Topic: 17cm vs. 20cm vs. 30cm and others

[stevetoney]

The earlier ORTF spacing question raised another series of questions in my mind, so decided to make a new thread...

I understand that 17cm mic spacing approximates the distance between the average size persons ears (or is that 20cm?) for creating stereo effect based on sound delay, but I'm wondering...

a) What are the other standard spacings based on? 

(IOW, what the significance of 30cm instead of...say...36cm?  And why is there a separate standard between 17 and 20 when they are so close to each other?  Can you really hear a difference between those two?)

b) How important is it that the mics are spaced at these exact spacings?  Why or why not?

c) Which is more important to be anal about when setting up...spacing distance or incident angle?

[jeromejello]

i tend to run ORTF (17cm /110*) almost exclusively with my akgs.  that said, i would say i am far from exact in these numbers.  close, sure, but unless you are running a kwon bar style there is always going to be a little slop in the set up imho/e.

btw, this was an answer to question d...

[Javier Cinakowski]

tonedeaf,  all of your answers can be answered by reading the Stereophonic Zoom paper by Michael Williams...

I will summarize for you though.

Question A:
Most of the standard spacings came from the broadcasting company that invented them.  Some are scientific some are arbitrary....

Questions B:
It is very important if you are interested in capturing the stereo image properly....  By not picking the proper configuration you can destroy the image becuase of angular distortion and reverberation limits...

Question C:
They are both equal and dependent on each other. 

[KenH]

I've been a stickler for the theoretical setups of ORTF, or DINa, measuring angle and distance btw caps as accurately as possible, but based on that Stereophonic Zoom it seems that there's a lot of variation possible.

Brian S described it well here: http://taperssection.com/index.php/topic,117030.msg1564907.html#msg1564907

I could get about the same stereophonic recording angle at 40deg, 34cm as I'd get with ORTF 110def, 17cm.  I'm very curious about checking this out.

Then again, maybe I'd resolve the excess bass issue by using roll off since the KM184's are pretty heavy on the bass end. 

[skotdee]

The pre-set configs have always baffled me. Any time I've set up a 90deg angle, or even worse a 110deg angle, my mics are pointed at the walls. Wouldn't it make more sense with directional mics to aim them at the speakers? With this in mind I usually aim at the outside of the stacks, POS I guess its called, and try to shoot for around 20cm spacing. Works great for me and produces great recordings.

Oh and no matter how many times I read that sterophonic zoom paper it is always WAY over my head. I get past the first few pages and just give up. I need something that explains it all in like 3rd grade english 

Oh well, I totally enjoy my recordings even if they're not scientifically dialed in exactly to the dimensions & acoustics of a room...

[Colin Liston]

The pre-set configs have always baffled me. Any time I've set up a 90deg angle, or even worse a 110deg angle, my mics are pointed at the walls. Wouldn't it make more sense with directional mics to aim them at the speakers? With this in mind I usually aim at the outside of the stacks, POS I guess its called, and try to shoot for around 20cm spacing. Works great for me and produces great recordings.

Exactly.  At the Freebird, ORTF points my mics at the end of the bar where everyone is ordering drinks.

[skotdee]

POS I guess its called

Check that, meant to say PAS. Pretty sure POS is something different entirely (like what my tape would sound like running ORTF in the freebird, huh Colin?)   

[run_run_run]

I get it close and say good enough, then again I am a philosophy major.

[SmokinJoe]

There was rationale behind putting those "standards" together, and I think it was real at the time, but I think it's fair to assume the rationale was based on the assumption you were standing in front of an unamplified chorus of people, or an orchestra, and you wanted to capture the whole ambiance of the room to some extent, and probably it was a beautiful room, and they taper got to set up in the perfect spot.  I also think that the chief engineer at RCA (for example) wanted to set some standard for his company so that when they sat down to mix tape at RCA studios they weren't having everyone doing his own thing (kind of like us), and it gave them a standard, like all McDonald's Big Macs are the same, for better of for worse.

There are some scenarios where that is still valid... school bands and church choirs... maybe some folk groups or stage lip bands.

But mostly we are sitting in the OTS at a crowded room, trying to capture the 2 mono stacks blaring from a bazillion watt PA, and NOT capture too much ambiance (the drunks at the bar).  You gotta do what you gotta do.  And mostly what you gotta do is improve your signal to noise ratio aka music to chatter ratio.

I had some non-taper guy give us crap last night because we were set up roughly DIN... eyeball 90 degrees, and hand's width apart.  He said we should be running at least 110 or 135.  I said "I want to tape the band, not the bar".  Everybody is an expert.

[run_run_run]

(former) taper Carl Beck has some good ideas on this

[Chuck]

tonedeaf,  all of your answers can be answered by reading the Stereophonic Zoom paper by Michael Williams...

I will summarize for you though.

Question A:
Most of the standard spacings came from the broadcasting company that invented them.  Some are scientific some are arbitrary....

Questions B:
It is very important if you are interested in capturing the stereo image properly....  By not picking the proper configuration you can destroy the image becuase of angular distortion and reverberation limits...

Question C:
They are both equal and dependent on each other. 

That stereophonic zoom is good stuff. I've read it many times. I even carry a card around with me that gives the angles and spacings. I have found it to be right on as far as approximations. For example if running farther away from the stacks if you narrow the angle, just increase your spacing for similar results. As others have pointed out, the ORTF, DIN etc... are based on recording orchestras, mostly. When recording orchestras you are recording from a postion that is a balance between the room sound and the orchestra. We don't always have that luxury.

[KenH]

Good stuff here!   

[DSatz]

skotdee, good question, but when you record in stereo the pair of microphones functions as a unit. Thus it can be quite misleading to think in terms of "pointing" the microphones of a pair "at" any particular sound source. Together the two microphones cover a certain angle; in this type of use they don't (individually) "point" at anything.

--best regards

[skotdee]

fair enough, but I'd still like to think you'd want that angle covered to encompass the stage/PA stacks area, ie: in front of the mics... With a 90deg angle I can see how that would work, but 110, or even 135? It just seems like the angle covered would be the extreme right & left sides, not the middle. But Im certainly no expert, thanks for your input on this. Im still trying to wrap my brain around the whole thing...

[Javier Cinakowski]

there is no doubt pointing the mic directly at the speaker stack will give you more music and less crowd, but for me that isn't the goal.  I prefer to have a natural soundstage/image in my recordings.  I realize that an image is more obvious stage lip at a jazz show, but I can still hear strange shit on rock n' roll club tapes too....

My point is,  if you are only worried about minimizing crowd noise than William's paper isn't much use.  Just point and shoot....