Best capsules with a diameter of less than 18mm?

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TheFibs

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Nov 5, 2022
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I recently began repairing a mic. It has a very narrow body and the opening through which the capsule will pass is around 19mm, so ideally I need a capsule with a diameter of 18mm or less. Does anybody have any suggestions? Had a look at some of the primo capsules like the EM200 but its quite pricey compared to other capsules of the same size and maybe you guys had a better suggestion.
 
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Primo, Primo, Primo! I can see how em200 could seem expensive, but that capsule sounds like a 400$ one. I'm amazed by how good Primo capsules are. Small cardioids tend to suffer from low end lack, Primos are the only ones so far that have no issues with this. Even the smaller ones. I gutted recently a Zoom mic for three capsules that seem to be Em415n. I'm making 3 tom mics out of these, tiny, great low end and phenomenal rear rejection.
 
Primo, Primo, Primo! I can see how em200 could seem expensive, but that capsule sounds like a 400$ one. I'm amazed by how good Primo capsules are. Small cardioids tend to suffer from low end lack, Primos are the only ones so far that have no issues with this. Even the smaller ones. I gutted recently a Zoom mic for three capsules that seem to be Em415n. I'm making 3 tom mics out of these, tiny, great low end and phenomenal rear rejection.
Yeah a lot of people seem to be of that advice. If they are that good I guess 40£ is actually a bargain lol. Thanks! Now to find a suitable circuit for it.
 
Primo, Primo, Primo! I can see how em200 could seem expensive, but that capsule sounds like a 400$ one. I'm amazed by how good Primo capsules are. Small cardioids tend to suffer from low end lack, Primos are the only ones so far that have no issues with this. Even the smaller ones. I gutted recently a Zoom mic for three capsules that seem to be Em415n. I'm making 3 tom mics out of these, tiny, great low end and phenomenal rear rejection.
I just did an orchestral recording with Rode NT45-O mains and a pair of EM200-based mics as spots; the tonal quality of the two pairs was indistinguishable! I must say it took me quite by surprise.

It was Mahler's 4th, and I'd spot mic'd the soprano soloist. During the post mix, as I slowly raised the level of the spots her voice didn't change at all, it simply 'moved' closer; no EQ was required at all to match the two pairs. My jaw hit the floor. These were my attempt to simulate the Schoeps V4U, by putting the EM200s in similar-sized beveled rings, that I posted about awhile ago.
https://groupdiy.com/threads/cool-use-for-primo-em200-204.78994/And, boy do those things have reach - they sounded like they were about 3' away but look in the photo how far they were (they were vertically-spaced 7") - ignore the handrail that is several yards behind.
 

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You would probably want to change the value of the mic FET biasing resistors.

Because I'm lazy, for my EM200s I just used the circuit boards out of Audio Technica AT841 boundary mics that I got cheap on eBay - they provide the recommended 5V; I just changed the FET source load resistor to 5.6k. For optimum results you'd want to adjust the resistor values to properly bias the actual capsules you have.

This is the biasing Primo recommends on the data sheet (it's the same for the EM200):
 

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Where do you see that? The data sheet just says 5V.
Whoops yeah. Deleted the message instead of editing. Yeah I’m pretty sure I saw somewhere that it was supposed to be between 5-10 and the optimal operating voltage was 5V. Don’t remember the resistor value.
 
kingkorg will have more deets - he's experimented with these more than I have; including the use of modified EM200 in the Line Audio CM4.
 
Whoops yeah. Deleted the message instead of editing. Yeah I’m pretty sure I saw somewhere that it was supposed to be between 5-10 and the optimal operating voltage was 5V
kingkorg will have more deets - he's experimented with these more than I have; including the use of modified EM200 in the Line Audio CM4.
Found this on the micboosters store https://www.micbooster.com/documents/EM200.pdf
It does indeed only say 5V and I don’t remember where I found the other data. Resistor bias seems to indeed be 5.6k ohms if I’m reading it right, which I very well might not. All I need to do is design a pcb which will fit into the extremely narrow body of the mic I’m fixing and adapt those schematics to fit on it.
 
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You're reading it right: 5V to the drain term, and 5.6k to ground on the source.

I simply added a switch to my AT841 boards to select the original 20k source resistor (for use with any of my many mics built with 2SK660 FETs) or 5.6k for the EM200 (or the EM273s in my stereo boundary mic I use for field recording).
 
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You're reading it right - 5V to the drain term, and 5.6k to ground on the source.

I simply added a switch to my AT841 boards to select the original 20k source resistor (for use with any of my many mics built with 2SK660 FETs) or 5.6k for the EM200 (or the EM273s in my stereo boundary mic I use for field recording).
So on the schematic Korg posted I’d change R5 to 5.6k, right?
 
R5 and R2 should be the same. So change both if needed. I just played with some salvaged bm800 boards, which are essentially the same circuit. They have 2.2K resistors there and work just fine. I don't think you should obsess much with absolute voltage/resistor values here, but feel free to experiment. The value of the resistors will depend on particular fet in the capsule.
 
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@kingkorg: Always the same suboptimal circuit :cry: R2 produces a lot of thermal noise and lowers the SNR significantly. This may not be audible for the cheap WM61 capsules but plays an important role when using the Primo EM200. Try to short R2 -> Signal output decreases by approx. 5 dB and A-weighted noise decreases by approx. 8 dB.
 
@kingkorg: Always the same suboptimal circuit :cry: R2 produces a lot of thermal noise and lowers the SNR significantly. This may not be audible for the cheap WM61 capsules but plays an important role when using the Primo EM200. Try to short R2 -> Signal output decreases by approx. 5 dB and A-weighted noise decreases by approx. 8 dB.
I get you, but this is typical schoeps circuit, i've never had an issue with noise. Nor do i know anyone who has.
 
The EM200 is worth every penny Micboosters is asking for them; I expect soon the price will go up.

https://micbooster.com/microphone-capsules/138-primo-em200-cardioid-electret.html
There isn't really anything else available that's that flat, that small, that quiet, and that affordable.

I guess Micboosters is charging more for the EM204 because for most hobbiists it's easier to use, but the EM200 is capable of much higher performance, especially if they're used for close-mic'ing. It's not surprising that Line Audio put all that effort into 'hot-rodding' them.
 
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Um ... so let's assume one does not use a Primo capsule ... is there a decent one from JLI / Tansound that will do a good job? Reason I ask, is I am repairing an old pencil style microphone and wonder if any of the JLI offerings would be good enough. Intended use - mostly vocals (speech) and occasionally acoustic guitar. Any ideas ... or should I spring for a Primo offering? Thanks. James - K8JHR
 

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