image description


Stereo Miking: Decca Tree
  Forum Index » Mic Techniques 
Author
Message
explosivejelly
Prenoob
[Avatar]

Joined: 13/10/2012 19:51:56
Messages: 61
Location: United States
Offline

The decca tree is a stereo miking technique generally using 3 omni-directional microphones in a T shape. The microphones are panned left, center, and right. This technique is most often used to record large orchestras, choirs, medium to large chamber ensembles, etc..

*Note - It does NOT work well in small rooms.

PDFs from http://www.wesdooley.com
- "The Decca Tree" - http://www.wesdooley.com/pdf/DeccaTreeD2.pdf
- "Instructions for Assembly and Usage" - http://www.wesdooley.com/pdf/mmpguide.pdf

Wikipedia article (it's not very in-depth):
http://en.wikipedia.org/wiki/Decca_tree

Youtube video of engineers setting up a decca tree:

This message was edited 1 time. Last update was at 14/10/2012 01:27:49

cristofe
Presonificator
[Avatar]

Joined: 12/03/2012 21:10:44
Messages: 3628
Location: Skaneateles, NY USA
Offline

Used this technique recently to record a gospel choir in Willard Chapel which is the last surviving chapel designed
and built by Louis Comfort Tiffany. I used a pair of Golden Age small diaphragm condensers for the left and right
channels and a CAD Equitek E-200 large diaphragm condenser,(set to omni to get some room ambience and crowd
response), for the center. Worked great!

PC'S: HP XW6000 Dual 3.2GHz Intel Xeon Processors, 8GB RAM WinXP SP2
HP 6005 Pro AMD Athalon X2 B24 3.0Ghz Processor, 4GB RAM Win8 Pro
HP Compaq NC6320 Laptop Intel Core2Duo 2.0Ghz Processor 3GB RAM Win7 Ult
Dell Latitude E4310 Laptop Intel i5 2.67Ghz Processor 4GB RAM Win7 Pro x32

Audio Interfaces: Terratec EWS88MT PCI (2), Audiobox 1818VSL USB & FP10 Firewire, Steinberg MI4 USB, Line 6 Toneport GX & PodXT, Roland GS-10, NI Rig Kontrol 3

Monitors: Yamaha HS50M's

DAWS/VST Hosts: S1 Professional, Plogue Bidule, Xlutop Chainer, Sieb VSTHost & Savihost

Hardware Synthesizers: Roland SH-32 & XV-3080 RedSound Darkstar XP2, Novation X-Station, Yamaha AN200, M-Audio Venom

Hardware Controllers: JL Cooper CS-10 Control Surface, Yamaha EZ-EG, Dillion Les Paul style acoustic electric guitar with Roland GK-3 pickup and GI-20 converter.

The Rest: Guitars, Amps, Stompboxes, Mics, Outboard Gear, VST plugins...too much to list!
[WWW]
talmen
Presonoid
[Avatar]

Joined: 28/07/2010 23:56:13
Messages: 3002
Offline

I just used a mini-decca on a bluegrass recording. It was at the insistence of one of the group members, and I thought it was a technique much better suited to a significantly larger ensemble. However, the results were quite respectable. We used a 1/2 sized tree arrangement.
Field Kit:
MacBook Pro 9.2 i5 2.5 GHz, 8GB RAM,
OS 10.8.5;
A & H Qu-16, AB1818VSL, Alesis IO14 / IO26,
PreSonus S1 v2.6.2.25990, Boom Recorder 8.3.2

Studio Kit:
iMac 11.3, i7 (Quad) 2.93GHz, 8 GB RAM,
OS 10.9.3,
M-Audio FW1814, PreSonus Faderport,
PreSonus S1 Pro 2.6.2.25590
Baroque Hillbilly
Prenoob

Joined: 22/01/2013 23:34:25
Messages: 5
Offline

talmen wrote:I just used a mini-decca on a bluegrass recording. It was at the insistence of one of the group members, and I thought it was a technique much better suited to a significantly larger ensemble. However, the results were quite respectable. We used a 1/2 sized tree arrangement.

