Peluso 22 251 - you wouldn't believe...

[granger.frederic]

interesting subject...
the transient response can be electronic dependent...(capsule, biasing,etc)
but, for me, can also be mechanically dependent.
Or both...
if there are some internal resonances , or some transmitted vibrations to critical elements, then the transient response is modified.
the critical elements (for vibrations) are (no order) :
- capsule mounting
- tube mounting and tube
- headbasket and body resonances
- HiZ wirings
- microphonic components (caps, hiZ resistors...)
- shockmount

 

[KrIVIUM2323]

I agree, everythings matter.

After all a mic is only a loudspeaker in reverse (or the inverse! ) and in the case of loudspeakers dampening of structural born resonance ( acoustic one but not only: resonance within the box's panel too), stable position and decoupling all make dramatic modifications to final sound.
This is without talking about microphony in the electronics parts...

Why would it be different for a mic? 

 

[KrIVIUM2323]

the metal body is damped with two lateral springs

Thank you pointing that, i've always wondered their purpose in the Elam.
But... are these tiny parts really effective in damping the large body structure? It seems counter intuitive to me.

 

[granger.frederic]

it tries to damp the body and the internal structure, and create a more compact superstructure in the end
(difficult to explain that in English for me...)
the same process exists in the U67/U87 (with smaller size)
the efficiency is debatable and perhaps improvable with recent damping materials

 

[KrIVIUM2323]

Frederic,
this is really interesting but going off topic, maybe it could be interesting to start a thread about that particular subject, it really deserve it and there is not many info about that from my own research.

This way you wouldn't have to repeat same things over and over again.

(difficult to explain that in English for me...

Same difficulties here... there seems to be a pattern for native french.  ;D

 

[granger.frederic]

YES  ;D

Why not, if i can find some free time...
i'd like to open a topic with pictures, measures and tests...

 

[KrIVIUM2323]

the efficiency is debatable and perhaps improvable with recent damping materials

I wonder why C.L.D.* is not used to damp the body.
Difficult to apply in practice for diy'ers but very efficient way to deal with the issue and probably easy to implement for large manufacturers with r&d department.

*: Constrained Layer Damping, multiple layer of differents materials with different sets of vibrational characheristics bonded together using special adhesive (this one being one of the layers) . In loudspeaker box build it is really effective.   

 

[Khron]

Makes a person wonder if / how effective some of those silicone "c*ck-rings" (like you see on some tubes to at least allegedly reduce microphony or something) might work to add some compliant mass and damp body vibrations in mics prone to that...

At least in speakers, you can only do two things - increase the mass, and/or increase the stiffness of the enclosure.

 

[KrIVIUM2323]

At least in speakers, you can only do two things - increase the mass, and/or increase the stiffness of the enclosure.

No you can do many things.
BBC as one counter intuitive approach which 'work'. Do a search in the BBC archive you'll find it described in details.

Otherwise you can divide panels into many different area, each one with a different resonnant frequency,...

CLD is one other way to deal with this and  much more recent approach.
Make some search about principle at works it is interesting.

Makes a person wonder if / how effective some of those silicone "c*ck-rings" (like you see on some tubes to at least allegedly reduce microphony or something) might work to add some compliant mass and damp body vibrations in mics prone to that...

I don't know about silicone rings but for tubes some of this solution (ptfe/titatnium ring, can't remember the name of the product but it is effective ) do reduce microphony (but do not expect miracles).

For mic (body) tube as pointed by Frederic some suspension use different approach than the usual elastic one and use technique to manage vibration. They don't damp them but shift them outside the audible range. This is one technique used by NASA to protect electronic circuits.
In audio this suspension are Enhanced Audio M600.

http://www.enhancedaudio.ie/technology.html

I suspect the small elastomer pads do some damping of body though.
From the one i own this is effective and you can expect some low mid 'clarification' from using them.
But if you are not in optimal situation ( floor not being stable reference, like some undecoupled wood) the effect is ruined.
End results are enhanced (!) by using their own stand too, based upon same principle.

 

[granger.frederic]

ultra interesting ...
we should open a topic...
not enough time...please help...
KrIVIUM, maybe , if you can...

 

[MS Vienna]

Quote

    the metal body is damped with two lateral springs

Thank you pointing that, i've always wondered their purpose in the Elam.
But... are these tiny parts really effective in damping the large body structure? It seems counter intuitive to me.

The actual purpose of these springs is the grounding of the body tube to archieve proper shielding. The housing tube is laquer coated on the outside - so not a safe electrical contact to the grill and screw base. The inside of the tube isn´t sprayed and a bare brass suface - hence the contact springs.
You can find a similar spring on the inside of the C12VR that contacts the inner fine mesh of the grille which is only inserted loosely. You can find contact springs inside the painted housings of Solidtube, C4000B, ect. too.
Just a way to insure reliable humm-free operation. Very simple.

You may have noticed that Neumann took over the M251´s basic construction almost 1:1 for their U67. It has a nickelplated, conductive, housing tube though.  Hence those contact springs were not copied.

 

[Khron]

And doesn't dividing the panels ultimately increase the stiffness? Like if you stick a dowel to "connect" the two side-walls (which are usually the largest surfaces)

No you can do many things.
BBC as one counter intuitive approach which 'work'. Do a search in the BBC archive you'll find it described in details.
You can divide panels into many different area, each one with a different resonnant frequency,...

