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Author Topic: Switch to DIN or ORTF for a situation like this? CA-14 cards  (Read 3696 times)

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Offline SquirrelMurphy

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Switch to DIN or ORTF for a situation like this? CA-14 cards
« on: November 27, 2016, 10:23:18 AM »
Hi guys. Been recording with CA-14s for a few years now and have gotten the general swing of it, but still learning of course. I usually record in clubs with cards in an AB configuration on a 6-in T-bar. Parallel and pointed at the stacks which I try to get close to to reduce room ambiance / reverb. Usually clamped or mounted to something high and close. I rarely use the omnis.

I often record a high school band in this same configuration a lot (see pic). I normally use cards in an AB config for this too and for the same reason (reduce room ambiance). There's a little wall in the soundboard area that is in a balcony... so I don't set up a stand and T-bar. I just clip the mics onto binder clips acting like mini-stands and point them. I'm happy with the recordings but seeking to improve and try different things.

I'm starting to think that maybe DIN or ORTF might be more appropriate? I've never tried a config like that but I see that many of you do. Given how far back I am, I'm worried that I'll get even more room ambiance and I'll lose bass. What do you think? I'm also thinking about trying my omnis on a 3-foot bar suspended in front of the balcony and pointed to the stage (I have access, and there's a mount-point there). For a high-school band, people are generally respectful and very quiet so omnis could work.

For this "venue", I have full run of the place so I could also set up in front of the stage, but the mics would have to be just above stage height (no obstructing views), my access for making adjustments evaporates because I'm so visible, and I risk someone bumping the stand because it's in a traffic area.  It's nice to sit in the back with no worries... plus I have access to the PA system and board if I'd like. But I'm far enough away that the room is present in the recordings.

Thanks for any suggestions...


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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #1 on: November 27, 2016, 01:24:55 PM »
You're going to get a lot of room sound that far away.  A rough starting point for ORTF is 2-3 feet behind the conductor and 7-10 feet above, often with the mics pointed slightly down.  This site

http://www.sengpielaudio.com/Fragen08.htm

can help you visualize various mic techniques.

Offline SquirrelMurphy

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #2 on: November 27, 2016, 02:29:18 PM »
A rough starting point for ORTF is 2-3 feet behind the conductor

Yowza... ain't going to happen. OK... so I stick with AB if I remain at that distance. I looked at that visualization site, and also did some other reading. This Shure publication was helpful too.

I'm starting to think Omni's will accentuate the room reverberation more than the cards given the distance and the fact that they will pick up reflected sounds from the sides.

Suggestion for distance between AB cards? In the pic, I'm pretty close, but maybe a 30-40cm separation will yield a better stereo image?

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #3 on: November 27, 2016, 05:51:56 PM »
There's a ton of info on TS about what you're wanting to record.  There's many ways to do it.  Here's one of many threads I think might help:

http://taperssection.com/index.php?topic=165248.0;all


Offline admkrk

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #4 on: November 28, 2016, 12:45:50 AM »
A rough starting point for ORTF is 2-3 feet behind the conductor and 7-10 feet above
While that might be ideal, and it looks like it would in that room, I would not write ORTF off based on that alone. I use it, mostly out of habit, but it works well for me in most situations, unless something else goes wrong. Here is a recording I did in a room about 3 X the size, and under the balcony, along with being stuck on the right side. I am pretty sure the biggest problem with this tape is being under the balcony, and otherwise it would have sounded much better, even being off center.

The bottom line is do not overthink it. What do you have to loose by trying ORTF the next time? 
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Offline bombdiggity

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #5 on: November 28, 2016, 01:22:51 AM »
At that distance I'd point cards straight ahead and hope for the best. 

Were I there I'd commandeer one of those seats in the front row center to set up a small stand and aim cards straight ahead.  That will be a lot better than anything from the distance shown.  You could do omnis up front similarly and compare one vs. the other over a two shows. 
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Offline Limit35

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #6 on: November 28, 2016, 02:06:05 AM »
I agree with bomb and setup a small stand up front of those center seats. A near-coincident card pair up close would be good based on that photo. Do you have omnis? If so, you could AB spread as far as you can across the stage, and go as high as they will allow you, if you could get a couple meters across great. Again, based on the photo. They don't need to be too high off the stage to be effective. It would be better than the pair I see at the back.

