Topic: DIN vs ORTF?

[Cobiwan]

I am wondering what is the difference sonically? I used to see ORTF all the time, but now I see more and more DIN recordings.
I know the difference in 90 degrees vs 110 degrees and 17 cm vs 20 cm, but what is this difference sonically? Is there more of a center in one or the other in the stereo imaging?
I'm sure there are variables for room, location, indoors/outdoors, etc; but how do you decided which to run if you have both a DIN bar and a ORTF bar?
Sorry for asking so many questions lately but I'm trying to get a better understanding of the why's, when's and how's.
TIA,
Coby

[aaronji]

They are pretty close.  ORTF is a little narrower and relies a little more on level than time differences (compared to DIN).  I would definitely read the Stereophonic Zoom paper, if you haven't already.  Also, this site helps a lot with visualizing the different configurations:  http://www.sengpielaudio.com/Visualization-ORTF-E.htm.  You can change up all the variables and see how things vary...

[page]

They are pretty close.  ORTF is a little narrower and relies a little more on level than time differences (compared to DIN).  I would definitely read the Stereophonic Zoom paper, if you haven't already.

This.

In a shitty room, you would want more on-axis information (compared to reverberation), hence DIN being a better choice for approximately the same SRA value.

[ScoobieKW]

Neumann Mic Tools  for iOS and Android has a Stereo configuration application that uses the concepts of Stereo Zoom. What I find educational is the two bars showing how much of the information is time arrival vs volume difference. (two bars that change as the configuration changes)

[Gutbucket]

Here's more detail explaining the specifics of what the others are talking about.

In general (some background)-

There are a couple of different yet interrelated things going on which affect the differences you'll hear between those two microphone configurations.  One aspect is the effect on playback imaging, another is the effect on the amount of direct sound verses reverberant sound you’ll hear on playback.  Of those two basic aspects, most listeners will prioritize a good direct/reverberant relationship over good imaging aspects, but both are important to a good recording.

The direct/reverberant aspect affects how much room and audience sound is heard, blended in with the main sound arriving directly from the stage and PA.  It affects clarity and how reverberant the recording sounds. The imaging aspects affect how wide the playback image sounds and the distribution of the sound sources within that playback width. 

There is overlap between these things, some imaging aspects have to do with how evenly the direct sound is distributed across the apparent playback width and how reverberant the stuff in the middle sounds compared to the sides. 


Here’s the clincher-

It is possible to adjust the microphone-spacing/angle relationship so that you have various setups which produce similar imaging but with different direct/reverberant aspects.  You can also work it the other way around.*



Specifically-

ORTF has an SRA window of about +/-48° or 96° total
DIN has an SRA window of about +/-50° or 101° total

The SRA of both is similar, being only about 5° different. 

The SRA window of DIN being slightly wider than that of ORTF means that the resulting playback image will sound slightly more packed together into the middle of the playback image. The sounds arriving through that wider SRA widow will essentially be squashed together more to fit the same available playback space between the speakers.  That’s the imaging part and hints at why the description of the relationship is called the Stereo Zoom.

Now, if spacing between microphones changes, but the SRA is to remain similar, the angle between microphones needs to change to compensate for the spacing difference.

ORTF has a spacing of 17cm and an angle between microphones of 110°
DIN has a spacing of 20cm and an angle between microphones of 90°

That’s a difference in angle between microphones of 20° which is likely to be more significant in its effect on the direct/reverberant aspect of the recording than the 5° difference in SRA has on imaging.  That part of this is what page is talking about.

[edit- one overly simple way of saying this is: the reason tapers often use DIN instead of ORTF is because it points the microphones more towards the source, which can be helpful in a less great sounding room, even though ORTF might sound better in a good room.  That's a gross simplification, but a way it's commonly thought about.  All this other stuff is an attempt to explain some of what's really going on and the deeper implications]



*Quick aside-  That’s more or less what’s going on with the improved PAS method I posted about recently.  In that case the primary goal beyond simple setup simplicity is achieving the highest possible amount of direct sound compared to reverberant sound from any given recording position.  With PAS, that’s accomplished by pointing directional microphones directly at the PA speakers.  What’s going on behind the scene to determine the most appropriate microphone spacing values shown on the PAS table is figuring out what spacing will produce the most appropriate imaging based on the angle between microphones and the width of the stage as seen from the recording position. 

