Blumlein for 360 degree sound field??

[boojum]

I have a stinker of a gig I record "for fun." It is a bluegrass jam with the guys mostly around a square table which is close to a wall, alongside a pool table and surrounded by a loud and gabby crowd mostly ignoring the players except to occasionally applaud. I have tried the spaced arrays (AB omni) which was not good because of all the chatter. The non-coincident arrays (ORTF/NOS/DIN) are OK but do not get the whole crowd into the picture. I even tried the Williams three card array but found it not much different than MS in this application: OK but not the solution.

I have a borrowed Busman Blumlein ribbon, a Chinese mic modded by the US vendor. I tried it on the group's edge as one would for Blumlien and it was awful. Not knowing any better I just dropped the mic into the center of the group, right above the square table and it sounded the best of any array/technique I have yet used. So, what's wrong with this approach? I am no wizard so I know it has been tried before. Has anyone here done this? What were your results; impressions?

I'll take my answer off the air.

[springer]

Hey Booj,
If it works then it works... "they" say that sounds in the same frequency range on opposite sides of the mic will cancel out in that sort of circumstance.
I would try MS from above. 414 in card and one in fig8. This would get the immediate circle of folks around that area.

[JEGG]

Try spaced cardioids, not too far apart, maybe turned out very slightly or not at all.

[boojum]

I have tried the MS from above: Schoeps CMC64+CMC68. Also tried the ORTF/NOS from above. NG as it gets too much of what is happening outside the circle . If I drop the mics in these configurations low enough to be shielded by the performers from what is outside the group I do not get them well as it is just about parallel with them. The Williams three cardioid array was about the same as the MS.

I may try the MS + the ribbon Blumlein next Monday just to see the difference and to get a baseline on the sound of the ribbon, a Busman.


Believe me, I have tried about every way I can to get the performers and not the crowd short of gassing the crowd. Hey, maybe that is the answer. LOL

[David Spearritt]

Booj, you need to be more enthusiastic with your search buttons. There is so much info on this subject both here on GS and out in many other places.

eg.
Full circle around a Blumlein Pair - a capella - Had a fun recording on Sunday. A vocal group at a college about 90 minutes away hired me to record them for an archival CD for the members. 17 singers - I had them stand in a circle around a Blumlein p

PSW Recording Forums: Klaus Heyne's Mic Lab => The glorious Blumlein

and an excellent article:
http://www.davidgriesinger.com/primer.doc

[NorseHorse]

I've seen a cappella groups recorded in this way on several occassions in studio(s). I've also used this method. I've haven't encountered any problems, but I also wouldn't hesitate to use a spaced pair either. Both would work fine, but the main advantage to using blumlein in a situation like an on-the-fly bluegrass jam is that you have flexibility in determining which direction your stereo field is facing.

[boojum]

Guys, the deal is that I have tried the arrays and they just cannot get the group without the clatter surrounding them. Williams has a cardioid array for 180 degrees of 12 cm apart and ~58 degrees angle of separation between the cards. I will run this in parallel with the Blumlien and hang it int eh center of these guys, above the square table and a little above head height. There has to be a solution. I could run MS, too, just to see how they all compare. But MS has not been a solution in the past as its effective angle when decoded is too narrow, not at all unlike an XY array.

Thanks for all the input. This board is the best.


Dave's suggested links were interesting and one was actually good. But I had asked for experience on this board. I know how to Google. ;o)

Cheers.

[audiothings]

with blumlein, as i understand, the acceptance angle is 90 degrees, the front facing quadrant only... i do not know about phase cancellations and all, but if you setup a blumlein pair and say, circle around it while playing a triangle, you will find that when you are facing one of non optimized quadrants, the resultant recording will have a very haphazard and unreal movement between the speakers, and it will not be representative of the actual stereo field.

if you want 360 degree acceptance with a coincident pair, i think the only way to go is m/s with an omnidirectional 'm' (and of course, a bidirectional 's').

and now, to catch up with the stuff david pointed to...

[hbphotoav]

If they're literally "around a table" it seems to me that a "stereo" view with its 2-dimensional L/R image might not be possible, or, for that matter, realistic... sounds like a good situation for a surround setup.

That said, what about a pair of boundary mics (perhaps DPA4061s in their boundary rigs, or Crown PZMs) at 180 degrees, on or close to the table? Might not ever produce a "stereo" image (can there even be one from an inward-facing 360 of players?) but it would give every instrument a "clear" shot into a transducer.

Better, what about getting the circle to become a semi-circle with a nice pair of cards out in the room a wee bit, merrily rejecting most of the chatter? Might mess with "the vibe" (or be totally un-doable, given that it seems to be tight, "available" space in a bar) but it will provide a genuine L/R tableau.

It does sound like fun, though. I'd be tempted to just stand up my Edirol R09HD on a nice bit of foam in the center of the table and let 'er run.

