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[klaus]

Where are the parallel opposing surfaces supposedly causing standing waves between the flat capsule diaphragm and the circular basket in the U 47?

There is a circular stone wall designed by the builders of Pioneer Place, Portland's town square, where kids, young to very old, enjoy standing in a particular spot in the center. You often have to wait in line, because no one wants to leave that sweet spot: the standing wave reflections of hearing one's own voice back are so eerie, that its enticement is overwhelming. Compared to a circular head basket, you have an even smaller area (relatively speaking) between the two surfaces forming the standing wave: a spot on the wall, and an ear canal.

The parallel surfaces in a U47 basket consist of the vertical plane of the front of the diaphragm and its corresponding vertical line of the basket's inside mesh.

Over the weekend, I corresponded with Neumann's Martin Schneider (Development, Acoustics and Mechanics) who confirmed this. I will translate his response later today.

[klaus]

Hello Mr. M Stage (I don't assume that's your real name? Please comply with the forums's rules and insert your real name in your posts!),
I full agree with the health concerns posed by using lead solder.
But I made a conscious decision to NOT use lead-free solder, because of its mechanical and sonic properties: It plain sucks to work with, and does not flow or connect properly. I'd also gladly sacrifice a few years of mental sanity by using a solder that I believe makes an audible difference in the high-quality, high fidelity work my customers pay me for.

[soapfoot]

I'll just interject that whenever I use lead solder (I also prefer the Kester 60/40 variety) I make sure to not touch my face until I have washed my hands thoroughly. Whenever I'm working with it, I treat my hands as "contaminated" and when finished, wash very thoroughly, dry, and then wash and dry again.

Hopefully this does a good job of reducing my exposure to levels that aren't too much higher than normal environmental exposure. My hunch is that we're all unwittingly exposed to very toxic things on a daily basis without our knowledge. I don't want to speed it along with my own recklessness, but I do not work with solder on a daily basis (at least not consistently), and I try to take care when I do.

[Jim Williams]

SN96 is a good sub for 60/40 tin/lead. It's 3% silver, 1/2% copper. Kester 48 is a good brand. I avoid lead these days, Califonia is a RoHS state.

[boz6906]

The curved grille creates a rough parabola where the incoming pressure waves are reflected back into a focal point, probably right on the front surface of the capsule.

That doesn't happen with the angled grille.

[Piedpiper]

The curved grille creates a rough parabola where the incoming pressure waves are reflected back into a focal point, probably right on the front surface of the capsule.

That doesn't happen with the angled grille.

I would imagine that that might contribute to the bit of upper mid push on the 47. Any confirmation on that? Anyone have accurate and appropriate graphs showing the relationship of a K47 equipped 47 and a 49? Not sure I've ever seen one.

[klaus]

Comparing whole mics to each other would have too many variables to extract what the baskets contribute. You would need to somehow fit an M49 basket over a U47 to understand that better.

[klaus]

In a couple of email responses, Martin Schneider, Development Engineer Acoustics at Neumann had this to say:
"One can simply refer to physics and room acoustics: as we avoid parallel walls or circular rooms in recording studios, Non-parallel-walled, non-circular basket forms are logically the better refection techniques. That was observed (and implemented) as early as the M49/M50."

I then found in the material for Siegfried Thiersch's capsule laboratory a reference that they use a U67 basket for their acoustic capsule testing, because of its (low-resonant) acoustic properties:
"Zur Messung bauen wir unsere Wandler in einen gering reflektierenden Schutzkorb ein, den Neumann- Korb vom U67"

None of this answers some of my contentions about a patented head shape design to suppress sound reflections.

I am currently sifting online through NWDR and Neumann's German patents and U.S. trademarks to find where I might have seen references to the acoustic properties of a wedge-shaped basket (Martin could not recall where he might have seen anything about it).