I’ll try an post more on ways to best use the Sengpielaudio visualization applet which aaronji posted a link to later to help understand all this..

[it-goes-to-eleven]

Another consideration is brightness.

You may find that DIN is a bit brighter than ORTF, depending on the microphone.

Since ORTF emphasizes off-axis performance a bit more, I don't think it is as appropriate for microphones that don't have great off-axis performance.

ORTF is my preferred config with mk4's and m20 Gefell cards, when it is... appropriate. When I'm a bit further back, or the sound is less optimal, I'm more likely to use DIN.

[Gutbucket]

The bit on the fundamentals involved which I posted above simplifies things by assuming microphones which have textbook perfect patterns that do not vary with frequency.  Eleven's point about brightness and tonality differences in the direct sound is a good one and hinges on the actual pickup pattern differences of real-world microphones.  Pattern inconsistencies of real world microphones usually increase the farther you get off axis, yet the farther off-axis the microphones are to the sound sources of interest, the more critical it is that they exibit polar pattern behavior which doesn't vary much with frequency. 

That's why its often noted that ORTF requires the use of small diaphram condenser microphones with well behaved polar patterns.

When the pair of microphones are arranged in such a way that they are pointed more directly at the sounds of interest, an especially well behaved polar response becomes somewhat less critical for the direct sound arriving from the source of interest, but is still important because variations affect the quality and tonality of the reverberance and audience reaction picked up from directions well away from the front.

[acidjack]

Practical reality:

Up very close = ORTF
Not so close = point at stacks
Afraid you don't know how to point at stacks and want something close = DIN

Those stereo zoom things are useful theoretical guides but are not guides to recording amplified PA systems at rock concerts from a distance, FWIW. It's good to understand the concepts, though, so you can better understand what you are doing in practice.

[Cobiwan]

Thank you all so much! I haven't read the Zoom Paper but have the PDF now. So much incredible info in this thread that I have to re read it again and again to soak it all in. I truly appreciate the tutelage that you all offer!

[Cobiwan]

I have to add that upon starting to read the Zoom Paper I feel like a complete idiot. Not that I cant comprehend it but because I realize there is SO much to know about the subject and I'm barely a noob at this point after taping for 20 years...

[page]

I realize there is SO much to know about the subject

Yep.

and it does take some time to sink in.

[Gutbucket]

Here’s a couple tips for using the Sengpielaudio online visualization app that aaronji posted a link to earlier, which is an excellent and easy to use tool which simplifies visualization of these Stereo Zoom relationships.  It’s useful for comparing different setups and wrapping one’s mind around the concept.  If you play around with it enough it should help in developing a seat-of-the-pants feel for this.

I’ll just mention a couple things which may not be obvious.  You’ll figure out the basics.

First, before doing anything else with it, set the Orchestra Angle.  I can’t emphasize enough that setting an appropriate Orchestra Angle is critical as it will affect everything else.  It is equivalent to choosing the position where you will be setting up your microphones.  (The Orchestra Angle is the width of the band/ensemble as seen from the recording position, for PA reinforced stuff it’s the angle between the PA speakers). 

The Orchestra Angle defaults to 90° in the applet, but you’d have to be setup pretty close to the stage for that to be appropriate in most cases.  When I set up on stage for a jazz trio that’s about right.  From farther back in a room, the Orchestra Angle will usually be narrower.  At an outdoor amphitheater I frequent, when recording FOB where I prefer to setup, the resulting Orchestra Angle is about 50° maybe 60°.  For the tapers setup in the typical section area just in front of the soundboard there, it’s probably more like 40°.

You can adjust it in the app in either of two ways- the value is displayed in the box over on the right, third row down. You can enter a value there directly, or you can click and drag either of the outermost colored bars arranged in the semi-circle just over the microphones, which represent the direct sound sources as seen from the microphones.  You can also adjust microphone angle and spacing by clicking and dragging the little circles on the microphones rather than choosing standard configurations from the dropdown on the left or entering values directly on the right.

[Gutbucket]

Second, notice the light grey line around the pair of microphones.  That represents the combined polar pattern of the microphone pair and corresponds to directional sensitivity of the configuration.  Pay attention to that.

The shape of the grey line looks similar to the polar patterns of individual microphones and is read the same way- if it’s a circle, the pair will behave omnidirectionally with equal sensitivity in all horizontal directions, even if you are not using omnidirectional microphones.  If it’s cardioid-like the configuration will be less sensitive to sound ariving from behind the recording position.  If it’s a peanut-like figure 8-ish shape the pair is less sensitive to sound arriving from the sides, which might be useful if you are in a narrow room with strong side wall reflections.
 
