Banzai's KM84 DIY Body & PCB kit build thread

[craigmorris74]

I'm happy to make a CAD drawing, I work in Rhino. I could produce 2D and 3D drawings.

I think the trick will be to make the kk84 patent drawings or kk84 measurements be the right diameter for the typical Chinese capsule.

 

[corgan4321]

I think the trick will be to make the kk84 patent drawings or kk84 measurements be the right diameter for the typical Chinese capsule.

Right, that makes sense. I remember seeing a photograph of all the parts inside the Banzai capsule but I can't find that photo now. Based off that other thread you linked to, it seems like how much you tighten the capsule affects the capacitance of the capsule. This is interesting because the capsule forms a charge pump with C2 determining the sensitivity of the microphone. I'm finding these mics to be much louder than my KM86 and I wonder if the capsules are not tightened down properly?
I think I will investigate this tonight. Based off the original KM84 schematics the KK84 cardioid capsule should be 36pF

 

[craigmorris74]

The number of grooves and holes is apparent in the pictures. We just need to determine their size.

 

[shabtek]

It is more likely that an adapter can be machined to allow the german capsule to thread onto an asian tube—or even re-thread an mxl or oktava body?
Building the capsule is no trivial matter—I know it is in the Diy spirit and a 1 off etc.
I’d buy an adapter if one was available.

 

[corgan4321]

It is more likely that an adapter can be machined to allow the german capsule to thread onto an asian tube—or even re-thread an mxl or oktava body?
Building the capsule is no trivial matter—I know it is in the Diy spirit and a 1 off etc.
I’d buy an adapter if one was available.

This is an interesting idea. My understanding is that Neumann still makes KK84 capsules for around $550 USD. If we had an adapter for the threads and the pin you'd end up with a pretty reasonably priced KM84.

That being said, I do have these Banzai capsules already. So it would be nice to use em and get something better for less than $550

 

[Whoops]

I do have these Banzai capsules already.

Hi Corgan4321,
something important to clear out, in the latest posts there has been some references to "Banzai Capsules" which is incorrect.
Those should be called "Maiku capsules" has it's clearly stated by Banzai in the kit description.
I don't see any reference anywhere by member Banzai that those are his capsules.

Maiku capsules are probably sourced from a Chinese manufacturer as Maiku is not a capsule manufacturer/production company.

The quality or authenticity of those "Maiku sourced from China capsules" is quite dubious and that is probably one of the reasons why the units made with this kit don't sound anything similar to a Neumann KM84, even though it's advertised that way

 

[Whoops]

also, there's no "Banzai KM84". I didn't start this build thread, and we've never called it that.

You are totally correct Banzai,
you never called this project "Banzai KM84".

You called it "Neumann KM84", although there's no one that seem to have been able to achieve a microphone with your kit that sounds even similar to a Neumann KM84.




So what name do you think it's the most correct "Neumann KM84" or "Banzai KM84"?

 

[Banzai]

You are totally correct Banzai,
you never called this project "Banzai KM84".

Guy who's never going to build this kit, sharing opinions! Yay!

You called it "Neumann KM84", although there's no one that seem to have been able to achieve a microphone with your kit that sounds even similar to a Neumann KM84.

Here's "one".

If you knew who this was, you'd stop posting in this forum altogether:


Some background on his build:



Could post more, but what's the point.

You're only here to start shit

 

[Banzai]

I'm finding these mics to be much louder than my KM86 and I wonder if the capsules are not tightened down properly?

Adjust C2 to set the sensitivity you want. You can replace it with any value you prefer.

Circuit and transformer decide what makes it from the capsule to your preamp, not the other way round.

Sounds like the usual symptoms I've read about with these capsules. I found this article from a guy who tried this mod you're thinking about, and got good results with taming the HF response. What tool would you use for this, dremmel? I'm interested too, altough I'm still yet to build mine..
http://www.audioimprov.com/AudioImprov/Mics/Entries/2012/12/5_Modifying_the_MXL_991.html

Not the same capsules. These don't need taming, but... chopping up metal for science is always a good thing

If anyone ends up with an oddball zingy capsule, get in touch and we can work out a replacement.

 

[Urskov]

EDIT: After some valid arguments from Banzai, my quote lizard marketer brain unquote wants to correct this to "It sounds like several people have had bad capsules displaying the same exact problems across batches.")
Glad you're offering people replacements.

