Head Basket Shape - how it effects tonality

[McIrish]

I've got a number of tube mics with various head basket shapes. I'm curious about how the headbasket effects the sound of the mic. I realize the capsule is the largest factor.

For instance, comparing a U47 to an M49. Both have an M7 type capsule but sound nothing like each other. The U47 has a very forward midrange and quite a bit of proximity eefect. The M49 sounds much smoother in the mids but lacks the low-end girth of a U47. Sound about right? How does the headbasket play into that. Why did Neumann create the angled headbasket of the U67 and M49?

 

[HerbertR]

Maybe In a round U47 basket frequencies can be amplified by reflections between the parallel walls, "standing waves"..?.The triangular shape of a M49 basket breaks up these symmetrical reflection patterns and reduces such effects. And therefore this leads in a more neutral sound image, more linearity. This could possibly lead in the U47 basket to a stronger emphasis on the lower frequencies, which is what gives the U47 its rich sound. Presumably this could be substantiated by calculations.

 

[k brown]

Those two mics also have very different electronics, so there's that.

The purpose of an angled headbasket is to prevent standing waves between the capsule and the inside of the basket, and between the front and rear of the basket itself.

Also the reason studios and reverb chambers don't have parallel walls.

 

[GeorgeToledo]

Just want to chime in that Herbert Grosskopf designed the M49 headbasket, not Neumann. Rights to produce M49 as a manufactured item were then assigned to Neumann. Further, angled headbaskets were used by some other company’s models prior to that.

 

[MagnetoSound]

What a bighead.

 

[Murdock]

I think headbasket and mic geometry is one of the most important factors just behind the capsule.
Even mesh-size contributes quite a lot.

 

[k brown]

I think headbasket and mic geometry is one of the most important factors just behind the capsule.
Even mesh-size contributes quite a lot.

It always surprised me how long it took Neumann to put out a mic with a hemispherical diffuser below the capsule; I still look at photos of the inside of U47/ M 49/M 50 and think huh?

 

[rock soderstrom]

It always surprised me how long it took Neumann to put out a mic with a hemispherical diffuser below the capsule; I still look at photos of the inside of U47/ M 49/M 50 and think huh?

Hemispherical diffuser - does this mean a hard acoustic material or an absorbent material such as Basotec? Which is better?

 

[GeorgeToledo]

I was coincidentally mentioning this to someone else today, who might end up reading this again…

But it has always stuck out to my eye that early on Neumann seemed to always put some silk or mesh around the outer circumference of the M7, presumably to separate the front from the back…for “reasons”. You can look at early M7 heads, early U47 trapezoidal capsule mount, and see this. I would guess it is to break up reflections and/or to influence the way sound waves travel front to back/back to front. I have also noticed that Neumann lollipop heads that were omni would never have that, iirc. I can’t remember what they did with the figure 8 heads though.

They seem to have given it up around the time M49/M50 debuted.

 

[k brown]

Hemispherical diffuser - does this mean a hard acoustic material or an absorbent material such as Basotec? Which is better?

Hard plastic, such as they did with the U 67 re-issue.

Then at some point they topped it with a ring of absorptive foam.

Annd...then with the U 87, they were back to a flat, hard disc below, so . . .

 

[Murdock]

Hard plastic, such as they did with the U67 re-issue.

Then at some point they topped it with a ring of absorptive foam.

They did not use this dome in the U67 re-issue. In fact I think only few of the vintage U67 came with the dome. They dropped it completely with the U87. Don’t know if they found that it made no difference or why they stopped doing it.
Sometimes I ask myself if the M269 is favored by many just because of that, cause I think almost all M269 came with a dome. And I would think it makes more of a difference (especially in the high-end) than the different tube and biasing…

 

[RuudNL]

Later Neumann advised to remove that ring of foam.
Probably because it is falling apart after a couple of years and also it holds humidity.

 

[k brown]

They did not use this dome in the U67 re-issue. In fact I think only few of the vintage U67 came with the dome. They dropped it completely with the U87. Don’t know if they found that it made no difference or why they stopped doing it.
Sometimes I ask myself if the M269 is favored by many just because of that, cause I think almost all M269 came with a dome. And I would think it makes more of a difference (especially in the high-end) than the different tube and biasing…

Yes, I guess I got that backwards; in that photo the reissue is on the left.

 

[k brown]

Some use a cone, some a dome, others a sort of concave cone; would be interesting to see measurements of the the three compared to a flat disc, in the same mic.

 

[rock soderstrom]

They did not use this dome in the U67 re-issue. In fact I think only few of the vintage U67 came with the dome. They dropped it completely with the U87. Don’t know if they found that it made no difference or why they stopped doing it.
Sometimes I ask myself if the M269 is favored by many just because of that, cause I think almost all M269 came with a dome. And I would think it makes more of a difference (especially in the high-end) than the different tube and biasing…

Thanks

Yes, I guess I got backwards; in that photo the reissue is on the left.

It is also interesting that the capsule in the vintage U67 is positioned much lower than in the re-issue.

Probably because it is falling apart after a couple of years and also it holds humidity.

I think the sponge is more likely to dry out completely and crumble to dust and then you can find it everywhere in the microphone, especially on the electrically charged parts.

 

[rock soderstrom]

Some use a cone, some a dome, others a sort of concave cone; would be interesting to see measurements of the the three compared to a flat disc, in the same mic.

+1

 

[k brown]

David Josephson is rather obsessive about this sort of thing, and uses a quite deep dome; nearly a half-sphere:

 

[rock soderstrom]

David Josephson is rather obsessive about this sort of thing, and uses a quite deep dome; nearly a half-sphere:

I've never held the C700 in my own hands, but is it really just one layer of microphone basket that forms the Faraday cage? It's amazing that that's enough! The holes are really huge...

 

[soliloqueen]

I've never held the C700 in my own hands, but is it really just one layer of microphone basket that forms the Faraday cage? It's amazing that that's enough! The holes are really huge...

I believe there's a second layer there. One giant layer and one very very tiny layer. The same sort of mesh they put over cellphone microphones. In this picture you can't see it directly but you can see the Moire artifacts

 

[rock soderstrom]

I believe there's a second layer there. One giant layer and one very very tiny layer. The same sort of mesh they put over cellphone microphones. In this picture you can't see it directly but you can see the Moire artifacts

Okay, thanks. At first I suspected it too, but I had also looked at other photos of the mic on Google, but you couldn't really recognize it, but it makes sense!