I missed this on the first go-round, I'll be sure to coat it correctly...
Thanks again...
I think any ESL smaller than a door would be limited below 100Hz due to the low frequency phase-cancellation (dipole roll off). And I think it's easier to build a really good hybrid than a really good full-range ESL; although I really admire anyone with the gumption to attempt it.
Bearing in mind that both full range and hybrid designs are compromised, I went with a hybrid line for the following reasons:
- Hybrids can use simpler/cheaper transformers.
- The panels can be physically slimmer/smaller (wife approval can be an issue)
- The diaphragm resonance problem can be is largely avoided.
- Bass output can be prodigious, clean and essentially seamless if done well.
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I haven't used mechanical stretching yet but it would have come in useful when I had my wider 8.5" panels.
It took quite a bit of try's with the heat gun to get enough tension on them to be stable.
You typically don't want to use more tension than you need.
I had seen a formula that was posted that worked out perfectly and coincided with the dimensions of my little panel and it's diaphragm's resonate frequency.
It has been stated that using a high tension raises the efficiency, But this is simply not true!
The only thing having a high tension does is that it raises the resonate frequency of the diaphragm, nothing else is gained by having more than what you need to make it stable.
Typically from what I gather for a 3.5" width support the formula showed to be about 70Hz to 90hz.
As measured I could get from 70Hz to as high as 110Hz of diaphragm resonance depending on how much heat treating I gave it with my 3.25" wide panel.
So, you can guestimate what your panel will be by the distance width the the ribbed spacers as doubling the width will half the frequency.
Here is the post that gave me this idea but the formula isn't in this post.
I found the formula sometime ago and it has been discussed several times before, I just wished I could remember which post it was 🙁
http://www.diyaudio.com/forums/planars-exotics/245454-glue-wire-stators.html#post3708397
jer 🙂
It took quite a bit of try's with the heat gun to get enough tension on them to be stable.
You typically don't want to use more tension than you need.
I had seen a formula that was posted that worked out perfectly and coincided with the dimensions of my little panel and it's diaphragm's resonate frequency.
It has been stated that using a high tension raises the efficiency, But this is simply not true!
The only thing having a high tension does is that it raises the resonate frequency of the diaphragm, nothing else is gained by having more than what you need to make it stable.
Typically from what I gather for a 3.5" width support the formula showed to be about 70Hz to 90hz.
As measured I could get from 70Hz to as high as 110Hz of diaphragm resonance depending on how much heat treating I gave it with my 3.25" wide panel.
So, you can guestimate what your panel will be by the distance width the the ribbed spacers as doubling the width will half the frequency.
Here is the post that gave me this idea but the formula isn't in this post.
I found the formula sometime ago and it has been discussed several times before, I just wished I could remember which post it was 🙁
http://www.diyaudio.com/forums/planars-exotics/245454-glue-wire-stators.html#post3708397
jer 🙂
There you go kouiky, Charlie has explained it better than I could. And just for the record, I chose to go with a hybrid design for the same reason that Charlie (and most others) do. Thanks Charlie..🙂
Yea Jer, I could't find the thread that I saw the elongation formula on either, that's why I asked last night.
I dug out my copy of Sanders book and re-read the chapter on curved cell construction, and what I gleaned from it was to stretch the diaphragm till it starts to deform, (not very concrete).
I'm with you about not wanting too high of a resonance point, I think with the crossover unit set at 48 dB per octave roll-off and 200-250 Hz knee, that a panel with a 100 Hz resonance should be just fine. I just don't know how much tension is required for that to happen.
Charlie's blog states 1-2% and he went with 1.5% and thinks his is about 100 Hz (though not measured).
Doing the math for my 80 inch stretcher (60 inch panel) 1.5% elongation would be around 3 cm, so if I were to stretch just over an inch I'm guessing I'll be in the ballpark at least. I wonder if stretching by that amount is going to 'deform' the Mylar as Sanders suggests to do...
Wish me luck,I guess...
Yea Jer, I could't find the thread that I saw the elongation formula on either, that's why I asked last night.
I dug out my copy of Sanders book and re-read the chapter on curved cell construction, and what I gleaned from it was to stretch the diaphragm till it starts to deform, (not very concrete).