I just came across your post in a search for setting up a Decca Tree. I'd be curious to have some details on the setup you used, and in fact the recording itself if it's a commercial CD.

I'm pretty much retired now and was mostly involved in classical recording but (perhaps oddly) I also like bluegrass. I still do concerts for a 40-piece wind band and have decided to build a Decca Tree rig to use with my Schoeps mics, for which I've also made my own spherical acoustic modifiers from 1 1/2" wooden knobs (!) The next concert is in a couple of weeks so I'm hoping to have it all ready to go.

Stuart
talmen
Presonoid
[Avatar]

Joined: 28/07/2010 23:56:13
Messages: 3002
Offline

The recording I was talking about there was made for TV broadcast. You can see/hear the results at http://www.BabyBlueArts.com. Go to the Search Artists tab and select Most Recent. Once you've done that a list will come up on the right hand side of the screen. The Decca method was used for the band Monroe Crossing.

A traditional Decca Tree is 2 meters between the outside omnis, with the center mic being 1.5 meters in front of the line which interects the omni mics. That is the size that would normally be used in a big hall or an a soundstage for something like a full orchestra. The smallest setup I've used is about 1/4 normal size.

Making your own can be tough, but do-able if you have the tools, materials, and skills to design and fashion it. It is much harder if you need to suspend very heavy large diaphragm mics, as rigidity, soundness and balance of the structure becomes quite crucial. There are a few commercially available rigs available, but they are quite expensive. I'd have a hard time believing that one couldn't make something for significantly less cash than those options.

If you build one and fly it, make sure that you have taken every possible precaution to make sure that all rigging is sound and up to the task, and the the tree itself is rigid and sturdy. If you create a stand mounted design, balance becomes crucial along with rigidity. On the rare occasions I use the Decca method I almost always use 3 stands and skip the frame.

Do a search on Decca Tree and you'll get lots more info, tips, and variations of the standard scheme. Surprisingly, WIKI has some pretty good information: http://en.wikipedia.org/wiki/Decca_tree -- I'd especially direct your attention the the reference links at the bottom of the page -- very helpful information to be found in those external links.

Do a search on Decca Tree and find some of the commercially available offerings, that way you can see how they have engineered their solutions -- and that may give you some ideas on how you'd like to appoach the task of home-brewing.

I'd love to know more about your acoustic modifiers and your Schoeps.

Good luck with the upcoming program, and let us know how things go.

Tim
Field Kit:
MacBook Pro 9.2 i5 2.5 GHz, 8GB RAM,
OS 10.8.5;
A & H Qu-16, AB1818VSL, Alesis IO14 / IO26,
PreSonus S1 v2.6.2.25990, Boom Recorder 8.3.2

Studio Kit:
iMac 11.3, i7 (Quad) 2.93GHz, 8 GB RAM,
OS 10.9.3,
M-Audio FW1814, PreSonus Faderport,
PreSonus S1 Pro 2.6.2.25590
Baroque Hillbilly
Prenoob

Joined: 22/01/2013 23:34:25
Messages: 5
Offline

Tim,

Many thanks for he quick reply. I'll check out the link. I'll also post a pic of the completed DT when it's done in a few days. I've seen pics of the rig that Wes Dooley offers and some of the others... and seen the prices, too. Mine is designed only for Schoeps (or DPA) small condensers, not TLM 150s so it will be quite a bit lighter. If it works I may try and figure out a way to fly (drop) it from the lighting rail at the venue where I record this ensemble. With a basic stereo pair or my Royer SF-124 stereo ribbon this is easy but a DT will be a bit of a challenge. For the upcoming concert I'll just use a central stand if the conductor doesn't object. The concerts are fairly informal so I don't think there will be any problem.

