47FET capsule?

[OneRoomStudio]

By the way, I don’t want any of this to come off as me attacking or criticizing you, @kingkorg. I have nothing but respect for you. I’m just trying to get to the bottom of the issue and understand it. I was always under the impression that the FET47 circuit was responsible for the difference in sound, and it’s certainly a different enough circuit from the U47 to seem that way. If you say it’s not the circuit, it has to be some other part of the equation. I’m just wondering what that could be.

 

[kingkorg]

You said, “K47 in FET47 doesn't have full bass,” but you also said it’s not the circuit, and you also said, “14v most certainly will not cause any audible effect in this case.” This leaves the head basket. Are you saying the FET47 head basket causes low frequency roll off as compared to the U47? Or something else?

I'm trying to help, i know my replies can come off a bit harsh. I guess i have my own weird way of using English.

There are many aspects that can affect bass response of a capsule. No, it is not the circuit, and not the polarization voltage, and most certainly not headbasket when it comes to low end response. The typical capsule found in FET47 has low end roll off due to it's tuning which might or might not be different to the ones found in u47. Due to ageing, different variations and tolerances.

The point is that you are comparing old tube microphones that have most certainly drifted over time, which might have had M7 capsules, to FET47 mics that are couple of decades younger and spent their "life" in front of a different source, and use slightly or totally different capsule (m7 vs k47 vs one sided k47 ) which is selected for cardioid operation, quite possibly discarded because unmatched sides. Yes, k47 for FET47 were selected for one-sided operation, and the sides don't have to be necessarily matched.

And then there's Maiku capsule which is brand new, out of spec, and simply won't give the same results.

I don't think there's direct answer to your original question simply because even if we had original Neumann's FET47 capsule, it wouldn't necessarily sound like the mics you refer to. There's no one u47 sound to refer to at all, and FET47 is whole different animal including the capsule used in it. It has nothing to do with the circuit besides FET's higher SPL capability. Neither Maiku or flat k47 wil give you spot on FET47 sound, to my knowledge there's no accurate FET47 capsule available at the time besides Neumann's.

Good news is that they are all k47 of the right construction, and using EQ to bring them to wherever you want wouldn't be much different than using an original with an EQ. Not like you are trying to EQ u87 into u47...

The other option is to do the capsule rolling thing until you stumble upon the right one.

 

[OneRoomStudio]

That makes sense. Thank you for going down this rabbit hole with me

I supposed I’ll have to live with EQ for now, unless there’s a chance that @soliloqueen will have some “b-stock” of the new “historic” K47’s when they’re released!

 

[soliloqueen]

the k47 is, in general, just an all-over-the-place capsule. I've heard them sound totally smooth, have huge peaks at 5khz, sound band-passed, etc. consistency-wise, they're kind of a mess. they changed all the time back in the old days. it's a very "picky" capsule design to how it's put together. i had a few flat k47s where the through holes were about 0.04mm too narrow and a hissy fit was thrown by the response of the capsule. it's probable that these differences between neumann units could be due to the thru holes being different as the tool wears down, or all sorts of things.

 

[kingkorg]

the k47 is, in general, just an all-over-the-place capsule. I've heard them sound totally smooth, have huge peaks at 5khz, sound band-passed, etc. consistency-wise, they're kind of a mess. they changed all the time back in the old days. it's a very "picky" capsule design to how it's put together. i had a few flat k47s where the through holes were about 0.04mm too narrow and a hissy fit was thrown by the response of the capsule. it's probable that these differences between neumann units could be due to the thru holes being different as the tool wears down, or all sorts of things.

On vintage M7 i work on currently backplate thickness varies from 5.478mm to 5.550mm towards the edge at various places. This was not intentional by any means as it's random, and the whole capsule is somewhat skewed. This is 72 micrometers of diference at different points! HUGE!!!

 

[soliloqueen]

On vintage M7 i work on currently backplate thickness varies from 5.478mm to 5.550mm towards the edge at various places. This was not intentional by any means as it's random, and the whole capsule is somewhat skewed. This is 72 micrometers of diference at different points! HUGE!!!

gap cut neumanns are gnarly. I've seen them go from 35 to 50 micron off the diaphragm in a single unit at their worst

 

[LevinGuitar]

Maybe playing with the values of C1 and C7 could bring you closer to the sound you are looking for? Of course, with an original k47 (fet or no fet, or even k49) capsule. I have some used ones and they sound great and bright