[boojum]

^^^ I have thought about getting them into a recordable semi-circle but they for a circle because that is the way they have always done it, for 20+ years. I think that is the best solution, but it is hard to overcome that kind of inertia. This really is a rough jam with folks showing up and sitting in an irregular pattern around the table. Eat your hearts out that you aren't mic'ing this one. LOL

The 4061's on the table would be a possibility except for the fact that they are banging on the table now and again, picking up their beer and replacing it and so on. This gig is a nosebleed and I love the challenge. The Blumlein-in-the center is about the best, so far. But I am trying the Williams 90 degree SRA setup of 12 cm separation with a 58 degree angle between the cardioids. There is a way to do this. I will run the Blumlein alongside the Williams array.

[12ax7]

This might be worth a shot:

Core Sound — TetraMic
(Click on it to go to their site.)

[LenM]

Originally Posted by boojum

...
I have a borrowed Busman Blumlein ribbon, a Chinese mic modded by the US vendor. I tried it on the group's edge as one would for Blumlien and it was awful. Not knowing any better I just dropped the mic into the center of the group, right above the square table and it sounded the best of any array/technique I have yet used. So, what's wrong with this approach?

Nothing wrong with it. Blumlein reverses phase for sources positioned towards the rear, so they appear in a stereo image on opposite sides than where they really were. As long as that's okay, if you like the result why not use it?

A soundfield-type ambisonic microphone, like our TetraMic or the mics from SoundField Ltd. will do the job better. You record four channels of audio information. The four channels capture essentially everything going on acoustically at that point in space. Those four channels of audio will never be used raw -- you must run them through a decode process in post-production (or during recording for use in monitoring).

In decode, you can set up whatever microphone setup you want. You can elect as many microphones as you want. You select each of the microphone's pickup pattern (omni, sub-card, card, super-card, hyper-card, figure-8 or anything in between). Each microphone can be aimed in whatever direction you choose in both horizontal and vertical (azimuth and elevation) planes. You can define Blumlein, X/Y, M/S, six hypercards and three cards, or pretty much whatever you want. And you can run as many decodes as you please, and then mix the results together.

So you can decode to a hyper card pointed at the guitar player, another aimed at the mandolin player, another at... (you get the idea). If the off-axis lobes are picking up audience noise, you can aim a cardioid's pattern null at the noise source and cut its level by 20+ dB.

It's unbelievably flexible.

And for what it's worth, our TetraMic is probably the finest Blumlein array in the world. Thanks to 12ax7 for mentioning it.

Len Moskowitz
Core Sound LLC
Core Sound

[boojum]

^^^^^ Len, I have seen it in photos used horizontally, can it be used upside down?

[David Spearritt]

Originally Posted by LenM

Nothing wrong with it. Blumlein reverses phase for sources positioned towards the rear, so they appear in a stereo image on opposite sides than where they really were. As long as that's okay, if you like the result why not use it?

Because its the two side-side out of phase quadrants that cause problems for the "all round the mic" positioned performers, not the front back quadrants.

[Ozpeter]

As it's "just for fun" this sounds like a job for...

the Zoom H2 (recording separate front facing and rear facing stereo pairs), then play around in your DAW after.

Things to help with the playing around -

AcousModules : Surround 5.0 à 7.1

Ambisonic Studio | Zoom2Five Plug-in

Best Surround Sound System, MP3 Surround Sound - Vortex Surround

[pkautzsch]

Front/Back isn't an issue, that's right. The L mic's rear points to the right, though, and vice versa.
What IS a problem is the area between the L mic's front and R mic's back lobe. Everything in that area will cancel out when played back mono. (and vice versa).
So if the L points to 12 o'clock (and rear to 6), the R points to 3 (rear 9), all sources between 3 and 6 and between 9 and 12 will disappear in mono.

A spaced pair of omnis will be better, if you choose the spacing to get an SRA of 180°. As they are sitting around a table, why not use them in a quasi-PZM setup.

[boojum]

The problem with the omnis is that they pick up too much of the room sound beyond the players. I may try them again with the DPA 4061's just to see how that works. I will run them alongside this Blumlein I have on loan. I tried omnis awhile back and it was not good.

This gig is a learning event for me. It has had me stumped now for awhile. I keep thinking there has to be a way to get the players and not the crowd. It is a fun night, too. Jams sometimes are and I know the guys so it is part social, too.

[boojum]

Originally Posted by Ozpeter

As it's "just for fun" this sounds like a job for...

the Zoom H2 (recording separate front facing and rear facing stereo pairs), then play around in your DAW after.

Things to help with the playing around -

AcousModules : Surround 5.0 à 7.1

Ambisonic Studio | Zoom2Five Plug-in

Best Surround Sound System, MP3 Surround Sound - Vortex Surround

Yeah, I've thought about the Zoom. But I am not sure that solution will take me in the direction I want to go. I am trying to learn how to mic this nosebleed with what I have and to learn enough I can maybe use it later.