Stuart

Addendum: I've got the Monroe Crossing files playing as I type this. Sounds great. Did you have a Tree flown above them, or do the three main mics I see form a sort of "low-branch" Tree? I read somewhere that the Del McCroury band use a central omni for live concerts too and do as Monroe Crossing do: come in to the mic for solos, a pretty radical/retro idea in these days of multiple mics up the ying-yang!

This message was edited 1 time. Last update was at 23/01/2013 08:21:04

Sometimes I wonder whether the world is being run by
smart people who are putting us on or by imbeciles
who really mean it. (Mark Twain)
Baroque Hillbilly
Prenoob

Joined: 22/01/2013 23:34:25
Messages: 5
Offline

talmen wrote:...I'd love to know more about your acoustic modifiers and your Schoeps.

Good luck with the upcoming program, and let us know how things go.

Tim

Here are some pics and details of the nearly-completed Tree. I won't have a chance to try it out for a couple of weeks.

The "base" of the Tree is made of 1/2" hard copper tube, the arms from 1'2" OD aluminum tubing.




The knurled-head screws go through 3/8" dia. aluminum rod epoxied into the aluminum arm and threaded 8-32. There is a slot cut into the top of the copper base tube so the screw doesn't have to be removed entirely, but merely backed out enough to clear the hole in the bottom of the base. The knurled brass knobs are soldered onto the screws, which have had the ends tapered a bit to allow for less-than-perfect alignment when passing through the bottom hole






I just realized that this pic isn't quite right- the modifier is put on backwards. The wooden knobs have a "flat" on the back side.
The front is rounded right to where it meets the mic head. There is a thin sheet of plastic glued into the knob to permit a tight slip fit.
I may relieve the sleeve a bit and put a small nylon screw in to secure the modifier.


This was the most labour-intensive of the whole thing. It would have been better/easier if I had a lathe or milling machine and been able to use solid aluminum rod as I could have just drillled it out lengthwise and threaded it, rather than epoxying the inserts in. In addition, they were just a bit too small, so I ended up wrapping them with nylon mesh (used to keep birds and insects out of soffit vents!) which had to be coated with epoxy. A very messy job.

I used satin black paint on the rig but the final coat will be flat, plus the arms will be painted as well. (Yes- the proper procedure would be to have all the metal parts powder coated.) In addition, I've made up three, 20' mic cables using thin mic cable to make it easier to rig. They will connect to my regular mic cables at the bottom of the stand, which is not the one in the pic but one I made up from two 8' lengths of EMT pipe.

One concern I have with the mic setup is that although I have 4 Schoeps Colette mics, I only have two MK2H omni heads, plus two MK21 wide cardioids and a fig-8. Sharp-eyed viewers will see that the centre in the overall pic doesn't look like an omni; it is in fact a wide cardioid. I am hoping that covering the side slots with the acoustic modifier may turn it into an omni of sorts.(!!) On the next mild, dry day I'm going to put the rig outside and do some tests with a "shaker" made from a plastic tube filled with rice or something to see what the HF polar response might be. However, a friend has offered to lend me one of his MK2H mics so if the modified wide cardioid is noticeably iffy, I'll just use that while I ponder the purchase of a third omni head!

ADDENDUM Sat. eve. I fired up the rig to check wiring, etc. and see if everything works. All was well. The acoustic pressure equalizers really do brighten things up, too. However, as I feared, there is no substitute for a proper omni head. The acoustic pressure modifier sounds horrible on a wide cardioid. (Should I be surprised?) I could EQ the wide cardioid (minus APE) to approximate the others but I it would only be a cheap and nasty quasi-solution. Anyone have a Schoeps MK2H head they're not using any more?

Stuart

This message was edited 3 times. Last update was at 27/01/2013 04:20:23

Sometimes I wonder whether the world is being run by
smart people who are putting us on or by imbeciles
who really mean it. (Mark Twain)
Baroque Hillbilly
Prenoob

Joined: 22/01/2013 23:34:25
Messages: 5
Offline

The aforementioned concert/Decca Tree initiation happened last Saturday. Results were... OK. I had the tree (L/R arms) about 2' behind the conductor and 12' up. The L/R mics were spaced about 5' apart and the centre mic just short of 3' out. The overall sense of space was really good and bringing the centre channel down about 9dB seemed to fill in the hole without negatively affecting the stereo spread.

