Something you might not know about condenser microphone capsules

B

Browneyes

New member
In a condenser microphone, the most important part is the capsule which works as a capacitor to convert acoustical energy into electrical energy. In the capsule, the diaphragm acts as one plate of a capacitor, and the vibrations caused by sound wave produce changes in the distance between the plates and therefore change the capacitance. .

Let’s have a close look at the most important part of a condenser microphone------the capsule, what does it look like?

In the picture below is one capsule, nice and clean. This type of capsule is called center-terminated capsule, you can see that the electric contact point is in the center of the diaphragm.
 

Attachments

  • 图8&_039.jpg
    图8&_039.jpg
    48.9 KB · Views: 1,117
Now have a look at the following pictures,these are some old (used) capsules taken apart from used microphones. You can see that there are stains on the surface of the diaphragms. The accumulation of the stains such as dusts, moisture condensation of the hot breath or sometimes hot and wet air etc will cause the drop of the insulation resistance between the capsule’s two plates.
 

Attachments

  • Q.jpg
    Q.jpg
    46.4 KB · Views: 1,083
  • QQ.jpg
    QQ.jpg
    55 KB · Views: 1,059
Browneyes said:
In a condenser microphone, the most important part is the capsule which works as a capacitor to convert acoustical energy into electrical energy.
Click to expand...

Yeah, the same as to say in the car the most important part is the wheels, which work as a medium to convert rotary motion into linear motion.

Best, M
 
Browneyes said:
Now have a look at the following pictures,these are some old (used) capsules taken apart from used microphones. You can see that there are stains on the surface of the diaphragms. The accumulation of the stains such as dusts, moisture condensation of the hot breath or sometimes hot and wet air etc will cause the drop of the insulation resistance between the capsule’s two plates.
Click to expand...

The top ones look like 797 capsules and the bottom are KK87. I've seen capsules in much worse condition, which were working just fine. Sorry, if I am still missing the point...

Best, M
 
Last edited:
Most of the good manufacturers sell replacement capsules for a fraction of the mics replacement cost. A high fraction in some cases. But sometimes you get lucky on the costly ones as they'll service them under warranty. Replacement part free, but shipping and labor not.

basically dirt == mass. mass == reduced high end.
 
What he's forgotten to say is that dirt and contaminants on the diaphragm can absorb moisture and cause noise and crackling.

This is what the "breath test" is for - if the mic. starts to crackle when you breathe on it, the capsule could be dirty.

However, a capsule can be cleaned by an expert with de-ionised water and a special brush.

However, if the contaminants contain tar or the like from cigarettes or smoking a spliff, then the gold can peel away as the capsule is cleaned, resulting in the need for a new capsule. I am told that the success rate for cleaning is about 40% (from the Neumann expert at Sennheiser UK).
 
Sounds like someone trying to show people (and convince himself) that he's an expert where mics are concerned. :rolleyes:

:cool:
 
Marik said:
Yeah, the same as to say in the car the most important part is the wheels, which work as a medium to convert rotary motion into linear motion.

Best, M
Click to expand...

Bad analogy. Wheels are the LAST part of the drive train (well, actually, the tires are, but most people think of a car's wheels as including the tires,) whereas the capsule is the FIRST part of the "drivetrain" or signal path in a microphone.

ausrock said:
Sounds like someone trying to show people (and convince himself) that he's an expert where mics are concerned.
Click to expand...

Most noobs come here because they DON'T know something- this guy comes on the forum and offers a bit of useful information- he does not identify himself as a mic expert, just points out ONE thing, and you rag on him? You jerk. Bugger off.
 
stevieb said:
Bad analogy. Wheels are the LAST part of the drive train (well, actually, the tires are, but most people think of a car's wheels as including the tires,) whereas the capsule is the FIRST part of the "drivetrain" or signal path in a microphone.
Click to expand...

Sorry, I fail to see what difference the "LAST", or "FIRST" makes? Besides, either "LAST", or "FIRST" really depend on which side to start to count from.

