[Gary Eickmeier]

"Frank Stearns" wrote in message
...
"Peter Larsen" writes:

"Frank Stearns" skrev i en meddelelse
...

"Gary Eickmeier" writes:

Session turned out fine, working on the CD now. Simple two mike ORT-F
configuration with cardioid mikes at 90°.

90? With cardioids? That's not quite ORTF

No, ORTF is a wording that is often used outside what it is valid for, I
have given up on explaing what it actually is. It is intended for longer
mic
to source distances than those I end up using.


Well, in answer to this and several comments below, about 12 years ago
when I got
back into large ensemble recording, I went through exhaustive and thorough
evaluation of several stereophonic techniques.

After going "outside the lines" with varying distances and angles, it
turns out that
the books are mostly right -- 110 degrees/17 cm/standard cardioid for
ORTF, 90
degrees/30 cm/standard cardioid for NOS, and 100 degree/50 cm/omnis with
diffraction
spheres.

Now, you can vary these all you want, and you'll even get nice results.

But are the results remarkable? That is, can you do a test walk on a stage
and get
an extremely accurate image left/right and front/back? How does the
ensemble sound?
Everything where it should be? Various imaging aspects degrade as you
stray from
those standards.

To a point, you *can* fuss with these standards to accommodate microphone
peculiarities and the room, but get too far and perhaps it's time to step
back and
try another approach. Something with the room or mics is possibly biting
you.

And for image size, I prefer to fudge exactly where the pair is placed
rather than
mucking with the geometry. (AB gives good flexibility in this regard.)

- at least with regular cardioids. Hypers, maybe, but I'd still splay
at 100 (which I do routinely with my M940 pairs). Regular ORTF needs
110 to get the smooth and proper left-to-right representation.

I get to disagree with you, my my my. You need to include the variable
"opening angle", close to a wide source as little as 45 degrees can be
what
works. Which is to say that you can not specify stereo pair angle between
capsules without also referencing intended stereo included image angle or
simply "angular width of stage/ensemble" and or distance to said
ensemble/stage.

See above; in this instance meaning if there is an odd-ball stage or
ensemble
configuration, maybe it's worth looking at a different approach. (In the
worst case
scenario, perhaps you spot mic and create good image in post. It can be
done, it's
just annoying.)


And you did use 17 cm spacing, right?

Now, if you want to use 90, switch to NOS, which calls for 30 cm
spacing.

Cardioids spaced 30 centimeters, at a guess - I have a protractor based on
the Stereophonic Zoom paper somewhere, another member of a now closed club
designed it based on it - you could end up with parallel microphones.

I've found NOS useful for wide and shallow ensembles.

A friend often uses fig8's spaced 40 centimeters and parallel, we also
tried
it with cards, works very well.

From my experiments, it seems unlikely that this would work as well as,
say, the
remarkable 50 cm omni pairs. (The imaging truly is eerie in its accuracy
left-to-right and front-to-back.)

But, one of these days I'll give it a try. I could see the 40 cm parallel
fig 8s
being helpful in a hall that has crap coming off the side walls.



Just used it a few days ago to give me some mix highlight capabilities
for an entire wide and shallow row of percussion folks at the very rear
of a big combo orchestra and wind band. Worked fine with a
pair of C451s, especially on a way over-damped stage that really sucks
the life out of stuff.

I have used the C451EB's with CK1's as close as they could get, ie. with
XLR's touching and about 60 degrees angle when close to ensembles. Frank,
there really is only one parameter that matters, it is decorrelation, it
can
be obtained via two tools: distance and angle, if you have the need for a
wide included angle - a wide ensemble - you need to go to more correlation
to avoid hole in the middle (!) and with a narrow ensemble you need to go
to
more decorrelation to spread them out and make them fill the stereo image
up.

Agreed, but that's were trouble can abound... The angles and distances are
indeed
interrelated. Screw with one and you can wind up with a hole in the
middle, near
mono, or subtle but still bad is an uneven or "non-linear" (if you will)
imaging.
There is no hole in the middle, and it feels good left-to-right, but
things are not
located where they should be. Or, worse than that, perhaps your
left-to-right is
good but now, unwittingly, the front-to-back image is messed up (or simply
no
longer exists).


You can trade angle for distance depending on how your actual microphone
capsules work, with too wide an angle the offaxis response becomes the
center image frequency response in which case distance may be the better
decorrelation tool and - hey presto - we are back at agreeing as that is
what you say you do.

To complicate it all, main pair setup is different with and without
supporting spot-microphones, it is ONE SYSTEM, be it somehow distributed
over the ensemble or on one stick.

Indeed. That's why spots are used carefully, and with appropriate delays.

Generally, I use two pairs on the one main stick: one ORTF which has the
property of
"reaching in" to an ensemble when that's needed in post, and the 50 cm
omnis. Lush
and wondeful, they do 90+% of the work.


A very neat property of MS setups, one that is often not understood, is
that
the center image gets on axis response instead of off-axis response.

With better microphones, this should be a non-issue. And with omnis, the
LF and
overall linearity is generally better. As a bonus, the local idiot cable
system (if
you're doing sound for orchestra broadcasts) can actually lose an entire
channel and
you'll still have reasonable sound.

And while I like some of the flexibility of MS, it (and XY) never provided
the
front-to-back imaging that I've found with the 50 cm omnis.


In the real world: leave all the papers on a chair - preferably outside
the
concert hall lest they confuse you - go set The Pair up, listen, tweak if
you didn't get it right but try to not tweak more than three times, too
much
finagling scares the talent.

Of course. I always do fussing out of view of the clients. I've got
protractors for
ORTF, NOS, and AB. I can be set to run with two pairs in just a moment or
two. And
I'll have repeatable and predictable results.

But, as always, YMMV.

Frank
Mobile Audio

I guess I will have to call it N.O.S. What I used was an existing bracket
that usually holds 3 or 4 mikes (all 90° from each other) and put two on it
at about 40 cm apart. I thought that the 90 degrees was the magic number for
good center fill with cardioids. So if I look down the barrel of each mike
it is pointing just outside the angle of the entire orchestra. I am
positioned at front row center, which is fairly distant from the orchestra,
I would guess around 60 ft. I just played it once so far, and it seems to
image fine, left, center and right fairly even all across, but with no
"pinpoint" imaging at that distance. But not for the audience either!

Gary