Fukada Tree - Boundary Microphone Array

[NorseHorse]

A boundary Fukada Tree is an array of four or more boundary*** microphones arranged in a square with a flat side facing the sound source. Each mic is mounted facing outwards towards a corner of the square. A panel can be placed between the mics to increase difference in frequency reponse (much like a jecklin disc). The signals from these microphones can be combined to great a number of pickups (such as ORTF, Blumlein, and Faulkner) and formats (stereo, quad, 5.1, etc.). According to the diagram below, two omnis are used as flankers, but the square can be used alone as demonstrated in the on Mastracco's page (with samples).

"This mike arrangement is chiefly intended to record a sensation of expanse of the hall." Here is a page from NHK describing its use in concert situation, including a "super" Fukada Tree (scroll up just a little after clicking the link to get a context for the figure):

NHK digital broadcasting.

James M. Mastracco has a great page here of a recording his did July 2008 using a Fukada Tree. You can view pictures and listen to derived versions of the pickup patterns:

Washington Collegium: The Birth of a Choir

***EDIT: Our initial discussion pertains primarily to boundary fukadas, but you could supposedly do it with other microphones (see the NHK paper). Mastracco's session documentary deals only with a boundary fukada.

[boojum]

OK, I am not quite as bright as the average bear. How different is the sound on the floor with boundary layer mics from the sound at head height or higher with a corresponding setup? And if it is different, why do I want to hear what is being heard on the floor? I am not trying to be flip but I am serious about how this would work.

Thanks.

[NorseHorse]

I think a good way to express it is that you aren't hearing what one spot on the floor is hearing. Instead, with boundary mics, it's like the whole floor - the whole building - becomes your microphone. You get a sense of a space and not a spot. I can't speak from experience on this, but that's the idea. I've sent an email to James M. Mastracco letting him know I've posted. Anyone else have experience with this? Someone correct me if I'm wrong here.

[jnorman]

hey norse - have you ever actually tried boundary mics? i have never tried them, but the recordings i have heard from them have been pretty uniformly terrible. of course that could easily mean the stuff i have heard was made by people who did not know what they were doing, but it certainly scared me off trying them.

[Audiop]

I have heard nice recordings with PZM's and I will try it myself some day.

I think one need to realize that stereophony is not about placing a pair of mic's where the ears would have liked it best (like with a binaural recording), but capturing a wavefront that is supposed to give a realistic result when the speakers have projected the recorded sound in the listening room.

Boundary miking may make sense since you side step the floor reflection that creates a dip/suckout in the frequency response which may be doubled by the floor reflection of a standard speaker.


/Peter

[BLP]

Very interesting! I'm a lover of the Fukada tree (Akira Fukada is a genius, as far as I'm concerned) and I've been known to use PZM's from time to time (great fix for bad room + unidirectional array that's giving a lack of low end), but this is a new one to me. This one is new to me, though. The NHK guys know what's what, so I just might have to give it a go!

[sonare]

I have used Schoeps and DPA boundary mics and ended up dumping the tracks. My conclusion was that if location could be idealized and it was boundary or nothing that they might be useful in that scenario. Other than that, no thanks.

Rich

[NorseHorse]

Originally Posted by jnorman

have you ever actually tried boundary mics?

I've only used floor/wall boundaries in live sound situations where they were pretty much already installed. I don't own any myself. However, I do have a Crown SASS that I love, and it's technically a boundary mic. It's a stereo PZM mic and excels at accurate playback stereophony. Not all boundary mics are PZM though. Here is information from Crown:

INTRODUCTION
A boundary microphone is a miniature microphone
designed to be used on a surface such as a piano lid,
wall, stage floor, table, or panel. Mounting a miniature
mic on a surface gives several benefits:
• A clearer, more natural sound quality
• Extra sensitivity and lower noise
• Consistent tone quality anywhere around the
microphone
• Natural-sounding pickup of room reverberation
Crown boundary microphones include the
PZM, PCC, MB, and SASS series microphones.

From Crown Boundary Microphone Application Guide: http://www.crownaudio.com/pdf/mics/127089.pdf

[Ozpeter]

I have four Radio Shack PZMs of considerable antiquity, modified for balanced operation, and have used them occasionally over the years in situations where I've been told that I'm not to use any kind of mic stand, eg in churches. I'm pretty sure that the recording I did in, er, I forget when at the Festival Hall in London when Moura Lympany gave a piano recital celebrating 60 years of performing employed 4 PZMs but that configuration would have involved two quite close to the piano (keyboard end and tail end) and two more further apart, mixed to stereo on the fly straight to DAT.

The configuration described in this thread is interesting and now that I have a four channel recorder (R-44) of course it would make an experiment more simple, allowing me to fiddle with the result afterwards.

Trouble is, I don't have a suitable occasion lined up at present. Still, I'll keep it in mind.

