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Sennheiser md441 resonant issue
Old 28th March 2019
  #1
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elektrovolt's Avatar
Sennheiser md441 resonant issue

Hi,
Recently I bought a Sennheiser md441-n microphone and it has a weird issue:

The sound is very resonant at 1696 Hz and I cannot figure out what is wrong with it. The microphone itself is in great optical condition with the original clamp and adapter cable. When looking inside everything looks clean. The circuit board inside the second canister is intact and both filters are working.
The membrane is moving, the only thing missing is the black foam part just behind the grille.
When connecting the capsule directly to an XLR connector the signal was a bit less strong and more boxy.

Could anyone help me out with this?

I made a test recording and a simple graph where you can see the strange response around 1696 Hz: a peak, plus a dip just below.
(never mind my voice, I a not a native speaker and neither am a voice talent)
Attached Thumbnails
Sennheiser md441 resonant issue-schermafbeelding-2019-03-28-om-14.22.55.png   Sennheiser md441 resonant issue-schermafbeelding-2019-03-28-om-15.31.09.png  
Attached Files

sennheiser 441 test.mp3 (1.37 MB, 291 views)


Last edited by elektrovolt; 28th March 2019 at 03:32 PM..
Old 29th March 2019
  #2
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Radardoug's Avatar
 

How are you measuring the microphone? Do you have a known good system such as an anechoic chamber?
Old 29th March 2019
  #3
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Unfortunately, the anechoic chamber we used to have is gone, but this measurement was done in a controlled room with a pink noise source up close.

I do know about proper measurement circumstances, but this issue is present in whatever room and source I am using. I also did another measurement with a flat omni to check if the room aboustics are interfering. This issue is in the md441 only.
Old 29th March 2019
  #4
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Dr. Jule's Avatar
 

Could be, rotted foam particles stick on the membrane. I had this with other mics. I think with 441 its not easily possible to open thr capsule, but you can try, while holding the mic upside down, to blow into or use a very soft brush to move/remove any particles inside the capsule.
Good luck!
Old 29th March 2019
  #5
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The capsule looks clean and the vents underneath are covered by this fine mesh, so I am not sure how any particles could get inside?
Old 3rd April 2019
  #6
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@ John Willett , do you have an idea what is causing this issue?
Old 3rd April 2019
  #7
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John Willett's Avatar
 

Exclamation

Quote:
Originally Posted by elektrovolt View Post
@ John Willett , do you have an idea what is causing this issue?
The foam is missing - the foam is an essential part of the damping of the capsule.

I would replace the foam and test again.
Old 3rd April 2019
  #8
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Thanks John! I wouldn't have thought that would make such a difference.
Would a normal disc shaped piece of foam be good enough, placed inbetween the front grille and the black cone?

Here is a picture of what it looks like now.
Attached Thumbnails
Sennheiser md441 resonant issue-2019-04-03-21.59.30.jpg  
Old 3rd April 2019
  #9
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The microphone does seem to sound better with a piece of foam fitted. However, it is still whistling at 1620 Hz. Very strange, isn't there some sort of resonant chamber that can be tuned?
Old 4th April 2019
  #10
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Is it always present with your voice as the source? Have you tried another voice?
Old 4th April 2019
  #11
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That is a good question, and yes I did. I've used a few different voices, a noise source, different rooms and a few instruments (guitar, banjo, flute, bagpipes, hurdy gurdy). The weird response is present everywhere. It is both audible and visible.
Old 4th April 2019
  #12
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John Willett's Avatar
 

Smile

Personally I would use the proper Sennheiser foam as the density and structure would have been designed to properly damp the capsule.

Only use something elsie if Sennheiser can't supply the foam.

About the 1620Hz whistling, I can't help unfortunately.
Old 19th May 2019
  #13
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Thanks for the reply!

Update: the issue must be in the capsule. The membrane center did move, but only just a little. After I had put it away in a box for a few weeks I took it out and now there is no movement in the membrane at all. It seems like the coil is stuck completely and I am not sure if I can make it work again So I guess the capsule needs replacing.
Unfortunately the Sennheiser service department does not answer my messages, so I am stuck with a broken mic.
Does anyone know how to get a replacement capsule and how much that would cost?

Last edited by elektrovolt; 19th May 2019 at 06:44 PM..
Old 10th June 2019
  #14
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John Willett's Avatar
 

Exclamation

Quote:
Originally Posted by elektrovolt View Post
Thanks for the reply!

Update: the issue must be in the capsule. The membrane center did move, but only just a little. After I had put it away in a box for a few weeks I took it out and now there is no movement in the membrane at all. It seems like the coil is stuck completely and I am not sure if I can make it work again So I guess the capsule needs replacing.
Unfortunately the Sennheiser service department does not answer my messages, so I am stuck with a broken mic.
Does anyone know how to get a replacement capsule and how much that would cost?
Sennheiser do standard repair costs now (it makes things faster and, in most cases, cheaper) - an MD 441 costs £ 162.00 incl. taxes.

Go to www.sennheiser.com - click on service and then repairs - select microphones - dynamic microphones - MD and select MD 441.

You will then be able to fill in details and get a returns number.

I can't give you the direct URL for the page as the website seems to detect the country you are in and sends you to the relevent page in your language.

I think the cost of a capsule on it's own is more than this and you get a proper, guaranteed, repair.

I know - the Sennheiser website is absolutely horrible to navigate - I had to do it a week ago to send my HD 800 back for repair and I would have had no idea how to do it if someone at Sennheiser had told me how.
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