[kingkorg]

Obviously there are solutions like this, which are very simple to try out.

However i strongly believe these spheres should not be used with hyper or cardioid mics, as it leaves an empty resonant chamber behind the capsule.

Since the holes of backplates are not sealed i can not imagine what kind of havoc it would do to FR of the mic, let alone pattern response.

[bremusound]

The version i am talking about.

This capsule is also used in the KM83, KM130 and KM183.
‚Honeycomb‘ reflectors are also used in Schoeps capsules.

[lampas]

Not realized yet, but I bought this:
https://www.ebay.com/itm/40mm-Diameter-Solid-Round-Acrylic-Sphere-Plexiglass-Ball-Ornament-Clear-5pcs/183144669862?epid=18002459477&_trkparms=ispr%3D1

and

thought about this:
https://www.ebay.de/itm/Oktava-MK-012-Omni-Capsule-Stereo-Pair-Silver-Brand-New-Free-Shipping/220400195022?hash=item3350e015ce:g:ovAAAOSwB0hcfEMp


I think that this would be the best price performance combination. The only thing I don't know, how much polarization voltage this capsule need.
Would be voltages from M50 schematics sufficient ?

Thanks

[kingkorg]

If it's 57v as specified in schematic, it should work just great.

As i used ST51 for this experiment 40v was a bit low, some noise issues at distance.

So i used an extra DC-DC board i had from Behringer B2 to get 60V, and it works great with my capsule.

edit:
Now that i am actually looking at the schematic for the first time, as i was going for Fet version, i see that 600pf cap anode to ground. Hm...

[kingkorg]

40mm ball arrived today, so here's an update.

[lampas]

40mm ball arrived today, so here's an update.

Looks great. Where did you get it ? And sound ?

[kingkorg]

https://s.click.aliexpress.com/e/oSIraolT9 

I have no m50 to compare it to, but it measures exactly as it should, and sounds great.

As it's meant to be a far mic the circuit is afjusted for lowest noise, not highest headroom.

So the capsule is polarized at about 80v, fet rebiased for highest output. It is very low noise, in range with my Shure KSM44.

[kingkorg]

Better late than never. So here's shootout of some of my ''clones'' against this fet version of M50 with my diy capsule.

I think the goal is achieved and it does what it's supposed to. It ''grabs'' wonderfully high end at distance, which is obvious on hi hat, and low end response is better that LDCs in the shootout. This is exactly opposite of stock capsule which was all midrange, and sharp peak at 8k, which doesn't exist any more.

My clones used in this shootout are u87, u67, u47, m50 and ECM8000 as a refference mic. All of which in omni mode.
Bear in mind it's not one take, it's one for each mic.

https://app.box.com/s/sxy3j8o6gvhsb5kz9g6jecsu7a0xamht

[stelin]

Is it really that simple to convert a cardioid capsule to an omni capsule,
by just blocking the holes in the (plastic) second backplate?

In the Neumann book "Microphones" at page 27 there is a picture of how different types of capsules are "tuned" (and why).
Condenser pressure microphones have a diaphragm that is "high frequency tuned", condenser pressure gradient microphones have a diaphragm that is "mid frequency tuned". 

This is also the reason why condenser pressure microphones are less susceptible to disturbance by wind
and body noise, footfalls, handling noises, etc. The diaphragm is "stiffer".

Any thoughts on that?

[kingkorg]

Well it isn't just closed at the back, there is a ball around it that does it's own thing. The pattent documents explain it in detail.

Also, the m50 capsule is not purely omni, its directivity is changed through the frequency spectrum, and it's unique mix of omni and cardioid.

I don't have the original capsule to compare it to, but the measurements i have taken and posted here confirm that it behaves as it should.

[kingkorg]

Btw, it is a piece of cake to tune this diaphragm tighter if one has gold plated mylar, i have done it several times. No tools required. It does make sense for some capsules, but diaphragms for km84 and similar Neumans don't have higher tensioned diaphragms for omni capsules compared to cardioids. One of the M50 versions has just km84 type capsule stuck into a sphere, just like this one.

[wlinart]

I'm also planning on building the M50's. Lately i'm doing some orchestral work, and a nice decca tree of M50's would be nice.
I'm taking a little different approach, which is closer to the original, but of course more expensive.
I'm taking the KK83 (KM83 capsule) and put a sphere around it. In some of the original M50's there was this capsule installed, so it's bassically the same. And the KK83 capsule is sometimes easy to find. I paid about €600 for 2 pieces, which is reasonable IMO.

[ln76d]

Nice work Matija!

Did you considered to make metal "ball" with mesh and leave it opened without outside headbasket?
It could work and definately it would look fantastic. I love IRT V30 visual design. There of course head wasn't to create omni pattern but i belive it could work this way.

[kingkorg]

Great idea!

Neumann M50

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