Offline SquirrelMurphy

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #7 on: November 28, 2016, 10:30:06 AM »
Thanks guys. Very helpful.

Here is a recording I did in a room about 3 X the size, and under the balcony, along with being stuck on the right side. I am pretty sure the biggest problem with this tape is being under the balcony, and otherwise it would have sounded much better, even being off center.

Sounds great. Bass is a little boomy, but I think it sounds nice.

Quote
The bottom line is do not overthink it. What do you have to loose by trying ORTF the next time?

This was my thought too. I've recorded several times from the same location in that hall, and I was thinking to try something new (and perhaps more proper) and see how it goes. Even if it's worse, it's OK for me to learn from. I'm trying to learn the general rules first rather than guess and try repeatedly. But trust me, am good with experimentation and failure.

At that distance I'd point cards straight ahead and hope for the best. 

That's my MO.

Quote
Were I there I'd commandeer one of those seats in the front row center to set up a small stand and aim cards straight ahead.  That will be a lot better than anything from the distance shown.  You could do omnis up front similarly and compare one vs. the other over a two shows. 

I can get that seat. I show up early to set up anyway. But I can't go higher than head-height and I can't run an omni-bar wider than the seat. The main issue is that I'll have to leave the board area and I sometimes help with house sound. You know, I can probably set up ON STAGE too if it makes sense. Except that I'd have to set levels and run away and hope things work out. There's no opportunity for a level test.

But still, AB? Why not DIN or ORTF from so close? Especially given that from the front seat the musicians are spread across maybe 120-degrees FOV from the mics.

The ace in my pocket is that we have 5 omnis that dangle over the stage + PA feed.... we use it though a mixer to feed video taping which is used for local community cable TV. I have recorded from the board and I can even control the mix. But when I do I feel like I'm missing out on learning about mic placement / technique. And I think my AB cardiods from the back sound perhaps 85% as good as the house mics anyway. The main difference to me is ambiance and reverberation which I pick up more because I'm so far away.

I uploaded a sample from the show pictured above (AB cards with a 18"-ish spread)... to give you a sense of how my recordings there typically come out.

Offline bombdiggity

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #8 on: November 28, 2016, 10:33:23 PM »
That actually sounds a lot better than I'd have thought though part of that may be the type of music involved.  Tiny mics and the height they're at will help in not necessarily reproducing all of the lower end reverb and reflections that tend to multiply with distance.  I'm sure this result is a bit brighter sounding than different gear or location might produce. 

I'd not worry much about the height up front.  You should gain quite a bit more by being close.  As far as configuration it's a matter of deciding what you like.  I basically point cards straight ahead regardless of distance and location.  I don't think you can go wrong with that.  Others may have other preferences. 

Trial and error seems the best approach in my experience.  If you have the opportunity to experiment I'd do so. 
Gear:
Audio:
Schoeps MK4V
Nak CM-100/CM-300 w/ CP-1's or CP-4's
SP-CMC-25
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Oade C mod R-44  OR
Tinybox > Sony PCM-M10 (formerly Roland R-05) 
Video: Varied, with various outboard mics depending on the situation

Offline phil_er_up

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #9 on: November 29, 2016, 02:10:24 PM »
...
« Last Edit: December 01, 2016, 07:36:25 AM by phil_er_up »
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Offline Gutbucket

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #10 on: November 29, 2016, 04:34:15 PM »
Excluding a PA, you can't go too far wrong with ORTF up front at the stage-lip or in the front rows. Same goes for DIN or NOS, all of which are minor variations on popular near-spaced microphone configurations. Try one or more of those configurations from those locations, which should then serve as a good recording reference point to which you can compare the recordings you've made already and any new options you try.   

You needn't fly very high from those locations.  Barely peaking over the edge of the stage can work very well.  Recording very low in the first row with the back of the seat acting to attenuate the close audience applause from the row immediately behind can be very effective and is essentially invisible to the audience.

