C414 EB P48 build

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to explain @kingkorg's message further, the difference between an edge terminated k87 and a true ck12 is due primarily to more stable polar patterns but secondarily due to transient shape differences due to different handling of pressure differential between the halves. transient shape is the properties of the waveform recorded by the transducer. imagine you were recording a perfect square wave (somehow). the leading and following edges of the square wave would be smoothed out or exaggerated by the transient response of the capsule. i conceive of it as being very similar to how damping changes headphone behavior (my first love in audio) but in reverse. a ck12 expert could likely explain better.

It is possible, if you understand how a ck12 works, to make a true brass ck12 that's reformulated to be much easier and cheaper to make and sounds mostly the same with modern manufacturing methods, but most CK12 producers are not interested in doing so because the result would inevitably end up getting mailed to a chinese factory for replication. I'm pretty sure Tim could do it, and I think I could do it too (and I've been more tempted than Tim because it's the only way I could make one with my physical limitations) but I don't think the market is ready for that particular nuke.
 
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I'll do my best yet again trying to explain why neither Maiku or RK12 won't get you anywhere in c12 or c414 builds.

First of all, asking such a question is exactly the same as: What amplifier can get my Stratocaster to sound like a Les Paul. Answer: No amplifier can achieve that.

The capsule is your guitar, and it's such a shame to waste so much energy into creating wonderfull circuit replicas(amplifiers) with accurate transformers, fets, layouts, bodies, bias points, and in the end use wrong type of guitar.

More or less high end on that RK12 (Maiku, AA, Røde...) type of capsule is determined by the volume of the holes under the diaphragm. It does not mater if you achieve this difference by using EQ or by altering the size of the holes. Paying extra for 2db of HF is paying for turn of the HF knob on an eq. It is the acoustical principle of the capsule that matters regardless of frequency response curve.

By far the best capsule of this type is produced by Rode, and it is found in NT2a, K2, Classic II... it is exquisitely well matched from piece to piece, and front to back. It is not hyped in HF at all, it is almost flat in response. The difference between the Rode models sound comes mostly from headbasket.

However, i've never heard anyone comparing Rode models to c414. So why put this type of capsule in a c414 or c12. In the end you will end up with a Røde mic no matter what circuit you use.

If i were making a c414 inspired mic(and not have CK12) i would try to get my hands on used c4000b, swap the capsule, sell the c4000b with "upgraded" rk12 type capsule and use c4000b for my build. You would need to mod the Akg mic to add polarizing voltage. If you don't need patterns c3000b is great too. Those two mics sound "bad" because of the built in Eq, not because of the capsules. There are also other inexpensive Akg models with similar capsules. The fact they are electrets don't change anything, the material is deposited on the backplate, doesn't affect the performance, and applying pol.voltage to these doesn't change anything.

How to test this without serious testing equipment?

Take Neumann u87 and just about any other mic with 34mm k67. Place them in front of a monitor, at the exact same position, and record pink noise under same exact conditions. Then run EQ Match and match the two recorded files. I promise it will be almost impossible to hear the difference.

Now repeat the same test with two mics that have different construction. Say original c414 and a mic with RK12 equiped capsule. Run the EQ match, and you will get the same exact frequency response while the takes will sound different! You will hear something that many characterize as 3d effect. One will be more 3d.

This is because of how the physical and acoustical principle works and sums 360° of sound into one mono take. The more room in the sound you have the more obvious. This is why i like to test my mics as drum rooms. It's super revealing. Vocals are contrary to what many would think quite poor shootout sources. Low spl, recorded in booths, don't go low, and are relatively poor in harmonics. Slow, and soft transients.

This would be a 1 dimensional, static test. If you start moving the mics around you would see how differently constructed capsules change the 3d response in regards to proximity effect, and off axis response.
Right, I probably should've been a little clearer. I know it's not going to perform the exact same way, and I know that the Chinese "CK12" (quotes because it isn't a proper one) ends up sounding very different because it looks like it has the same boosts the K67s do because that's what it's built like. I know both the RK-12 and the capsules 3U Audio uses follow this trend, and I'd assume Maiku capsules will too.

Perhaps what I should've said is, I'd like something that in cardioid, figure 8 (and hypercardioid probably) that will give me the scooped sound I'd expect, but also that is a bit smoother than the CAD M179.

Are the XLII capsules constructed the same way as the old capsules? Also do you have measurements of the true CK12 capsules like the CT12?
 
Are the XLII capsules constructed the same way as the old capsules?
Old capsule? The current akg snaps together : someone posted disassembled and how they replace degraded foam internal part of duff capsule. Though there seem to be a few version/revs of this white plastic style I assume there are many similarities.
 