In any case, this analogy was rather to show that either one is an integral part of entire system and any system is only as good as its weakest link. To say that the capsule (well, actually, the diaphragm is, but most people think of a capsule as including the diaphragm), or for that matter wheels in the car, are the most important part of a system is... how should I put it... little unthoughtful.

Best, M
 
Last edited:
I love a good completely unnecessary fight thread!

Rule #1: We don't talk about Fight Thread!

Rule #2: We don't talk about Fight Thread!

:laughings:
 
John Willett said:
What he's forgotten to say is that dirt and contaminants on the diaphragm can absorb moisture and cause noise and crackling.

This is what the "breath test" is for - if the mic. starts to crackle when you breathe on it, the capsule could be dirty.
Click to expand...

Thank you John, this is a very important point but I failed to mention.
 
ausrock said:
Sounds like someone trying to show people (and convince himself) that he's an expert where mics are concerned. :rolleyes:

:cool:
Click to expand...

Well, I am certainly not an expert, :) just some guy who feels to share some of my experiences with everyone here and hope to learn more from you.
 
How about those foam filters that hide the grille?

Seems to me constant use of a foam filter would help keep the capsule clean if not somewhat drier from airborn
dust and humidity.
I could be wrong and if so, I would like to know why.
 
When the oxide layer grows all over the surface of the diaphragm and reaches the back plate, it acts like a resistor with great resistance paralleled with the highly insulated capacitor.
 

Attachments

  • image-2.jpg
    image-2.jpg
    14.6 KB · Views: 275
The resistance of this “resistor” will decrease when the moisture level around it goes up, and will increase after you dry it. In other words, it’s changing constantly in pace with the surrounding conditions.

We don’t “see” the “resistor” working, but we certainly can feel its existence. I am sure some of you have had experiences like:

“The microphone works well at the beginning of a session, but the volume drops suddenly. It gets better if I pull my mouth away from the microphone for a while, but it happens again when I continue. ”

Or, “I keep my microphones in a dryer at a constant temperature and humidity, but once I take them to a place where the humidity level is a little higher, I hear a constant hissing sound from the microphone.”

An experienced recording engineer will tell you that all these are the influence of the humidity to the capsule. Some might say it’s no big deal, just put the microphone in a dryer, everything will go back to normal. Well, it is not that simple. Because once the particles formed a pathway under the electrical field and had the first crackling, it will do it repeatedly. And after a while, the microphone will have a loss at the high frequency, sounds muffled and loses a lot of details when recording with.
 
Last edited:
Twinhit said:
How about those foam filters that hide the grille?

Seems to me constant use of a foam filter would help keep the capsule clean if not somewhat drier from airborn
dust and humidity.
I could be wrong and if so, I would like to know why.
Click to expand...

Except that these foam things degrade with age as well. They turn into dust in and of themselves. Dust that might have an electrostatic attraction to the mics business end. In combination with the moisture of breath can be quite the mud maker.
 
In Germany the "capsule" is considered the housing portion of the mic which is comprised of the grill, its support structure and the transducer.

In this conversation what we are examining, that part that converts sound to electrical energy, should really be referred to as the "transducer".
 
Browneyes said:
....

Also, there would be a growing oxide layer as the microphone ages.
Click to expand...

If my memory is not that rusty, the oxide is a chemical composition of oxygen and some kind of material. The part of the picture you show contains Mylar, as well as plastic (the clamping ring), which both to my knowledge are immune to oxidation (i.e. fusion with oxygen).

Furthermore, Gold (the Mylar coating) is not a very easy metal to get oxidized, either. In the pictures you posted above I am still trying to understand what is wrong with those capsules, as apart from slight signs of Gold peeling (most likely amateurish attempt to clean), they all look they should work just fine.

Best, M
 
PhilGood said:
In Germany the "capsule" is considered the housing portion of the mic which is comprised of the grill, its support structure and the transducer.

In this conversation what we are examining, that part that converts sound to electrical energy, should really be referred to as the "transducer".
Click to expand...

Finally .... a true reference.
 
You must log in or register to reply here.
Back
Top