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Author Topic: Some things to think about when choosing mics.  (Read 1754 times)

hargerst

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Some things to think about when choosing mics.
« on: July 03, 2004, 01:43:39 PM »

Each mic design has trade-offs, usually accuracy for noise. The most accurate mics are small omnis, but as the size decreases, the noise goes up. Ya don't hafta be a rocket scientist to figure out why; the smaller diaphragm doesn't put out as much signal as a bigger diaphragm, so you hafta crank it more and you amplify the noise along with the signal.

Condenser mics can only do certain things very well, especially when you get into different patterns. Large diaphragm mics get wonky off axis (which means they can be shitty on sounds coming from a lot of different directions at once). That's why large diaphragm condensers are usually best as a vocal mic; the mouth is a pretty small source, and occasionally very quiet. Large condensers are great for picking up quiet sources. Trade offs.

Small diaphragm condenser mics have better off-axis response, so they're "usually" better for miking bigger stuff (guitars, drum kits, choirs, etc.), in other words, anything where the sound is coming at you from a lot of different places. But, because they're smaller, they won't be as sensitive as large condenser mics. Trade offs, again.

So what's the best vocal mic? Usually a large diaphragm mic is the first thing the pros reach for.

What's the best mic for larger instruments? Unless you own a very well-designed large diaphragm condenser mic, usually a small diaphragm will work better (unless it's a very quiet source and you're willing to give up some accuracy for extra low noise output).

Finally, most mics aren't truly flat - most have little spikes and dips that occur all over the place. The frequency response charts that you see are smoothed to eliminate those short peaks and dips, but they're still there. And they're different for every mic - even two that are exactly the same brand and model.
Now here's the important part: When you happen to sing or play a note that corresponds to a peak or dip, the sound is gonna change.

So, what does that mean? It means that a mic that sounds great on one voice, one guitar, or even in one key, may sound very different on another voice, another guitar, or even in a different key.

And that's where the problem lies when people try to compare a mic to other mics, and especially when you hear people say things like "this XXX mic sounds identical to a U87", or whatever. For that singer, that guitar, or in that key, that may be true. It just means that the peaks and dips in the two mics didn't get pushed so hard that you could hear the differences between the two mics. On something else, the differences can be night and day.

The other factor is that, unless you've been doing this stuff for a long time, you're ear isn't trained to hear some of the differences, and you'll think only in terms of louder and brighter, or more bottom. It's really easy to miss hearing the small peaks and dips, which only comes with longer listening sessions and some ear training.

When you compare mics, if a mic sounds "brighter", or "more detailed", make sure you're not confusing high frequency peaks and/or treble boost for those qualities.

While it's not cut and dried, be suspicious of louder mics - it often means that some accuracy has been sacrificed, and try to figure out where that "extra loudness" is coming from.

Remember, "bigger" can means "louder", but it can also mean "less accurate". "Less accurate" is not in itself a bad thing, if it's more flattering, but just be aware that it is less "accurate".

There are always trade offs in choosing equipment; try to make those trade offs work for you over the long haul, and you'll be fine when choosing a mic for a particular task.

The "big thread" (in the sticky at the top of this forum) covers a lot more detail about those trade-offs, but remembering these points (that we've just discussed) may just help you hear "better", and faster.
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Harvey "Is that the right note?" Gerst
Indian Trail Recording Studio

Eliott James

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Re: Some things to think about when choosing mics.
« Reply #1 on: July 04, 2004, 03:26:04 PM »

Great post, Harvey! On the money.
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tom eaton

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Re: Some things to think about when choosing mics.
« Reply #2 on: July 05, 2004, 02:52:56 PM »

Harvey wrote:

"Each mic design has trade-offs, usually accuracy for noise. The most accurate mics are small omnis..."

and then two parahraphs later:

"But, because they're smaller, they won't be as sensitive as large condenser mics. Trade offs, again."


I think generalizations about this stuff can be very misleading.  You need to carefully define your terms (like: sensitivity meaning spl output resulting from a given input).  But even then, it depends on the amplifier following the capsule, not on the size of the capsule.  Many SD mics have lower self noise than many LD mics.  The smaller size of the diaphragm can result in a more accurate tracking of the incoming sound pressure (meaning the mic is more sensitive to the details), but even that's dependent on how the diaphragm is held in place.  Capsules that are wired from the center move differently than capsules that are edge wired...this can be seen in the progression of 414 mics.  The Shure KSM series exhibits extremely low noise and high output.  These mics use a class A output amp and sound quite neutral. Some mics are transformer coupled, some not, and all of these things lead to differences in sonics and noise performance.  

I agree that folks should understand that mics color the signal, and that each mic has its own fingerprint, but I don't think that defining two camps of sounds and performance based on capsule size is the best or most accurate way to break things down.  There are just too many other variables.

And SD mics can be awesome for lead and background vocals, depending on the mic, the singer, the room, the preamp, the recording medium, the song, the mix approach...

There are large and small dynamic mics, and large and small ribbons, too.  Getting to know the sonic fingerprint of the specific mic is far more useful (in my opinion) than putting it in a camp of what it might sound like (or how much self-noise it will exhibit or preamp gain it will need) based on its size.  

My three cents!

-tom
acoustic music guy
http://www.thomaseaton.com

hargerst

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Re: Some things to think about when choosing mics.
« Reply #3 on: July 05, 2004, 04:13:51 PM »

I think David Satz addresses your points far more eloquently than I could in his post on Klaus' forum:

http://recforums.prosoundweb.com/index.php/mv/msg/981/10840/
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Harvey "Is that the right note?" Gerst
Indian Trail Recording Studio

tom eaton

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Re: Some things to think about when choosing mics.
« Reply #4 on: July 09, 2004, 03:20:17 PM »

Hey Harvey-

David made my point exactly in another thread:

http://recforums.prosoundweb.com/index.php/t/1061/2571/

{QUOTE}
"The premise of your question seems to be that as a class, large-diaphragm microphones have some particular sonic character or usefulness in common while small-diaphragm microphones as a class have some other, differing character or usefulness in common.

"That assumption may be believed by some people but it is untrue or, more precisely, it makes little basic sense as a concept. Maybe it's not an assumption that you're actually making, though, so I won't harp on it unbidden. (Ain't I courteous?)" {END QUOTE}

That's all I was trying to say!  I just found it today...funny.

-tom
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