Turning a Sennheiser MKE10 into a PZM

Hi,

I thought that may be worth a try.
I started with a Sennheiser MKE10 lavalier mic, a scrap piece of Wenge-wood (think Warwick bass necks) and 1,5mm brass sheet.




I then routed the cavity for the microphone and a cover to hold it firmly in place. I don´t have a milling machine so I used a Dremel mounted on a small "router base" as sold through Stew Mac guitar shop supply. A handy little gadget.






And the finished PZM




Since I had sufficient wood I made two of them. Those mics are nice for stereo recordings.


Professional PZMs have irregular shapes and the capsules placed out of center to avoid audible artfacts caused by diffraction of sound waves from the plates´ edges for example. The Neumann and Schoeps PZMs were constructed using computer simuation. Mine were made using just improvisation by hand  I simply made one and used it as template for the second one.

Wenge is a very hard (reflective) wood. I made the surface directly surrounding the caspule from brass to give it even better reflective properties for the highest frequencies. Again those brass disks are not round but have a slightly irregular shape.
I´ve done test recordings at jam sessions and I´m positively surprised about the sound qualitiy these mics are capable of.

Merry Christmas everybody!

I like it, and they look amazing. 

Cool project!

I'm a true sucker for wood to begin with. 

And I think boundary mics are under-represented here (or in general).

A little extra on wenge. It is indeed a  very dense and hard wood. A possible con is that is has really large pores.  Those can be filled (to some extent at least). And the brass insert here seems like a good idea to me.

Also, wenge is among the most resonant of woods, on par with some of the rosewoods. This can be a good or a bad thing. If the wood is loosely placed (not fixated) on a flat surface, it will start singing when the main resonance/frequency of the piece happens to hit it. This might be something to watch for. That said, metal can be pretty resonant, too.

As always!

GREAT WORK

Hi,

happy new year!

Yes, wenge has quite large pores, they can be seen well in the first pictures above.
I filled them with epoxy on the reflective upside of the plates, sanded and polished it for a smooth surface.

I thought about glueing brass sheet on the bottom to make it more sturdy and decrease possible resonance effects. But before thinking too much about possible theoretical stuff I simply did a real world test run.

I recorded a Trad Session using a Zoom H6 recorder. I took a picture during a break.


That´s how it sounds:
https://www.dropbox.com/s/xftezicoa8wp5rp/Trad%20Session%20MKE10%20PZM%20Wenge.WAV?dl=0
It´s the straight recording, no EQ.

There was a harp player too:
https://www.dropbox.com/s/xso6i4me9kp6j44/Harp%20MKE10%20PZM%20Wenge.WAV?dl=0



No U47s or 1073s but still usable IMHO   
I don´t notice any disturbing resonance artifacts.
The mics lay on the floor on their bare wood surface, not even felt padding in between...

Works for me.

Thanks for the update. This is what they are made for. Looks like you guys (and gals) had some fun, too. 

Good to hear the results were satisfactory. Unfortunately, the music won't play on my system (yet?).

I don´t notice any disturbing resonance artifacts

Click to expand...

That's good news, as well. No 100% guarantee it won't ever happen, but you'll know if it does.
Did you have any problems with the stone walls and floor? Well, in any case they'll add liveliness.

Anyway, good to see some boundary mics at work. I really like the principle to begin with and your tasteful build only adds to it.

Sorry to hear it doesn´t play on your computer. There might be an unrequested popup window in the way. Just click on "Nein danke,..." at the very bottom. Optionally you can download the files (48kHz/24bit) via the button "Herunterladen".

I like that particular room very much. It´s lively in a nice way. There´s a structured wood ceiling and one wall is actually a rough rock face! A nice natural diffusor 

I attached a pic of that wall taken on a different session (only visible logged in for some privacy protection of the shown people and of course the dog)

I did the recording just for me to memorize the event. There were great musicians from Ireland, Germany and Italy present and it was rare pleasure to play with them.

BTW, I used a different pair of MKE10 mics here. I soldered them to a 3,5mm stereo plug. They need just 3V and can be run with "Plug-in-power"-inputs. Not professional but really handy!
The ones shown above have DIN connectors and are used with phantom power converters (e.g. Sennheiser MS14P).