The baffle would represent something of a tripping hazard in a live situation, unless one made it tall enough to be safe, but then it would be a bit obtrusive.

[tenor39]

The DPA 4060/4061 can be used in a boundary layer configuration with the disc that DPA sells for just such a purpose. Contrary to Rich's experience, I've found them quite useful in recording Opera, where no mic can be seen. Taped to the stage floor near the edge, they do provide a pretty darned good capture of the singers. I have 4 of them and will have to experiment with this arrangement. BTW, the Crown PCC's are cardioids, where as the DPA's are omni's.

[leddy]

I've been experimenting with boundary mics and PZM mics for the last month or so. I bought a Crown Sass off Ebay, and I built a device to hold my Avensons at a 90 degree angle about 5 inches apart. The boundary plates are wood, about 6 x 6 inches (a bit small, but it's for live use).

I have mixed results. The Avensons in my homebrewed boundary device sound good but they are picky on placement. The Sass images better, but the sound quality is not as good.

Here is a sample of the Avensons on my Jazz trio on a live gig in a bad room. There is a little bit of spot mic on the bass. The only mics are the Avensons and a Beyer M88 on my bass. The Avensons are a little too close to the piano vs the drums - so the balance is not the best. They sound a little thin & crispy to me compared to how Avensons usually sound when not in this rig - but there can be some advatages to boundary mics.

Still evaluating their potential...

[boojum]

OK, now my interest is piqued and I see that the DPA kit with two mics, a bucket of accessories and the two rubber discs is not all that dear. But, what does the PZM think about people walking around?? What does it hear for foot traffic? In an opera I would think this could be a problem, but does not seem to be. OK, please enlighten the <average bear.

Thanks

[BLP]

Sanken makes the most awesome boundary mics I've ever used. All I can say is that you forget their boundaries! Tiny little buggers, too. The other success I've had was taping two Schoeps omnis to the stage, flanking a sting quartet. Added a nice low end and some warmth to an otherwise somewhat constricted recording.

[boojum]

Originally Posted by BLP

Sanken makes the most awesome boundary mics I've ever used. All I can say is that you forget their boundaries! Tiny little buggers, too. The other success I've had was taping two Schoeps omnis to the stage, flanking a sting quartet. Added a nice low end and some warmth to an otherwise somewhat constricted recording.

Any microphonic interference from the physical contact between the mics and the floor?

[JEGG]

Originally Posted by boojum

Any microphonic interference from the physical contact between the mics and the floor?

I think you mean something other than "microphonic."

No mechanical sensitivity with omni mic.

Directionals exhibit the same behavior as they do in any other scenario:
Increasing mechanical sensitivity towards figure 8.

There is absolutely nothing different about using a mic on a boundary v using the same mic without a boundary-except for the 6 dB gain in mechanical sensitivity. They remain the same mic's that they are when not used on a boundary.

The SASS really is not a boundary mic at all.

It is a baffled omni setup, and works very well in terms of spatial perception. The liability in the past was the terrible sound from the Crown mic's. Perhaps they've improved them.

In the distant past, they offered the SASS with the option of using (then) B and K capsules. Even then, I'm not sure what the electronics were like.

It's a very effective baffle. The mic's, perhaps, a different story.

[boojum]

I suppose I did mean something more like "mechanical coupling" or something like that, but i beg off as a Liberal Arts major. We can all talk, we just cannot talk with clarity. LOL

Now I am really tempted to tape a pair of 4006 TL's to the stage of a chorale and see how they sound. This defies all that my <average brain tells me, but I am game to try it. If it works well I may pop for the DPA 4061 boundary kit. Drugs are cheaper than audio, but not near as much fun.

Thanks, all, for your help and patience. You are a great group and wonderful teachers.

[leddy]

Originally Posted by boojum

Now I am really tempted to tape a pair of 4006 TL's to the stage of a chorale and see how they sound. This defies all that my <average brain tells me, but I am game to try it. If it works well I may pop for the DPA 4061 boundary kit. Drugs are cheaper than audio, but not near as much fun.

I've heard some omnis work better than others when taped to the wall or floor.

Everytime I have tried to lay mics flat against a boundary, I've had wierd results with more comb filtering rather than less. The diaphragm is really supposed to be parallel with the boundary rather than perpendicular I'm pretty sure.

I drilled a hole in a piece of wood and stuck an omni through it so the capsule was flush with the board and finally had success. Now the size of the board plays a critical role; the larger it is the more low end response.

[Audiop]

Originally Posted by leddy

The diaphragm is really supposed to be parallel with the boundary rather than perpendicular I'm pretty sure.

Yes, but if the mic/capsule is small enough it will not be any problems with combfiltering. I'm going to try my Earthworks omnis against floor/wall.


