Dampening resonance of the base, extra dampening for capsule saddle/holder, keeps wires isolated from the base.
Piotr, there is many kind of 'technical foam' so could you provide a link to the specific one you use please (or define the material more precisely) ?
i think that the teflon pins between headbasket and body are canceling any contact/any friction between the wires and the metal.
it "breaks" the transmission.
I don't know if it break the transmission but i think it lessen it. It follow the thought i had about the spacers stand off. But we may be wrong.
we need someone with solid knowledge about mechanical vibrations analysis and simulations...
I do agree. Simulation could be great! It could be of great help to dampen the body tube for example. We probably will come back to this latter.
i think we underestimate the capsule micro-movements/vibrations on loud sources...
Maybe not underestimate but like you i think this is a major point. With the analogy about loudspeaker, it is well known that parasitic vibration of the whole structure do induce coloration but at the same time 'smear', 'mask' (or both at the same time!) low level information in loudspeaker box.
I think i've already read some serious analysis about that and iirc, differences of up to 1/1.5db have been recorded between the same hp in differents enclosure with different build techniques... I'll try to fin that in my hdd i may have kept this.
This thread makes me digg deep into my hdd's... and rise the need for a better organisation of info to find them again... :
I'll turn into a salesman for Alpha,
You are not Banzai! This is really interesting and of great help. And it will not break the bank to try it.
But the non-microphonic properties of wirewrap builds are very well known. Makes it a great technique for mic building that pretty much no-one uses.
I've already seen it mentionned a few time from different sources in the 'audiophile' world. Problem being that it is from audiophile world most do think this is pure BS.
Ok so i've got a bit of time last night to make some rendering about a possible way to limit vibration transmission to headbasket baseplate and 'isolate' capsule mount/saddle from the one for the body using CLD.
This use two baseplate. The lower one being attached to rails and rest of the body, the second upper one see the capsule mount attached to it. It is fairly simple and should be easy to do in practice, two aluminium disc 1/2mm thick used as baseplate.
Both are glued together using a
VERY THIN layer of
VISCOELASTIC glue or dedicated viscoelastic material. No other form of contact should exist between the baseplate than the viscoelastic material or the effect is defeated or largely attenuated.
It can seem counter intuitive (at least for me) but the viscoelastic glue layer must be very thin for it to work as a CLD.
And the glue must be viscoelastic not only elastic.
CLD do work by transmitting vibration to the intermediate layer and transform them in heat by means of
SHEAR DEFORMATION, not mass increasing.
As the name implies it does damp the structure but not by the more intuitive 'increase of mass' to achieve it.
This is really a situation where there is mismatch of 'mechanic impedance' between layers.
Base material could be other than aluminium, steel works no problem.
This technique i widely used in the industry (a lot in the marine industry where vessels induce problematic behavior of sound transmission because of the all metal stuctures) but as well in the pure studio acoustic field.
In the studio this is often build using two plasterboard from same thickness (in France it is BA13 - 13mm, or BA18- 18mm thick) separated by some form of bituminem materials sheets (4mm thick).
It can be argued that this is so form of mass damping in this case and yes for some kind of frequencies this is it, but as you move away this does indeed become a CLD and shear deformation is at play.
Ok back to the base plate, as seen in the sketch clearance must be allowed to have rail bolts not to touch the upper plate, and the bolt to mount the capsule holder not touching the lower plate. I have not drawn holes to have the wire go through but same principle apply.
The upper plate should be a little bit smaller than the lower one to be sure not to have contact with body or headbasket.
The sketch does more or less copy the arrangement that you can find in most chinese U47 body style.
Ok now the difficult part... Where to find some viscoelastic glue or material?
Well, 3M has some dedicated tape for that kind of things: 'Ultra Pure Viscoelastic Damping Polymer 242f01'
It is convenient as it is a double sided tape so no mess with glue... It is used to damp HDD noise by the way... But i do not know if the glue used will be enough for the weight it'll face. It is very likely yes.
https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&cad=rja&uact=8&ved=0ahUKEwjCyfqRls3XAhWIFuwKHe-6B0EQFghbMAc&url=https%3A%2F%2Fcdn2.hubspot.net%2Fhubfs%2F99603%2F3M_Ultra-Pure_Viscoelastic_Damping_Polymer_242F01_242F02_sales%40gleicher.com_distributor_converter.pdf%3Ft%3D1493911022522&usg=AOvVaw0G_b2ni_f_SF8ctZGRGPC6
I've found glue from Permabond that could be used too: something like their TA4246 should work.
http://www.permabond.com/wp-content/uploads/2016/05/TA4246_TDS.pdf
