I thought about custom fabrication but didn't follow thru on getting a price. One of the past projects at work required that we furnish perfed panels for a strainer assembly. can't remember what they were straining. in any case, my ears perked up because i was thinking that not only could there be a border but that there might be a meaningful scheme where the perfs ranged in size from the center to the outer edge of the panel. possibly a way to affect dispersion, damping... who knows?
This site looks interesting. Too late for this particular build, but in the future...
Metalex | Perforated Metal | Perforated Metal Applications
Anyone ever use these guys?
Metalex | Perforated Metal | Perforated Metal Applications
Anyone ever use these guys?
Yes, that is a very good general rule of thumb.
Especially for diagphram widths larger than say 5 to 6 inchs.
However this rule quickly runs into practical considerations as the panel gets wider than say 9" or more.
The lowest frequency of operation must be taken into account as well.
As not too run out of room for large excursions at the lower frequency's of operation.
There was a good chart that I knew of that suggested the minimum D/S as per lowest frequency of operation.
However I am having a difficult time trying to find it on the web or the original document has been modified since and no longer has the data that I am looking for.
I do have it in my archives somewhere though.
Even with my little panel with a width of 3.25" and aprox. D/S ratio of 1:45 I have been able to clip the diagphram into the stator at Frequency's lower than about 200Hz to 250Hz even with a spacing of .072" (+/- .003").
Even more so when I hit the resonate frequency of the diagphram of about 70hz to 90hz.
May I add that this much excursion for my little 3.25" X 9.75" diagphram is quite very loud!!
A 1mm spacing may be good if you are planning on crossing over at a rather high frequency of say 1Khz or even 1.5Khz or higher and definitely if it was intended to be strictly a tweeter panel.
IMHO .0625" or as Charlie had mentioned a spacing of 1.5mm to 2mm is a very good place to start and should be good for those peaks at around 300Hz.
Remember that the excursion doubles for every octave lower in order to produce the same SPL as the starting fundmental.
Here is a very good read on the subject although it pertains mostly to headphone drivers,
HeadWize - Project: Notes on DIY Electrostatic Headphones by Chu Moy
And here is a much more detailed version as well just scroll back to page 138 for the beginning,
Loudspeaker and Headphone Handbook - Google Books
And here as well,
Audio and Hi-Fi Handbook - Ian Robertson Sinclair - Google Books
This is a very good thread that had touched on the subject as well,
http://www.diyaudio.com/forums/plan...sl-suitable-x-over-frequency.html#post2266701
The last time I was able to run my little panel I found that I got about +/- 30 degrees of usable dispersion off of the center.
And at about 45 degrees off the center there was noticeable drop off of the high frequency's as expected.
Enjoy !!
jer
I must correct myself.
The excursion quadruples for every octave lower for the same SPL.
Here is a nice little calculator that helps determine SPL's for a given displacment(Xmax) vs frequency.
this calculator assumes a monopole or Closed box/IB (Infinite Baffle).
Just convert your total surface area into driver diameter.
Piston Excursion calculator
According to the calculator my little panel was doing 114.5 db at 300Hz clipping into the stators !!!
Very Very loud as I remember as I didn't have an SPL meter at the time. He,he,he,he
jer
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What was the d/s spacing on your little panel doing 114.5 db?
Is the first touch of a diaphragm to a stator a failure event requiring a rebuild?
Also, funny how I am seeing perforated metal in so many places now. I noticed the 2' x 2' ceiling vent where I work might make a good stator, albeit more squarish than is typical.
Still, if you could be OK with the shape, they are only $25 each and don't need much additional prep.
Air vents, AC Vents, Ac Diffusers, Air Return, AC Return part way down the page on the left.
Is the first touch of a diaphragm to a stator a failure event requiring a rebuild?
Also, funny how I am seeing perforated metal in so many places now. I noticed the 2' x 2' ceiling vent where I work might make a good stator, albeit more squarish than is typical.