If it sounds good up there at the stage-lip or in the front row, then that's the place to record from.  If lots of stuff is going through the PA and that stuff sounds dull and boomy from that location, then that's a good motivation to move further back, or to also record a soundboard feed to mix with your stage-lipe/front-row microphone recording.
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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #11 on: November 29, 2016, 05:17:21 PM »
ORTF requires a microphone from a category referred to as first order.  First order cardioid mics can be turned outward to 55º each side, for a combined off-axis response of 110º. Not all cardioid mics are capable of first order response. In order to fit the first order response category, they need to be able to be turned to that extreme off-axis response (55º x2) with the only effect being an attenuation of signal strength, without any frequency altering, or distortion of the presented signal.  Its safer to stay with a combined off-axis response of 90º (45º each mic).
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Offline Gutbucket

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #12 on: November 29, 2016, 06:10:16 PM »
As for trying stereo microphone configurations other than ORTF, DIN, NOS and the like with your cardioids, start from consideration of the basic relationship governing angle and spacing between any pair of microphones used for stereo recording-  1) The less angle you use between the microphones, the more spacing you should use between them, and vice-a-versa.  A coincident X/Y microphone arrangement requires a very wide angle between microphones to produce a good sounding stereo recording (but don't over do it), whereas a spaced A-B recording with parallel arranged mics requires significantly more space between the microphones (but don't over do it), regardless of the microphone's pickup pattern. 

Using a single pair of cardioids, I'd skip trying a coincident configuration for this.  In general, the cardioid pattern just isn't directional enough to work very well in a coincident X/Y arrangement for a good-quality stereo recording of an ensemble in a live space.  If you consider the 110 degree angle between microphones specified by ORTF to be somewhat on the wide side (which is specified due to the microphone spacing of just 17cm or a bit under 7"), then consider that if those cardioids were placed in X/Y with no spacing between them, even 180 degrees between microphones isn't really enough.   Sure, 90 degree X/Y cards will work, but most listeners will prefer DIN, which also uses the same 90 degree angle between mics except with a spacing of 12", producing a much more appropriate pattern/angle/spacing combination for this type of recording.  Coincident cardioids have their place, and could work well if you were also recording your omnis, widely spaced to either side of the X/Y cardioids with the intent of mixing the coincident cards and wide-spaced omnis together, but that's getting well ahead of ourselves and complicating things.  Let's keep it at 2 channels for now.

If you want to use a angle of less than 90 degrees between cardioids, space them more than 12" apart, possibly a lot more.  And increase that spacing the further your recording position is from the source as you move back into the room..

Which leads to the next basic relationship which helps determine what pattern/angle/spacing relationship to choose- 2)  As the recording position is moved further away from the source, compensate by using less angle between the microphones and more spacing between them.  So if ORTF works great from the stage-lip, try the same cardioids in a wider spaced but more narrowly angled configuration if you are recording from further back in the room.  The logical extreme to that is A-B spaced cardioids with the mics parallel to each other, as if you were using a pair of omnis.  That would be appropriate if you had to record from the back of the room, wanted to maximize pickup of the direct sound as much as possible with regards to room reverb, and still wanted to preserve as much "stereoness" as possible given those constraints.

How much space between narrowly angled microphones?  Below is a chart which recommends spacings between cardioids based on whatever angle between microphones a taper ends up with after pointing the mics directly at the PA speakers.  It takes the point-at-stacks (PAS) taper technique and suggests an appropriate spacing between mics.

Notice that it gets wide quickly as the angle diminishes.  As a rough starting point I'd suggest spacing omnis, or in your case parallel angled cardioids, 3 feet apart.  More can work, less can work, but 3' is often about right.  Consider 3' A-B as a good starting point, sort of like ORTF/DIN/NOS or there about is a good starting point for near-spaced cardioids.  Also consider 3' A-B to be something of an extension of the chart above, out to a Mic angle of 0 degrees and a suggested spacing of 100 cm.
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Offline Gutbucket

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #13 on: November 29, 2016, 06:11:11 PM »
As for trying the omnis, I have two suggestions-

1) Space them 3' apart or so along the front stage lip edge.  Most patrons won't even notice them.  Excellent natural sounding recordings can be made this way and good proximity to the performers will limit overbearing room reverberance even though they are omnidirectional.  I'd still suggest pointing them at the performers, since omnis are slightly directional and you'll get better detail and transients by pointing them directly at the main sources of interest.

