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Microphones go Bad? Video by Dave Rat.

iMickey503

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In his video "Vocal Microphones Go Bad" Dave Rat goes over how to test your microphones with simple gear that you already own. He also indicates how important it is to do maintenance on your microphones as spit and other foreign objects can collect on the diaphragm and alter its frequency response after just one singing session. Something I did not put much thought into. So its important to have multiple microphones especially for vocalists.



Vocal Microphones are often offered at great prices on the used market. And some of you are also into sound recording as a business venture. Being able to verify the performance of your used microphone purchase second hand should be obvious. Especially if you are buying parts or doing a rebuild.

Saving a Buck? Makes you a buck. When dealing with more then 2 microphones? The costs savings really add up.
Lets take the Audix OM-7 that has a Retial price of $$249.00.
Case_OM7-1199x842.png
Used examples can go for as little as $50 USD to $150 on Reverb depending on condition. That's a FANTASTIC deal compared to a new model at $240. And that before Taxes and VAT for those of you out of the USA.

Rarely do you use just one microphone, so being able to test its performance out in the field can be essential for live and on the road gigs. This method that Dave Rat showcases in the video is not only easy? But can be done Quickly without special tools or calibration gear.


Voice matching of Microphones is where I have had the most issues. And when you only got one shot to get it right? Finding out this info before the gig would really put my mind at ease. Its not often easy to test this with just a simple Mic Check. And often you don't have much time to get things tested before a gig. Not a problem most times. But this can be really helpful. But not Foolproof as Dave Indicates.

Since the OM-7 and other microphones are often serviceable? Verifying that you are getting replacement parts that match up to the characteristics of the OEM parts is nice since there are a TON of counterfeit stuff out there right now.
Prices for these parts can vary. And this is a helpful way to rule out if you are getting the Real McCoy.
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Or saving money on Aftermarket or N.O.S. Part in the future.



I'm not sure how well it would work for calibration or directional microphones, so I will leave that to others that would be more versed on this subject & hardware. I am making the assumption that the technique would be the same with a higher level of difficulty. But not as good as using software and a professional calibration Laboratory.



I have included a Link bellow about the OM7 from Dave's Website that goes over how to build the excellent Audix microphones and some tips and tricks that might be useful or could apply for other Microphone brands.



Also a Fun Bonus Video about a Microphone Capsule Speaker.
Might be a cool way to use those Old Capsules. :)

 

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Blumlein 88

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Okay I guess. Would have been quicker, more accurate and as simple to feed the REW signal over a speaker with the two mikes alternated on a mic stand. Use REW to get a frequency response without changing gain, and seen how they differ in both gain and frequency response. So many variables in his method they have to be pretty far off to see anything different. He had everything to do this other than a speaker, and I have to assume he has one of those. No need for the little noise source. No need for the box with felt in it. No fiddling about with anything.

Here are some examples. I used an LSR 305 in the room fed a signal by my interface and measured with REW from about 2 meters. Simply swapping each on a mic holder on a mic stand. You do need to be careful to position the microphone the same each time.

First are three Audio Technica AT4033a micphones of various unknown ages as I purchased them used.

1663144514365.png


Three Shure KSM 32's that spanned more than 10 years in age.
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A couple of CAD M179's in Omni pattern. One a year old and another 6 months old.
1663144676582.png
 
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Lopsided

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Okay I guess. Would have been quicker, more accurate and as simple to feed the REW signal over a speaker with the two mikes alternated on a mic stand. Use REW to get a frequency response without changing gain, and seen how they differ in both gain and frequency response. So many variables in his method they have to be pretty far off to see anything different. He had everything to do this other than a speaker, and I have to assume he has one of those. No need for the little noise source. No need for the box with felt in it. No fiddling about with anything.

Here are some examples. I used an LSR 305 in the room fed a signal by my interface and measured with REW from about 2 meters. Simply swapping each on a mic holder on a mic stand. You do need to be careful to position the microphone the same each time.

First are three Audio Technica AT4033a micphones of various unknown ages as I purchased them used.

View attachment 230868

Three Shure KSM 32's that spanned more than 10 years in age.
View attachment 230869

A couple of CAD M179's in Omni pattern. One a year old and another 6 months old.
View attachment 230872
Can you reprocess the data to do a gated measurement? Really interested to see anechoic response.
 

Blumlein 88

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Can you reprocess the data to do a gated measurement? Really interested to see anechoic response.
These are gated measurements. I can dig up the details I suppose, but it is on a hard drive from a previous machine.
 

Lopsided

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These are gated measurements. I can dig up the details I suppose, but it is on a hard drive from a previous machine.
The CAD one is quite unexpected. Spec shows peaking >10khz in omni. These mics seems to differ a lot from their ultra-smoothend declared response. Thought this was a in-room response, seeing all the peaks and troughs, and omnis tend to become directional in the high treble range. I'm baffled.
 

Blumlein 88

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The CAD one is quite unexpected. Spec shows peaking >10khz in omni. These mics seems to differ a lot from their ultra-smoothend declared response. Thought this was a in-room response, seeing all the peaks and troughs, and omnis tend to become directional in the high treble range. I'm baffled.
First off this is of a speaker in a room. Secondly I took the graph like in your link and created a correction cal file. That has been applied. So yes it has that high treble peak, but I've corrected for it.
 

Lopsided

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First off this is of a speaker in a room. Secondly I took the graph like in your link and created a correction cal file. That has been applied. So yes it has that high treble peak, but I've corrected for it.
That’s comforting to know.
 

DonH56

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A wind shield or "pop filter", essentially a foam cover, is good to use even indoors, especially with singers who like to "eat" the mic. I, and I am sure many of us who have done some recording, can tell some very gross tales about washing the wind screens...

All microphones degrade over time as the diaphragms and suspensions age.
 
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