A B Pair Spacing - Opinions

[mrsteaks]

Hey, all - this could be construed as an idiotic question, but when you use an A B pair, what sort of spacing do you generally use, and why? Do you use outriggers with the A B pair?

Me - I've used as close together as two feet and never more than eight feet apart. I've discovered (no stone throwing, please) tht the wider spacing works when you can't get the array as close to the source as you'd like, with caveats. Narrow, IMHO, is better.

Thanks in advance!

~~~~Mark S
Pretty Good Recordings

[d_fu]

Interesting question...

My standard setup for years was a pair of AKG diffuse field omnis, tilted outwards for additional channel separation, and at about 60 cm. Since I've started using a pair of free-field Neumann KM 131 mostly, I usually keep them at about 1m.

Then I recently peeped into a radio truck that was recording a Handel Oratorio in a hall where I was supposed to record a scenic opera performance the next day (BTW, my second recording that is a true world premiere recording... ).

They radio engineers had set up a huge AB, around 3 meters or so (DPA 4006 TL). I asked the sound engineer in charge why she had chosen this setup and she said it was good in halls where one didn't really expect much from the hall's own ambience (i.e. in places that are completely dry...). It also was good for editing with material from recordings with and without audience. She also said there was no danger of a "hole in the middle" because there were plenty of spots to fill the middle. All in all, they used 37 (!) microphones...

I decided to not go quite as far apart, but tried something that was about 1.5m wide and higher than what the radio had used, and I quite liked the result... I ended up with 14 mics all in all, which is quite a lot by my standards. And almost 20 GB of data (24/48).


Daniel

[mpdonahue]

She also said there was no danger of a "hole in the middle" because there were plenty of spots to fill the middle. All in all, the used 37 (!) microphones...

Volker Strauss would be proud........

All the best,
Mark

[hughesmr]

Does that photo look absurd to anyone else but me?

[d_fu]

Originally Posted by hughesmr

Does that photo look absurd to anyone else but me?

How so? No, this wasn't a performance of 4'33''...
Couldn't take pictures during the concert.

[Don S]

Originally Posted by hughesmr

Does that photo look absurd to anyone else but me?

Looking at it quickly, yes, a little. Upon a closer look, not so much. The photo is taken from audience level, so the main stand looks a little high. Also, I can't identify the mics used, so depending on pattern, the placement may look a little off in the photo.
But most importantly, I'm sometimes amazed at what my configuration looks like after a careful sound check. Also, we must take in consideration that unless the mics are flown into position, sometimes we can't get them into an optimal position because of the concert situation. So it becomes an even greater comprise from the sound we want.
I record some very fine ensembles that don't want to pay (extra to stage crew) to have mics flown, only to have the manager or conductor tell me they don't want to see a mic stand. Just another variable in the equation of live concert recording.

[mrsteaks]

Originally Posted by Don S

....sometimes we can't get them into an optimal position because of the concert situation. So it becomes an even greater comprise from the sound we want.
I record some very fine ensembles that don't want to pay (extra to stage crew) to have mics flown, only to have the manager or conductor tell me they don't want to see a mic stand. Just another variable in the equation of live concert recording.

Exactly, Don! I run into this all of the time. It is rare indeed when I can get the mic(s) where I want them, not where sight lines or other considerations dictate.

~~~~Mark S.
Pretty Good Recordings

[hughesmr]

Originally Posted by d_fu

How so? No, this wasn't a performance of 4'33''...
Couldn't take pictures during the concert.

I'm referring only to the setup. It just looks like microphone overload considering the type of repertoire being recorded. I don't know, maybe it's just me ... I think they could get something more natural sounding with fewer than 37 ears ...

[d_fu]

Originally Posted by hughesmr

I'm referring only to the setup. It just looks like microphone overload considering the type of repertoire being recorded. I don't know, maybe it's just me ... I think they could get something more natural sounding with fewer than 37 ears ...

This isn't the 37-mic radio setup, this is mine with "only" 14... I was being as economical as I could, e.g. I "spotted" the continuo as a group, not individually (celli, bassoon, picking up some viola as well...). The radio setup looked quite different, even though they had all these Schoeps tube extensions...

