Barstow U-47 Mod of Marshall MXL2001

Hey Andy,

i remember that you wrote about it in some topic.
It was "c12" donor body, right?
Did you checked overall ground connection of headbasket and the rest of the body?
Sometimes is worth to scratch a little chrome/nickel headbasket base (in place of screw slots) to improve continuity.
Anyway hum is much more possible with grounded capsule (front diaphragm like in C12) than without.
I removed meshes in many different microphones and never had that problem.
That's why is worth to remove mesh only from the front for cardioid microphones - less possibility of  hum problem.

Khron said:

The original MXL 2001 capsule is a single-sided (cardioid-only) K67-clone.

"Front" of the microphone doesn't necessarily mean "outside layer of mesh" - there's an outside layer both on the front and the back of the microphone (duuuh ).

The idea was, i'm sure, to remove the internal mesh on the front side of the microphone (ie. the side where the gold-plated diaphragm is), but to leave it in on the rear side (ie. the back of the microphone, where the null of the cardioid capsule is).

Surely it's not THAT complicated

Click to expand...

Thanks for the clarification!  You see, I'm a newbie and am not familiar with mic terminology.  :-[  I was about to remove the entire internal layer of the headbasket - front and back.  Thanks for stopping me! 

Hey guys, what do you think of putting little conical foam absorbers around the base of the capsule mount?  Is it a good idea?  This is one of the mods that Michael Joly of OkatavaMod does to absorb and diffuse high frequency reflections inside the headbasket.

I've read of pieces of felt being used there.  Scroll down to the last couple of photos:

http://www.audioimprov.com/AudioImprov/Mics/Entries/2013/3/29_Microphone-Parts_RK-12_Capsule.html

From many years am using damping materials inside the body. In some also inside hedbaskets.
For example shure PG42 have dampers inside headbaskets out of factory
For body pipe am using technical foam, silicone paste, butyl tape.
Butyl tape is also easiest for hedbasket damping.
Overall idea is to cover only frame parts inside headbasket.

Khron said:

I've read of pieces of felt being used there.  Scroll down to the last couple of photos:

http://www.audioimprov.com/AudioImprov/Mics/Entries/2013/3/29_Microphone-Parts_RK-12_Capsule.html

Click to expand...

Thanks!  So you can also put dampers on the top of the headbasket.

ln76d said:

From many years am using damping materials inside the body. In some also inside hedbaskets.
For example shure PG42 have dampers inside headbaskets out of factory
For body pipe am using technical foam, silicone paste, butyl tape.
Butyl tape is also easiest for hedbasket damping.
Overall idea is to cover only frame parts inside headbasket.

Click to expand...

Thanks!

What is butyl tape?  Are you using it as a damping material?

Instead of technical foam or butyl tape, will this high-density rubber foam weatherstrip tape work well also?...

http://www.homedepot.com/p/Master-Lock-E-O-3-8-in-x-5-16-in-x-10-ft-Black-High-Density-Rubber-Foam-Weatherstrip-Tape-R538H/100189634

I have a lot of this stuff at home and it would be great if I can use it for this purpose so I don't have to buy technical foam or butyl tape.  So please let me know if it will work equally well or if its acoustic response will not be as good as technical foam or butyl tape.

Thanks again! 

Beware of foam.

Especially as it ages.

I'm pretty sure any sort of foam is too light / non-dense to yield any notable mechanical-resonance-dampening, i think.

Khron said:

I'm pretty sure any sort of foam is too light / non-dense to yield any notable mechanical-resonance-dampening, i think.

Click to expand...

Is felt better than foam for dampening?

Guys - technical foam - high density like use in cases for equipment for example.
It doesn't aging like low density foam.
It's really good for resonance damping.

micaddict said:

Beware of foam.

Especially as it ages.

Click to expand...

What happens to foam as it ages?

mtl777diy said:

What happens to foam as it ages?

Click to expand...

Temperature and humidity.

Don't even look for lowdensity foams.
Again - technicalfoam is completely different material - look for it.
Butyl tape:
http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=butyl+tape&_sacat=0

I would assume high density foam would do less in this application. Maybe not.
In any case it should be open cell, no?

But all foams degrade IME and when they do they leave a very nasty mess. Both crumbly and sticky. And at that stage it can eat other components. Don't ask me how I know.

I'm sure some foams are better than others, but I would never let any kind near my precious capsules.

Rather

micaddict said:

I would assume high density foam would do less in this application. Maybe not.
In any case it should be open cell, no?

But all foams degrade IME and when they do they leave a very nasty mess. Both crumbly and sticky. And at that stage it can eat other components. Don't ask me how I know.

I'm sure some foams are better than others, but I would never let any kind near my precious capsules.

Click to expand...

No, open cell is used to be sound transparent in front of the diaphragm.
Idea is too use, stripes of technical foam, only in place of the frame.
Rather dipahragms in your precious capsules will die sooner than technical foam

ln76d said:

Temperature and humidity.

Don't even look for lowdensity foams.
Again - technicalfoam is completely different material - look for it.
Butyl tape:
http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=butyl+tape&_sacat=0

Click to expand...

Is butyl tape similar to painter's putty but in the form of a tape?  Does it feel wet to the touch or is it completely dry?

It's much more like silicone, but you can divide it without any tools.

ln76d said:

It's much more like silicone, but you can divide it without any tools.

Click to expand...

That doesn't sound anything close to being foam-like to me.  And yet it can dampen the frequencies?

Foam doesn't do much resonance damping - you need MASS, but without rigidity.

As i've pointed out earlier, it's too light and non-dense for that. We're talking about hundreds of Hz to low kHz.

Try then you will see.
For body pipe it is easy to check.
Take unmoded microphone, connect it, and tap into the housing.
If it's shitty, you will hear that in your speakers, it resonate.
Glue technical foam and try again.
Then record loud drums (since you are drummer) with it and without.
Do you think that you need to pour liquid lead to damp such resonance?
Resonance don't correspond to the whole frequency spectrum but only on these on which is susceptible meterial, its shape, size etc.
Try measurements with Kundt's tube and different damping materials, you will be surprised with some.