/Peter

[tenor39]

Here is Susannah's Aria from Floyd's Susannah. I used (2) DPA 4041's flown over the orchestra pit and (3) DPA 4061's w/boundary layer discs as L/C/R at the lip of the stage. All tracks were time aligned with the flown pair. Except for the movement of stage props at the beginning, foot noise is minimal. I pick up as much foot noise with the flown mic's as I do with the ones taped to the floor.

http://www.recordclassical.com/file%20music/Suzanna'sAria.mp3

[NorseHorse]

Originally Posted by JEGG

The SASS really is not a boundary mic at all.

Actually, the SASS is a PZM boundary mic (it's two of them, actually). For reference, see the CROWN informational paper I've posted earlier in the thread: http://www.crownaudio.com/pdf/mics/127089.pdf. It has great information regarding comb-filtering too. Also: SASS-P MK II

It's just that the SASS has its mics already mounted to a surface, permanently. The benefit of the SASS is that its been designed to give a dead-on accurate, mono-compatible, stereo picture without any adjusting - all in a single unit. I've seen some engineers mount their PZMs to two plexiglass panels (again, see the paper) to acheive the same stereo effect. You can make your own homemade "SASS" with your own PZMs. There are no rules saying something has to be mounted to floor or wall to be a "boundary" mic.

Going back to the Fukada tree. The four mic set up is an expansion of the same principals used in the SASS and OSS (Jecklin) miking techniques: omnis plus frequency differences plus time-of-arrival differences. I wonder if Fukada is effective without a baffle?

[huub]

Has anyone an example of this technique by any chance?
My experience is that boundary mics can be fun to mix in a bit, but on their own sound really crappy.. But, hey... Could be me

[Corran]

Always interested in reading about new stereophonic micing techniques. Too bad I don't have any boundary mics though!

Norse, I really like the idea behind the SASS mic, but I must say the size of that thing is just prohibitive. I get enough grief about sightlines with my Earthworks mics - I think I'd have a riot if I put that thing up!

[NorseHorse]

Originally Posted by huub

Has anyone an example of this technique by any chance?

As mentioned in the original post, this link has samples and even derived tracks of the different possible patterns: Washington Collegium: The Birth of a Choir

[boojum]

Originally Posted by tenor39

Here is Susannah's Aria from Floyd's Susannah. I used (2) DPA 4041's flown over the orchestra pit and (3) DPA 4061's w/boundary layer discs as L/C/R at the lip of the stage. All tracks were time aligned with the flown pair. Except for the movement of stage props at the beginning, foot noise is minimal. I pick up as much foot noise with the flown mic's as I do with the ones taped to the floor.

http://www.recordclassical.com/file%20music/Suzanna'sAria.mp3

I cannot get this file to load in FF or Chrome. It works with the dreaded IE.

How do you determine distances between mic in boundary layer work? I use Williams for regular mic spacing and angle. Is there a method for boundary layer stuff?

I like the sound. The soprano is quite nice.

[huub]

Originally Posted by NorseHorse

As mentioned in the original post, this link has samples and even derived tracks of the different possible patterns: Washington Collegium: The Birth of a Choir

As usual I did not read very well.. thanks.

[tenor39]

Originally Posted by boojum

I cannot get this file to load in FF or Chrome. It works with the dreaded IE.

How do you determine distances between mic in boundary layer work? I use Williams for regular mic spacing and angle. Is there a method for boundary layer stuff?

I like the sound. The soprano is quite nice.

Hmmm... it loads into Windows Media Player just fine. You can download it first by right clicking and selecting "save target as" into a folder on your computer, and then use any player you wish.

[digitalolive]

OK, I've read through the posts a few times. Granted, my eyesight ain't what it used to be but could someone point me to the part where it says a Fukada Tree uses boundary mics?
James M. Mastracco may have used boundary mics set up in a Fukada tree pattern but Akira uses cardioids and omnis (DPA cards and Sanken omnis I think). Akira's english is very limited but I believe I understood him correctly. Here is a page that talks a bit about it. I went to a lecture by him at AES a few years ago where he went IN DEPTH about his experiences with different mic patterns and the listener's responses. I'll see if I can find the photos I took of his slides.

Steve

[NorseHorse]

Good point, maybe we're talking about boundary fukadas and not all fukadas. Definitely post that info for us if you can find it.

[digitalolive]

Here is a definition of the original Fukada tree.


Fukada Tree

[BLP]

Originally Posted by boojum

Any microphonic interference from the physical contact between the mics and the floor?

No, it worked nicely! No great mechanical noise to speak of (the stage was nicely filled, so no clunking around ended up on the tracks). As for phase stuff, there was some issues with the piano that was in for one piece on the concert. Since it was pushed back quite a bit from the edge of the stage (and of course, the main array had to be "off stage" for some BS reason...), there was a floor reflection + direct sound + boundary direct sound thing that sounded a bit strange when the piano was solo.

All in all, though, I almost ditched the main pair for the slower movements of the quartet!