the effect of a grille

omeiko

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Has someone who has more experience in this stuff noticed any general rules how a grille effects the sound of a mic? Something like 'finer mesh/more treble' or so on. I've made some experiments with grilles and it does effect the sound but I haven't been able to do any conclusions about this subject.

It would be interesting to make a test setup where I could compare different grilles in a controlled fashion. Like to put a measurement mic inside the grille and record some freq sweeps.

Thanks,

-Okko
 

PRR

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> someone who has more experience

No experience; just meditation.

> general rules how a grille effects the sound of a mic? Something like 'finer mesh/more treble' or so on.

For lumped-parameter analysis, it must be a low-pass filter.

Bigger enclosed volume means lower cutoff.

Less-open mesh means lower cutoff.

Smaller holes (or fine fuzz) add resistance which damps the cutoff.

For about any practical grille: you won't get cut-off, you get a mild droop.

However, a 2-inch enclosed space will also have distributed-parameter effects. If totally enclosed, it would have strong standing wave resonance in the top of the audio band. Find a bass-mode calculator that can take a 2-inch "room" and it will give the frequencies. Obviously if the grille is 99.9% open, no resonance. But maybe there is a value of screen/mesh that gives audble resonances.
 

Scodiddly

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I've noticed nasty HF stuff in the 2" diameter mic body I recently built. Just some brass mesh, fairly open (12 wires per inch, I think) but I could definitely hear it. I ended up lining the thing with thin open-cell foam, and that cut it down.
 

Larrchild

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First Reflections can be lasting ones.
In addition to the "tuning" of the mesh, the enclosure is creating a host of near-in first reflections.

When I heard that the C-12 and 251 had the same capsule, I about dropped a load.

Windscreen shape and dimension variations must have been at least partly responsible for the big sonic differences of those 2 mics.
 

omeiko

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Thanks.

The reason I ask this is because I once had astudio projects c1 microphone that now has been heavily modded. I didn't like the sound at all and I changed the capsule and electronics but it still has this unpleasant resonant high end that it has had from the beginning.

I think I'll try to experiment with different grille materials and capsule placement.

By the way, have you noticed that many of those desirable vintage mics have the capsule mounted much higher than in the todays designs? In the elam-251 the capsule is almost touching the upper mesh.

cheers,

Okko
 

Gus

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Okko

What capsules did you install in your C1?

I have been meaning to place some foam below the capsule. Maybe moving the capsule closer to the top could be good: however the trim might be wide enought to cause a refection that can be heard.

I am still learning about all the things a capsule, grill, cavity, echo chamber. is all about. Look how Gefell mount the M7 capsule.
 

omeiko

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I used peluso cek-12 and cek-89 capsules. Cek-12 was the more usable of the two but still not perfect. I haven't thought the foam thing. What do you think this would do to the sound?
Look how Gefell mount the M7 capsule.
I couldn't find any picture that shows the capsule position. How is it mounted?

Okko
 

mfdu

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there's been a fair bit said about this in relation to the current crop of low-cost ribbon mics (the shinybox etc)

i ain't gonna go quoting everyone but if you go searching, you'll find it. from memory, TLMaudio said he tried removing a couple of the layers of baggles and found the sound less pleasing than with them all in place.

chris.
 

Scodiddly

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[quote author="mfdu"]there's been a fair bit said about this in relation to the current crop of low-cost ribbon mics (the shinybox etc)

i ain't gonna go quoting everyone but if you go searching, you'll find it. from memory, TLMaudio said he tried removing a couple of the layers of baggles and found the sound less pleasing than with them all in place.[/quote]

I've been thinking about this recently. I didn't hear much of a difference when I removed the rectangular hardware cloth & silk liner, but now I'm tempted to go back and make another comparison. My theory now is that that rectangular box broke up the cylindrical reflections off the outside (cylinder) mesh screen.
 

kvintus

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I made a study about this a while ago when I studied sound engineering. A U87-shaped grille and a cylindrical grille from two china microphones were measured upon in an anechoic room. Unfortunately I don't have the paper I wrote anymore, but this is what I remember:

- The grille is not a mesh between the capsule and the sound source. It must be seen as an enclosed environment with its own acoustic properties.

- larger grille volume results in less grille impact on low frequency response

- The mesh, support strips, capsule mount and the capsule itself cause very complex diffraction patterns inside the grille that affect the sound waves reaching the capsule. I measured over 10 dB differencies in the high frequency range between measurements made with and without the grille mounted in place.

- the more open the mesh is, the less will the grille affect the sound

- The U87-shaped grille caused somewhat less disturbance in the mid and high mid frequencies than the cylindrical (U47-shape)

I know there were more stuff in my conclusions and I will post them as soon as they pop up in my head.

Hope this helps!

/Anders
 

Gus

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SP had a 3 part article in Mix in it is a graph of a u47 with and without the grill. Might be a link in the meta

The U49, m50, u67,u87 grill has a design that helps to minimize grill reflection. Is it true that neumann has trademarked this type grill design?

Also look at a soundelux E49.

Okko, google gefell microphones
 

dale116dot7

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Yes, it makes a difference. I changed out a capsule in an Apex 430 mic (piece of crap) to an AKG 2072Z0005 capsule - big change. The sound was suddenly much nicer. BUT there was still a bit of that high end raspy sound that didn't go away. I removed all but the outer grill wire and it sounded much better. I was surprised that there was no buzz. The original grill was painted, in addition to being three layers, so you could not see the capsule when you looked into the grill.
 

chrissugar

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[quote author="Gus"]
The U49, m50, u67,u87 grill has a design that helps to minimize grill reflection. Is it true that neumann has trademarked this type grill design?
[/quote]

Yes, I think is true. I remember reading about it, long ago.

chrissugar
 

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