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

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Hmm...I used to think SPL meant that louder sounds might break the mic (so a low SPL figure meant something like "guarantee is void if you stick this into a kick drum").

One thing I wonder: Is it always desirable to have as high SPL as possible? Or are there situations where it could be an advatage to use a mic with a lower SPL?

Cheers
/Henrik
 
SPLs way louder than the maximum SPL usually means increased distortion. Some mic designs (like the Sennheiser MD421) can handle 150dB without any problems - so can a lot of small omnis.

In general, large diaphragm condenser mics CAN handle quite a bit, but the internal preamp often overloads first, so a pad is used to lower the capsule outputby 10 to 20dB typically. Kick drum is a special situation, since the main concern is the draft of air the kick head causes. That blast of air is what can kill the mic, not the high SPL level.

Some mic designs ((older ribbon mics for example) CAN also be damaged by high SPLs or drafts from fans, speaker ports, doors closing, or even shutting the lid too fast on the carrying case.

So why use a ribbon mic (that typically has a low SPL rating)? Ahhh, the sound is wonderful. Many ribbon mics use ribbons that are only 7/10ths of a micron thick (a typical human hair is about 20 microns thick by comparison).

The ribbon in a ribbon mic has essentially minimal mass and responds beautifully to a lot of signals, such as voice, strings, horns, etc.. The resonance can be set very low (20Hz on an RCA 44BX), and that single piece of corregated aluminum ribbon has almost no other resonances, so it's very flat and smooth throughout its entire response range.

An RCA 44BX or 77DX on a Marshall 4x12 cab, about 2 feet away, is a sound to die for. Lush, rich, beefy, gorgeous, you pick the adjectives. As the frequency goes up, the SPL rating of most ribbons increase dramatically - about 6dB more power handling per octave. MAny pros will use a ribbom mic or large condenser mic for kick, by placing the mic away from the kick (4 to 6 feet), in a long packing blanket tunnel in front of the kick.
 
"I'm sure they'll be some questions, and I'll try to answer them all, if I can. Thanks to everybody for hanging around this long."

Thank you for hanging around, preparing content and evidently dedicating more time to this thread than anyone Harvey!

Are there frequency bands that tend to distort first? Are various mics sensitive to distort over specific frequency bands depending on their internal resonances? Proximity effect comes to mind as an obvious low frequency problem, but is it always in the low and low-mid that the mic will hit its max SPL first?

Sincerely appreciative

Chad
 
cyork said:
"I'm sure they'll be some questions, and I'll try to answer them all, if I can. Thanks to everybody for hanging around this long."

Thank you for hanging around, preparing content and evidently dedicating more time to this thread than anyone Harvey!

Aww, shucks !!!

Are there frequency bands that tend to distort first? Are various mics sensitive to distort over specific frequency bands depending on their internal resonances? Proximity effect comes to mind as an obvious low frequency problem, but is it always in the low and low-mid that the mic will hit its max SPL first?

Well, the diaphragm has to move the furthest at low frequencies, so that's usually where the problem starts. For the same output level, a mic diaphragm has to move twice as far for each lower octave.

Sincerely appreciative

Chad
Click to expand...
 
Originally posted by Harvey Gerst
It's a big subject and I didn't go into it as fully as I maybe should have, but tried to make it as useful as I could to the broadest spectrum of posters here.
Click to expand...

I can't imagine you could have gone into this subject any more fully without using physics equations and detailed tutorials on how to build a microphone from the ground up. ;) This thread is, in my opinion, a definite "must-read" for prospective microphone buyers.

That said, I could just be missing something, but where is the maximum SPL listed for the SM57? Do most manufacturers advertise this specification? If not, is there a way to figure it out?
 
You're right, Shure doesn't show max SPLs for the SM-57, 58, the Beta versions, or the SM-7. I'd guess at around 138 to 145dB max SPL for a good quality dynamic, but that's just a guess.
 
Harvey, the MXL 603 specs claim 137db for 0.5%THD, I know that you have a pair and that you have stated that some of their printed specs may not be completely accurate, do you think this SPL rating is correct? would you feel comfortable using the 603 on a snare or cranked up amp for example?
 
HomeRec,

I think my answer is pretty consistent with Shure's answer, and I think my numbers may even be a little more realistic, since I believe they're talking about what kind of SPLs would cause physical damage to the mic (as opposed to moderate distortion which I was discussing). We both talked about how the low end is the most damaging.

vox,

That 603 spec sounds about right. For 1% distortion, that would translate to about 142dB. I wouldn't be worried in the least about using it on a snare or a loud guitar cabinet.
 
Harvey Gerst said:
HomeRec,

I think my answer is pretty consistent with Shure's answer, and I think my numbers may even be a little more realistic, since I believe they're talking about what kind of SPLs would cause physical damage to the mic (as opposed to moderate distortion which I was discussing). We both talked about how the low end is the most damaging.
Click to expand...

So the maximum SPL rating for an SM57 would vary according to the kind of sound being recorded, instead of there being a single SPL rating for all applications?
 
Well, actually, kinda, sorta, yeah. It depends on the mic design, the resonance of the diaphragm, and the day of the month, but in general, max SPLs are often measured at either 1 kHz, or around 250 Hz. Ribbon mics, like the Coles 4038, even specify the maximum permited SPL at different frequencies.

Most mics can handle most signals, but ribbon mics and a lot of pressure gradient condenser mics don't like singers in close, singing F, P, B, V, W, and T, or anything that produces an air blast, which can bottom out the diaphragm or stretch the ribbon.
 
Harvey Gerst said:


So why use a ribbon mic (that typically has a low SPL rating)? Ahhh, the sound is wonderful. Many ribbon mics use ribbons that are only 7/10ths of a micron thick (a typical human hair is about 20 microns thick by comparison).

