How does diaphragm size/polar pattern relate to mic applications?

  • Thread starter Thread starter Chris F
  • Start date Start date
Status
Not open for further replies.
Is George still available to possibly advise you on mic placements? I'm sure he would have some excellent suggestions, since he's far more knowledgable than I am in this area.

My only other suggestion is to put on the demo disk and walk around the church, till you find the best spot to put up your mics.

It sounds like a really fun project.
 
omni vs. true pressure transducer

Harvey,

In your posts in this big thread you have mentioned a number of times the term "true omni" -- meaning a true pressure transducer in the context of your posts. It seems that in practice the two terms omni and pressure transducer are in fact not interchangeable -- hence the qualifier "true". I'd appreciate your time in explaining it a bit.

1. Does it follow that there are other mics which claim to be omni's but actually are NOT true pressure transducers? Then what type of mic are they actually -- a special type of pressure gradient transducers modified to achieve an omni pattern (just guessing)?
I'll call them "non-pt" omni in this post -- meaning non-pressure transducer -- for want of a better term.

2. What form do these "non-pt omni's" take, e.g. dual diaphragm switchable pattern mics? In fact, Schoeps' web site implies that dual diaphragm omni's are not true pressure transducers -

..."Unlike dual-diaphragm capsules, in the omnidirectional setting it is a true pressure transducer with flat response down to the lowest frequencies."...
http://www.schoeps.de/E/mk-ccm5.html

3. Suppose I am shopping for a true pressure transducer, and I come across a mic that claims to be an omni. How can I tell whether it is a "true" pressure transducer or not, short of asking the manufacturer? Can I tell it just by the look of it or by the functions/parts that the mic possesses/does not possess?

4. What exactly are the differences in characteristics between a "true" omni and a "non-pt" omni? In other words, what are the characteristics possessed by a true omni but not a "non-pt" omni, e.g. -
- directivity at high frequency?
- relatively high self noise?
- higher accuracy?
- flatter on-axis response?
- no proximity effect?
- ability to be used in the far-field?

Many thanks.
 
You've answered most of the question already. Pure pressure transducers are not "multi-pattern, dual diaphragm mics". A dual diaphragm multi-pattern mic can mimic a true omni's non-directional characteristics, but not at all frequencies, and without the omni's inherent flat response.

True omnis have some directivity at high frequency, but unless they are designed for diffuse field measurements, they'll be dead flat on axis.

In the case of omni capsules, the relatively high self noise is usually due to the smaller size of the diaphragm.

Omnis are known for their higher accuracy and flatter on-axis response, without proximity effect.

Because they respond to pressure only, omnis have the ability to be used in the far-field, without loss in frequency response.
 
So the Marshal MXL 603s are cardiod SD condensors. Correct? And what would be an omni Condensor? Omni's are SD condensors correct? What would the Behringer ECM8000's be?

Also how would you do a stereo recording with Two large diaphram condensors? Like of the ice cream cone style LD's. XY seems like it would be difficult because of the shape and size of the mics.
 
Sorry if I didn't make that very clear. Yes, the MXL 603 is a small diaphragm cardioid mic and the Behringer ECM8000 is a small diaphragm omni mic. But omnis don't hafta be small diaphragm mics in order to work. The DPA 4041 is a large diaphragm omni mic.

With large diaphragm, side address mics, the typical x/y set up would be one mic positioned upside down above an identical mic, with their tops as close as possible.
 
THATS WHAT I THOUGHT!!
Wow that's cool, i just put together the most logical way to do it in my mind and i came up with that. Nice to know i got one thing right!

I'm still working my way through the thread, it's great!
 
I am trying to build a good mic cabinet for home recording that will grow with me. I am considering the FMR RNP and RNC to use as the front end for laptop-based recording. The music is primarily blues-based material, and the primary mic requirements are for vocals (mostly male, but some female as well), electric guitar, and acoustic guitar, with occasional fiddle, cello, and percussion.

Right now I am thinking about buying a Shure SM57 and a Sennheiser MD421-II, but I'm torn between several options beyond those two mics. I am considering a Shure SM7B, a BLUE Baby Bottle, and an AT4047/4040/4033 mic to cover vocals, but I'm not sure where that leaves me for acoustic instruments. My recording environment has no sound treatment now, so I am concerned about how well a LD condenser will work for me at this stage. Would the SM7B be a better choice for vocals, and does it work well with the RNP/RNC? What mic would be best for acoustic instruments under these circumstances? Is an SD condenser as sensitive to ambient noise as an LD condenser?

