Barstow U-47 Mod of Marshall MXL2001

Cross Linked Polyethylene Foam -  i think it is the type am using.
Am buying it as technical foam but maybe it isn't called the same everywhere.
http://image.made-in-china.com/43f34j00sjMaiwIdQmbR/Crosslinked-PE-XLPE-Rubber-Foam-for-Case-Insert-for-Packaging.jpg
It's hi density like a mix of foam and a rubber.

On something like an Alctron MC001 / Apex 435, you can even feel it in your hand, ringing at a few hundred Hz if you tap it

And no, liquid lead isn't necessary - i "only" meant that something like a couple of strips of rubber sheet (a few mm thick) would do a better job than the same volume of, say, open-cell foam

Liquid lead would solidify when it cools down, and while you would indeed have more mass, you'd have stiffness as well.

In speaker building, bitumen sheets are often used to dampen the walls of enclosures - adding mass, but not rigidity.

ln76d said:

Take unmoded microphone, connect it, and tap into the housing.
If it's sh*tty, 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?

Click to expand...

To avoid confusion, I think we need to make a distinction between the acoustics within a headbasket and the damping of a (ringing) body tube.

No! Am talking about both (and completely not talking about open cells foams - is it clear now?).
Am talking about rubber foam (i don't know how to call it different) which you can cut with a knife and it has no cells at all (at least visible).
It is good for both - body pipe and headbasket frame structure - don't talking bout use it on the mesh (or front/back of headbasket).

I might have misunderstood, but I thought the discussion started about treating the reflective bottom of the upper chamber (basket).

For damping resonances (of pipe and frame) I fully agree with heavy and flexible material.
Or dense and rubbery if you will.

What's the "bottom of the upper chamber"??

Never mind. It may only add more confusion.

Please carry on. 

Am curious

Find some pic or mark it on the pic in paint

http://www.audioimprov.com/AudioImprov/Mics/Entries/2013/3/29_Microphone-Parts_RK-12_Capsule_files/P1010456.jpg

ln76d said:

Am curious

Find some pic or mark it on the pic in paint

Click to expand...

Oh man

A bottom of the saddle?

It isn't needed when it's like orginal dome in mxl.
Rather it can be even worse than better.
A clean free space over the capsule is what you need.
Thin rubber foam between it and metal base is something what you can make (to fill metal space).

"Worse" how?

Test and see

ln76d said:

No! Am talking about both (and completely not talking about open cells foams - is it clear now?).
Am talking about rubber foam (i don't know how to call it different) which you can cut with a knife and it has no cells at all (at least visible).
It is good for both - body pipe and headbasket frame structure - don't talking bout use it on the mesh (or front/back of headbasket).

Click to expand...

If that's how you describe it ("rubber foam"), then the cheap high-density rubber foam from Home Depot might work:

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

This is also known as "closed cell foam tape".  When you look at it from afar, you can't see the cells.  You'd have to look closely with a magnifying glass to see the very tiny cells.

On the other hand, for something much more dense than this, there's also EPDM rubber.  This is the rubber jacket material that's used in the Belden 8427 tube mic cable.  It's another option for me, as I have some extra lengths of this cable and can strip off the rubber jacket to use it as dampening material.

So, between high-density rubber foam tape and EPDM rubber, which one do you think is better?

Hey, it seems you guys had some some fun while I was asleep. I left at one o'clock (AM) as I was kinda sleepy, which may have shown in my last posts. But reading back I may not have been the only one who was a little sleepy.  ;D

Anyway, the original question was this:

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.

Click to expand...

First off, the OP made a distinction between absorption and diffusion, and rightfully so.
If you have a slender post on a flat base (not so difficult to envision, come to think of it), there's not much of either going on.
A (hard plastic) semi-sphere, for instance, will offer diffusion, but no absorption to speak of.
If you would want to add absorption (not saying you should) then foam would be last material to choose IMO.

Then the discussion shifted to damping of the body shell or tube and the basket frame.
This is important and worth discussing, too, but another matter altogether.
Internal reflections versus body resonances.
In the end everything relates to everything, but I tought it might be useful to mention this distinction, as well.
If only for the reader's sake.

I hope it is more clear now. 

Ok - from my point of view.
OP mention some jolly mod, which interest me as all jolly mods... so i even didn't check what it is.
There was also foam mentioned so i write what in my opinion is worth to do and later what not.
Then we couldn't agree about the foam so i tried to explain what type it's (still don't know do i gave good example).
If you Henk read entire topic, you will see that this whole topic is one big offtop
That's why i don't bother with keeping topic continuity, rather share my opinion about some things.
So!
In my opinion is worth to use rubber foam to damp internal frame of headbasket and metal base  and nothing else around the capsule. 

Speaking of off-topic, I am unable to remove the screws that hold the base of the capsule mount to the headbasket frame.  The screw heads have been damaged because they were too tight and I tried to turn the jeweler's screw driver and it would just slip, as the screw driver has a very small handle and I couldn't apply enough force to loosen the screws.  After trying several times, I realized that the screw head had become damaged.    Do you know of any way to remove a screw with a broken head?

Max 1mm drill bit and gently (low speed) drill it.

I like all microphone topics.

On- or off-. 

mtl777diy said:

Do you know of any way to remove a screw with a broken head?

Click to expand...

Or, if you have the physical space and means to do it, you could try cutting a slot into the head, and then use a flathead screwdriver to unscrew it.

Thank you, guys! 

I will try your suggestions when I get home tonight.