 

[granger.frederic]

The actual purpose of these springs is the grounding of the body tube to archieve proper shielding. The housing tube is laquer coated on the outside - so not a safe electrical contact to the grill and screw base. The inside of the tube isn´t sprayed and a bare brass suface - hence the contact springs.
You can find a similar spring on the inside of the C12VR that contacts the inner fine mesh of the grille which is only inserted loosely. You can find contact springs inside the painted housings of Solidtube, C4000B, ect. too.
Just a way to insure reliable humm-free operation. Very simple.

You may have noticed that Neumann took over the M251´s basic construction almost 1:1 for their U67. It has a nickelplated, conductive, housing tube though.  Hence no contact springs on the inside are needed.

hmm, i'm not convinced
even with laquage, the ground continuity is done by the cable/xlr/bottom screwed ring/body/headbasket
internal springs are not absolutely needed for grounding, even if they can...

 

[granger.frederic]

And doesn't dividing the panels ultimately increase the stiffness? Like if you stick a dowel to "connect" the two side-walls (which are usually the largest surfaces)

yes,
most classical mics are using that method

 

[KrIVIUM2323]

And doesn't dividing the panels ultimately increase the stiffness? Like if you stick a dowel to "connect" the two side-walls (which are usually the largest surfaces)

As i see this is a side effect, the first one being to have different resonnant frequencies, but this is arguable i do agree.

If i see what you mean the "dowell" is used to spread the energy to the whole box (less energy on one panel only) not nescessarely to increase stiffness. Here too i see it like a side effect. But i m open to be corrected.
This approach is sometimes used directly on the driver to make it in contact with the rearwall.

In fact in CLD your trying to have the wall panels not to be connected together and are allowed to vibrate by themself to self damp...

In fact depending of frequency range you have conflicting approach needed... Large low freq don't need the same treatment as high freq...

Same as microphone!

Nice to have MSVienna in here! Your thread about the Brauner modification have some very interesting strategy for reducing vibration (as already mentionned by Fred).

 

[Khron]

I'm pretty sure that the resonant frequency (and its Q, meaning how quickly or slowly it dies out) of an object, or panel, or whatever, is directly related both to its mass, and its stiffness.

Greater mass => lower frequency and longer decay
Greater stiffness => higher frequency and shorter decay

Hit an anvil with a hammer - the anvil is both heavy and stiff, so you'll get a nice sharp "clink", which may or may not sustain over a few seconds. Hit a large-surface thin metal panel with a soft mallet (plate reverb anyone? or old-school thunder sound effects), and you'll get a low-pitched long-sustaining "blam".

As i see this is a side effect, the first one being to have different resonnant frequencies, but this is arguable i do agree.

If i see what you mean the "dowell" is used to spread the energy to the whole box (less energy on one panel only) not nescessarely to increase stiffness. Here too i see it like a side effect. But i m open to be corrected.
This approach is sometimes used directly on the driver to make it in contact with the rearwall.

In fact in CLD your trying to have the wall panels not to be connected together and are allowed to vibrate by themself to self damp...

In fact depending of frequency range you have conflicting approach needed... Large low freq don't need the same treatment as high freq...

Same as microphone!

Nice to have MSVienna in here! Your thread about the Brauner modification have some very interesting strategy for reducing vibration (as already mentionned by Fred).

 

[granger.frederic]

instinctively i would say greater mass = shorter decay.
rigidity is mass related.
greater rigidity with low mass = longer decay.
but a mic should not be too heavy for practical requirements...

hence the importance of damping methods.

 

[KrIVIUM2323]

is directly related both to its mass, and its stiffness.

Yes, but strategy to deal with that is sometimes counter intuitive. CLD is an example.
I can't argue about it in english... you know i'm French!
Do some search about the principle and you'll understand what i mean.

About the rigidity: overall this is needed for the bass content.
About the mass: this is needed for the high end.
Both in case of loudspeaker enclosure... But wait what do to with the medium freq?

The strategy to shift the resonnant point outside the audio range need ONLY stiffness. Hence the use of Aluminium in the m600 suspension...

Ok know we are really off topic!  ;D
And THIS really DESERVE a DEDICATED THREAD!  :  ;D

 

[granger.frederic]

not necessarily out of topic...

indeed very hard to explain...

i'll search in the CLD domain...
http://www.sciencedirect.com/science/article/pii/S0020740302000425

https://books.google.fr/books?id=cPa6CgAAQBAJ&pg=PA109&lpg=PA109&dq=cld+vibration&source=bl&ots=wPNif8uKof&sig=sSTtTQC3PRmv1Dza07f5rkNFGao&hl=fr&sa=X&ved=0ahUKEwjK0KneqcPXAhUFXBoKHde5AhAQ6AEIXDAM#v=onepage&q=cld%20vibration&f=false


but i'm convinced that many classic mic re-creations are showing bad colorations, because of that...

 

[KrIVIUM2323]

but i'm convinced that many classic mic re-creation are showing bad colorations, because of that...

One of the strong point you are constantly pointing. And i think you are right.
I'll open a thread about that these evening i've got some info about CLD burried in one of my pc but it won't be easy to find...