The ribbon in a ribbon mic has essentially minimal mass and responds beautifully to a lot of signals, such as voice, strings, horns, etc.. The resonance can be set very low (20Hz on an RCA 44BX), and that single piece of corregated aluminum ribbon has almost no other resonances, so it's very flat and smooth throughout its entire response range.

An RCA 44BX or 77DX on a Marshall 4x12 cab, about 2 feet away, is a sound to die for. Lush, rich, beefy, gorgeous, you pick the adjectives.
Click to expand...


Hmmm... Makes me wonder when Marshall or Project Studios will release a cheapo ribbon? Alan? You there?
 
Hi Harvey,
Thanks again for your help and all the great info in this thread,
I'm still trying to figure the best way to record guitar and vocals at the same time.
I hope you don't mind me squeezing in here to ask you about this again.

I was thinking,watching groups performing on T.V. they always use a dynamic or black electret for vocals and a small condenser for acoustic.
The sound they get is equal to or better than the studio sound.
(Stained was on unplugged the other nite,they were fantastic!)

Do you think this is a possible way to go in a home studio?
It seems like the plus for a dynamic or black electric on vocals would be elimination of room and backround noise, and the advantage of good close proximity effect for untrained voices,one of which I have the pleasure of owning.
The big disadvantage being,you don't get the sound of a large diaphram.
Am I on the right track with this?

I'm also a little confused about the different cardioid patterns,
can you clarify the differance between cardioid,hypercardioid,and supercardioid.
Are there advantages and disadvantages to the different designs?

Iv'e been looking at the Shure beta 87a and c,one is cardioid and the other is supercardioid,both black electret I believe.
Also the sm7,which is a dynamic.
I'm not sure which would be the best for my situation,any advice or other mic options would be appreciated.

Thanks again
Pete
 
Muzeman,

It's a little tricky to explain without the design theory, but lemme see if this'll help a little bit:

Cardioids have a heartshaped polar pattern at most frequencies, but they tend to be more omnidirectional at low frequencies.

Hypercardioids are less wide compared to cardioids, but still have some omni characteristics at lower frequencies.

Supercardioids are similar to hypercardioids at high frequencies, but they act more even at low frequencies by creating a deeper rejection point at around 125° off axis.

So what the hell does all this mean when it comes to choosing the right mic, based on polar patterns?

If you're getting a mic for recording just your voice, it's easier to use a smooth cardioid mic that will be fairly flat and natural and you don't worry too much about picking up bleed from other instruments due to the wide pattern of most cardioid mics.

If you're playing guitar at the same time, you want to try and keep the sound of the guitar out of the vocal mic, so you need a tighter mic pattern (like a hypercardioid) and you try to put the guitar in the null of the pattern so that it doesn't get heard by the vocal mic. And it holds true for the guitar as well; you might use a second hypercardioid on the guitar to keep the vocal out of the guitar mic. But hypercardioids aren't perfect, especially at lower frequencies.

That's where the supercardioid comes in; it's got a solid null point at 125° at just about all frequencies.

So why not just use hypercardioids and supercardioids for everything? Part of the problem is that hypercardioids and supercardioids don't always have the best frequency response, so you pay a price in performance for that deeper rejection. And they have more proximity effect (which is not always a good thing).

For stage and live work, the rejection in a hypercardioid and supercardioid mic is a blessing, especially when working with on-stage monitors, but it's not as important in the studio, where accuracy counts more.

Does it make a little more sense now?

BTW, it's a "back electret", not a "black electret". That means the condensor element is pre-polarized (carries a permanent charge) by putting the charge on the back plate rather than the diaphragm. The difference in voltage between the diaphragm and the back plate is how a condenser mic works.
 
Hi Harvey,
Thanks for clearing that up for me,once again your professionalism and wealth of knowledge shines through in the ability to explain complicated subjects in simple enough terms so that even I get it!

I owe you an apoligy,I realized after my post last night that since you own probably the most infamous SM7 in the world,you already knew it was a dynamic.
Sorry man.

Well I'm going upstairs to lite some incense and repeat my mantra for this evening,
"Back electret not black electret"
"Back electret not black electret"
"Back electret not black electret"

Kinda has a nice ring to it.

Thanks again,
Pete
 
Sorry if this seems self-serving, but it seems like we have a lot of new people here that are asking questions that this thread may be able to answer. Thought I'd bring it back up near the front again.
 
Thank You !!!!!

Harvey,

what a blessing it was that you did refresh this thread. I am simply blown away by the wealth of information that you put forth in such an easy to understand manner. I'm new to the post and would never have seen it....

WOW. I took an intro recording engineering class and you covered more in the thread then we did in 4 months.

Please keep it coming!

I never would have left Texas if I knew there was a Jedi Master in Sanger.... hehe
 
and its quickly moving near 10,00 views....while # of views may not always necessarily mean the info contained is proportionate, this time it is dead on....this should should go to 6 stars.....

ok guys, use those bookmarks on your browsers and pass this on to newbies......
 
a cappella

Harvey,

This thread is the coolest! I stumbled onto it a week ago. Goldmine! It's like having an expert in your back pocket! Thanks for all of your time on this. I read the whole thing until now and have enjoyed learning things about microphones that had never occurred to me.

There is a lot about recording instruments and solo singers, but what about recording a 4 part male a cappella group? We have 13 guys, 4 basses, 3 baritones, 4 Tenor 2's, and 2 Tenor 1's. At any one time, we have 11 guys singing backgrounds, 1 soloist, and one Vocal Percussionist.

What would you suggest as far as recording this group? Would it be best to record the entire group together, further out, with an X-Y? Should we add to that mics for each section? Or should we record each section separately?

Any imput you have would be greatly appreciated!

Jeremy
 
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