Omni vs Cardiod spaced pairs

[Doug Young]

Someone asked offline if I'd ever tried spaced pairs using omni's. It's been a while, but I did a quick compare last night, using my Brauner VM1's which are multi-pattern. Sharing in case anyone else is interested. The setup was spaced pairs, 18 inches apart, about 10 inches from the guitar. 2 takes, of course, so there are some performance differences.

My first impression was that the sound was pretty close, but then was able to tune into some differences. The cardiod recording seems a tad wider to me, and it's not as phase correlated. Most noticeably, the cardiod take has more low end than the omni take, probably proximity effect. The omni track sounds more "natural", probably closer to how the guitar sounds in person.

Here's the tracks:

Sound Cloud - Omni Vs Cardiods

[rick-slo]

Thanks for the demo. Agree with your comments. Might be greater difference in sound in a room with poorer acoustics.

[mesa]

Thanks Doug, I liked the omni track, it did indeed sound more natural.

[billgennaro]

Very interesting and a great comparision Doug. You can really hear the proximity the cardioids provide.

[runamuck]

Thanks Doug.

[Doug Young]

Originally Posted by billgennaro

Very interesting and a great comparision Doug. You can really hear the proximity the cardioids provide.

You can control that, of course, by distance, with the tradeoff being more room sound as you get further away. I was maybe a little closer here than I normally am.

[Dan Lampton]

An advantage of using omni mics is that one can get much closer without the issues of proximity effect. This can be used to control the amount of room sound as well. Moving the mics closer than possible with cardioids and place some baffles behind the omnis can help deal with many room issues.

[Ty Ford]

I read a snippet of an article a few years ago that said that coincident omnis were and interesting technique used by a pretty famous engineer. Al Schmitt, if I recall correctly.

If they're omnis, why bother to place them coincidently, you might ask?

Most omnis are still directional at high frequencies, so you do get some stereo imaging.

Go figure!

Regards,
Ty Ford

http://en.wikipedia.org/wiki/Al_Schmitt

[ChuckS]

Originally Posted by Doug Young

Someone asked offline if I'd ever tried spaced pairs using omni's. It's been a while, but I did a quick compare last night, using my Brauner VM1's which are multi-pattern. Sharing in case anyone else is interested. The setup was spaced pairs, 18 inches apart, about 10 inches from the guitar. 2 takes, of course, so there are some performance differences.

My first impression was that the sound was pretty close, but then was able to tune into some differences. The cardiod recording seems a tad wider to me, and it's not as phase correlated. Most noticeably, the cardiod take has more low end than the omni take, probably proximity effect. The omni track sounds more "natural", probably closer to how the guitar sounds in person.

Here's the tracks:

Sound Cloud - Omni Vs Cardiods

Hi Doug,
The timing for posting your comparison was perfect. I've been considering getting a pair of Omni capsules; I currently record with cardioids in a spaced pair setup. Another forum member had graciously sent me a comparison of cardioid vs Omni (spaced pair at greater distance and greater separation than your setup, in a treated space). So, it was nice to hear the effect, and difference in effect, with your setup compared to his.

These types of recordings with the setup defined are great, but for me it is especially helpful when folks like you give their impressions of the effect on the recordings. I don't have any training or any significant experience to know what to listen for and how to pick up on the subtle differences. Could you explain a bit as to what you mean/hear when you said the cardioid was "not as phase correlated"?

I agree about the proximity effect and greater stereo width of your cardioid recording. To me, the Omni recording does seem to have a natural sound, and even though the stereo width seems less than the cardioids it still seems spacious/full. Have you done recordings with omnis, combined with a Jecklin disc, to increase the stereo width?

Thanks,
Chuck

[Doug Young]

Originally Posted by ChuckS

H Could you explain a bit as to what you mean/hear when you said the cardioid was "not as phase correlated"?

My wording there may have been misleading. In an extreme case, you can hear phase differences just listening to a stereo track. For example, we sometimes get people posting examples where one mic has reversed polarity - 180 degrees out of phase. That produces an ultrawide image that seems a bit unbalanced. It's kind of a head-spinning sound that's hard to describe, but once you hear it, you can probably recognize it. You can also check phase issues by summing to mono and seeing how much the sound changes.

But this case wasn't that extreme, and I didn't really "hear" the phase, I was just watching a phase correlation meter, and the omni tracks stayed positively correlated while the cardiods bounced into negative correlation now and then.

If you're asking about phase in general, that's a big subject. Here are a few links that hopefully explain it in detail:

http://www.soundonsound.com/sos/apr0...emystified.htm
http://www.resoundsound.com/mono-compatibility/
http://www.protoolsproduction.com/phasescope/

Have you done recordings with omnis, combined with a Jecklin disc, to increase the stereo width?

It's been a while, but I played around with a Jecklin years ago, it's still in the closet :-) But it can produce nice results. Here's a pretty old recording I did with a jecklin. Same guitar as I used in this experiment, but I was using Schoeps CMC6/MK2 omni capsules here:

Jecklin Disk recording

[ChuckS]

Doug,
In general, I had an understanding of phase but was not familiar with tools such as phase correlation meters. Thanks for the links. Your recording using the Jecklin disc and omni mics was also informative.

[haplo]

Thanks for the post, Doug. I asked about the spaced omnis that the engineer used at the studio on my nylon string guitar. He said they were DPA 4006 omnis, which are a bit out of my price range right now. I hope to have some more budget friendly SDC omnis on hand soon from a friend and I will post a similar comparison for anyone who is interested.

On that topic, if anyone has recommendations on budget-friendly (say under $500 per mic) SDC omni mics, please let me know. We tested a lot of mics that night before settling on the DPAs, and I think the SDC omnis were by far the best at providing a clear low end on a classical guitar.

Here is the take, but keep in mind this was in a well treated and acoustically friendly room and the vocals were taken at the same time, so there is bleed from a Neumann U87 mixed in there. The omnis were about 8 to 10 inches from the bridge and the 10th fret, respectively. It was also sent through an external buss compressor. I will try to get the original wave and update this post later (with the Neumann muted).

https://soundcloud.com/wade-tyner/fa...-new-recording

[Doug Young]

Sounds really nice! I believe the Oktava mics that many people recommend here come in an omni form. No experience myseld, but they seem like a budget option with a lot of flexibility (different capsules available)

[ChuckS]

3 zigma CHI sdc mics are around $500 each. You can get various capsules and they have free field and diffuse field omnis. I just got a pair of free field omnis but I need room treatment before I can make best use of them. I believe Pro Audio Toys has 15% off right now.