[boojum]

Originally Posted by audiothings

with blumlein, as i understand, the acceptance angle is 90 degrees, the front facing quadrant only... i do not know about phase cancellations and all, but if you setup a blumlein pair and say, circle around it while playing a triangle, you will find that when you are facing one of non optimized quadrants, the resultant recording will have a very haphazard and unreal movement between the speakers, and it will not be representative of the actual stereo field.

if you want 360 degree acceptance with a coincident pair, i think the only way to go is m/s with an omnidirectional 'm' (and of course, a bidirectional 's').

and now, to catch up with the stuff david pointed to...

I have tried MS with middling success.

[Daniel Stark]

what about double m/s? could be a fun experiment to try. and way cheaper than buying a soundfield etc.

[boojum]

Originally Posted by Daniel Stark

what about double m/s? could be a fun experiment to try. and way cheaper than buying a soundfield etc.

Ah, yes, the Schoeps DMS. I have the gear I need but am stumped with building a mic stand for it. I could run the Mk4's with KC5's (remote cables) and the CMC68 just plain. I have the clip for the forward facing Mk4 for MS but am stumped about hanging the rearward facing Mk4. The rearward facing Mk4 needs its diaphragm aligned with the Mk8 and other Mk4 which means its butt is sticking out in front. Butt ugly, but maybe I can think up a way. It would be really a lot of fun to play with this rig. It is simple, only three channels, no screwing around with two intermediate formats and the decoder is free from Schoeps. I have gotten it already.

Now you've screwed up my Thanksgiving! ;o) I will be thinking of how to do that the whole time. LOL

Carbon fiber??? Hmmmm

[12ax7]

Originally Posted by boojum

Ah, yes, the Schoeps DMS. I have the gear I need but am stumped with building a mic stand for it. I could run the Mk4's with KC5's (remote cables) and the CMC68 just plain. I have the clip for the forward facing Mk4 for MS but am stumped about hanging the rearward facing Mk4. The rearward facing Mk4 needs its diaphragm aligned with the Mk8 and other Mk4 which means its butt is sticking out in front. Butt ugly, but maybe I can think up a way. It would be really a lot of fun to play with this rig. It is simple, only three channels, no screwing around with two intermediate formats and the decoder is free from Schoeps. I have gotten it already.

Now you've screwed up my Thanksgiving! ;o) I will be thinking of how to do that the whole time. LOL

Carbon fiber??? Hmmmm

Can you hang the array from a ceiling?

Sounds like DIY time!

(Coat-hanger wire, rubber bands etc.)

[boojum]

Originally Posted by 12ax7

Can you hang the array from a ceiling?

Sounds like DIY time!

(Coat-hanger wire, rubber bands etc.)

I cannot hang the rig from the ceiling but I can hang it from the boom on my large studio mic stand which is what I now do with the Blumlein.

I will get some carbon fiber bits and fashion some sort of cage or whatever to do this. If I can get the DMS to work at this site I can use it anywhere. I have been mic'ing these guys for a couple of years now with only middling success. It is a wonderful challenge. The constant problem is getting just the musicians and not the crowd which is right outside the performers. The crowd is drinking and eating burgers and chattiing, applauding at the end of each number, or almost each number. This is not a pro performance but it is a challenge. And as I said before, it is a fun night out and a chance to hear some pretty good music, eat a burger and relax. Now if I could just do what I am going there for: get a good recording!


12AX7! I had more than one amp with those in there. Push-pull pentodes?

[pkautzsch]

MS with two fig-8 mics?
That would be Blumlein-like to set up, just rotated by 45° and decoded.

Just thinking.

[boojum]

Originally Posted by pkautzsch

MS with two fig-8 mics?
That would be Blumlein-like to set up, just rotated by 45° and decoded.

Just thinking.

Peter - Two cards and one F8. Schoeps has some info about it on their website: SCHOEPS double-ms

It is a tempting array in that it is simple (once the mounting gear has been built) and offers a lot of possibilities. I have to give some thought to the construction of mounting gear.

[pkautzsch]

Originally Posted by boojum

Peter - Two cards and one F8. Schoeps has some info about it on their website: SCHOEPS double-ms

It is a tempting array in that it is simple (once the mounting gear has been built) and offers a lot of possibilities. I have to give some thought to the construction of mounting gear.

Took a while to get the idea out of my head that DMS had to be surround.
You can perfectly sum the front and back M mics together.

What Blumlein, MS with two fig-8, and DMS have in common: they form a toroid pattern, that way keeping out all the crowd noise reflected from the ceiling.

[boojum]

OK, solved this nosebleed with the sweet Pearl DS 60. The left drift problem in the recorded soundfield was solved by our friends in GB: Roland and Roger. Combining the LR and FB cards into one stereo file, flipping phase in one side of each stereo channel does the trick. Yes, right rear does appear in the soundfield as left front, and vice cersa. Oh, well. If you were not there with a camera, how would you know? You didn't hear it from me.


I have not worked with the Schoeps DMS plugin enough to get it to do the Blumlein or MS decode I want into two channels, yet.