2) Space them 3' apart or so back at the soundboard, but tape them directly onto the front face of that wall which faces the stage on which the mics are sitting in the photo you posted above. This is called boundary-mounting and works best if the wall is hard rather than soft.  It's a somewhat unusual technique that in the right situation can seemingly work magic, providing astounding clarity and a dramatic reduction in reverberation.  Boundary mounting works best with the mics as close to the wall surface as possible, so taping your small lightweight omnis directly to that wall can be a good option.  I'd point the omnis directly to either side, facing 180 degrees apart instead of trying to point them directly at the stage.  With boundary mounting, the direction the wall is facing will do most of the "pointing", and that gets the diaphragms closer to the wall surface while providing a small about of directional difference at the highest frequencies.  Ideally the omnis would be mounted so that their capsule surfaces were flush with the wall surface itself, but taping them to the wall works fine as long as they don't vibrate.   This technique makes the omnis behave more like cardioids, they become "hemispherically directional" instead of omnidirectional, and increases the direct-sound to reverberant-sound pickup ratio in a way no other technique can.  It's an odd-ball technique which can be a real problem solver and I think is worth a try in this situation, especially when you need to record from the back of the room instead of from up front.
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Offline Gutbucket

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Re: Switch to DIN or ORTF for a situation like this? CA-14 cards
« Reply #14 on: November 29, 2016, 08:02:28 PM »
ORTF requires a microphone from a category referred to as first order.  First order cardioid mics can be turned outward to 55º each side, for a combined off-axis response of 110º. Not all cardioid mics are capable of first order response. In order to fit the first order response category, they need to be able to be turned to that extreme off-axis response (55º x2) with the only effect being an attenuation of signal strength, without any frequency altering, or distortion of the presented signal.  Its safer to stay with a combined off-axis response of 90º (45º each mic).

Moke is correct in that ORTF works best using cardioids which have "well behaved polar patterns" in which the frequency response does not change significantly even for sounds arriving from far off the main axis of the mic.  That's due to the rather large ORTF 110 degree angle between microphones, which points each more off-axis to sources in the center of the stage than other configurations which use less angle between mics.  But I wouldn't let that stop you from trying it, along with DIN and NOS, both of which use a narrower 90 degree angle between mics but slightly different amounts of spacing.  We do all sorts of things as tapers that are not the prefered way of recording, and ORTF using inexpensive mics is a relatively minor infraction!

Actually all microphone configurations will perform better using microphones which have good polar response behavior, as the microphones off-axis behavior colors the pickup of all sound that arrives from everywhere else in the room except directly in front- most of the applause, room reverberation and recording ambience.

I hesitate to contradict him, since he has been doing this much longer than I have and has taught me much over the years with regards to taping, basically welcoming me to TS over a decade ago.  However, I will make a correction here- the term "first order microphone" does not refer to an achieved build quality of a particular microphone.  It instead refers to a mathematical description describing directivity behavior.  Mathematically, all "first order microphones" can be modeled and thought of as the combination of a pressure component (the omnidirectional component) and a pressure-gradient component (the bidirectional or figure-8 component) mixed together in various combinations.  A true omni is 100% omnidirectional component and 0% bidirectional component.  A bidirectional figure-8 is 0% omnidirectional component and 100% bidirectional.  A true cardioid consists of exactly 50% of each.  A subcard or wide-cardioid has more omni component than bi, and a supercard or hypercardioid has more bidirectional component than omni.  We can even mix a real-world omni with a real-world figure 8 in equal proportions and create a virtual cardioid pattern.

Here's a drawing illustrating the mathmatical addition of the pressure and pressure-gradient components to form a first-order cardioid pattern as mentioned above-



That's pretty much all you need to know, or perhaps more than you need to know, but for anyone interested and in support of my contradiction in my next post I'll dish some dirt on higher microphone pattern "orders".   Feel free to ignore all this, it's something of a thread-jack!
« Last Edit: November 29, 2016, 08:04:23 PM by Gutbucket »
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