DIY fig-8 'minis'.

[k brown]

Inspired by this post from analogguru Multipattern electret?, I decided to get a pair of the Shure AMS26s and put back-to-back AT853 capsules in them, for super-compact figure-8 spot mics (I haven't received the Shures yet, but I expect they have some cheap little aluminum-case capsules in them; they're only intended for speech).

After cutting away the 853s' black plastic cases, which mainly serve to act as 'stops' when screwing the capsules onto the mic bodies, I soldered leads to both center pins, then soldered the brass housings together.

Checked out just great in a test body.

Should fit very nicely in the little Shure mics, after major mods to the capsule holders.

I've actually recorded Classical chamber music concerts with nothing but a pair of these tiny 853 cardioids, when minimum visibility was called for. When coupled with much better electronics than they are supplied with (they were designed mainly for reinforcement/installed sound), the capsules themselves are capable of quite good sound; they're just rather noisy, but not noticeable in a live concert. 2-micron gold diaphragms in machined brass housings.

Thanks analogguru for the terrific heads-up! I knew nothing about these Shure mics.

 

[k brown]

Success!

The Shures finally arrived, gutted them and got the two little AT853s installed. Was able to adapt the stock capsule holders.

At first I thought I might just use the capsules they came with; appeared to be fairly high quality - not the aluminum cheapies I expected. Just under 1/2", machined brass and gold diaphragms. However, when tested with known good electret circuit, level was extremely low and noise was extremely high (?).

Only hiccup was, the coarse mesh of the head grilles was insufficient shielding for the ungrounded housings of the back-to-back capsules, so had to wrap them in fine mesh.

Got a pair of them built - they perform just as expected; will be some very handy tools - 'cause there's no way I'm ever going to afford a pair of these (or the bodies to put them on):
https://www.sweetwater.com/store/detail/MK8g--schoeps-mk-8
Thanks again to analogguru for mentioning these Shures which I'd never heard of - perfect for this project.

 

[k brown]

Turns out the original 1/2" capsules were a little better than I thought - so happens the only one I tested was defective (maybe why the mic was being sold).

Though very noisy, they have very flat, smooth response; no high end crunchies at all.

A construction I've not seen before - ground/body terminal is a solder tab, but the center terminal is a component lead socket that the FET pin plugs straight into. Also unusual rear vent is just a single hole on the center, with very fine metal mesh under it. Rear response sounds quite flat.

I wonder if Shure used these in any other mics; since the AMS mics were intended for speech only, I wonder if these were capsules designed for better mics, and these were examples that failed noise testing. Just seems surprising they would use such a well-built, smooth-sounding capsule in such an undemanding product, rather than a generic stamped aluminum job.

Now - what to do with these? . . .

 

[k brown]

New 'tuxedo' livery for these; inspired by the Beyerdynamic line, which I always thought were very handsome designs.

 

[k brown]

Just wanted add @analogguru, so he sees my thanks on this thread.

 

[TromNek]

I'm looking to build a similar mic, but I want a single bi-polar capsule.
( I can't afford a nice MK8 capsule either )

I was wondering if the Mid inside the shure MK88 is a single capsule
Or the Zoom AM7, Zoom MSH-6 add on mics

Has anyone ever taken any of these apart to see what's inside ?

 

[k brown]

It's possible one or more of them is using the Primo EM283.

https://drbadphil.com/category/diy-projectshttps://micbooster.com/microphone-capsules/168-primo-em283-bi-directional-electret-capsule.html
But fear not the back-to-back cardioids approach - it was used in one of Neumann's most highly regarded mics, the KM 86.

http://recordinghacks.com/microphones/Neumann/KM-86

 

[TromNek]

the Primo EM283 specs seems a little noisy. Does anyone have practical experience?

I use figure 8 to record guitar and vocals at the same time. With the vocal mic null pointing at the guitar and the guitar mic null pointing at the vocals.
I'd like to use a nice sdc figure 8 to record the guitar. But I need low noise for nylon string guitar while I sing.

 

[matt milton]

Reviving this thread... I will hopefully be able to share experiences using the Primo fig 8 capsule soon. Nick Roast of micboosters is going to make me a custom figure 8 clippy using the capsule (when he has some spare time). It does look like a noisy capsule - but, interestingly, it's the same reported self-noise as the AKG Blueline CK94, which many sound recordists use unproblematically. We'll see.

@TromNek: the best separation I've achieved so far when recording guitar and vocals has been by using a clip-on instrument mic (the audio technica ATM350C, which is now discontinued and replaced by the AT Pro 35). I remove it from its foam enclosure and use blu-tack to put it directly on the guitar at the bridge pointed at the soundhole. I use the mic's roll-off switches (on its battery pack) to roll off the bass. This achieves better separation than I've ever had by using the figure 8 method - I record in an untreated bedroom so I can only assume that the room is just too reflective for using figure 8 mics. It takes a lot of experimentation of placement to find the good spots on the guitar's body, but the bridge area seems to be the brightest and least boomy. It doesn't sound like the mic's on the guitar's body, it sounds surprisingly more natural than that.

The attraction of the Primo EM283 for me is that it is so small - I'm hoping to use it right up close, though figure 8 proximity effect might compromise that.

I've also found that dynamic omni microphones are my next best option. They are very bright for dynamic mics. They don't have a lot of bass to them, and they don't have any proximity effect. So you can put them right in front of the soundhole. I find the Electro Voice EV635a sounds best - sounds very natural on acoustic guitar - but the AKG D230 and the Audio Technica ones (I forget the model names) also work well. Great thing about dynamic omnis is that there's usually at least one going cheap on eBay or Reverb at any given time. My current working method is pairing the EV635a just to the side of the soundhole with the lavalier mic by the bridge.