Wow, some cool rock!
No, not as in music style.  ;D

The stone floor is dead flat obviously, but there your boundary mics will prevent comb filtering. 

The girl with the pipes is looking kinda sad and dreamy or introspective.
Makes me wonder what the guys with the fiddles were playing there ...

Beautiful!

Wow, really beautiful recording!
What a nice room and great project!

I just picked up a pair of mke10 with ms14p specifically to do boundary mic applications.
(they should arrive in a few days)
So, I'm rebooting this thread to ask;

MS Vienna,
Any further ideas or thoughts about this ?
Would you do anything different if you started over again ?

I'm thinking to create a variety of mounting options.

• Small mounts similar to what you did
  • Any further ideas about this?
  • In your practical experience, do you really think the following is significant ?
    • Professional PZMs have irregular shapes and the capsules placed out of center to avoid audible artifacts caused by diffraction of sound waves from the plates´ edges
• Both of them mounted on a single larger board
  • I'm thinking a 1 meter by 2 meter MDF board. To hang on a wall or lay on the floor.
    • I can do a variety of placements within the board to experiment with stereo imaging
      • I record mainly in my (cluttered) living room with is not acoustically 'sound'. But I could go to other venues with it to experiment.
      • What might any of you think are placements that are worth investigating ?
• Embedded in my living room wall
  • This would be real nice to mix mix with my close mic'ing to get some room into my recordings

Thanks
I'd like to hear everyone's ideas and suggestions and thoughts

The mics look pretty good,
congratulations

Just to pick the nit a bit here - these are not PZMs (Pressure Zone Microphones), but BLMs (Boundary Layer Microphones).

Bee-yoo-teeful work, though.

TromNek said:

I just picked up a pair of mke10 with ms14p specifically to do boundary mic applications.
(they should arrive in a few days)
So, I'm rebooting this thread to ask;

MS Vienna,
Any further ideas or thoughts about this ?
Would you do anything different if you started over again ?

I'm thinking to create a variety of mounting options.

• Small mounts similar to what you did
  • Any further ideas about this?
  • In your practical experience, do you really think the following is significant ?
    • Professional PZMs have irregular shapes and the capsules placed out of center to avoid audible artifacts caused by diffraction of sound waves from the plates´ edges
• Both of them mounted on a single larger board
  • I'm thinking a 1 meter by 2 meter MDF board. To hang on a wall or lay on the floor.
    • I can do a variety of placements within the board to experiment with stereo imaging
      • I record mainly in my (cluttered) living room with is not acoustically 'sound'. But I could go to other venues with it to experiment.
      • What might any of you think are placements that are worth investigating ?
• Embedded in my living room wall
  • This would be real nice to mix mix with my close mic'ing to get some room into my recordings

Thanks
I'd like to hear everyone's ideas and suggestions and thoughts

Click to expand...

The shape of the plate really does make a difference; I'd strongly recommend sticking to the shape of the Neumann GFM 132, and the precise placement of the capsule in the plate.

k brown said:

Just to pick the nit a bit here - these are not PZMs (Pressure Zone Microphones), but BLMs (Boundary Layer Microphones).

Bee-yoo-teeful work, though.

Click to expand...

Yes, that's right PZM is a specific Boundary mic with an omni-directional capsule actually pointing down to the plate.

thanks,
I think I'll start with a large board first (maybe 1,2m x 1,2m)

k brown,
I can't find dimensions of the Neumann GFM 132 on the web.
Does anyone here have one to supply exact measurements ?
If not, I'll guess using a picture.

GFM was 213mm x 168mm x 13mm. Actual dimensions of the three sides can be interpolated from the overall length and width. The most important thing is that all three sides are a different length. Position of the capsule on the plate is also important. The original research paper concluded that a spiral shape was ideal, but the triangle was more practical to mass produce.

I made a couple of the spirals out of tempered hardboard.

Looks like an Archimedes spiral.
I read that paper and have been planning some triangle builds
I was thinking of using plastic cutting boards I do like you idea of tempered hardboard

Simple idea, really - every point along the edge of the spiral is at a different distance from the capsule, so diffraction effects are spread out and no one frequency dominates.