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Mic losing volume - Problem?
Old 26th January 2013
  #1
Gear Nut
 
๐ŸŽง 10 years
Mic losing volume - Problem?

I've got a pair of AKG C451B mics I purchased about 10 years ago. I believe they are a matched set, and came in 1 box. I have them setup as drum overheads, and they've been in the same spot on the stands for the last 10 years, with the exception of the 2 times I've moved (but each time, once the drums were set up again, they were put back up on stands and haven't been used for anything else).

Recently I noticed that one of the mics was quieter than the other, which hadn't been the case in the past. Listening to some older recordings, I can see that in the very old recordings they were the same volume, but in the past year or two, one of them has been softer than the other.

I've compensated for this by bringing up the gain for the softer mic currently, but I'm wondering what would cause this, and if it is a sign that the mic is failing, or if it is something that I shouldn't worry too much about.

Probably worth noting is that I've had them plugged into the back of my 003 the entire time, which stays powered on, and since I started thinking about it, I realize that probably means that they've been getting phantom power 24 hours a day for the last 10 years or so (in my head I assumed that the phantom would turn itself off when the computer shut down, but that's probably not the case). I've since put them onto a different mic preamp, which only gets turned on when drums are being recorded.

Could excessive phantom power cause one of them to start having a problem? Is this a common issue for older mics that I wouldn't have noticed if I didn't have a matched pair? Is it going to crap out on me any moment?

Let's assume for the current moment that the sound quality of both is exactly the same (I haven't taken them down to do a side by side test, but when listening to the drum overheads, nothing sounds different from the Left and Right sides, other than stereo placement).
Old 26th January 2013
  #2
Here for the gear
 
DavidHughesAudio's Avatar
 
๐ŸŽง 10 years
There are a bunch of options that could be causing the problem. First, do you leave the mics out all the time? Do you put them back in the box after use? If you leave them out all the time...I'm going to guess that there will be some dust and dirt build up that could be causing the capsule to react differently. This could cause the loss of volume.
Old 26th January 2013 | Show parent
  #3
Registered User
 
Rick Sutton's Avatar
 
๐ŸŽง 15 years
Quote:
Originally Posted by DavidHughesAudio โžก๏ธ
There are a bunch of options that could be causing the problem. First, do you leave the mics out all the time? Do you put them back in the box after use? If you leave them out all the time...I'm going to guess that there will be some dust and dirt build up that could be causing the capsule to react differently. This could cause the loss of volume.
Dirt may be the culprit but I'd suspect other things. If the mics were oriented in a downward trajectory and the space is reasonably clean dust usually isn't an issue. I've had mics on stands for decades on my studio drumset. IIRC 451's (at least the ones I had) had screw on capsules. If these do, the first test I'd do is swap the capsules and bodies and see if the problem follows any one of those pieces. Also, cleaning the contact pin on the capsule while you are swapping can sometimes solve problems like this. I'm assuming the OP has already swapped the mics and cables to eliminate other variables.
Old 26th January 2013
  #4
Registered User
 
Rick Sutton's Avatar
 
๐ŸŽง 15 years
OK. I've done some research and the capsules on your mics are a little more difficult to swap than they were on my mics C451eb. It still can be done if you have a very small screwdriver, good eyes and a steady hand.
Here are the instructions:
http://www.akg.com/mediendatenbank2/...5d1ffc4013.pdf

Another thing to try is exercising all the switches on the mics.
Old 26th January 2013
  #5
Lives for gear
 
๐ŸŽง 10 years
Did you check the pad on the mic? On the preamp?
Old 26th January 2013
  #6
Gear Nut
 
๐ŸŽง 10 years
I exercised all of the switches on the mics several times over the last few weeks to make sure that wasn't the issue. The mics are left out all the time on stands over my drum kit, pointed down. They've only been moved once in the last 6ish years, since I've decided I want to go with a different spacing and layout for the mics, but other than that they remain in place and untouched all the time.

I don't know that I'll go through the trouble to remove the capsules unless I notice one of them sounding off, or there is another problem. I was mainly wondering if this was a normal thing, and there was a common issue that would need to be addressed. Recording nowadays doesn't bring in enough money to warrant sending it out for repair unless it stops working or sounding right, so I'll just keep on going with one of them turned up louder on the preamp.
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