Behringer B1 mods

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LevinGuitar

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I have two Behringer B1 (797 revA) mics to have fun with. They were non working because of a bad solder in some parts, but now solved and cleaned they are ready to mod :)
They already sound very good for the price, chinese market is crazy.

KM84 would be pretty easy here saving the DC converter for the 61v polarization, but with this k67 capsule it wouldn't be so big change to spend time and a transformer.

U87 would be the right thing but before changing all circuit, would like to see what can be done as an easy mod.

First I tried a jumper over C15 to skip the unnesesary capacitor, the sound change is veeery small, but still is: something cleaner, more real. The bad thing is we have a 5v over R16 that now goes to the diaphragm lowering the polarization to 56v (61v-5v), and loosing a bit of gain as result.
(Edit: the gain loose is because of getting the bias off jumpering C15)

Since I have no big idea how a DC coverter works, how could I rise the polarization on backplate to 66-70v to compensate the 5v on the diaphragm? Is there a link maybe that explains this maths?

I attached a schematic of my version (Rev A) with some updates of the schematic I found on web.
 

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kingkorg

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I don't remember specifics, but i remember there are a couple of errors on that schematics. Try 15nf capacitor drain to gate of the upper fet (r13 q6 junction to q6 gate) with stock circuit, and tell me what you think. It might be all you need.
 

LevinGuitar

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Thank you, will try!
For now I haven't found more errors. The R9 was 75k and there were R14 and C16 missing.

Edit: D3 was missing too.

The Q6 and Q7 seems to be Siliconix J305 fets

 

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LevinGuitar

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I have updated the schematic again, with D6 and tried the 15nf cap where you have suggested if I understood you right. There is less high frecuency, not much, but something worth to get rid of, but there are more noise.

I have been experimenting a bit more and found that disconnecting the wire from D3/L1 to 10uf removes a bit of HP filter. Is this possible?

The combination of 15nf, and removing the wire start to make a noticeable difference with a stock microphone and all is easy reversible. But the result is nothing like U87 in anyway, just a lot of low end and still overly bright lacking mids microphone.
 

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kingkorg

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Try to change R20 to 20K, and use the mic with lo cut turned on. This will give you the right shape of the u87 low end. Increasing the resistor to 20K will emulate the effect of deemphasis network in u87 - the low end part, but you have to flip the switch and use it that way. It will no longer have the original function of the lo cut of course. To get rid of more high end just increase the value of the 15nF cap. I also think you have to put that wire back for the lo cut filter to work. It shouldn't affect the high end.
 
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LevinGuitar

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Thank you, will try! I would not increase the 15nf, but instead I have lowered it to 10nf, to reduce noise.

For now, inspired by this thread and your insistence on the importance of the acoustic resonance of the grille shape and so, I tried something in that way. And the result is WOW! That thing really changes the sound, in this case it help a lot to bring mids up. For sure this is not the best shape but it already makes me smile listening the microphone. Will investigate more :)
 

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LevinGuitar

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I found the main problem of jumpering the imput cap, the bias of the fet goes lower! So a better way is just connecting the capsule on the other side of that cap, leavin it where it is.
For the 5v compensation, removing D8 and lowering R9 to 14K gets 65v on polarization, solved :)

I tried 15K on R20 (other day will try 20k) and with the low cut connected and turned ON it seems to make the mic sound nicer, thanks!

Still with that 10nf connected and the headbasket dampering this mic now sound as good or in some ways better than a stock NT1000, still a bit brighter and a bit more noisy but not problematic.

Not bad for an "easy mod" :)
 
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LevinGuitar

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I had some noise issues connecting the capsule directly to the fet, but not sure really why, so had to turn it back to the original configuration. But I also tried to make a "K103" attempt dampening backplate holes to a damaged B1 (still holds the capsule quite good with just one screw) and it went quite sucessfully :) No harsh highs and still a lot of low end! Its not so easy but worth to experiment with a cheap or bad microphone!

I wonder if Rode capsules also have the membrane glued to the ring like this 797 k67s

Edit: Still have noise issue, so that was not because of the circuit mod.
 