But like I said in the other heated discussion on the Maiku LDC capsules, you seriously need to consider your defensive strategy. You responded with a turd-emoji in response to RuudNLs valid - or at least I think so - demonstration and arguments. And to Whoops, who I think has a point despite the somewhat aggressive tone, you respond to with sarcasm and mockery. Not the kind of response that gives people confidence in your product.

These people are not out to threaten your livelihood (considering you mentioned that you sell hundreds of kits of ~140 euros per batch, I think it's safe to say that it must be a part of it, though I know most DIY is borne out of passion), but ensure fellow DIY'ers aren't duped by false advertisement.

I know all elements factor into a mic, but from everything I have ever read on pro audio microphones by experts - granted I'm no expert myself - the capsule is THEE most important factor of the sound of the mic. Put a U87 circuit with authentic transformer and all into a Chinese mic with those shitty stock K67-style capsules, it won't sound like a U87. Put a proper U87-style capsule in there, it's a new mic. Whether it's made with a Schoeps-style circuit, KM-84 or U87-style circuit or whatever. Most everyone I've seen agrees with that, including people with substantial knowledge about the inner workings of mics.

I don't doubt from the reputation of the Maiku LDC capsules that the SDC capsules has a high quality/price-ratio, too. But it's like Whoops is saying - you are calling it "Banzai's Neumann KM84 DIY kit" -NOT simply "Banzai's KM84 DIY kit", "Banzai's Neumann KM84-style microphone DIY KIT" or "Neumann KM-84-inspired DIY kit" or whatever. That sort of naming mentioning the original brand name calls for a very high level of authenticity, which I don't doubt is what you're going for. But it does make you vulnerable to criticism when it doesn't sound right.

Also, for the price of the kit with all parts included - don't get me wrong, I don't think it's expensive by any means compared to say micparts or micandmod - you can almost get a 3U Warbler 127 that are already painted, assembled, properly biased, stereo matched (if you buy a pair) and documented to sound very close to a KM84. I do think that calls for you to have everything in order to be a viable alternative for DIY'ers.

You're trying to defend your product, I get that. But you're also muddying the waters by suggesting it's the transformer or FET-types or a cap value causing the deviating frequency response. All points to bad capsules in the cases in this thread. Perhaps you should ask the original manufacturer and/or Maiku to up the quality control, if possible, if it hasn't been a problem before. But again, good you're offering returns.

 

[kato]

Yes, my understanding is that this is a crucial element to the function and design of a KK84… do these capsules not have this?

I would assume not. I don't think any of the Chinese-made capsules go to that level of detail. They usually have a concentric circle pattern, something like this:



Interestingly, the recording hacks page where I got this image mentions that earlier revisions of the MXL603s had perforations in the center ring to get closer to the sound of the Neumann capsule. But in later runs, they stopped doing that.

The article's from 2013 so anything might have changed since then.

 

[Banzai]

It sounds a lot like a bad batch, then, Banzai. Glad you're offering people replacements.

Only McIrish posting here has built kits from the 4th batch. Others like Corgan and Craigmorris don't have kits from 2021. So we're not going to question the quality of a large batch because of the results of one or two people.

Of course it's possible some people end up with problematic capsules or transformers. Nothing is 100%. The way to resolve those issues is to get in touch with us, like you would with any other product.

But it's also impossible to satisfy everyone and not every negative comment is automatically a manufacturing problem.

But like I said in the other heated discussion on the Maiku LDC capsules, you seriously need to consider your defensive strategy.

Encouraging people to experiment with their builds and try different parts is not being defensive. There's no strategy here, nor do I want one.

You responded with a turd-emoji in response to RuudNLs valid - or at least I think so - demonstration and arguments.

Read between the lines: he never built the kits, let alone compare them or build an adapter.

If you disagree, feel free to explain how you build kits without PCB's:

And to Whoops, who I think has a point despite the somewhat aggressive tone, has a point, you respond to with sarcasm and mockery. Not the kind of response that gives people confidence in your product.

Overtly dickish tone is a better description.

"Thanks for saving me hundreds of euro's because your mic sounds horrible" ???

... and you want me to be polite and considerate?

These people are not out to threaten your livelihood (considering you mentioned that you sell hundreds of kits of ~140 euros per batch, I think it's safe to say that it must be a part of it), but ensure fellow DIY'ers aren't duped by false marketing.

Bad assumptions. We don't sell anywhere near enough kits to live from this, and as demonstrated above, some of these people are trying to influence opinions.

Otherwise this kit has no marketing. Only user reports from members of this forum.