The degree to which the pattern has more area towards the top verses area towards the bottom reflects a forward-facing pickup bias which will favor sound arriving from in front (both the direct sound and any the reverberant sound arriving from the front as well).  The narrower it is on the sides the less influence sounds arriving from the sides will have.  Those are the primary factors we are manipulating by choosing to use ORFT up front and DIN from further back in the room, other than the frequency response ‘brightness’ thing which it-goes-to-eleven mentioned.  That aspect isn’t addressed in the applet as it's caluclations assume microphones that have ideal polar patterns which don't vary with frequency.  For the same reason, omnis as represented in the applet are 'true omnis', which behave omnidirectionally at all frequencies, so pointing them in off-axis will make no difference.  In the real world it often does make a difference how you point them with respect to the pickup of high frequencies.

This directional sensitivity of the pair also has an indirect influence on the direct / reverberant pickup, depending on the location.  Just keep in mind that it doesn’t have anywhere near as much influence as actually moving the recording position closer or farther away.  Still it can help to make the best of a less than perfect recording position.

In any case, the shape of the grey line is the only indication on that visualization applet of this critically important aspect.  Everything else you see on there and read in the Stereo Zoom paper concerns imaging distribution (and reverberance distribution) rather than overall configuration directionality. 

[Gutbucket]

In regards to the imaging part of it, here’s the basic concept of the Stereo Zoom in a nutshell-

On playback, the sound sources that were inside the SRA will be distributed between the left and the right speakers. Sounds from outside the SRA will be reproduced panned fully over to the speaker locations for the most part.  A larger SRA will produce a narrower playback image, crushing the spread of sounds toward the center.  A smaller SRA will produce a wider stereo playback image, stretching the placement of sounds out towards the speakers.

Different microhone setups which have similar SRAs produce different distributions of those sound sources within the playback image.

[Cobiwan]

Great info GB! Much appreciated and keep it coming. You are a wealth of knowledge!

[Gutbucket]

I think that's about it.

I'm trying to get a better understanding of the why's, when's and how's.

These types of threads were a large part of I was looking for when I first started lurking around TS years ago.  I enjoy them, and tend to get even more long-winded than normal in attempting to clearly explain the basic relationships of the "why" part.  The more interesting and valuable approach for me has usually been trying to understand the "why" and setting up things based around those insights, rather than setting things up based on standard conventions.  Sometimes standard convention is appropriate and has become the standard for good reason, yet sometimes there may be better ways of doing things if you have a strong understanding of the basic “why” relationships and can figure out how to apply that appropriately. 

Acidjack summed up the "when" succinctly in his last post.  The "how" part simply translates to the application of whatever you take away from all this.

Hope that helps.  If you have questions I'll try to answer them the best I can. 

[rjp]

Those stereo zoom things are useful theoretical guides but are not guides to recording amplified PA systems at rock concerts from a distance, FWIW. It's good to understand the concepts, though, so you can better understand what you are doing in practice.

On the other hand, if what you're recording is purely acoustic (e.g. an orchestra, an a cappella chorus, a string trio, etc.), they're a great place to start.

[lastubbe]

Recording rock and roll concerts open air off a PA in a decent room reasonably close to the sound source, IMO ORTF beats DIN 99% of the time.

[F.O.Bean]

I use DIN for my mk4s MUCH MORE than I use ORTF. DIN is more focused and evenly balanced in most cases IMO. YMMV. I have the active bars, so I can easily run DINa/DIN/NOS/ORTF/WideORTF. I run mk4/DIN 99% of the time. And mk41/DINa 99% of the time. I can honestly say that I'm consistently happy running those configs. I run mk4/ORTF usually at stage-lip or onstage. This may sound weird, but when I had my MBHO's back in the day, I would run Hypers/NOS occassionally if I was pretty close and DFC. I need to try that with my mk41s. I bet it sounds good up close! Ive been meaning to run my mk4s/NOS too, but I keep my NOS bar in my mk41 bag for some reason I used to run my mk21s/NOS. That seemed to be the best config for the mk21s the few times I ran them!

It really just comes down to trying them out and finding what you like best

[ButchAlmberg]

Thanks fellas. Some really good information here. Hope no one minds if I give it a bump.