AKG D12 repair attempt...

[Whoops]

I dont think im gonna mess with it too much now that it seems like the mic is actually picking up correctly.

That's a great decision as for people that are not experienced in repairing these mics, the risk of permanently damaging it is quite high. After man-made damage occurs then there's no way back, it's gone

 

[sr1200]

That's a great decision as for people that are not experienced in repairing these mics, the risk of permanently damaging it is quite high. After man-made damage occurs then there's no way back, it's gone

I would still like to find someone i can send this to for a once (or twice) over as im sure whatever i did was just accidental and not a permanent fix.

 

[Whoops]

I would still like to find someone i can send this to for a once (or twice)

The only person in the World that I know that is very experienced and successful in fixing these microphone at the capsule/diaphragm level is member “Panman” in this thread.
He fixed already 2x D12 for me in the past, plus some other dynamic mics.
I highly recommend Panman.

Let me know by PM if you need the contact

 

[beatnik]

There is no amount of alignment that can improve the bass response if there is any metal dust on the diaphragm, that is going to reduce the excursion of the membrane.

I have successfully repaired dozens of these microphones - also thanks to the guidance found on this thread - and in my experience most of the times the poor bass performance is caused by debris on the membrane.
For some reason this also seems to happen to the microphones fitted with the felted diaphragm cover, i guess fine dust can still make it through and accumulate over time.

The proper way to do this is to remove the diaphragm, it's a precision job and you need a steady hand and good magnifier, but I wouldn't say it requires some kind of specialist.

Sometimes the coil wire end is corroded and it will just disintegrate just by looking at your solder iron in the eyes, but it only happens to the microphones that have really bad oxidation.

 

[raketenmann]

I have successfully repaired dozens of these microphones - also thanks to the guidance found on this thread - and in my experience most of the times the poor bass performance is caused by debris on the membrane.

Well - I don't want to pull off a fight, but just to be honest: i cleaned also around 20 of these mics off of magnetic dust. You can get some low end back, but not always (in my experience not even close) get it to where the sound needs to be originally. If you don't have a very good sounding D12, how would you tell that the mic is in 100% working order?
The magnetic dust forces the diaphragm to hold down sometimes for around 30, 40, or even 70 years. Just removing it doesn't bring back the mic to its original state because it is deformed and won't move back to its initial place. This can cause all sorts of different behaviour. lack of bass, lack of treble, boxy midrange and so on.

I do totally agree with you that cleaning the diaphragm improves the sound a lot, also realign it - but in some cases, this only brings you close, but not exactly to the sound you're after.
In my experience, later D12's such as the D12E and some of the ones with a plastic frame you get pretty close after cleaning. The old ones (black laquered brass frame) have different material of diaphragm, some look paper-like, some very dark.... these seem to be thinner or more prone to deformation.

 

[panman]

I know you commented on another post, but the information there is not accurate. In my experience, every AKG D12 has a bass chamber, regardless if there is a tranny or not. Sure, the tranny sits inside the bass chamber, but there is still a bass chamber behind it. so the part underneath the capsule itself is both: bass chamber and transformer housing. But yes: THERE ARE SOME OEM D12's that have such a big transformer that the bass chamber is stuffed so much the low end isn't as good as on a standard D12. As far as I know this can only be found in Norelco, Philipps and probably some other OEM D12's.
There's also a Version of the D12, called the Echolette Top12 that doesn't have a transformer, not even the bigger housing underneath it. The bass chamber there sits at the back of the capsule and even if it is way smaller, it delivers the same low end as the regular AKG D12 design.
Actually, I can't confirm if all the D12's over the years really had the same specs, but I would say they were pretty close in the low end, with or without a tranny in the chamber.

@panman you are the expert and can probably say, if they all sound sort of the same (if in fully working condition).

In fact the Diaphragm materials of D12- family varied through times a lot and because of that the frequency-responcy did vary too. We do not talk about big differencies(well, what is big), but there are thicker and thus stiffer diaphragms, that cause the the bass extending less low. Even if the diaphragm would be in perfect condition and no coil- rub or dirt in the magnet gap, the differencies are easily heard in the lows. As Raketenmann said above, the trafo in the bass -chamber does not affect the bass, except in some rare special cases, where trafo was big enough to fill most of the chamber-space. The very old 50ties diaphragms produced less highs than the later ones. Between the lows and highs the D12s sound pretty much the same, if in perfect condition. It needs to be mentioned, that AKG gave the freq.-responcy +/-3 dB. Now that "allows" up to 6 dB variation in the curve and in fact that more or less covers the mentioned differencies.

All the things above apply to mics working properly up to specs. That includes the baskets and suspension. Disintegrated windscreen affects the bass a lot too. Preamp impedance is an important factor, because the D12s have 60-200 Ohm output-impedances and some have high. D30, D36 and D45 have 75 Ohm voice coils and the bass chamber is applied differendly from D12, D20 and D25.