I know all elements factor into a mic, but from everything I have ever read on pro audio microphones by experts - granted I'm no expert myself - the capsule is THEE most important factor of the sound of the mic. Put a U87 circuit with authentic transformer and all into a Chinese mic with those shitty stock K67-style capsules, it won't sound like a U87. Put a proper U87-style capsule in there, it's a new mic. Whether it's made with a Schoeps-style circuit, KM-84 or U87-style circuit or whatever. Most everyone I've seen agrees with that, including people with substantial knowledge about the inner workings of mics.

No microphone expert would say all that. You're confusing two different things:

1. The capsule decides what quality CAN be achieved.
2. The circuit, tube, transformer, power-supply etc decide what quality IS achieved.

Everything enters the mic through the capsule, which makes it the only part along with the headbasket that can set the maximum attainable quality and resolution of a microphone. Everything else behind it has to work with what the capsule provides.

But what is your pre-amp connected to, the capsule or the transformer?

Commercial microphones aren't designed around fixed circuits either. Circuits are a toolbox, designed to fit and control the parts around them. You can adjust and change circuits. You can add and remove parts, add EQ filters, adjust sensitivity, add pattern controls etc. Looking at a circuit as this immutable and useless object is a complete waste of opportunity.

And no, your Neumann K87 capsule in a cheap Chinese mic won't sound like a good mic. It'll be unbalanced and probably unusable. But the proper U87 circuit and transformer with a cheap K67 will sound like a U87. Won't be a great one, but it will have the right character.

I don't doubt from the reputation of the Maiku LDC capsules that the SDC capsules has a high quality/price-ratio, too. But it's like Whoops is saying - you are calling it "Banzai's Neumann KM84 DIY kit"
-NOT simply "Banzai's KM84 DIY kit", "Banzai's Neumann KM84-style microphone DIY KIT" or "Neumann KM-84-inspired DIY kit" or whatever. That sort of naming mentioning the original brand name calls for a very high level of authenticity, which I don't doubt is what you're going for. But it does make you vulnerable to criticism when it doesn't sound right.

Neumann is in the thread title to credit them as the source. We didn't create the KM84 circuit. We can change it to something else, it's not important.

Being vulnerable to criticism isn't a problem either. Critique from people who build the kits is welcome and that's how all products are improved. But we could do without the "input" from people who have no intention of building this kit, in a build thread...

But you're also muddying the waters by suggesting it's the transformer or FET-types or a cap value causing the deviating frequency response.

Stated the circuit can be used to adjust the frequency response, and each transformer type affects the frequency response of the mic differently. Both statements are true.

If they have no effect on sound, then why bother building a KM84 circuit? Why not just build a generic flat circuit with a flat capsule?

Or every time you don't like something in a mic, you're just going to endlessly swap capsules until it sounds right? How much money are you made of?!

All points to bad capsules in the cases in this thread. Perhaps you should ask the original manufacturer and/or Maiku to up the quality control, if possible, if it hasn't been a problem before. But again, good you're offering returns.

No returns. It's a DIY kit.

Not liking the sound of your build, or kit not matching expectations is not a bad capsule problem.

Problems with sound where your 1st capsule is wildly different from your 2nd is a bad capsule problem. Both your capsules showing problems and being unusable is a bad capsule problem (that includes anything from not working to having poor frequency response)

Also, for the price of the kit with all parts included - don't get me wrong, I don't think it's expensive by any means compared to say micparts or micandmod - you can almost get a 3U Warbler 127 that are already painted, assembled, properly biased, stereo matched (if you buy a pair) and documented to sound very close to a KM84. I do think that calls for you to have everything in order to be a viable alternative for DIY'ers.

Then you might as well buy from Stam instead of building anything on this site. For most people DIY is about the process. It's about making something yourself. Not everything is about money.

(can we please leave this thread for those who are building the kit? Anyone who wants to discuss the validity of this project or marketing strategies, take it to the white-market thread)

 

[kato]

Also, for the price of the kit with all parts included - don't get me wrong, I don't think it's expensive by any means compared to say micparts or micandmod - you can almost get a 3U Warbler 127 that are already painted, assembled, properly biased, stereo matched (if you buy a pair) and documented to sound very close to a KM84. I do think that calls for you to have everything in order to be a viable alternative for DIY'ers.

Then you might as well buy from Stam instead of building anything on this site. For most people DIY is about the process. It's about making something yourself. Not everything is about money.

