Wire stator gluing method

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Perhaps this will be of interest. I use a 2 hour epoxy applied with a rubber ink roller. This produces a very uniform result. Not as strong as I would like, but adequate.
 

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About a year ago, thinking I would never again wind wire stators, I stupidly took it apart. Destroyed it.

The wire was spaced with threaded rod, but wound on top of wax paper covered plate glass. The critical end was a series of hooks and rubber bands attached to a board which in turn could be retracted for additional tension. Each loop had its own hook and rubber band--a plethora.
1.5" particle board served as the base.

I originally tried tensioning the wire without the bands and hooks, but found that the magnet wire would stretch excessively, producing wildly varying tension and thus uneven spacing along the wire length. The rubber bands compensated for this.

I coated the acrylic louver with epoxy, turned it upside down, placed it on the wire and weighted it with another piece of glass, foam, mdf, and about 100 lbs of sand bags.

I'm thinking about trying this again because I like the sound of wire stators, but want to develop a method and jig that is not as complex.
The stator in the photos were made about 10 years ago.

I may have a hard copy picture, come to think of it. I'll look tomorrow.
Dave
 
Yes they can, but at ridiculously high frequencies.

I saw an article some years back where the builder tensioned the wires by bowing the plastic eggcrate, gluing the wires at the ends, then unbowing. I've been wanting to build more wire stators (the ones I have are salvaged from some Acoustats) and am very tempted to try that scheme.
 
SY said:
Yes they can, but at ridiculously high frequencies.

I saw an article some years back where the builder tensioned the wires by bowing the plastic eggcrate, gluing the wires at the ends, then unbowing. I've been wanting to build more wire stators (the ones I have are salvaged from some Acoustats) and am very tempted to try that scheme.

That article was in Speaker Builder. The eggcrate had holes drilled in the ends through which the wire was weaved. The crate was then unbowed, tensioning the wire. He then used a syringe to apply an epoxy fillet to each wire/crate point of contact. His wire spacing was quite wide, if I recall, perhaps 6/inch; but the method is elegant and I'm sure works fine.

I searched for a picture of my jig, but no joy. I can't imagine that anyone would want to reproduce it, but I regret failing to photograph it.

I primarily wanted to share the method of glue application, which works very well if the fabrication method employed requires applying glue to the entire crate surface before mating the crate to the wire on a corresponding jig.
Dave
 
I don't know cube sizes that are in pictures , but i think that first resonant frequency is calculated by f = 330/(2*l) , where l - cube width/height , or deph.
So , if we have cubes of, say , width = 2 cm , f = 330/(2*0.02) = 8250 Hz.
Not so high ! i was experimenting with plastic grid of such sized cubes , it changes sound noticeably.

Are my formulas correct ?

Lukas
 
I like your idea!

WHen you think about the tension that is required to keep everything good and flat it is a great help to distribute it along the entire length of egg crate. Keeps it flat not bowed as it has a tendency to do when you tension it from the ends only.

With the correct viscosity the epoxy will ensure that the wires are fastened well and there will little to no extraneous vibration to! Again nice work indeed. Something that I will definitely try when I build mine.
Thanks for the pictures.

MArk
 
Mark,
Yes--after epoxy is rolled onto the surface, the eggcrate is turned upside down and placed on the wire. In this way, the glue tends to flow downward and into the wire/crate contact point, producing the visible fillet.

I keep thinking that my method was excessively work intensive, but I'm not sure this can be avoided regardless of technique when fabricating wire stators. Actually, most of the work I recall entailed developing the technique. The actual jig was not that hard to make.
I'll draw up an illustration if anybody is interested.

I think that is #24 nylon insulated magnet wire, purchased from Mouser.
Moray James double insulated suggestion may be better.

Regarding vibration: Actually, the copper wire - acrylic crate produces a composite structure that does seem to be fairly inert. Stators made with Styrene crate is less so and did not sound as good, but is still acceptable.
Dave
 
Instead of copper wire, why not use hardened tool steel wire/rod like the stuff they make drill bits out of? It's not like you need a low resistance wire as your diaphram constant charging circuit is ~10MΩ. That should get you the rigidity you want without much tension on the frame assembley.
 
Hi,

light diffusers are OK, but to avoid any issue with cavity resonances i make my frame out of "pertinax", which is isolating hardpaper. Light diffuser get briddle under UV-radiation and in addition the adhesion of epoxy to polysterene get worse over the time.

The wires i use are very thin (0,0035") and open area is 50%. This requires 96 wires for 0,78" cell width.

The key to success (and the cheapest stator) is the jig to stretch the wires. Wires will never arc at even very high stator voltages and you can easily apply segmentation to reduce high frequency directivity.

capaciti
 

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Capaciti said:
Hi,

light diffusers are OK, but to avoid any issue with cavity resonances i make my frame out of "pertinax", which is isolating hardpaper. Light diffuser get briddle under UV-radiation and in addition the adhesion of epoxy to polysterene get worse over the time.

The wires i use are very thin (0,0035") and open area is 50%. This requires 96 wires for 0,78" cell width.

The key to success (and the cheapest stator) is the jig to stretch the wires. Wires will never arc at even very high stator voltages and you can easily apply segmentation to reduce high frequency directivity.

capaciti
I'm unsure of the whether cavity resonance is actually a problem with diffuser material. I think for 1/2" cubes the predicted resonance frequency is around 14 khz, but possibly of very low Q since the cavity length approaches and in fact equals the cavity width.

Moreover, the equations describe the behavior of a single cavity. A diffuser consists of a cluster. Just taking some partially educated guesses here. Open to correction.

In any case, I've never heard any coloration that remotely suggests substantial cavity resonance problems. That being said, your method certainly guarantees no cavity resonance, and is very elegant.

Acrylic seems to be superior to styrene in most respects. It resists deterioration and I think it sounds better, but have not rigorously sought to prove this. Epoxy bonds are stable, but I thoroughly sand the surface prior to gluing.
Dave
 
I coated the acrylic louver with epoxy, turned it upside down, placed it on the wire and weighted it with another piece of glass, foam, mdf, and about 100 lbs of sand bags. Dave [/B]

If you have a vacuum pump you could borrow a technique from composite lay-up and vacuum bag the assembly to apply pressure while the epoxy hardens. A small diaphragm pump can easily pull about 20" Hg vacuum which translates to 10 lbs per sq inch over the entire surface. Model rocket and airplane guys often use vacuum food sealers for this job.


Question for Capaciti:
With so many fine wires, how do you make the electrical connections? I am thinking that a single connection to one end of the wire in each stator might be a problem with so much wire acting as an inductor. Do you run some sort of bus connection down the length of the driver?

I_F
 
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