Although this doesn't really belong here, I've altered the picture above to show the setup in detail..

[mrsteaks]

If the room was good, I'd have tried it this way (using what I have in my mic cabinet, which is pretty meager) Royer SF-12 main, Blumlien or M/S (depending on the acoustic). Two Earthworks SR-71's on the choir, a Peluso CEMC6 (cardioid cap) on the Thierbo. MAYBE the Naiant MSH-1's for outriggers. Not world class, no, but I think it would have done the job.

~~~~~Mark Stearns
Pretty Good Recordings

[zarembo]

excellent thread-

Daniel, when you finished the 14 mic recording did you actually need all 14 channels in the final mix?

In larger setups like this do you ever find some mics to be redundant with what information is available in your main pairs?

I really appreciated seeing your photo with notes included.

thank you,
walter

[d_fu]

Originally Posted by mrsteaks

If the room was good,

It isn't..

I'd have tried it this way (using what I have in my mic cabinet, which is pretty meager) Royer SF-12 main, Blumlien or M/S (depending on the acoustic). Two Earthworks SR-71's on the choir, a Peluso CEMC6 (cardioid cap) on the Thierbo. MAYBE the Naiant MSH-1's for outriggers. Not world class, no, but I think it would have done the job.

Not sure... The choir was standing there in three groups of three (and actually partly consisted of the soloists...). You would also not have caught the soloists in the front very well. The main mic had to be close to the stage because of the audience. If you had placed the main mic lower, the soloists would have been at almost 90 degrees from the main mic's center axis, not so good for Blumlein, I believe. I would also personally consider the SR71 to be too noisy for classical work. I've tried the SR78 and it was.

[mrsteaks]

Originally Posted by d_fu

Although this doesn't really belong here, I've altered the picture above to show the setup in detail..

I too appreciate the photo, especially with the detail. I'd love to hear your recording, too.

Okay, another question - what do folks use for a mic bar for A B - the Bogen three mic bar or something similar?

~~~~Mark S
Pretty Good Recordings

[mrsteaks]

Originally Posted by d_fu

If you had placed the main mic lower, the soloists would have been at almost 90 degrees from the main mic's center axis, not so good for Blumlein, I believe. I would also personally consider the SR71 to be too noisy for classical work. I've tried the SR78 and it was.

The SR71 isn't bad, especially for spots on vocals, percussion or piano. For low level sources (like a thierbo), it can be a triffle noisy. In the case of soloists, well, use the Royer in M/S, then. I've run into exactly that problem before and M/S saved the day.

Possibly the Peluso's on choir spots?

~~~~Mark S.
Pretty Good Recordings

[pkautzsch]

Daniel's setup looks similar to what I'd have done based on what I'm seeing of the hall.
Though I'd probably have had the main pair spacing way smaller, about 2 ft. That would probably have made the harpsi mic redundant. In such a wide spacing, I guess the "hole in the middle" will be filled by harpsi and choir mics?

I have two DIY bars, one giving 54 to 60 cm spacing depending on what mic clamp I use, and the other doing 90 to 100 cm. The former being used when closer, the latter for farther away, often with some threesome setup (think Mercury curtain or Decca tree) covering the orchestra. This is sufficient for most stuff I do, always concert recordings, always audience, always optical people.

[d_fu]

Originally Posted by pkautzsch

Though I'd probably have had the main pair spacing way smaller, about 2 ft. That would probably have made the harpsi mic redundant.

Maybe... If I hadn't had the chat with the radio engineer, I would have used my usual 1 m setup with the Neumanns. Apart from that, I did want to try to get a bit closer to that "radio sound", that's why I used a good deal of mics.

Not much use to post a sample, though, most of the ambience in the recording is Samplitude's convolution reverb. The hall is just dry...

In such a wide spacing, I guess the "hole in the middle" will be filled by harpsi and choir mics?

Partly, and I don't pan the violins and continuo and other spots dead L/R...

[mrsteaks]

Well, we've diverted this thread, but that's what good discussion is all about. Daniel, if I had access to the number and quality of mics that you do, I'd use many spots as well. Oh - I read your thread on the MKH 80 vs KM 131 with great interest. It tied to this thread rather nicely. I use the microphones I do because they are what I own (right now). I'm trying to learn the best ways to use them - mask their weaknessess and bring out their strengths.

So, to sum what I've learned so far in this thread - closer spacing - 1 meter or less, is preferable to wide spacing.

True?