Right, I probably should've been a little clearer. I know it's not going to perform the exact same way, and I know that the Chinese "CK12" (quotes because it isn't a proper one) ends up sounding very different because it looks like it has the same boosts the K67s do because that's what it's built like. I know both the RK-12 and the capsules 3U Audio uses follow this trend, and I'd assume Maiku capsules will too.

Perhaps what I should've said is, I'd like something that in cardioid, figure 8 (and hypercardioid probably) that will give me the scooped sound I'd expect, but also that is a bit smoother than the CAD M179.

Are the XLII capsules constructed the same way as the old capsules? Also do you have measurements of the true CK12 capsules like the CT12?
Like i said eq curve is irrelevant. It's just how you tune the capsule. I have several measurements of different CK12, however i have some reasons why i can't share them. You will have to trust me on this. Some are dead flat with rolloff after 10k, not scooped at all, and some are scooped af. It's how you tune them. C3000b and c4000b are scooped. RK12 type can't have the same shape they often just have a bump at 50hz or so, and bump at 10k, they are flat in between. CK12 has continuous, smooth v curve.

What i suggest if you are strictly just after that curve is to use smoothest capsule you can find, i would go for used Rode nt2a capsule, and make built in eq, tune it to taste. You can go for RLC filter in Schoeps, or do all kinds of stuff with opamps. Original c414 circuit can be modded as well.
 
Like i said eq curve is irrelevant. It's just how you tune the capsule. I have several measurements of different CK12, however i have some reasons why i can't share them. You will have to trust me on this. Some are dead flat with rolloff after 10k, not scooped at all, and some are scooped af. It's how you tune them. C3000b and c4000b are scooped. RK12 type can't have the same shape they often just have a bump at 50hz or so, and bump at 10k, they are flat in between. CK12 has continuous, smooth v curve.

What i suggest if you are strictly just after that curve is to use smoothest capsule you can find, i would go for used Rode nt2a capsule, and make built in eq, tune it to taste. You can go for RLC filter in Schoeps, or do all kinds of stuff with opamps. Original c414 circuit can be modded as well.
Have you measured the Telefunken TF51 or Peluso P414? Since I can't try either of those out where I am I've been looking at Audio Test Kitchen and their graphs suggest the P414 and TF51 are have less of a high frequency boost than the usual Chinese edge terminated capsules and suggests the graph in the Telefunken TF51 is accurate, which looks mostly flat with a 3 dB boost at 10KHz compared to most of them being something like +5 dB in that area. They show the P414 as also being somewhat like that too, but the P12 is like +6 or 7 dB there. Could those mics be using some sort of de-emphasis circuit if Audio Test Kitchen is accurate?
 
Sounds good, keep us updated on your build
I bought one of those fake lewitt mics to use as a donor. Was pretty hilarious when I got it. Inside the plastic body was a chunk of lead for weight, no circuit board at all and the xlr was wired directly to some tiny electret capsule. Because of the plastic body I returned it. Should have snapped some pics. I doubt these will make a good donor. The ad said it was metal but is was crappy plastic.
 
little update for futher ref

i have recently replaced my sm57s on snare top and bottom for c414 eb p48 on top and a audio technica snare/tom dynamic mic on bottom, to good results

i have found this though:

https://www.mobytransformers.com/u54
the original transformer that moby transformers is making is 6:1 ratio rather than 2.25:1 as per the info within the early part of this thread.

I have 2:1 OEP transformers in mine, so will try some 6:1 ratio transformers and compare the difference, at the moment there is no sign of distortion using the 2:1.

I also am using the J113 (T3) and J201 (T1)along with the BC550C (T2&T4)

using electrolytics at the moment but have some tantalum replacements to try for all caps.

Im also going to order some cheaper bodies to move the three ive built into to use as Tom/Snare mics so easier to mount them, and they will be replacing the AKG C418 clip on mics i have.
The change from sm57 to c414 on snare really seemed to be quite a big jump in quality and punch
before i was really fighting to eq the snare and level it within the mix, to now keeping the levels much lower and the snare cutting through nicely.

Considering having a pad on there but i seem to be able to do it with the preamp pad and sound pretty good.
 
very good point, i'll probably put some very thin foam in there to minimise this, also this may tame a little of the top end with hihat bleed, i also need to put in a baffle between mic and hihat to reduce bleed.
 
I just wanted to report that i have succesfully biased my C414's correctly now.
i have used a trimmer in R5 (25k) and R8 (10k), i apply 48v and measure R7 (2.2k) with volt meter.
I turn (twiddle) R8 until i have 4.8v at R7 and then check voltage of both T1 (4.69v) and T3 (3.11v) source.
i now have symmetrical waveform, where as before waveform was mostly all above.
i then replace each trimmer for the amount it is trimmed too.

I just wanted to add in case it wasnt clear, when measuring R7 (2.2k) i am measuring either side of it, so im looking for 4.8v that R7 is dropping, hope this is clear now.
 
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