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Author Topic: Microphone Sensitivity, Polar Patterns, and Myth busting  (Read 1068 times)

Luke Geis

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Re: Microphone Sensitivity, Polar Patterns, and Myth busting
« Reply #10 on: November 21, 2019, 11:05:01 pm »

Mic selection is about two things.

1. Practical application. Is it being used for vocals, drums, guitar or.....

2. The subjective opinion of the sonic result for the use of that microphone in said application.

Simply, what are you using the mic for and how does it sound in use.

Microphones are essentially a perfect tool. They have no bias and no difference in results will occur given exact circumstances. The difference between mic A and mic B is what makes one microphone better suited for any given application. The factors that determine ultimately what a mic will likely be used for are things like proximity effect, off-axis coloration, and off-axis rejection or polar pattern control.

Some mics have a better off-axis sound quality but may have a wider pattern that also allows more sound to enter into the mic at any given angle. Some mics may have better/tighter pattern control that may not sound as good off-axis, but what comes in on-axis is louder and sounds subjectively better. There are a million variables and in the end, it all boils down to application and the subjective opinion of the result.

Certain mic types tend to be better suited for certain applications. A hyper-cardioid mic is often utilized for drums to reduce bleed. Cardioid mics are often selected for vocals because proximity effect and quality of sound is often very good. There are no hard rules for that though. The Sennheiser MD421 is an example of a mic that gets used very often for drums because it sounds great and works really well, but it is a cardioid mic. You don't often see the MD421 used on vocals though. The Neuman KMS105 is most often used on vocals and is rarely seen used on anything else. The KMS105 is a super-cardioid mic for reference. The long and short of it is that there is no magic bullet when it comes to microphones.

For me, the only real considerations I make for microphone selection is what my monitor setup will be and ultimately how does it sound in use. If I have a particular monitor setup ( texas headphones vs. a single monitor for instance ) I will pick a mic that best suits that first and then after listening to the artist I can make a final determination if I should choose another option and deal with the compromises. In the end, it all comes down to listen first, asses, correct and repeat.
I don't understand how you can't hear yourself

Art Welter

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Re: Microphone Sensitivity, Polar Patterns, and Myth busting
« Reply #11 on: November 22, 2019, 03:32:19 pm »

One thing that was a bit surprising. The dropoff from "lips touching mic" to 4" was about 30db! In other words, a 0db signal with lips touching becomes a -30db signal at 4".

That level change seems a bit extreme for most vocal mics, but good on you for the test!

The inverse distance law, -6dB for doubling of distance works just fine for microphones as well as speakers, however (as Chris mentioned) the distance with from the windscreen varies with microphones, so "lips touching" might be anywhere from .25" to as more than an inch using a external foam screen.
On top of that is the cardioid microphone proximity effect, an increase in bass output at near distances.

Measure the distance between screen and diaphragm of microphones noted for more "gain before feedback", and you find they are usually less than the "old standard" SM58. In fact, an easy 6 dB can be gained from any old SM58 by simply squashing the grill flat.

0dB .25"
-6dB .5"
-12dB 1"
-18dB 2"
-24dB 4"

0dB .5"
-6dB 1"
-12dB 2"
-18dB 4"

For what it's worth, just measured a drop of about 14 dB from singing (G#, 208Hz) at the screen of a Shure 565 SD to 4", had to go to about 9" to drop to -30 dB. The 565 diaphragm is about 3/4" from the screen. Removing the ball, singing in to the diaphragm's inner screen, the -30 dB distance dropped to only 3", with about 10dB more gain before feedback available.
Of course, that gain is only available before the windscreen saturates...


« Last Edit: November 22, 2019, 03:40:55 pm by Art Welter »

Tim McCulloch

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Re: Microphone Sensitivity, Polar Patterns, and Myth busting
« Reply #12 on: November 22, 2019, 11:16:51 pm »

This thread probably should be moved out of the AV section, but while I'm thinking of it, how many of you have heard the famous story of Robert Scoville and how he got Tom Petty to stop singing into a 57 and into a KMS105 (or some other Neumann)?
As he explains it, it wasn't so much that he hated the vocal sound he got from the 57, and level wasn't an issue, since Tom basically eats that mic, but it was the off-axis tone that was the big problem. Petty's backline was (is?) so loud that Tom's vocal mic would pick up tons of guitar and other instruments, but when they hit the 57 off-axis, they sounded really bad. With the Neumann, the off-axis tone was similar to the on-axis, just lower in level, so when Tom moved away from the mic the backline sound through his mic was at least tonally acceptable.

I recall him saying something to the effect of "if it's going to pick up the whole stage it needs to sound good."

Having a coherent phase response let him align the sound-making things inputs with their acoustic arrival at Petty's vocal mic. Since the Heartbreakers set up the same every night, once done it was done.  Brilliantly simple in concept.
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

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Re: Microphone Sensitivity, Polar Patterns, and Myth busting
« Reply #12 on: November 22, 2019, 11:16:51 pm »

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