Wgtcenter k67 double sided Brass back plate discoloration?
« on: August 01, 2019, 03:42:39 PM »
I’ve noticed some dark spots on the brass plate behind the diaphragm on both sides of the capsule.  Side B with significantly more discoloration to the point it looks like the silver metal underneath is showing.  Is this something to be concerned of?  The microphone is very warm and less detailed and crisp than most have claimed on these capsules. 


Khron

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #1 on: August 01, 2019, 04:20:38 PM »
The "warm and less detailed and crisp" part might be because this is a "K47" type capsule, not a "K67".

The latter is made up of two identical halves, and the drill pattern is on a grid.
http://khronscave.blogspot.com/2017/05/a-litle-k67-microphone-capsule-fun.html
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #2 on: August 01, 2019, 05:11:42 PM »
I havent seen this before. I guess someone who deals with capsule manufacturing might chime in and give opinion. Tim C. or Ben  Sneesby?

Could be impurities in metal, or some kind of oxidation. I guess the capsule shouldn't sound different due to this, but  it potentially might corrode or something, I have no idea, just guessing.

The one I ordered once had a slight dent in membrane. Sounded as it should though. I noticed several people got warped diaphragms. These are all obvious things, and still went through QC. I start to wonder if they sell scraps, therefore the price.

I have the same feeling about capsules I find in Sterling Audio ST51. I love to mod that mic, its crazy inexpensive, however every one I ever bought had some issue with the capsule.

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #3 on: August 02, 2019, 09:44:19 AM »
I think that may be the case.  Not only did he send me discolored capsules, but the wrong ones at that.  I ordered k67/k870 but he sent me k47.  I guess another 3 weeks from China is in order.  Im hoping the next one is good.  I'll be sure to update here. 

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #4 on: August 02, 2019, 10:26:09 PM »

Hi Guys.  The reason for the discoloration is due to the grade of brass (in fact the amalgum used doesn’t even techically meet the specification for brass or indeed bronze!)
For many years, the grades of metal used in these OEM capsules has steadily moved away from what is technically brass.  As the copper content is reduced, the stains increase.


I havent seen this before. I guess someone who deals with capsule manufacturing might chime in and give opinion. Tim C. or Ben  Sneesby?

Could be impurities in metal, or some kind of oxidation. I guess the capsule shouldn't sound different due to this, but  it potentially might corrode or something, I have no idea, just guessing.

The one I ordered once had a slight dent in membrane. Sounded as it should though. I noticed several people got warped diaphragms. These are all obvious things, and still went through QC. I start to wonder if they sell scraps, therefore the price.

I have the same feeling about capsules I find in Sterling Audio ST51. I love to mod that mic, its crazy inexpensive, however every one I ever bought had some issue with the capsule.

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #5 on: August 03, 2019, 01:10:35 PM »
Thank you!  Well that’s good to hear that it isn’t due to corrosion but how does this affect the sound quality of the capsules? 

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #6 on: August 06, 2019, 11:09:56 PM »
I have a spare K67 capsule capsule I could send you. It's the 34mm one made by iSK (same one you'd be ordering through WGTcenter).

I don't know if it'd be any cheaper or faster than ordering one from their site though, since I think they offer free shipping (I mean it would cost less than $50 for me to ship the capsule to you though).

It's a used capsule though, from my BM-600. I messed up the mod I was trying, and haven't really felt the need to mod another one because I have some pretty decent mics now.

I will say that the warm sound is probably what you'd be after if you're using a K67 capsule with a proper EQ circuit. You won't get that exact U87 sound but you'll still get something Neumann-esque that you can put into a flat circuit like the Schoeps style ones.
« Last Edit: August 06, 2019, 11:16:46 PM by Icantthinkofaname »

Khron

Re: Wgtcenter k67 double sided Brass back plate discoloration?
« Reply #7 on: August 07, 2019, 04:19:37 AM »
... Not that adding a nF-range cap (or an R-C) across the JFET's drain resistor in a Schoeps circuit is all that complicated... :)

I will say that the warm sound is probably what you'd be after if you're using a K67 capsule with a proper EQ circuit. You won't get that exact U87 sound but you'll still get something Neumann-esque that you can put into a flat circuit like the Schoeps style ones.
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans


 

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