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[Brendan Thompson]

Right,

So I've decided to make a stereo bar... that will hopefully let me do both ORTF and XY.

How far apart should the 3/8" bolts for the mic clips be?

It'd be nice to be able to do both XY and ORTF, but if that's not possible, then whatever, I'll settle for one or the other.

Any ideas?

[hargerst]

Depends on the mics and clips you use.  With X/Y, the mic diaphragms should cross at 90 degrees, one above the other.

With ORTF, the mic capsules are 17 cm apart and angled out 110 degrees.

You'll need two sets of bolt holes; one set for X/Y, and a wider set of holes for ORTF.

Set up the two mics you plan to use for X/Y and measure the distance between the clips.  Then, move them out to the ORTF positions and mark the bar for that positioning.  

The holes for a couple of Shure SM81's will be spaced different than for a pair of Oktava MC012's.

A lot of hardware stores sell metal strapping tape with holes every inch.  You could buy a short piece of that stuff to get into the ballpark as far as distamces are concerned.

[Brendan Thompson]

Wow, that was quick... Merry Xmas, Harvey!

I'm actually having issues picturing this... I can see XY easily enough, but the ORTF is quite a puzzle to me...

Should the mics be crossing over, in ORTF, on a stereo bar?



Just say the clips are 10cm apart for XY... I don't see how putting them further out makes it easier to get 17cm at 110 degrees... it seems like the clips would almost need to be right on top of each other?

[hargerst]

With ORTF, the angle and spacing is kinda designed to mimic human head spacing, so the mic diaphragms are about 6-3/4" apart and angled outward about 110 degrees. Like this:

\____________/

As I said, it really depends on the mics and clips you use.  You might be able to get by with a single set of bolt holes by sliding the mics forward and backward in their clips.  It depends on the mics.

[Brendan Thompson]

Well, I don't have a stereo pair as of right now, but I'd be looking at something like the NT5's, I think...

This is more for

1) when I'm in at JMC, where we have no stereo bar, so I'd be using 451's or NT5's on it

2) when i'm out on these classical recording gigs, and for some reason the bars made by the guy who i'm assisting don't work

3) for messing around with a highly unmatched "stereo" pair in my bedroom - ECM8000 + NT3... I happen to like the NT3 pointed at the bridge of my acoustic, the ECM pointed up the neck... so a stereo bar would help me out a bit there!

It's nothing serious, really - but if there's some "accepted" distance, then i'll go with it - it seems the fixed-position commercial bars go for a 15cm wide bar, but I don't see how you could do ORTF with that?






Wait, wait, wait.



For ORTF... is it 110 degrees between the mics, making a crazy little triangle, or am I picturing this all wrong? I actually have a cardboard cutout of a triangle with one angle of 110 degrees, and then the side opposite the angle, being 17cm...


This is what I mean by crossing over, btw:

[hargerst]

That's one way to achieve an ORTF spread; here's another:

[compasspnt]

Brendan,

Can you make something where the hardware that holds the mic clips to the bar can be infinitely moved left to right, and then held in place by screwing it tight?  That would give you any combination you wanted.  Perhaps a bar with a long "slice" out of the middle of it, with knurled, screw-on hardware that tightened into any position?  I am now getting curious about experimentation on this.

Also, have you tried the NT-4?  Two 5 capsules mounted into perfect X/Y config.

[Fibes]

compasspnt wrote on Sun, 25 December 2005 13:10

Brendan, Can you make something where the hardware that holds the mic clips to the bar can be infinitely moved left to right, and then held in place by screwing it tight?  That would give you any combination you wanted.  Perhaps a bar with a long "slice" out of the middle of it, with knurled, screw-on hardware that tightened into any position?  I am now getting curious about experimentation on this. Also, have you tried the NT-4?  Two 5 capsules mounted into perfect X/Y config.