~~~~~Mark S.
Pretty Good Recordings

[d_fu]

Originally Posted by mrsteaks

Well, we've diverted this thread,

Mea culpa...

I use the microphones I do because they are what I own (right now). I'm trying to learn the best ways to use them - mask their weaknessess and bring out their strengths.

Great - You've got a Royer, which I don't have... I never intended to criticize your collection. When I said I wasn't sure your setup would do the job, I was just referring to some positions that I thought could do with spots that you left out - esp. the singers. Sorry this has turned into a discussion on spot mics...

So, to sum what I've learned so far in this thread - closer spacing - 1 meter or less, is preferable to wide spacing. True?

Maybe... I wouldn't really do the 3 meter thing (then again, why not try out some day?).
But I've already moved from 60 cm to 1 m to 1.5 m. Just like I've started using more and more spots over the years... Considering I've recorded Mahler symphonies in the same hall with 6 or 7 mics, 14 for a baroque opera is a fair deal more. No wonder this took a good deal of time to set up. And even two hours to pack up... But I digress again.

Of course, the width of an AB also depends on the distance from the source a bit. If you're close, you need less width to get the same theoretical channel separation. But I normally don't go and calculate the required width this way...

[mrsteaks]

Originally Posted by d_fu

Great - You've got a Royer, which I don't have... I never intended to criticize your collection. When I said I wasn't sure your setup would do the job, I was just referring to some positions that I thought could do with spots that you left out - esp. the singers. Sorry this has turned into a discussion on spot mics...

Daniel, please don't think I took your comments as criticism of my collection! Not at all! There's a slight twinge of jealousy on my part , that is all!

As for the thread turning into a discussion on spots, well, that's the nature of a conversation, isn't it? It is certainly constructive, and informative. Also, I don't think you can talk about recording a live performance with a main array without mentioning spots and how to place them, and why. Personally, I'm glad it came up!

As for wide spacing, I asked the question knowing that I DO NOT like wide spacing (over a meter). The image is too vague, there are too many phase artifacts (to my ear, and my ear is bothered by phase), and then there is the "hole in the middle". It was a rhetorical question. I prefer near coincident or Blumlien, primarily for the depth and stability of the image they render, but I say that knowing that one can't use such an array in all cases. I don't have microphones that work well in an A B pair array (I have Rode NT2's), but - but when I do, I will try them in a close spaced A B array. Right now I'm just trying to learn from capable, experienced and gifted folks such as yourself, and believe me, learning I am!

