Question about a quote from the DPA site on spaced omnis

[jnorman]

on the DPA website, in their discussion of stereo techniques, they include this comment about spaced omnis:

"Since the stereo width of a recording is frequency-dependent, the deeper the tonal qualities you wish to reproduce in stereo, the wider your microphone spacing should be."

can one of you please try to explain to me how spacing would have an effect on frequency response? thanks.

[joelpatterson]

A wild guess... the further you are from things, the less crisp and clear the high end?

Are they trying to say that the further away you get, you start to lose the highs but the lows are carrying okay?

Am I answering a question with a question?

[DaveUK]

omnis tend to go down lower(frequency wise) and are generally used as spaced pairs
whereas cardiods are used for xy or ORTF style pairs(not as wide)

[hughesmr]

The wider the mic spacing, the more decorrelated the LF information ... and hence the more "enveloping" the sound. ("Enveloping" = "Deeper tonal qualities"?? Who knows...)

Of course this comes at the expense of realistic imaging, so it's all a balancing act, like everything else in life.

[boojum]

Jim, that is a weird one. Wider as opposed to what? Their pics on the site of concert recordings show their mics at the standard European spacing of ~40cm, or so it looks. I would guess that the mean as opposed to an array is truly side by side omnis.

Best thing: write DPA. They are very helpful both here and in Denmark. I'd write Denmark.

If you so, please let us know what they say. BTW, Williams might be helpful here. If I can find his mic spacing book in my house I will let you know.



Cheers

[rumleymusic]

It is simple really. "Deeper" really means lower in this context.

Omnis work off the principal of delay. In order for us to determine direction, there has to be a mic separation of at least a 1/4 wavelenth of a frequency. Lower frequencies have a longer wavelengths and need more separation between mics to determine direction.

[mpdonahue]

Originally Posted by rumleymusic

It is simple really. "Deeper" really means lower in this context.

Omnis work off the principal of delay. In order for us to determine direction, there has to be a mic separation of at least a 1/4 wavelenth of a frequency. Lower frequencies have a longer wavelengths and need more separation between mics to determine direction.

Which is why coincident mic techniques don't do as good a job of recreating the sense of space when compared to spaced pairs; the LF information in coincident is virtually in mono.
The relationship between "Imaging" and "spaciousness" are really diametrically opposed. The best recordings take both into account and strike a balance between the two.

All the best,
-mark

[Teddy Ray]

15kHz wavelength = 0.9 inches
8kHz wavelength = 1.69
2k wavelength = 6.75 inches
500Hz wavelength = 27 inches
60Hz wavelength = 225 inches

In general:
Stereo perspective can only be achieved, all other things being equal, at frequencies with microphone spacing greater than the wavelength of the incoming signal.
The greater the spacing, the lower in frequency stereo effect will be perceived.
The greater the time arrival between mics, the wider the apparent stereo perspective as well, frequency dependant as noted.


the above isfrom Bruce Meyers

the Danes.well english is their 2nd language.

[Peter Allison]

so, and I hope I am reading this right, so correct me please. Is this why most people recommend a 40cm spaced pair of say (budget NT5's in my case) for recording a cathedral pipe organ, because of the low 32's etc. And this is just as a pure hobby, never made any money from it
Peter (Yorkshire, UK)

[jnorman]

daniel, mark, and teddy - i think that clears it up. i guess i was just reading it wrong - i thought they were indicating that the separation affected the overall freq response somehow, but re-reading it, i see they were just talking about the low freqs being percieived in stereo. thanks.

[rumleymusic]

Is this why most people recommend a 40cm spaced pair of say (budget NT5's in my case) for recording a cathedral pipe organ

A full pipe organ is capable of lower frequencies than any other instrument I know of. DPA recommends 40-60 for general applications. The problem with an organ is the positioning of the pipes, the direction of the frequencies is almost random. Trying to cover all the frequencies with a directional charactaristic is almost a waste of time, and usually it is best to try to capture the space with a standard setup.

[MichaelPatrick]

Absolutely awesome question.

This "problem" was addressed by Alan Blumlein and he tried to solve it with his shuffler. He wasn't successful and Michael Gerzon also tried but didn't really succeed. I'm still waiting for a good one.

Francinstien
http://www.audiosignal.co.uk/Resourc...ffling_USL.swf
Gerzon Archive

[klaukholm]

The word for deeper in scandinavian languages is also used in reference to lower pitch.
What they are saying is that you need to go wider if you want lower frequencies to be represented in stereo.

I find the quoted passage to be perfectly clear and I see no need to bash the danes language skills.

[joelpatterson]

I am even understanding it at this point... and that certainly says something.