson]

Originally Posted by MichaelPatrick

... about the same distance no matter what...

This is an excellent rule of thumb. The "problem" is always going to be having the mics too far away from the source, and ending up with an indistinct/blurry/too-much-room-sound kind of sound.

Clarity and presence and realism is what makes a recording enthralling under repeated listenings. You're going to get the sound of the room wherever the mics are... are you going to get the sound of the players, now that's where the focus needs to be.

[fifthcircle]

I find that for me, the majority of the time, I'm going for a midfield reverberation... I go for a location where I get some direct and some reverb. The room dictates how that works. In a very live room, I end up closer for clarity, in a dead room, I move back a bit for a more open sound...

In the end, the mics go where my ears tell me to place them.

--Ben

[7rojo7]

As long as we're using anatomical terms with our advice, then, 'the ears' is 'the rule of thumb'. Works every time

[David Rick]

I like a good balance of direct and reverberant sound. Sensitive players react to the room they are playing in, and a recording that excludes the room is excluding relevant musical context. But if you have any doubt about your monitoring situation on site, it's safer to move the main pair a little bit closer and put up an ambience pair to capture the room.

Ideally, I listen to the ensemble before I place the mics. If I have to set up in advance, I start with the mics somewhere around the room's critical distance. From there I can quickly get a dryer or wetter sound by moving the stand only a few feet forward or back.

I view getting the desired direct/reverberant ratio as more important than getting a particular stage width with a pre-determined mic array. Once I've decided where the mic stand will go, I modify the mic spacing, angle, and (sometimes) pattern to make the working angle match the ensemble.

David L. Rick
Seventh String Recording

[mathieujm]

Just an important thing to add. We talk about direct and reverberant sound and their ratio. But we have also to consider the reverberant sound itself.

I had some recordings in a big gothic cathedral with very long reverb. The first time I put my pair very close to the ensemble. Then I was surprised by the dry recording. In fact the walls were far from the musicians, so there were no much first reflections in the reverb and then a 7s long tail. For the next recordings I put my mics further (10m) and it was ok. Same situation in an old cistercian abbey. I was singing and recording, so no much control on the recording. My mics were 7m from the choir and there were not enough blend and only the long reverb afterward. To obtain something better I added a little bit of room reverb to add some first reflections.
In these situations, omnis are catastrophic because they don't add more first reflections, but add a lot of long reverb tail.

In the contrary, I tend towards to put my mics closer in small rooms and small churches because of the prominance of the first reflections which make the sound.

JMM

[Roland]

I've worked in rooms where they sounded pretty dry, but on opening up the mic's there is an awful amount of reverb. Conversely I've worked in rooms that have a lot of reverb, but because of their physical size when the mic's are placed in approximately the right area for the ensemble it sound's virtually dead. Unfortunately you can't always correct this by just moving mic's forward or backwards, this also changes the perspective on the performers.

All I would add is that there are good and bad rooms and your engineering skill is to make the bad ones sound better and to capture the brilliance of the good ones.

Roland

[aracu]

Each room is a different puzzle to figure out.