BaiFei Li C414 34mm capsule (PCB & Capsule pictures)

[daschnoz]

I may try getting a JLI electret. Do you know what circuit it is replicating? I am curious if anything can be done to improve it, or what it's attempting to clone.

I have no idea on the circuit. I doubt they reverse engineered then simplified the circuit from its Austrian namesake. It's likely something tried, true, and very generic. But the board in the 25mm version does have a transformer on it, so it can't be all bad.

It's probably the JLI electret capsule you're refering to?

https://www.jlielectronics.com/microphone-capsules/jli-3412/
https://micbooster.com/microphone-capsules/266-jli-3412-cardioid-electret-microphone.html

{snip}

Actually, it's this capsule:
https://www.jlielectronics.com/microphone-capsules/jli-3413au01/

The added thickness of the green rings made it a royal pain in the ass to get into the head basket. All of the internal plastic that holds the capsule... I ended up designing and 3d printing a whole new one. The capsule needs to go into the head basket at an angle to clear the frame, even after shaving down some of the frame with the Dremmel tool, and the stock piece didn't allow for the twist.



If I were to do this mod again, I would use the this capsule instead:
https://www.jlielectronics.com/microphone-capsules/jli-3410au/

It looks like the same capsule, but without the plastic decoration glued to the thing (likely is, judging by the numbers and freq. response). I wish I realized this sooner... I'd still need to print the capsule holder, but the capsule would likely fit without the need for the Dremmel tool.

Though I do think it looks pretty sweet when you look through the head basket and see that smooth shiny surface.

 

[kingkorg]

Here is a little recording of the 12" tom and kick 22" (muffled then open) of my Yamaha kit recorded with my laptop a bad Native instrument interface a SPL goldmike preamp and the baiFei Li 34mm. It's straight from the mic, no EQ nothing else. I'll post better takes with my pro computer and interface later.

View attachment 134660


View attachment 134658


It sounds really good to me. Kick is really deep and hi end is not pronounced at all even on the tom attacks. I don't notice any distortion at the microphone level. I don't think a mod for a PAD at the capsule is necessary. This is a success to me. Now I need to check the pickup pattern to see if there's a lot of bleed.

On the other hand, it sounds to me, you are not really pushing those drums hard?

 

[damien]

On the other hand, it sounds to me, you are not really pushing those drums hard?

I'm not a heavy hitter but I was hitting the tom like I would normaly do when recording.
I went from very soft to the strength before it chokes the head with hand at shoulder level when high, so not really gentle neither
The tone is on the dark side with the pinstripes.

No noticeable/bad distortion to me with the BFL414.

 

[kingkorg]

I'm not a heavy hitter but I was hitting the tom like I would normaly do when recording.
I went from very soft to the strength before it chokes the head with hand at shoulder level when high, so not really gentle neither
The tone is on the dark side with the pinstripes.

No noticeable/bad distortion to me with the BFL414.

Sure, if it works for you that's all that matters. I record all kinds of drummers, so i try to stay on the safe side making sure the mics can cover wide SPL range.

 

[damien]

Not sure if you have bangers in the room they won't clip, I thought about adding a pad and a low cut in them with micro push buttons on a PCB mounted to the back. Circuit wize it's very easy, just a capacitor to the capsule and a pair of capacitors on the emphasis for the low cut à la MXL603.

You'd get -10dB and low cut at 100Hz.

 

[globalpurpose]

i m curious about this polystyrene cap mod , what value
would You use ???

 

[damien]

i m curious about this polystyrene cap mod , what value
would You use ???

Xicon 23PW210 film capacitors STYRENE 50V .001uF.
https://www.mouser.com/ProductDetail/Xicon/23PW210?qs=LLoUvApQnRQP4Qc1L2vSdw==

I recommend buying several of them just in case because they are very sensitive.

 

[Comakepi]

I just received a 34mm one.



No regret for this price, but look at those low frequencies


FT mesurement with a shity superlux ecm999 as ref micro.

 

[damien]

@Comakepi Mids and Hi are really not that bad, just 2dB bump between 4k-10k is pretty smooth. This 4K peak is also interesting for articulation.
BUT the low end, and I felt that, is generous.
It would just require to change a pair of capacitor to shelve down the 40-120Hz area.

On the usual MXL circuit, you have a pair of 0,22uF capacitor for that purpose to give a flatter response.
If you switch 0,22uF to 0,01uF you'll get a 100Hz Lo-Cut.
Here you have a pair of 104J100 capacitor (0,1uF 100V) on both lines.



I guess if we go lower we should tame that lo-end bump and flatten it.
It would require some tuning though not to lose too much bass.
MXL990 have 0,1nF for exemple.





From https://www.halfshavedyaks.xyz/pcb/BM700-schoeps.php

If we were designing for neutral / flat response without phase shift then C5/6 should be as large a practical. 100nF will give full range bass response when considered purely in terms of corner frequency, but will introduce a low frequency phase shift that extends into the audible range. Increasing C5/6 may be desirable in some uses to avoid this, but the difference is subtle, and depnds on the rest of your signal chain. Conversely if you want a built in LF rolloff you can reduce C5/C6 to make a high pass filter.

In most practical situations for most users having a subsonic rolloff (to avoid rumble and LF noise eating headroom) may be more desirable than phase neutral response. In this case the caps should be kept to 100nF or so.

It is possible to obtain film caps that fit - in values up to 1uF. These should be high quality film caps. I use panasonic ECQV 50v as they sound good to me, and are small for their value. Wima FKP2 would also be a good choice sonically, but they are quite a bit larger and the larger values may be difficult to fit.