Still, if you could be OK with the shape, they are only $25 each and don't need much additional prep.
Air vents, AC Vents, Ac Diffusers, Air Return, AC Return part way down the page on the left.
I had it about .072" to .075" (1.6mm to 1.8mm) D/S.
I detected the stator clipping with a micropone and you could hear it as well.
Ahhh,ha,ha,ha,ha,ha, You have the bug now !!!
Everything you see your gonna think about "Hey, I could use that to build an ESL!!! ".
I use window screen and plastic lighting grate (egg crate) and I have even made some out of gift Credit cards,wire,PCB material and aluminium foil, almost anything can be used!!!
My very first one was made out of a piece of perforated aluminium soffit material and this worked great except the open area was quite low and restricted the sound too much.
The failure and demise of my little panels was the failure of stator coating pushing in excess of 25kv p-p across them.
This was the first time it had burst into flames and I was able to repair it, But sadly not the second time around.
jer
I detected the stator clipping with a micropone and you could hear it as well.
Ahhh,ha,ha,ha,ha,ha, You have the bug now !!!
Everything you see your gonna think about "Hey, I could use that to build an ESL!!! ".
I use window screen and plastic lighting grate (egg crate) and I have even made some out of gift Credit cards,wire,PCB material and aluminium foil, almost anything can be used!!!
My very first one was made out of a piece of perforated aluminium soffit material and this worked great except the open area was quite low and restricted the sound too much.
The failure and demise of my little panels was the failure of stator coating pushing in excess of 25kv p-p across them.
This was the first time it had burst into flames and I was able to repair it, But sadly not the second time around.
jer
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I think not.... I'm sure the nasty transient pop I've heard on occasion at high volume was due to my subwoofer acoustically coupling to the diaphragm and driving it into a stator; momentarily discharging the diaphragm. So far no apparent damage, though. Burning holes in the diaphragm has practically no effect but I suppose if it happened repeatedly at the same location, the arcing could burn thru the stator coating and that would be a problem. I think one advantage to using a high-resistance coating on the diaphragm is that it can't then pass enough current to sustain a really hot arc to the stator.... just speculating but it sounds logical to me.
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I see no reason why that wouldn't work provided you mist on the coats and allow enough flash off time between coats (so as not to entrap solvents)-- and you build sufficient coating thickness. The paint in aerosol cans is necessarily thinned quite a lot to allow it to spray at such low pressure. Thus, it will likely take a sh*t load of cans to build enough coating.
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Here are some excerpts ( links) to my recent experiments use spray can types of paints.
The whole thread deserves a good read through.
Stay away from gray primers and stick with the red as well as any pigmented paints particularly grays and white and anything that has Titanium Dioxide as a pigment.
If you must have a color than use a coat on top of the primer and then use only clear acyrilc to build up your coating thickness.
I have found that the canned stuff can yield very good result as far as volts per mil.
Although depending on the size of the panels this can become quite costly.
I have also found that the 3X Clear Acrylic is much much more cost effective.
But you may be better of with a gallon of paint and reducer to be cost effective for the size of your panels if you have access to a sprayer and/or compressed air.
Remember that you are going to need a coating thickness no lessthan 7mil and closer to 10mil is better if not more as 15mil is pretty much a free of any problems zone.
A micrometer is a good thing to have around and it doesn't have to be an expensive one either.
I think I paid like $15 for mine and I use it to accurately measure sub mil of my diagphram materials with and without coatings with no problems.
I just picked up two decent sprayers at Harbor Freight for cheaper around $25 and $15 for a smaller top feeding detail gun.
I will be trying them out in the next few weeks with some Minwax Poly for some cabinets and in the mean time I will be making a few more test samples for the coatings thread.
I know Dochungwell has used these same sprayers and he says they work great for what we are doing with them.
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2825793
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2825297
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2825793
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2828247
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2893839
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2894427
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2894629
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2902754
Washing them off with some Lacquer thinner or Acetone is good and I generally like to give them another wash down with some Denatured Alcohol as well before starting to coat them.