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kingkorg

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I had some noise issues connecting the capsule directly to the fet, but not sure really why, so had to turn it back to the original configuration. But I also tried to make a "K103" attempt dampening backplate holes to a damaged B1 (still holds the capsule quite good with just one screw) and it went quite sucessfully :) No harsh highs and still a lot of low end! Its not so easy but worth to experiment with a cheap or bad microphone!

I wonder if Rode capsules also have the membrane glued to the ring like this 797 k67s
No idea if they glue the mylar, if you find out let me know.
 

LevinGuitar

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I have one capsule from NTK that makes strange things, in the original mic it made the bias off (and a lot of noise) so guess it have some internal short? Was thinking of "opening it" and give a look inside, but can't believe this can be an internal issue because of the QC of Rode capsules, must be missing something easier.
 

Khron

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I have one capsule from NTK that makes strange things, in the original mic it made the bias off (and a lot of noise) so guess it have some internal short? Was thinking of "opening it" and give a look inside, but can't believe this can be an internal issue because of the QC of Rode capsules, must be missing something easier.
I'd try that capsule in another mic first, to rule the electronics out as a suspect. Then you'd know if the noise comes from the capsule or not. Or were you implying that another capsule (already) works well in the NTK?
 

LevinGuitar

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Yes, I tried other k67 capsule and the NTK went ok, today I briefly tried the NTK capsule in other mic and it almost did not work, sound came randomly when shaking the mic, like if there was bad connection somewhere, but it could be my fault also, will check the leads (I have checked for continuity between backplate and the frontring and there was none and the capacitance is around 100pf)

The capsule is in great looking condition btw
 
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MicMaven

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Perhaps I am not the only one who finds the B-1 a bit dark, bass heavy and not especially articulate in the mid- to higher frequencies. I twice replaced the original B-1 capsule with $25 Chinese capsules acquired on eBay.com, finding both of them more open, airy, and articulate (crisp?) in the mid- to higher frequencies (which, I believe, is as expected?) I found each replacement capsule - a) more sensitive with substantially increased output, and b) slightly more noisy, with some high end hiss, and less bass rumble. I eventually restored the original capsule, and consider selling the B-1 because I have assembled alternatives using the "world renowned" OPA Alice boards and a TS capsule, which (to my ears, anyway) sound cleaner, more open and expansive, more articulate, and quiet. At least that is my current impression. Any traction? Happy trails to all. James - K8JHR
 

LevinGuitar

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I haven't used the B1 in a pro recording but can't be happier listening the test of the last experiment. Definately worth it, but also is a delicate work dealing with capsule diaphragm and the holes.
Even just dampening the grille resonance makes an improvement, but in a different way, flatter, for voices I prefer the capsule mod with the dampening too.

How much will you get for it? Make a good sounding mic instead :)
 

LevinGuitar

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Today I tried with a B2 pro capsule. I have to insist that this is a delicate thing to do!
Maybe not the best K103 attempt, but still funny to experiment and the result sound nicer than the original with that circuit. Around 0.5db less output but with same noise level is not problematic.
 

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dima_k85

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The ring groove was originally needed only for the exit of the turning tool, which lowers the working plane by 40 microns. Then Neumann refused this lowering in favor of a spacer. Currently, this groove only reduces the edge effect of membrane vibration at extremely high sound pressure levels. In fact, it is not needed.
 

kingkorg

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The ring groove was originally needed only for the exit of the turning tool, which lowers the working plane by 40 microns. Then Neumann refused this lowering in favor of a spacer. Currently, this groove only reduces the edge effect of membrane vibration at extremely high sound pressure levels. In fact, it is not needed.
This is not true. The groove has an effect on dampening of the diaphragm and changes significantly the frequency response. More air behind the diaphragm - less dampening. Another reason why what you say makes no sense is that diaphragm is barely moving ar the ring area, simply because it's too close to the edge. This area is not affected by high spl.

The only reason i'm replyin to you is so that people don't get thrown in the wrong direction by your misinformation. It is beyond me why you spend so much time trolig this forum.
 

LevinGuitar

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Edit: this was a reply to a deleted post from Dima


Please, be respectful, all ideas and knowledge are welcome, but no need to offend!
Most of us aren't using their first language, so maybe someone get lost, misunderstand or explain wrongly something (as I do many times).
 
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