messing with intensity domain on omnis?

[jnorman]

a while back we had a thread about using omni pairs in off-axis configurations, like ORTF or NOS. some folks indicated not to do that as it would mess up things somehow, while others said it worked fine.

so, cardioids give a stereo image by using both time and intensity differences, while omnis use only the time differences. the omni stereo image is rahter vague and spacious (because time differences alone do not give your ears quite enough info to decide clearly where something is located?), while the ORTF cards give fairly precise placement of the isntruments in the sound stage.

since omnis are somewhat to fairly directional in the higher frequencies, it seems like you could add in some intensity diffrences in the stereo image by using them off-axis like ORTF. it might offer sort of a compromise between the clearly defined placement of ORTF cards and a normal AB spaced pair of omnis. also, using cards off-axis often helps smooth out any high-end emphasis that many SDC cards display. seems like using omnis off axis would also help mellow the top end on omnis that have a more diffuse field character.

is there any reason not to use omnis in a quasi-ORTF type configuration to assist in a more precise placement of instruments in the soundstage? have you tried it?

thanks.

[NorseHorse]

Using omnis off-axis is not unheard of. Some engineers do ensemble recordings with omnis pointed at the ceiling to negate any on-axis HF-lift (though then you get a HF-boost of the ceiling?).

You really have to pay attention to sound and polar patterns of a particular mic to see what works. Using omnis like Earthworks or DPA 4061s off-axis is unlikely to produce a meaningful change. I guess I'll stop speculating now and let people who have actually tried this type of thing respond...

[d_fu]

Originally Posted by jnorman

so, cardioids give a stereo image by using both time and intensity differences,

No, cardioids (or less specifically, pressure gradient transducers) per so don't, but some of the configurations they are used in (e.g. ORTF, NOS) do, while others (XY, MS) don't, which only work with intensity.

seems like using omnis off axis would also help mellow the top end on omnis that have a more diffuse field character.

True, that's been discussed here several times. I have done so with my AKG CK62DF omni caps for many years (usually set up with a distance of around 60 cm and sometimes pointing them outward at least 45° or so). I did feel that the extra touch of separation that the high-frequency directivity offered also contributed to the pleasant sound I kept getting with this setup.

is there any reason not to use omnis in a quasi-ORTF type configuration to assist in a more precise placement of instruments in the soundstage? have you tried it?

ORTF in the strict sense is not possible with omnis - as a matter of definition, and you also need the extra directivity at this relatively small distance for sufficient separation.

Nothing wrong in principle experimenting with pointing omnis outwards, though, but the separation will mostly take place at very high frequencies, it's just not comparable to cardioids.

As with most similar questions and ideas, the answer is "It depends" and "try it out"...

Daniel