AKG D12 repair attempt...

Help Support GroupDIY:

dapolk

Member
Joined
Jul 25, 2015
Messages
20
Hi - I'm taking a shot at fixing my friend's D12E, which is passing zero signal at all.

After taking the capsule cover off, I found that both the lead-in wires from the voice coil were disconnected from the diaphragm wires. So I thought simply re-connecting those would fix it.

Both the voice coil lead-in wires have continuity along their respective blue and green output wires.

However, after soldering both diaphragm wires back to the voice coil lead-in wires, I still have zero signal (though plenty of crackling whenever I touch the lead-in wires)

I very gently pressed on the diaphragm w/ a piece of thin plastic - it moves smoothly.

I screwed the capsule cover back on, hoping the tension would get the diaphragm to start passing signal - still nothing.

Now I've removed the diaphragm, to inspect the rest of the capsule, and things look fairly clean to me (picture attached), so I'm really stumped.

Any ideas on what I'm missing?

Thanks.

PS - this particular mic doesn't have the sleeves/clamps that the lead-in and diaphragm wires go into, which is then clamped under a screw on the top of the capsule. Does anyone know how I can find a pair of those on Mouser?
 

Attachments

  • IMG_0193.JPG
    IMG_0193.JPG
    90.5 KB · Views: 25

beatnik

Well-known member
Joined
Oct 18, 2009
Messages
916
Location
Dorset, UK
sometimes the enamelled wire on the coil doesn't take solder well, but it can also be the coil is open internally. check continuity on the voice coil itself, unfortunately if it's open there is not much you can do.
for the sleeves you could try cutting down and bending m2 solder tags.
 

raketenmann

New member
Joined
Oct 20, 2021
Messages
4
Location
Switzerland
Hi everybody
I did find this one of the best D12-repair Blog all over the internet and I would really like to get deeper into the D12 repairing than before. This said - I had already about 5 D12's in my hands, some very old ones with the metal housing, most of them with the plastic housing and the plastic chamber & trasnformer housing. I was able to get rid of electromagentic dirt with a strong magnet and to get the low en back from them (if they really suffered). But so far I never was brave enough to mess with the diaphragm, but I saw on at least 3 of these D12's that the dome of the diaphragm wasn't aligned parallel to the motor (magnet). Well, as far as I understand, aligning the diaphragm has more to do with shifting the diaphragm so, that the voicecoil is centered to the motor and doesn't touch the magnet - am I right? So my question is: how can I adjust the height and adjust the diaphragm the way it is parallel to the motor?

Right now I do habe an Echolette top12 on the bench. As far as I can tell it sounds great and has a full bass response, but if you look on the photo you will see that the diaphragm is aslant. Can I try to fix this also with the 100Hz testtone method?

Also I do not understand, what screws I really need to loosen: there are 6 bigger screws that hold down the diaphragm with the washers and then there 3 smaller screws. Which ones do I need to loosen to adjust the diaphragm?

Just to clarify: I don't want to removce the diaphagm completely: the motor and the magnet gaps looks very clean. I would only like to realign the diaphragm, that's all.

I would appreciate any help! best regards, Fabian
 

Attachments

  • Bildschirmfoto 2021-10-25 um 08.25.54.png
    Bildschirmfoto 2021-10-25 um 08.25.54.png
    973.4 KB · Views: 21

dmp

Well-known member
Joined
Oct 28, 2009
Messages
3,083
Location
Madison, WI
Right now I do habe an Echolette top12 on the bench. As far as I can tell it sounds great and has a full bass response, but if you look on the photo you will see that the diaphragm is aslant. Can I try to fix this also with the 100Hz testtone method?

Also I do not understand, what screws I really need to loosen: there are 6 bigger screws that hold down the diaphragm with the washers and then there 3 smaller screws. Which ones do I need to loosen to adjust the diaphragm?
If it sounds great and has full bass response, don't mess with it. The visual position of the diaphragm doesn't matter at all. What matters is the coil alignment (red) in the groove. If the mic sounds healthy, the alignment is good. Loosing the diaphragm will only risk making it worse. The tolerance between the gap and the coil is really small, so if you move it at all you will cause interference. And the first time trying this, you have a decent chance of things not going well, so try it first on the worst mic you have.

The 6 screws hold down the dipahragm. Loosen them slightly to adjust.
 

raketenmann

New member
Joined
Oct 20, 2021
Messages
4
Location
Switzerland
If it sounds great and has full bass response, don't mess with it. The visual position of the diaphragm doesn't matter at all. What matters is the coil alignment (red) in the groove. If the mic sounds healthy, the alignment is good. Loosing the diaphragm will only risk making it worse. The tolerance between the gap and the coil is really small, so if you move it at all you will cause interference. And the first time trying this, you have a decent chance of things not going well, so try it first on the worst mic you have.

