Electrical field strength

[Bazukaz]

Hi,
I am thinking about design with 0,75mm magnet wires , spaced apart ~0,6mm. I could use thinner spacers for high efficiency(0,8mm D/S spacing).
As i understand , too close a D/S spacing and it would lead to increased distortion due to varying electrical field , while diapraghm moves.
So , do you think higher spacing (lets say , 1,3mm) is better for sound quality ?

Regards,
Lukas.

[Capaciti]

Hi Lukas,

i use 1mm spacing (stator-membran) and my measurements show very low distortions as long as you stay away at least one octave from fundamental resonance. The field density is linear enough, even with closer spacing.

There is an increasing problem the closer you make spacing - static instability. Due to manufacturing tolerances, you will never achieve a perfect symmetric stator construction. The closer the spacing, the larger non-symmetrie (in percentage) will be even at minor tolerances. electrical force increases the closer the mebrane comes to the stator. At wider spacings the membrane compliance will decrease (tension increase) due to increase of inner tension. This is because the membrane forms a bow and that inceases inner tension.This increased tension compensates the increasing electrical force. At smaller spacing the membrane cannot form a bow, before touching the stator. My experience is that spacing closer than 1mm requires perfect made stator design (eveness,flatness) and still is very sensitive regarding high voltage. Mostly stable at certain high voltage it collapses at sudden due tominor changes (humidity...)


regard,capaciti

[Bazukaz]

Hi,
Thanks for repply.
I have been thinking about the following wire stator constructions :
1) Aluminium strips or rods , spaced ~35 mm apart , glued to plywood.
Problem: most of epoxy glues does not bond really well to aluminium.
Quite much of work to build;

2) The same method as in 1. but with Tekstolite rods. Epoxy should bond to it. I am not sure if tekstolite would not bend due to high tension force of wires.

3) Ventilation plastic grids(square hole size is ~17 x 17 x 5 mm.
Would probably create standing waves at 10 kHz(f = 344/2*l). Easier to build , and thinner wire could be used.

Any thoughts highly appreciated;

Regards,
Lukas.

[Calvin]

Hi,

I used simple Pattex glue. Aluminium strips as well as Steel bonded well to PVC and Acrylics

jauu
Calvin

[Capaciti]

Hi bazukaz,

or you use laminated paper for the frame and supports and glue it with epoxy (use aerospace-type only). You should glue the wires witth epoxy as well. take care that epoxy is rather liquid to ensure that the wires are embedded into the glue for best attachment.

Capaciti

[Bazukaz]

Hi,
Thanks for support,
Your method seems simple. Is this paper somethink like "floor laminate "?

I would like to ask a few more questions :
The laminated paper should not be very strong , how does it withstand the tension force ? Did you use the same material for vertical support ?

I was thinking about somethink like it (probably laminated water-resistant plywood). In this case i'd have to find a man who could cut the sheet into strips.I guess sheet thickness of 6-8mm and stick height of 10 mm should be ok.
Also , i may obtain some 0.75mm magnet wire.The question is , does the magnet wire tend to resonate more than PVC-insulated ? I was thiking that PVC insulation may damp the wire resonances somewhat...

Regards,
Lukas.