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Author Topic: Hanging CA-11 omnis from venue ceiling  (Read 1070 times)

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Offline skinnypaul

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Hanging CA-11 omnis from venue ceiling
« on: September 11, 2016, 08:59:51 AM »
I have the opportunity to try recording using my CA-11 omnis in a ~200 capacity venue. Everything is already spot-miked and recorded by the venue so the CA-11s would be room/ambience mics (though I'd like the recordings to be as good as possible in their own right). Music varies from acoustic free-jazz to loud electronics. PA is a pair of speakers hung from either side of the stage with some floor subs. Depending on the performance all, some or none of the sound will be through the PA  ;D.

I'd like to try hanging the mics from the ceiling with a bit of tape and using them as a spaced pair (~maybe 18" apart?). I wonder if anyone had any thoughts as regards positioning? I'm guessing this will depend to some degree on how the style of music, how much is being sent to the PA etc but are there any rules of thumb? At the moment I'd tending towards about a third back from the PA. I'd expect non-sensitive omnis to sound distant and mushy at the rear of the venue (i.e. at the board).

I plan to go CA-11 > Ugly pre > stereo passive DI > board inputs.

Thanks in advance!

Offline jagraham

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Re: Hanging CA-11 omnis from venue ceiling
« Reply #1 on: September 11, 2016, 10:32:11 AM »
IMO go as close as you can. You can tape from right up on the stacks with these mics. At least I have bad luck with it in the past. I would probably set them up just inside the stack and a couple feet back. That way you'll be able to get more from the stage as well as the PA.
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Offline skinnypaul

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Re: Hanging CA-11 omnis from venue ceiling
« Reply #2 on: September 12, 2016, 06:26:39 AM »
Thanks - I'm not worried about being too close to the speakers as I know Church mics are good to about 114db.

I wonder what the horizontal dispersion of the speakers is though. If I'm central-ish (the mic cable isn't long enough to put one over each speaker) but too forward I wonder if I'd be too far off-axis for the main drivers and pick up lots of horn but less low-end. Of course I might be over-thinking this  :hmmm:

Offline Gutbucket

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Re: Hanging CA-11 omnis from venue ceiling
« Reply #3 on: September 12, 2016, 09:43:30 AM »
I'd place the microphones so that each is approximately 6' to 12' away from, yet more or less directly on-axis with the PA speaker on each side.  That's going to wide space the mics significantly, so you'll want to shift them inwards towards the inner edge of the radiation angle from each PA, but make sure the mic placement is still fully within the rather narrow on-axis radiation angle of the speaker.  One way to assure that is to make sure you can see fully down into the driver throat of the high-frequency horn as viewed from the mic position on each respective side - that is, each mic "seeing" fully into the horn on it's own side, not the horn of the speaker on the opposite side.  I'd then angle the microphones so that they point directly towards center stage (rather than directly at the PA speaker) to maximize their high frequency pickup of any direct sound emanating from the stage.  Yes, the mics are omnidirectional, but they will pick up more "acoustic sparkle" if pointed directly at center stage.

The idea behind this is to get a good blend of clean monophonic SDB through the PA, along with sufficient direct sound from the stage, in combination with the right amount of indirect ambient audience reaction and room sound.  Placement too close to the PA will make the SBD part so loud it overwhelms everything else, and if there isn't everything represented in the PA, whatever is in there will be overly dominate everything else which isn't.  Don't worry about the seemingly quite wide-spaced mic placement, the sound through the PA will be mono or mostly mono and will thus solidly fill the center of the playback image as if the mics were close together.  The inwardly pointed angle of both mics facing towards center stage will also help provide sufficient solid center image.  Yet the wide spacing will nicely decorrelate the ambient pickup of audience reaction room reverberation.
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline skinnypaul

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Re: Hanging CA-11 omnis from venue ceiling
« Reply #4 on: September 15, 2016, 07:11:41 AM »
Well, some things I learnt:

Low sensitivity mics aren't the best choice for very quiet chamber music.
Keep unbalanced cables away from noisey power cables and things like high-powered lights.

Will try again with a louder source  ;D

Offline Gutbucket

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Re: Hanging CA-11 omnis from venue ceiling
« Reply #5 on: September 15, 2016, 10:39:39 AM »
You are probably already doing this, but figured I'd mention it anyway- best to situate the preamp with the mics and make the long run to your board after the preamp.  Using a CA-UGLY that long run after the preamp will not be balanced, but will at least be at a much higher level.  Plus, you don't want those mic leads much longer than about 10' or so due to increasing HF capacitance loss.  If you have a small mixer or something you could place that just after CA-UGLY and then run balanced cables back to the board.

A couple days ago I was searching the early DR-2d threads and came across a short discussion of one of the similar recording setups I was thinking about when I suggested wide-spacing your ceiling mounted omnis so that they are 8' or so away from and on-axis with PA.  Richard (TS handle = illconditioned) also used to use a similar installed setup with low voltage omnis (AT's maybe, I don't remember) maybe 9 years ago up in Canada with very good results.

Here's the posts and archive link from the DR-2d thread- http://taperssection.com/index.php?topic=154697.msg1956900#msg1956900

The other night I ran AKG 481 (ceiling mounts, 25' split @ stacks) > Oade m248 > Tascam DR-2d (line-in)

Check it out:  http://archive.org/details/54Bicycles2012-03-29.akg481.flac16

Thoughts and comments appreciated.

Thoughts and comments appreciated.

Dig the wide split.  This is why the kind of taping we often do (recording music where a large percentage of the sound arrives through a PA) is often a completely different thing than 'standard' recording techniques found in books and taught in audio engineering.  All standard techniques evolved from either large scale classical recording or small scale studio mic'ing techniques.   Nowhere in the 'standard' recording world is there an instrument which emits highly correlated sound through two very widely spaced speakers.   The PA is a freak in the standard recording world, just as stereo reproduction is a freak of the natural sound world.  Both, stereo especially, are contrived from the start to exploit human hearing tricks.  Sometimes standard techniques apply nicely, but when you have widely spaced twin mono (mostly) sources, techniques no classical or studio engineer would normally even consider can work well.  You'll never read about that in any standard book on recording, only between the lines.

Somewhat amazingly really, this 25' split is predominantly mid channel (mono) information, due to the mostly mono PA mix and presumably symmetrical mic to stack placement on each side, but there is clear and distinct panning of the effects, jangly percussion stuff and anything else mixed in stereo through the PA.  At the same time the room ambience and crowd reaction is highly decorrelated by the spit so that portion is wide and ambient sounding. The result is sort of like a SBD/AUD matrix without any matrixing.. 'matrixed in air'.

Nice job Bob.. and thanks for the chance to blather on that one lurking in the back of my head for years now.

Thanks for the insightful review, gutbucket.

You are correct. The mics are mounted in AT 8410 mounts which are each screwed into upside down clamps that are mounted on a single steel beam running parallel to the stage/PA stacks. Each microphone is pointed directly at the middle of each stack and is approximately 8' from the PA speaker.

Many thanks to Todd Trego for installing these clamps and running cable up and across the ceiling to the far side of the stage.  Unless you point them out, the mics are invisible.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline skinnypaul

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Re: Hanging CA-11 omnis from venue ceiling
« Reply #6 on: September 15, 2016, 12:30:29 PM »
Thanks for the suggestion and the links.

I used a passive stereo DI box so most of the run back to the board was over balanced connections (I wonder if an active DI would be better - hmm). I'm using a ~3m 'stereo minijack to 2 x mono jacks' cable to hook up the ugly to the DI so that run isn't too long. I think the source was basically incredibly quiet!

 

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