Thanks for the great discussion, Daniel.

~~~~Mark S.
Pretty Good Recordings

[liuto]

I know a few charts that show the interdependence of recording angle and microphone spacing in AB, based on different figures for the minimal time delay necessary for full spread of soundstage between the loudspeakers. These figures are quoted between 1ms-1,5ms. Sources can be found here:

Williams: The stereophonic zoom"
http://www.rycote.com/products/pdf/T...nic%20Zoom.pdf

Sengpiel:
http://www.sengpielaudio.com/Laufzei...fMikrbasis.pdf

Schoeps Mikrofonaufsätze (Wuttke):
http://www.schoeps.de/D-2004/PDFs/Mikrofonbuch_Kap1.pdf

Wittek:
Image Assistant 2.0

So there seems to be quite some individual variation in the perception of the time delay cues.
I personally like to use smaller AB bases of around 35-50cm, depending on the size of the ensemble, for better imaging. Then I tend to mix in room microphones with bases of around 1-3m for a more spectacular room ambience. This also gives me post production flexibility to change the direct/indirect sound ratio.

Best regards
Hermann

[d_fu]

Originally Posted by mrsteaks

There's a slight twinge of jealousy on my part , that is all!

Most of my mic collection is from ebay...

As for wide spacing, I asked the question knowing that I DO NOT like wide spacing (over a meter). The image is too vague, there are too many phase artifacts (to my ear, and my ear is bothered by phase), and then there is the "hole in the middle".

While I'm personally not overly concerned with pinpoint imaging, I suspect that there may be less of potential phase issues in a hall as dry as this one, even with larger ABs. Soloing the AB main pair does bring about a certain hole, but no significant audible or measurable phase issues (which my ears are also fairly sensitive to).


Daniel

[mrsteaks]

Originally Posted by d_fu

Most of my mic collection is from ebay
Daniel

eBay has been good to you! I've not been so lucky there, I'm just never ready financially when something good comes along. Take the QTC30's that are on there right now.....

Rats!

Yes, agreed, a dry room doesn't seem to have the phase artifacts that a wet room does. Stands to reason, with phase artifacts being the result of arrival times, and wetter rooms having many more reflections, hence more "arrivals".

I've tried close mic'ing a choir or source then mixing in room mics for ambience. I've never liked the result.

~~~~~Mark S.
Pretty Good Recordings

[pkautzsch]

Originally Posted by d_fu

Maybe... I wouldn't really do the 3 meter thing (then again, why not try out some day?). But I've already moved from 60 cm to 1 m to 1.5 m. Just like I've started using more and more spots over the years...

I've been through that too, finding when using more spots the main pair can become wider, and it also becomes less important. So: when it's not really predictable (ie audience when recording, but no audience when setting up) I often go for more mics than when non-concert recording. I've done 3 meter things, and every time felt the need for a center mic. Actually works quite fine in concert recording, since one is really close to the orchestra. I love three Straus packets spread across the orchestra about 1 to 2 metres in (not out!).

No wonder this took a good deal of time to set up. And even two hours to pack up... But I digress again.

That's why it's mostly radio stations which do those multi-mic recordings. I don't do more than 8 or 10 channels without an assistant who at least helps me setting up and wrapping mic stands and cabling.

Of course, the width of an AB also depends on the distance from the source a bit. If you're close, you need less width to get the same theoretical channel separation. But I normally don't go and calculate the required width this way...

Calculating and using tables is only good for rough guidelines. Sengpiel's table tells me I need to be about 50 cm if really close, and to be about 1 m when far away. I don't measure the angle the orchestra occupies from the mics' point of view...just rough estimation by eyesight.

[d_fu]

Originally Posted by zarembo

Daniel, when you finished the 14 mic recording did you actually need all 14 channels in the final mix?

In this case, I used them all...

In larger setups like this do you ever find some mics to be redundant with what information is available in your main pairs?

I don't do this kind of large setup often. But I think I've always used all sources, even if it's only a bit...


Daniel

[zarembo]

thanks Daniel.
that's kind of what I figured, but you never know....
btw I've started tracking the Indian Classical music I asked you about and it's really going well. Thanks for the tips!

[d_fu]

Originally Posted by zarembo

btw I've started tracking the Indian Classical music I asked you about and it's really going well. Thanks for the tips!

Interesting... So what has it turned out to be? PM me, if you want, lest we hijack this thread even more...

Daniel

[mrsteaks]

Hijack away!!

~~~~~Mark S.
Pretty Good Recordings

[d_fu]

Originally Posted by zarembo

Daniel, when you finished the 14 mic recording did you actually need all 14 channels in the final mix?
In larger setups like this do you ever find some mics to be redundant with what information is available in your main pairs?

Still working on this - and I find I keep reducing the spots, the harpsichord mic is down 27 dB... But it's an MKH 80, which is rather loud. It still makes a difference to the mix, -27 dB is better than muted...

Daniel

[zarembo]

Originally Posted by d_fu

Interesting... So what has it turned out to be? PM me, if you want, lest we hijack this thread even more...

Daniel

check your PM as I hate being a hijacker and realize my original question here had nothing to do with AB spacing.