 

[damien]

I'll try replacing those cheap 100nF first with WIMA MKP2 to see if a better quality helps with the response. Same with the 22nF, WIMA will be so much better.

 

[pasarski]

@Comakepi
If we were designing for neutral / flat response without phase shift then C5/6 should be as large a practical. 100nF will give full range bass response when considered purely in terms of corner frequency, but will introduce a low frequency phase shift that extends into the audible range.

I'm really not sure if this makes any sense, but it has never stopped me before so:

Are you sure that the phase shift of the electronics isn't actually correcting the phase shift of the capsule? Like in the case where two speakers that are at different height, causing phase cancellation and thus change in the frequency response, to de-emphase that you need to use a minimum phase eq rather than a linear phase eq so you fix both the fr and the phase shift.

I don't know how and if this applies to condenser capsules, but IIUIC the frequency response deviations in capsules are caused by phase cancellations/reinforcements.

Tl;dr: Are you sure phase shift is bad in this case?

Disclaimer: I may have some
serious misunderstandings about the subject

 

[Comakepi]

Two additional measurements for comparison with large diaghragm cheap mics, Studio Projects B1 and AKG C3000



EDIT

But it's always hard at compare two mics cause of placements, few centimeters can change many things, so there i just switch placements and lines of the BaiFeiLi and the Studio Projects ....



So, it seems real difference is the low range, the 3kHz an the high frequencies.
400Hz / 700Hz and 1.3kHz are excluded, cause it's placement difference if my reasoning is correct...

 

[damien]

I'm really not sure if this makes any sense, but it has never stopped me before so:

Are you sure that the phase shift of the electronics isn't actually correcting the phase shift of the capsule? Like in the case where two speakers that are at different height, causing phase cancellation and thus change in the frequency response, to de-emphase that you need to use a minimum phase eq rather than a linear phase eq so you fix both the fr and the phase shift.

I don't know how and if this applies to condenser capsules, but IIUIC the frequency response deviations in capsules are caused by phase cancellations/reinforcements.

Tl;dr: Are you sure phase shift is bad in this case?

Disclaimer: I may have some
serious misunderstandings about the subject

It's not from me but from someone who designs microphone circuits. When he's talking about phase shifting it's probably related to passive RC filter network : https://www.electronics-tutorials.ws/filter/filter_3.html




With 100nF and 150KOhms network you have a cutoff frequency at 10Hz if I understand well and my calculation is good though.

With 0,01uF you have a cutoff freq @ 100Hz. (The same values on the Alctron SDC and MXL when they have locut switch)
With 0.015uF will give you a corner freq @ 70Hz and so on

Please check that you don't have any kind of AC noise hum because the bump happens to be around 50-60Hz... just check your microphone with SMART but without playing white noise.

 

[pasarski]

It's not from me but from someone who designs microphone circuits. When he's talking about phase shifting it's probably related to passive RC filter network : https://www.electronics-tutorials.ws/filter/filter_3.html

View attachment 137628


With 100nF and 150KOhms network you have a cutoff frequency at 10Hz if I understand well and my calculation is good though.

With 0,01uF you have a cutoff freq @ 100Hz. (The same values on the Alctron SDC and MXL when they have locut switch)
With 0.015uF will give you a corner freq @ 70Hz and so on

Please check that you don't have any kind of AC noise hum because the bump happens to be around 50-60Hz... just check your microphone with SMART but without playing white noise.

RC filter definitely introduces phase shift. My point was that when de-emphasing capsule response it maybe doesn't matter, it actually could be beneficial. But I am not a least bit sure about it.

 

[solowiej]

Has anyone tried a side by side with the 25mm and 34mm board versions both swapped to the same type capsule? If I order a couple of these to play capswap with, does anyone think it pays to start with the cheaper model?

 

[Comakepi]

Has anyone tried a side by side with the 25mm and 34mm board versions both swapped to the same type capsule? If I order a couple of these to play capswap with, does anyone think it pays to start with the cheaper model?

I will probably buy a 25mm soon for testing...

 

[damien]

RC filter definitely introduces phase shift. My point was that when de-emphasing capsule response it maybe doesn't matter, it actually could be beneficial. But I am not a least bit sure about it.

I checked and the calculated phase shift for those values are around 0.5 to 1° so, it shouldn't be an issue.
I'll test my "414" 34mm this weekend to see if I have the same 50Hz bump, if it's the case, I'll swap the capa with WIMA, same values, and see if it's better. I'll let you all know

 

[Comakepi]

Please check that you don't have any kind of AC noise hum because the bump happens to be around 50-60Hz... just check your microphone with SMART but without playing white noise.

No hum around 50/60Hz

 

[Comakepi]

I optimize mics placement there... Still a B1 vs C414 FFT comparison

 

[damien]

@Comakepi that's strange.
I don't have calibration microphone, so I can't really give precise answer about that.
I compared with another SDC which has a smooth lo end response and in REW I couldn't see a major bump like this with both my BFL414.

Forget the non linearities from my uncalibrated speakers.

SDC T02AMOD, the low end is pretty smooth until 100Hz and follows the monitor response curve :



BFL414, note that the 50-100Hz is still quieter than the 100-400Hz zone, no major bump here:




Not sure if it can help though but if mine was like yours we would see a shelf like boost in the 20-100Hz area.

Both are based on the shoeps CMC circuit, the sdc has 0.22uF/220nF hi pass capacitors, the BFL414 has 100nF.
The higher the capacitance, the lower the cutoff frequency.

No idea what's happening on yours.