SDC capsulses-ring tension, capacitance and frequency response

[kingkorg]

Now, look at who is using these capsules on toms

https://youtu.be/SMqR57OCZto?t=10m57s

 

[craigmorris74]

If I ever mix toms, I'll use the neck  out of these!

 

[Marik]

How does the tension of the brass ring that holds the components of the capsule affect the capsules capacitance?

If you mean ring with glued on diaphragm then it does not. The only things to change capacitance would be the physical size of the diaphragm and backplate, and spacing between those. Changing the tension does affect the tuning frequency, which defines the balance between top and bottom end roll offs.

Also, how does capacitance affect the frequency response of the capsule?

Capacitance does not affect affect the frequency response, per se... meaning it does, but indirectly. That is, different spacing between diaphragm and backplate results in different damping--that what changes the response.  The MXL603 capsule is a not well implemented design. Changing those, only, will not help to get rid of its main problems. That's why once I re-designed it with one additional backplate to optimize frequency response vs pattern characteristics. It requires precision machining. Its plastic molded second backplate is a total nuisance...

Best, M

 

[abbey road d enfer]

If you mean ring with glued on diaphragm then it does not. The only things to change capacitance would be the physical size of the diaphragm and backplate, and spacing between those. Changing the tension does affect the tuning frequency, which defines the balance between top and bottom end roll offs.

Marik, check my answer #8, that says exactly the same.
However, subsequent answers #9 & 10 seem to bring a different light.

 

[craigmorris74]

Mark said capacitance does change with tightening of the brass ring, because tightening the brass ring inside the capsule changes the spacing between the backplate and the diaphragm (which isn't glued).  He said capacitance wouldn't change if the diaphragm were glued (it's not in this case).

The only reason that I brought this tread up is to put these capsules back together after modification.  I'm pretty happy with my modifications for what I want to do with the mics.  For others, the stock sound fits their workflow better.

The only things to change capacitance would be the physical size of the diaphragm and backplate, and spacing between those.

Best, M

 

[kingkorg]

I'll repost the picture. These are factory capsules, one is cardioid, the other one is hyper(the one with wider plastic backplate holes).

Otherwise all the parameters are the same. Spacers, diaphragm tension etc.

You might notice that bras backplate holes are slightly smaller on hyper. But you can't do much about that. I haven't noticed that makes huge difference.

This is hightly experimental, and i don't have gear to measure polar pattern response, but you get less high end and dip in high midrange which is typical for hyper response compared to cardio for these capsules. And more sound reaching diaphragm through backplate is logical way to make hyper/super cardioid.

Try with gradually widening of holes. And be prepared to destroy capsule if you are doing this for the first time.

 

[kingkorg]

There is Eargle's - The Microphone Book. Several places you can make free accounts and read it. Reading that one,  and some of Neumann's and others capsule pattents will give you idea how capsules work. And what you might try. However there is no formula. Even original Neumann patents describe there is a lot of experimentation involved.

This chinese capsule is simplified version of km84 which is built kind of in a similar way.

 

[gyraf]

On that pictured type of capsule, it should be possible to add (inside the threaded end,non-invasive) a thin slice of acrylic with the same holes as in the back of chamber - and gradually rotating this to block or unblock holes would vary amount of velocity-component (fig8) added to the basic omni of the capsule. Fully closed=omni, fully open=fig8 (but only if back was wide open, which it's not).

This adjustment should give you at least some information about capsule dynamics...

Jakob E.

 

[kingkorg]

Now that is phenomenal idea, thanks Jakob!

 

[szegedin]

On that pictured type of capsule, it should be possible to add (inside the threaded end,non-invasive) a thin slice of acrylic with the same holes as in the back of chamber - and gradually rotating this to block or unblock holes would vary amount of velocity-component (fig8) added to the basic omni of the capsule. Fully closed=omni, fully open=fig8 (but only if back was wide open, which it's not).

This adjustment should give you at least some information about capsule dynamics...

Jakob E.

That sort of works, but it has to be a quite rigid material.
See the Shure SM141:
https://www.fullcompass.com/common/files/13224-UsersGuide.pdf