This helps to insure that they are completely oil free should any get left behind and from handling them.
You can just spray it down and let it run off and air dry as long as there is no oils you are good with whatever method you use.
Just make sure that there aren't sharp edges!!!
Sorry, But I can not express this enough along with having a good coating thickness!!!
Charlie has some very good painting tips But I don't know which thread it was in.
jer
P.S. Yes, Charlie is right,Diagphram won't be hurt if it touches the stator at all.
The whole thread deserves a good read through.
Stay away from gray primers and stick with the red as well as any pigmented paints particularly grays and white and anything that has Titanium Dioxide as a pigment.
If you must have a color than use a coat on top of the primer and then use only clear acyrilc to build up your coating thickness.
I have found that the canned stuff can yield very good result as far as volts per mil.
Although depending on the size of the panels this can become quite costly.
I have also found that the 3X Clear Acrylic is much much more cost effective.
But you may be better of with a gallon of paint and reducer to be cost effective for the size of your panels if you have access to a sprayer and/or compressed air.
Remember that you are going to need a coating thickness no lessthan 7mil and closer to 10mil is better if not more as 15mil is pretty much a free of any problems zone.
A micrometer is a good thing to have around and it doesn't have to be an expensive one either.
I think I paid like $15 for mine and I use it to accurately measure sub mil of my diagphram materials with and without coatings with no problems.
I just picked up two decent sprayers at Harbor Freight for cheaper around $25 and $15 for a smaller top feeding detail gun.
I will be trying them out in the next few weeks with some Minwax Poly for some cabinets and in the mean time I will be making a few more test samples for the coatings thread.
I know Dochungwell has used these same sprayers and he says they work great for what we are doing with them.
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2825793
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2825297
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2825793
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2828247
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2893839
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2894427
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2894629
http://www.diyaudio.com/forums/plan...tric-coatings-fact-fiction-2.html#post2902754
Washing them off with some Lacquer thinner or Acetone is good and I generally like to give them another wash down with some Denatured Alcohol as well before starting to coat them.
This helps to insure that they are completely oil free should any get left behind and from handling them.
You can just spray it down and let it run off and air dry as long as there is no oils you are good with whatever method you use.
Just make sure that there aren't sharp edges!!!
Sorry, But I can not express this enough along with having a good coating thickness!!!
Charlie has some very good painting tips But I don't know which thread it was in.
jer
P.S. Yes, Charlie is right,Diagphram won't be hurt if it touches the stator at all.
Yes, Using spray paints you must have a wet coat but not to wet so that it is running.
If it gets too thick it will intrap the solvent and cause it to form tiny microsopic bubbles in the coating and this will weaken the insulating factor.
Also make sure that you are in a dust free room if possible.
Sometimes I have had to do this outside and little bugs and spiders are flying in the air and you cannot see them until they hit your stator!!!
Good Luck !!!
jer
If it gets too thick it will intrap the solvent and cause it to form tiny microsopic bubbles in the coating and this will weaken the insulating factor.
Also make sure that you are in a dust free room if possible.
Sometimes I have had to do this outside and little bugs and spiders are flying in the air and you cannot see them until they hit your stator!!!
Good Luck !!!
jer
DeltaCad is super easy but it's only 2D. Google Sketch-Up is 3D and it's free; although any 3D program will have a steeper learning curve. I'm too old to learn new sh*t so I just stick with DeltaCad and orthographic views.
Minor setback. While getting ready to figure out a stretcher for the Mylar, I got the stators out of the shed to find the front / back (based on suggestions to orient the diaphragm-facing sides as those that had metal punched away from them). I noticed that the shelf-lining material that I used to separate the stators had actually bonded to some not quite dry yet clear coating.
Ugh.
So, I guess I will try a few methods to clean that stuff off before resorting to sand paper, which would imply a repaint...
Ugh.
So, I guess I will try a few methods to clean that stuff off before resorting to sand paper, which would imply a repaint...
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