Not to make it too long and confusing, I promise to come back to the faults in a later point of better time.

 

[beatnik]

Well - I don't want to pull off a fight, but just to be honest: i cleaned also around 20 of these mics off of magnetic dust. You can get some low end back, but not always (in my experience not even close) get it to where the sound needs to be originally. If you don't have a very good sounding D12, how would you tell that the mic is in 100% working order?

Personally I keep a D12 with particularly extended freq response which has been picked from testing dozens of mics and use that as a reference whenever I repair another one. I can always get a repair reasonably close to that sound, and never had to reject a diaphragm unless it was beyond repair.
I don't understand how you can claim the freq response is not where it should have been originally, unless you have a freq response report for each microphone when it left the factory ? Or if you didn't even hear the microphone sound before the capsule degraded ?
As mentioned above you also need to take into account the tolerance in frequency response is quite big, these really aren't high precision microphones.
I would encourage anyone to try repair these microphones, it really isn't rocket science.
It looks like many people know the secrets already, because prices for defective AKG D- mics are not what they used to be years ago !

 

[raketenmann]

I don't understand how you can claim the freq response is not where it should have been originally, unless you have a freq response report for each microphone when it left the factory ?

That is really very difficult, indeed and I agree that one will never be able to tell, how the mic sounded out of the factory.

I really dob't want to pull off a fight about repairing mics. I also want to encourage a lot of people to take care of old mics. In my opinion it is just not as easy as cleaning the diaphragm and realign it. If it is shifted downwards because of yearlong downward pressure, it get difficult to comp for that. Thats all I am saying. And no - no rocket science but still work that needs a skilled person to do.

 

[beatnik]

Since you have repeated this twice already let me point out that if your theories are brought into question, that doesn't mean someone wants to have a fight with you.

I get that a deformed coil would not perform exactly as intended, but in my personal experience most of the times there is just a little bit of fine particles deposited in the concave area right above the voice coil. I have serious doubts this amount of material can cause a deformation that massively impacts the microphone frequency response, and in fact even on specimen I had without the dust cover and with a lot of dust as well as bigger particles sometimes even a screw, the performance was perfectly acceptable after cleaning and aligning the diaphragm.

I don't understand how you are able to quantify the deformation and its relative impact on frequency response, but if you have diaphragms that are supposedly out of spec because of the deformation, I would be interested in buying them.

 

[raketenmann]

I don't understand how you are able to quantify the deformation and its relative impact on frequency response

I just realigned & cleaned several diaphragms that still sounded thin or boxy afterwards. Mostly these were old ones with brass frame, the ones with plastic frames often did work out well.

but if you have diaphragms that are supposedly out of spec because of the deformation, I would be interested in buying them.

They will all be repaired one day in the future by panman

 

[dmp]

This may be helpful for the DIYer's here.
I don't mind the warnings to new posters that this is a difficult repair but let's remember this is a DIY forum (Do It Yourself).

 

[dmp]

Has anyone compared a 60 ohm to 200 ohm version for low end frequency response?

 

[beatnik]

They will all be repaired one day in the future by panman

I am sure panman does great work and I don't mean taking business away from him but I strongly recommend anyone to follow the advice on this thread and you have all the information needed to repair these microphones, it's not some kind of black magic.
Even if the diaphragm has supposedly been pushed back a fraction of mm, the issue could probably be resolved just by adding more paper shims under the membrane.

 

[Whoops]

This may be helpful for the DIYer's here.
I don't mind the warnings to new posters that this is a difficult repair but let's remember this is a DIY forum (Do It Yourself).

Mate, I don't disagree in any way with you that this is a DIY forum, but some very specific repair work can have devastating impacts if done wrong.
This is one of those very specific cases, because a replacement Diaphragm doesn't exist any-longer so if when trying to service it somehow you damage the diaphragm, by ripping it, or making an hole, or deform it then you just thrashed a 500/600€ microphone in a split second.
Maybe a replacement diaphragm (more or less similar or compatible) can be obtained from a cheaper donor microphone, I don't know, but if you need a donor diaphragm because you damaged the original one then you will be already making extra expenses and work, when you could have it serviced by an experienced person in the first place.

Beatnik already repaired dozens of these mics, raketenmann serviced around 20, Panman serviced and repaired also many many more, so these are experienced members in performing service work on D12 (and family) type of microphones, probably they had to fail a few times to be able to get experience and be successful. But if you're a member that just has one D12 microphone, a valuable microphone, and has no experience you have to be aware of the many risks involved in damaging your own and only D12 microphone for good while attempting a service that you never done before.

I recommend Panman because I know his work and dedication, and because he successfully repaired many of my mics, D12 and others, he is also a gentleman and a great person. Even though I'm a totally DIY guy, and I'm always eager to repair anything in this very specific case the work is very delicate and the pay out of failing is very high, that's why I recommend sending the mic to someone with experience.

 

[panman]

I am sure panman does great work and I don't mean taking business away from him but I strongly recommend anyone to follow the advice on this thread and you have all the information needed to repair these microphones, it's not some kind of black magic.

Yes, repairing especially D12-family mics has been a kind of a business to me for a long time already and still is. So I kind of have a duty to comment. All missinformation spread in this thread is not taking it away from me. I need to come back to those issues on a later point. What "Raketenmann" has written is very true and valid information and I am sad to see that dismissed by you. You are free to go on believing, that most D12s just need a little cleaning and adjusting, but that just is not true. In fact only a very small percentage of the cases are like that.

Even if the diaphragm has supposedly been pushed back a fraction of mm, the issue could probably be resolved just by adding more paper shims under the membrane.

"Pushed back a fraction of mm"? Probably if that is the case, you don`t even need to add paper. But unfortunately those cases are really rare. No, adding paper will not correct the sound to specs, if the diaphragm is deformed concave as is the case especially with the old ones.

 

[beatnik]

You are accusing others of misinformation, while at the same time you are exposing theories without any supporting evidence whatsoever.

As always, people can believe whatever they want. Some will repair on their own, some will go to the self proclaimed gurus.

 

[Whoops]

You are accusing others of misinformation, while at the same time you are exposing theories without any supporting evidence whatsoever.

What theories?
I don't see any supporting evidence of your claims also, neither I see any supporting evidence that you are even able to perform successful repairs on D12 microphones.

You dismissed Raketenmann posts, and really seemed to want to pick a fight.
Now you seem to want to attack the most knowledgeable person on D12 repairs that is on this thread.
I don't see were Panman attacked you he was sharing his experience, and if you are interested in D12 repairs and want to improve your skills you should listen and learn from his kind insights.
Being humble is the best way to learn.

It's a privilege to have someone with the experience of Panman in this thread, let's chill out and have a peacefull and friendly conversation. We are all interested and intrigued by the same topic.

As always, people can believe whatever they want. Some will repair on their own,

Or destroy their own. or destroys what's own by others...

some will go to the self proclaimed gurus.

I didn't see anyone in this thread proclaiming himself as a Guru, so that seems a very sour and uncalled remark.

Actually it was me that praised Panman's work, I actually know all the dedication he put for many many years into fixing the D12 family of microphones and also other valuable dynamic microphones, he is a great craftsman and has a true passion for fixing and servicing these mics.
He is by far the best person in the World for someone to trust the service of his/her D12 microphone, and it's the only person I recommend for this service.

 

[beatnik]

What theories?
I don't see any supporting evidence of your claims also, neither I see any supporting evidence that you are even able to perform successful repairs on D12 microphones.

Fine, you can accuse me of misinformation. But nobody is immune from that accusation unless they bring actual facts and proofs to the table.

Or destroy their own. or destroys what's own by others...

On this thread alone there are several success stories, and it wasn't from people who are supposedly the best in the world.
If you don't want to believe me, you should at least notice I am not alone.

On the forum we have people discussing condenser microphones on a daily basis, including cleaning capsules. Servicing ribbon mics replacing and tensioning ribbons.
The list goes on.
I really don't understand why for this kind of microphones there should be so much worry and they should be regarded as untouchable except by a few selected people.

To me this is just your personal opinion that some reason you seem very determined to make it become universal law.
You elect all by yourself who is "the most knowledgeable person" and "the best person in the World" yet you are suggesting others "being humble".

About the microphones I already said what I had to say. People is free to follow whatever advice suits them.
About this partisan argument, I frankly had enough.

 

[friedd]

Hi there !
every img hosting links in this thread are dead.
Any chance someone have pictures of the procedure ?

Thanks !

 

[systemtruck]

Yes, repairing especially D12-family mics has been a kind of a business to me for a long time already and still is. So I kind of have a duty to comment. All missinformation spread in this thread is not taking it away from me. I need to come back to those issues on a later point. What "Raketenmann" has written is very true and valid information and I am sad to see that dismissed by you. You are free to go on believing, that most D12s just need a little cleaning and adjusting, but that just is not true. In fact only a very small percentage of the cases are like that.

"Pushed back a fraction of mm"? Probably if that is the case, you don`t even need to add paper. But unfortunately those cases are really rare. No, adding paper will not correct the sound to specs, if the diaphragm is deformed concave as is the case especially with the old ones.

Panman, Is it possible to inquire with you about a D12E repair? Not sure how to send private messages here!