The 6 screws hold down the dipahragm. Loosen them slightly to adjust.
Okay, well, if you say that the visual position doesn't matter I will leave it this way!

I would really like to know how to do that. I do have an Electro Voice RE20 where the voicecoil touches the gap, but there I can't do anything because the diaphragm is glued onto the motot and I really don't want to cut off the diaphragm....
 

dmp

Well-known member
Joined
Oct 28, 2009
Messages
3,083
Location
Madison, WI
Depends on how old the RE20 is. Newer ones can be disassembled and repaired - old ones are near impossible. If it's the old type where it is glued, you have the option to buy a rebuild kit from EV

Check out this thread:
 

raketenmann

New member
Joined
Oct 20, 2021
Messages
4
Location
Switzerland
Depends on how old the RE20 is. Newer ones can be disassembled and repaired - old ones are near impossible. If it's the old type where it is glued, you have the option to buy a rebuild kit from EV

Check out this thread:
It is an old one, unfortunatelly. I called Bosch Germany and they only sell the whole capsule for 228.- Euros, wich is just a lot of money.... What do you mean with "rebuild kit"?
 

panman

Well-known member
Joined
Feb 8, 2014
Messages
118
Location
Switzerland
First of all, you cannot know if your D12(or Top 12) sounds right without having a fully working one to compare with. So, those "succesfull repairs" mentioned in this thread are truly questionable. The diaphragm pictured looks to be badly down on one side(as you also discribed?). If the diaphragm is warped like in your case, that affects the sound. It may even have a lot bass, but tends to make mid-peaks, that disturb or make the mic sound "honky". In this case though, if you think it sounds ok(no peaks or honky) , as dmp said, it may be better to leave it as it is. You cannot correct the deformation of the diaphragm by adjusting it. That would have to be done with heat and is likely not your beer.
 

raketenmann

New member
Joined
Oct 20, 2021
Messages
4
Location
Switzerland
First of all, you cannot know if your D12(or Top 12) sounds right without having a fully working one to compare with. So, those "succesfull repairs" mentioned in this thread are truly questionable. The diaphragm pictured looks to be badly down on one side(as you also discribed?). If the diaphragm is warped like in your case, that affects the sound. It may even have a lot bass, but tends to make mid-peaks, that disturb or make the mic sound "honky". In this case though, if you think it sounds ok(no peaks or honky) , as dmp said, it may be better to leave it as it is. You cannot correct the deformation of the diaphragm by adjusting it. That would have to be done with heat and is likely not your beer.
Yes. I actually did compare all of the D12's that went through my hands 1 by 1 on my bassdrum and my voice. Mostly I did get pretty similiar results after my cleaning procedure. Oft course they all sounded different, but definitely in a certain ballpark. I always kept the mic that sounded best for me, so the top12 shootout will be against my reference D12 - but I wasn't able to test in the studio so far... But this sort of deformation I actually saw on almost every D12 I opened. Some have it more - some less. Hard to tell where this is actually coming from....
 

dmp

Well-known member
Joined
Oct 28, 2009
Messages
3,083
Location
Madison, WI
It is an old one, unfortunatelly. I called Bosch Germany and they only sell the whole capsule for 228.- Euros, wich is just a lot of money.... What do you mean with "rebuild kit"?
That's what is available, EV sells the whole internal capsule assembly and it's not cheap.
 

Whoops

Well-known member
Joined
May 9, 2008
Messages
5,924
Location
Portugal
Hi everybody
I did find this one of the best D12-repair Blog all over the internet and I would really like to get deeper into the D12 repairing than before. This said - I had already about 5 D12's in my hands, some very old ones with the metal housing, most of them with the plastic housing and the plastic chamber & trasnformer housing.

I would appreciate any help! best regards, Fabian

Hello mate,
repairing D12 is really difficult but possible. Unfortunately only someone really experienced is able to do that without damaging the capsule for good, so it's a tricky thing.
There's only one person in the World that I know that has the needed experience and is able to repair these mics, it's Panman here in this thread.

He already repaired my 2x D12 mics plus some others from some friends of mine, he is based in Switzerland like yourself so it's easy for you to send him the mics for repair, in my case it's a bit harder because we always have to find a way to deal with Customs and avoid custom fees.

Best help I can give you and best advice is, don't touch the mics, dont try anything yourself just send them to Panman and all will be well.

My best regards
 

Whoops

Well-known member
Joined
May 9, 2008
Messages
5,924
Location
Portugal
If it's the old type where it is glued, you have the option to buy a rebuild kit from EV

Thats great to know, can you please provide more info on that Rebuild Kit from EV?
Do you have a link?

how can it be ordered?
 

Whoops

Well-known member
Joined
May 9, 2008
Messages
5,924
Location
Portugal
Top