This. 100%. I'd never recommend someone GroupDIY to save money.
The experience of DIY'ing a crowdsourced project is priceless. We have a guy in this thread silverplating mic bodies in a pickle jar for chrissakes. That's magical.

I feel extraordinarily thankful for this project, and all the projects in the White Market because my studio is full of bespoke circuits that cannot be bought.

It sort of pains me to watch people who seem to have a bone to pick go after our creators seemingly because he won't sell them an individual capsule. To that, I say, "Banzai is not a business." He's one of us. I think people sometimes forget that.

 

[FarisElek]

If it makes anyone feel better, I'll be tracking my new album with the KM84 clones as my cymbal mics this weekend. Will report back. I haven't done extensive testing beyond whether they work or not.

 

[mrgrooves666]

I am, please let us hear how they behave if you want to share, thanks. Let's leave all this grievance for once already

 

[kato]

What is the problem with the 2n3819's? They're from mouser so supposedly not fake?

They're legit, manufactured by Central. But I don't think they're manufactured to the same specs as they were in the 60's. I think they're a near equivalent product badged as 2n3819 to fill a market demand, similar to buying an NTE equivalent where the specs are close enough for rock and roll.

I measured the CEN 2n3819 that came with Banzai's kit, as well as a bunch I bought from Mouser years ago. They all measure exactly the same as a bog-standard J112, which is an entirely reasonable substitute, but none came in with an Idss under 2mA. I suppose folks just feel more comfortable using the part number Neumann used, so Fairchild and Central provided that.

At first I didn't think the FET type would make much difference. As a straight amplifier, it should not have much bearing on the sound, but the source resistor is going to have an effect on the overall drive current into the transformer.

By all accounts, the purpose of the FET here is impedance conversion, not so much voltage amplification. The difference is outside my level of understanding. So I'd rather use something in line with the specs Matador provided earlier.

I measured every jfet in my house earlier today.
The only one with IDSS under 2ma (let alone under 1ma) was the LS846.

(Not implying there aren't half a dozen good substitutes that will work fine. But I'm definitely not going to be using SK170's for this application.)

This is one random LS846:

 

[craigmorris74]

I don't want anyone to think front like and use the hell out of my mic, I keep pushing ideas besides it's fun.

 

[waltzingbear]

If anyone ends up with an oddball zingy capsule, get in touch and we can work out a replacement.

Of course it's possible some people end up with problematic capsules or transformers. Nothing is 100%. The way to resolve those issues is to get in touch with us, like you would with any other product.

No returns. It's a DIY kit.

I mentioned that my capsule fell apart, you blew it off and then recommended that I use an entirely inappropriate glue to fix it. So which is it, you will support capsule problems or no returns.

and yes I do know Seth/jrmintz What he has said it that the mic can sound good/great. not that it is a KM84, thats a world of difference. He's one of the reasons I decided to try your kit. underwhelmed.

Cheers
Alan

 

[corgan4321]

I did a bunch of experimenting today with tightening and loosening the retaining ring in the capsule. As expected I could easily change the capacitance of the capsule and this had direct correlation to the sensitivity of the capsule. I tested the capsule with capacitance between 30pf-38pf. While is did alter the frequency response independently of sensitivity, it wasn't much, maybe 1-2dB deviations in small areas. See graphs. I also experimented with removing the front plastic grill. I did FR measurements as well as an acoustic guitar test and I didn't notice too much of a difference. I've considered replacing the grill anyway though because I think it makes the capsule look cheap. Any ideas on where to get some very fine mesh like the stuff that covers the vent slots?
I took photos of the capsule parts if you're curious too.

I think I would like to incorporate a de-emphasis circuit like the one in the U87 to tame the high end harshness of this capsule. If that is feasible, could I also incorporate the low cut in the U87 circuit too? Would the de-emphasis be as simple as connecting the drain of the FET to the backplate by way of a 1M resistor bypassed by a 220pf. Would I need that C9 0.47uF cap from drain to the 1M resistor?

 

[corgan4321]

I would assume not. I don't think any of the Chinese-made capsules go to that level of detail. They usually have a concentric circle pattern, something like this:

View attachment 84345

Interestingly, the recording hacks page where I got this image mentions that earlier revisions of the MXL603s had perforations in the center ring to get closer to the sound of the Neumann capsule. But in later runs, they stopped doing that.

The article's from 2013 so anything might have changed since then.

Are the perforations in the center ring what we see above in the Maiku capsule?