The rig itself worked well. It is pretty lightweight but rigid enough for these mics. I'm going to replace the 3/8" flange nuts, which lock the shock mounts in place, with wing nuts to allow me to tighten them more easily. But other than that it is just fine.

The negative observation regards tonal balance. I was using Schoeps 2H mics, which have a slight HF boost for semi-nearfield pickup. When I use these as a spaced pair (about 30" apart), they are usually a bit farther back. Also, I'm not sure exactly what effect the home-made spheres have. The Schoeps KA40 (40mm dia.) give a gentle rise between about 2k and 7k. Mine are 1.5" (38mm) so they should be close in reponse but I can't be sure. The result, to my ears is that the sound is a bit aggressive. I was able to improve things a bit with some EQ but I'm going to try the same rig on the next concert (not until June), without the spheres and with the stand about 4' or 5' behind the conductor. I'd really like to be able to "drop" the rig from the lighting rail above (as I do with a stereo pair). This pretty much requires a lightweight telescoping pole (ie a reverse mic stand) so I might be able to come up with something. It will need to be able to extend to about 22' (!)

All in all, it was a good experiment, good enough to warrant a second attempt. If I like the results the second time, I'll probably buy a third Mk 2H head, rather than imposing on my other engineer friend to borrow one of his yet again.

Sometimes I wonder whether the world is being run by
smart people who are putting us on or by imbeciles
who really mean it. (Mark Twain)
talmen
Presonoid
[Avatar]

Joined: 28/07/2010 23:56:13
Messages: 3002
Offline

If you have the flexibility in your assembled rig, I'd put the center mic a little further forward. The classic proportion for the tree is 2: 1.5, so with a 5' spacing of the rear pair you'd ideally want the center to be 3.75' forward. (That is nit-picking, though, and you may get perfectly acceptable imaging results with your current dimensions). Interesting results about the tone. With the slight HF rise the mics have I imagine you don't need the spheres at all if it sounds that aggressive to you.

I may try an experimental "micro-tree" in a few weeks (with the AB spacing at about 24") to record a brass quintet. If I end up using that I'll let you know how it turns out.
Field Kit:
MacBook Pro 9.2 i5 2.5 GHz, 8GB RAM,
OS 10.8.5;
A & H Qu-16, AB1818VSL, Alesis IO14 / IO26,
PreSonus S1 v2.6.2.25990, Boom Recorder 8.3.2

Studio Kit:
iMac 11.3, i7 (Quad) 2.93GHz, 8 GB RAM,
OS 10.9.3,
M-Audio FW1814, PreSonus Faderport,
PreSonus S1 Pro 2.6.2.25590
Baroque Hillbilly
Prenoob

Joined: 22/01/2013 23:34:25
Messages: 5
Offline

Thanks, Talmen. After I built the tree I realized that the traditional proportions were 2m wide x 1.5 deep! The soundstage on this test was OK, although I suppose it might have been better with the "correct" spacing. It was a 40-piece wind band rather than a full orchestra so I didn't need the full width.

No problem making up a longer leg for the centre mic. The next time I'm at the hardware store I'll pick up another piece of aluminum tube. Unfortunately there isn't another concert until the summer and I'm pretty much retired from the biz now and living in a small town so I likely won't have much opportunity to try it out sooner. With the tree a bit further back the spheres may not be so aggressive. But I'll leave 'em off. I can always add a bit of presence if the result isn't bright enough.

I'd be interested in the results on the brass quintet.

Sometimes I wonder whether the world is being run by
smart people who are putting us on or by imbeciles
who really mean it. (Mark Twain)
 
Forum Index » Mic Techniques
Go to: