I want to build a stereo U48 type mic

[zephyrmic]

And a collection of the LDC mics I have made so far.
zephyrmic

 

[Nollman]

Hey Zephyrmic, nice work! To make that grill I set up to do the radial cuts with a rotary table on my Mill/lathe with the cross slide locked in place. I do a rough cut and then a cleaner final cut taking off about .005" on the second pass then moving to the next horizontal cut.  Then I set up the vertical  cuts 90 degrees to the first cuts (across the mill/lathe) again with the cross slide locked in position (no movement from the feed-drive mechanism). I was careful to make all of the cuts feed into the cutter so left side cuts fed toward me and right side away. I did a rough cut and a final cut here as well. It was a nightmare of setting up for each cut and it took about  4-1/2 hours to finish with only a bit of clean-up with a file.  I hope this is the last stereo mic I make. LOL

 

[Nollman]

Here's my first DIY mic project, a C24

 

[Nollman]

And my M251

 

[Delta Sigma]

WOW! Looks great Nollman. I was shocked to see how nice the C24 looked and more shocked when I saw the 251!

What did you do for your C24 capsule mounts? Did you make them yourself?

 

[Nollman]

The C24  has Tim Campbell Capsules that come with the metal yoke. I installed them on top of posts I got from Funkenwerk to get more height from the baseplate. The guys at TAB Funkenwerk have been super helpful in all of my mods and projects. That C24 was my first total DIY project.  I had to turn all of the parts on the lathe which is a pretty new machine to me.  The top capsule rotates 180 degrees so I can get different patterns. I need to paint the back grill black so I can tell at a glance which way the capsule is facing, it's confusing now without that feature.

 

[dougch]

Wow Nollman! I love your work. I'm interested to know how you approached the pattern switch on the 251. Also, how does one make a rotating head for a c24? Great diy.

Doug

 

[dmp]

Great work in this thread on real mic DIY.
Very impressed.
Curious what you are using to hold the mic body while milling? Do you have a XYZ adjustable mount?

 

[Nollman]

DMP, I use a rotary Table with a 3-jaw chuck bolted to the cross-slide of my Smithy Mill/Lathe. That gives me X-Y-C (circumference)axis.
dougch, The rotating head is joined in the center by a screw with a bushing for the wires to wrap around and a channel around the edge with a pin and two stops in it (0 and 180 degrees). It has a couple sections of brass tubing soldered inside to keep the wires in place and is  like a more primitive version of the AKG C24. I made it with 2" tubing so I wouldn't have to struggle with tiny little parts and my 251 used the leftover body tube. The head grill on the 251 was a PITA. I had to make dies to stamp the mesh into shape, not fun. The switch was tough too, it's acrylic body with a rotor and 9 brass button shaped contacts on one side, three brass tabs with springs under them on the other. It falls apart if you unscrew it and it takes forever to get it back together. LOL but it all works somehow. I wish the engraving guy I used put the polar patterns in the right place. that bothers me but the body tube was super easy to make out of everything else I had to re-invent.

 

[Nollman]

I took the time to turn some dies to stamp the headgrill mesh. I'm pretty happy with the result, now if I can only get the solder right. Does anybody use a soldering iron for these? I have  a 40 watt adjustable that is not even close, a 100 watt "gun" type which is really slow and messy and a 200 watt monster iron that was way overkill on the M251 I did. I tried a propane torch and burned the mesh so any advice about solder type and soldering irons would be very appreciated.

 

[Nollman]

And the Headgrille is done, mostly... I still have to drill the mounting holes.

 

[dougch]

Looks great! You do quick work.

 

[Nollman]

My Solution to the WAAAY overpowered soldering iron was to make an outlet box on a dimmer to turn the power down a bit. It worked great!

 

[dougch]

May I ask what size mesh you are using?

 

[Nollman]

There are 3 layers. The outside is a coarse 10 strands/inch .025" thick, then a fine layer 40 strands/inch .010", and finally a medium layer  of 18 strands/ inch .017" . It's as close to Neumann specs as I could find materials for and looks really good. It's brass instead of the traditional bronze mesh. I'm mot sure if that makes a difference.

 

[Nollman]

Zephyrmic, you inspired me to build a uni-body style U47FET reminiscent of what you do. I like the clean lines and simplicity. Here's my day's work

 

[zephyrmic]

Very nice!! I don't have a lathe, so all my work has to be by hand.
Cheers,
zephyrmic

 

[Nollman]

Zephyrmic, do you solder the mesh or metal grill in place?

 

[zephyrmic]

No. I was not able to do that, so I bared the lower mesh, already spray painted before fitting,  which is a tight fit in the body, and then glued it in place where it joins on the vertical, as well as spots on the top and bottom of the mesh. The mesh was made by rolling it on a former to make a cylinder that fits neatly into the body. For the top, I made a die, not as glorious as yours, but it works, and after forming the mesh top, I cut it to fit neatly in the top. Glued in as well. Then I made sure I had bare metal contact to th mesh as the rest to the  innards slide in to the body, and a thin copper flat spring to maintain contact. With any of the mics I have made, I have had no trouble with the mesh earthing to the body. Hope that helps.
Kind regards,
zephyrmic

 

[Nollman]

  Thanks for the detailed response. I was curious how you would have soldered so far into the tube.  I ended up soldering the three layer mesh in. The first, biggest layer first then the fine and medium layers were soldered to the first mesh layer together after tinning them.  It was really tricky to solder the top on from the outside without dripping solder onto the lower layer. I soldered the three layers of the top together then squeezed them in the die until they would just fit in to a piece of similar stock as the body tube. I then ground off any excess mesh and solder and just set it into the top of the tube. There are a few spots where solder wicked up into the fine mesh a bit higher than I would have liked. I hope the nickel plating hides some of it but if not, it still looks pretty great.