I'd appreciate hearing some advice on these issues.

RMK
 
I don't understand the description of a LD x/y pattern. Could you describe it just a little better for me? Would the capsules essentially be parallel to each other, just in different horizontal planes, or would they be vertical, one atop the other, in a type of "v" shape? Maybe I'm just way off?
 
Imagine two identical LD condenser mics, like a pair of V67s, or a pair of SP B1s or C1s, since everybody should be familiar with those mics. You're going to record a choir, using those two mics arranged in an x/y setup, with each mic pointing about 45° away from a center line thru the choir. Each mic is positioned on the center line thusly:

The right side mic is on a straight stand in the center about 10 feet out from the choir. The XLR cord is hanging down from the bottom normally, and the mic is rotated so that it's aimed at the right edge of the choir.

The second mic is mounted upside down on a boom mic stand, so that the XLR connected is aimed at the ceiling. This 2nd mic is placed ABOVE the first mic, so that the tops of each mic are nearly touching. The 2nd mic is then rotated in it's shock mount so that it's capsule is pointed at the left side of the choir.

Is that any clearer?
 
ScienceOne said:
Ok, rad. I totally understand now. Thanks.
Click to expand...

I don't claim to be an expert or even advanced at stereo work, as matter of fact one choir is running me up the wall with a reflective space (but that's another post). I just thought I'd give you a link though for some simple pictures of stereo mic setups. First try this one http://www.dpamicrophones.com/eng_pub/ . Then click on Microphone University and select through diffferent stereo pair setups. Also try Coincident and near Coincident for a search terms that gets some sites otherwised missed.

Please don't get flamed if above link is under you but it's one of the more linked stereo pair locations on the net.

Good luck and if your in a place where you can and have the tracks available more mics and locations will not be a waste. You may find that the extras are the ones you will use, I've done just that several times when I did not forsee a problem with a setup.
 
My edit time ran out so after finding this link that referenced several sites I'v looked at in the past I had to repost. Granted several of these links are deep but glance at them anyway many times reading over my head some good info soaks in anyway.
Josephson Mike Technique

Hope this is helpfull in some way.
 
Two excellent sources, jeepers. David's site was mentioned by me in the very first post I did in this thread, and I believe I mentioned the DPA site in the section on stereo miking techniques. But. it's good to repeat the links - both are wonderful sources of great, accurate information.
 
original quote: "How does diaphragm size/polar pattern relate to mic applications?"

I've been thinking about this for a long, long time, but, I still don't have a clue.
 
hixmix said:
original quote: "How does diaphragm size/polar pattern relate to mic applications?"

I've been thinking about this for a long, long time, but, I still don't have a clue.
Click to expand...

OK, let's see if I can sum it up in just a few words:

"Use small diaphragm mics with wide polar patterns at a distance to record large sources. Use large diaphragm mics with narrower polar patterns in closer to record smaller sources."

"Small diaphragm mics have more accurate off-axis response. Large diaphragm mics have more interesting off-axis response. Which is most important is up to you."

Ignore these rules if your final results sound better.
 
Harvey Gerst said:

The right side mic is on a straight stand in the center about 10 feet out from the choir. The XLR cord is hanging down from the bottom normally, and the mic is rotated so that it's aimed at the right edge of the choir.

The second mic is mounted upside down on a boom mic stand, so that the XLR connected is aimed at the ceiling. This 2nd mic is placed ABOVE the first mic, so that the tops of each mic are nearly touching. The 2nd mic is then rotated in it's shock mount so that it's capsule is pointed at the left side of the choir.

Is that any clearer?
Click to expand...

Harvey, do you ever position your overheads like this? Why?

thanks
 
No, I don't use coincident xy setups for drum overheads, simply because I have far greater control over what the mics pick up when I use wide spaced omnis or cardioids and careful positioning.

Plus, it requires a very even-handed drummer, which we don't get in very often. I would consider it for recording jazz drummers, if they were very good, and I wanted a more minimal setup for a particular sound.
 
Status
Not open for further replies.
Back
Top