Different noise level depending on pattern setting?

[Nate74]

I recently picked up a Studio Projects C3 to have a relatively inexpensive figure eight pattern mic to do the mid-side micing technique on some guitar tracks I'm working on.

As I was setting up last night I noticed a very clear difference in the amount of noise the mic produced at the three various patterns. Omni was dead quite, Cardiod had a bit more noise than I would have expected and the Figure 8 had the most.

Is this a common occurrence with multi-pattern mics? Is it common for lesser expensive multi-pattern mics? Or did I get a lemon?

Don't get me wrong, using it this way with the mid-side mics only contributing about 10% to the overall sound and the close mics contributing the rest, it is totally usable, but I'm wondering about how it will do when it's the main source mic...

Thanks all

 

[Cosmic]

Nate,

You didn't specify whether you mean noise (as in electronic noise and such) from the mic itself, or if you are referring to the amount of room noise the different patterns produce.

If you are referring to the acoustics, yes, omni will be quiet under many circumstances due to phase cancellation. Omni can be a good helper for noisier rooms.

Is this what you were referring to?

Best,
C.

 

[ittam]

And electrically, when you change the polar pattern the
sencivity of the mic changes some db´s and so the
noice floor vs output. -my educated impression-

Matti

 

[ofajen]

If you are referring to the acoustics, yes, omni will be quiet under many circumstances due to phase cancellation. Omni can be a good helper for noisier rooms.

Actually, you will probably notice ambient noise more with the omni setting than with a directional setting (if you're using the directional setting properly.) The omni setting will pretty much accurately record the sound in the room, including ambient noises from all directions. Also, it has no proximity effect, so the low end rumble from the truck out on the street or the washing machine upstairs or central air conditioner will be accurately presented along with your fine musical sounds. Directional mikes allow you the opportunity to orient the polar pattern to strongly accept sounds from a direction you want while largely rejecting sounds from other directions.

The low end on directional mikes will not be nearly so extended as it is on omni mikes. Sometimes I have the mikes turned on and I see a strong signal on the VUs but I can't hear anything. Usually it turns out that the studio doors are open and the washing machine is in fast spin mode and vibrating the floor above at some subaudio frequency that gives no perception of pitch but which my omni mikes accurately pick up!

Don't get me wrong here, I may well use omni microphones (and true omni mikes at that, not a pair of opposed cardioids on a multipattern mike) a higher fraction of the time than anyone else on this forum (except maybe harrylarry). I usually prefer the accurate tonal balance I get with my omni mikes and the option to use a Quick Sound Field recording technique. But I also take great pains to make sure my recording space is quiet, since those omni mikes accurately present all the ambient noise, as well.

Cheers,

Otto

 

[Tim Gillett]

I think he might have meant the actual self noise of the mic capsules and their pre's. This would seem to make more sense. In "omni", you are getting the same signal, essentially, in both capsules, so the self noises should be lower than if it was just one capsule, as the total self noise is randomised against the essentially in phase ambience coming into both capsules, from the room or whatever. A 3db reduction in noise?
I say this because I have a multipattern mic myself and while I've not tested it to confirm this, I would expect there to be less self noise in the omni pattern, for the reason above.

Cheers Tim.

 

[ittam]

Tim, you explained it better ;-)

Matti

 

[cusebassman]

I can understand that if there is a certain amount of self-noise coming from cardioid (when 1 capsule is engaged), that Figure-8 would have twice the self-noise since another capsule is being engaged. But if multi-pattern mics only simulate omni using the two existing capsules inside, why does the self-noise drop for the omni pattern? Is it just phased out since they are facing opposite directions?

 

[Nate74]

Thanks for the thoughts guys and Sorry to take a bit to get back, but it afforded me a chance to use the mic again last night and explore a bit more what I was hearing... not that I figured anything out definitively.: confused:

To Cosmic’s question: The sound seemed to be very constant, perhaps even traditional 60Hz Hum, but it didn’t seem to be coming from the mic - pre -speaker path. It sounded almost distant if that makes any sense. Like I had put a mic 10' in front of a generator or something.

As I looked at the physical setup of the room where we were recording the amps, I realized one half of the figure 8 was "pointing" towards my entertainment center. I had a heavy blanket over it to minimize reflections, but underneath it, the TIVO box was left on (long story about my wife’s addiction to ‘Big Love’).

Also on the other side of that wall is my refrigerator... another possible culprit or at least contributing factor.

We were on a tight time table last night to finish up several tracks so I didn’t experiment with different orientations for the mic, but I believe that this weekend when I try using it as a vocal mic for some backing tracks in a different room, I will have a much better handle on things. I’ll try it in Figure 8 in a room with no electronics and see if the results are the same.

Thank you for the different thoughts on this. I’m really floored at the various possibilities that exist. Enough so to prompt me to do some additional reading on the various uses/limitations/advantages of multi-pattern mics!