Check out the Gefell bars which do exactly as Terry describes and reverse engineer an afforable one. I beleive they are on the Mercenary site...

[Brendan Thompson]

compasspnt wrote on Mon, 26 December 2005 05:10

Also, have you tried the NT-4?  Two 5 capsules mounted into perfect X/Y config.

Never tried the NT4, but at the moment can't see where I would have much use for a DEDICATED stereo mic.



I was actually thinking something like this would work:





Also, it seems that if the mics are longer than 10cm, there will be  at least SOME crossover, seeing as a triangle with the longest side as 17cm, with a 110 degree angle opposite it, must have two sides of approx 4 inches long.

[Barry Hufker]

You can do this more cheaply but here is a great, flexible from Shure.  I've had one for years.  The ends are knurled and can be removed.  You can them flip the sections to make the sit further apart or closer.  It fits on one stand and the ends are marked in degrees.  It's good for X/Y, M/S and ORTF.

Barry


http://www.shure.com/accessories/a27m.asp

[sdelsolray]

Yep.  Get Shure's product.  Versitile and much less expensive than the high quality bars sold by Gefell and AEA.

[resolectric]

Also, if you buy the new C2 microphone from Behringer (39 Euro) you'll get a couple of C2 condenser microphones (that you can throw away if you dislike them) but you get, as a bonus, a very nice bar just like Gefell's, with continuous sliding adjustment, allowing for infinite XY and ORTF variations.

Also included is a pair of windscreens and two flexible mic clips that fit most small diaphragms. You'll also get a nice rigid plastic box with handle for your new Stereo pair setup.

As a side note, the C2's aren't that bad either.

[Scott Helmke (Scodiddly)]

Brendan Thompson wrote on Sun, 25 December 2005 08:09

Harvey! I'm actually having issues picturing this... I can see XY easily enough, but the ORTF is quite a puzzle to me... Should the mics be crossing over, in ORTF, on a stereo bar?

Imagine somebody holding a hand behind each ear to better catch sounds in front... in other words, the mics are about where your ears might be located, and generally pointing away from each other.  55 degrees away from the centerline, to be precise.

[Gunnar Hellquist]

Some inspiration:

I use a K & M stereo bar. Picture example here
 http://www.proaudiosystems.co.uk/acatalog/K_M_Stereo_bar.htm l

Note that you will really like to have a spacer for one of the mics in both XY and ORTF. I typically use a pair of threaded mic stand adapters, one of these
 http://www.fullcompass.com/Products/pages/SKU--23108/index.h tml
and one of these
 http://www.fullcompass.com/Products/pages/SKU--24173/index.h tml

Generally I use a few drops of LocTite to lock the two adpators to each other, they typically loosen up otherwise.

Finally a picture of what ORTF might look like. Here the holders are in the "business end", I generally have the holders at the back-end just from habit. Remember 17cm 110 degrees is the exact recipe for ORTF and it is to be measured from the center of the microphone diagram. (I guess the French Radio at the time would fire you unless you kept that down to the millimeter.) Of course there are alot of other setups: NOS, DIN, dutch radio and so on all using slightly different angles and distance.

http://www.mercenary.com/migem3mapaor.html

Good luck

Gunnar

[compasspnt]

resolectric wrote on Mon, 26 December 2005 10:39

Also, if you buy the new C2 microphone from Behringer (39 Euro) you'll get a couple of C2 condenser microphones (that you can throw away if you dislike them) but you get, as a bonus, a very nice bar just like Gefell's, with continuous sliding adjustment, allowing for infinite XY and ORTF variations. Also included is a pair of windscreens and two flexible mic clips that fit most small diaphragms. You'll also get a nice rigid plastic box with handle for your new Stereo pair setup. As a side note, the C2's aren't that bad either.

Thanks for the advice!

http://recforums.prosoundweb.com/index.php/t/9189/6490/?SQ=a 73a5e5a731b7a3701dbbb09fa27658c