I'm with you about not wanting too high of a resonance point, I think with the crossover unit set at 48 dB per octave roll-off and 200-250 Hz knee, that a panel with a 100 Hz resonance should be just fine. I just don't know how much tension is required for that to happen.
Charlie's blog states 1-2% and he went with 1.5% and thinks his is about 100 Hz (though not measured).
Doing the math for my 80 inch stretcher (60 inch panel) 1.5% elongation would be around 3 cm, so if I were to stretch just over an inch I'm guessing I'll be in the ballpark at least. I wonder if stretching by that amount is going to 'deform' the Mylar as Sanders suggests to do...
Wish me luck,I guess...
Yes, There will be a point where you will noticed less of a stretching action happening.
This is good as this is called Tensilizing.
Just be careful as you will be very close to the breaking point anywhere above 2%.
I think that Mylar is good for about 2% to 5% elongation being the larger value for the thicker materials.
Most Mylar's you can get are not tensilized (pre stretched) or at least not very well if they claim to be, from what I have read.
Once it is pre-stretched to a certain point then there is less of a chance for it to stretch anymore from use causing it to lose its tension.
I think that this is the issue I was having about stability with my First wider panels and the fact that the plastic grid material was not perfectly flat and flexed too much as is it bowed outward away from the diaphragm from the tension well.
But they finally did work great once I got enough tension on them.
jer 🙂
This is good as this is called Tensilizing.
Just be careful as you will be very close to the breaking point anywhere above 2%.
I think that Mylar is good for about 2% to 5% elongation being the larger value for the thicker materials.
Most Mylar's you can get are not tensilized (pre stretched) or at least not very well if they claim to be, from what I have read.
Once it is pre-stretched to a certain point then there is less of a chance for it to stretch anymore from use causing it to lose its tension.
I think that this is the issue I was having about stability with my First wider panels and the fact that the plastic grid material was not perfectly flat and flexed too much as is it bowed outward away from the diaphragm from the tension well.
But they finally did work great once I got enough tension on them.
jer 🙂
Correction: My stretching jig is not 80 inches as stated above (I was going by [bad] memory) sorry.
The two points where the actual stretching will occur is 96 inches, so my 3 cm measurement was also not correct. The 1.5 percentage elongation for 96 inches would be 3.66 cm (1.44 inches) Sorry for any confusion.
-wreck
The two points where the actual stretching will occur is 96 inches, so my 3 cm measurement was also not correct. The 1.5 percentage elongation for 96 inches would be 3.66 cm (1.44 inches) Sorry for any confusion.
-wreck
I too have heard it said that higher tension gives greater efficiency. While higher tension in and of itself would not raise efficiency, I believe the intent behind the assertion stems from a premise that when energized by bias voltage, the diaphragm will always be pulled toward one of the stators (rather than remaining centered between the stators), and that higher tension better resists this deflection. Thus, the actual assertion would be that higher tension allows using higher bias voltage and the higher bias would raise efficiency.
Sanders' book also asserts that higher tension provides a greater "restoring force" to the diaphragm.
BTW, I'm not sure that 1.5% elongation in both directions, as used with flat panels, is equivalent tension to 1.5% elongation applied in only one direction, as would be used with a curved panel. And I haven't seen anything posted about this either.
Our friend Calvin is the master of curved panels, so I think he would be the guy to ask advice on this.
Sanders' book also asserts that higher tension provides a greater "restoring force" to the diaphragm.
BTW, I'm not sure that 1.5% elongation in both directions, as used with flat panels, is equivalent tension to 1.5% elongation applied in only one direction, as would be used with a curved panel. And I haven't seen anything posted about this either.
Our friend Calvin is the master of curved panels, so I think he would be the guy to ask advice on this.
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Yea Charlie, I may have to talk to Calvin before I assemble, better safe than sorry...🙂
On a side note about resonance, I found this thread very interesting:
http://www.diyaudio.com/forums/planars-exotics/147801-diaphragm-resonance-change-hv-bias.html
All the best
-wreck
On a side note about resonance, I found this thread very interesting:
http://www.diyaudio.com/forums/planars-exotics/147801-diaphragm-resonance-change-hv-bias.html
All the best
-wreck
I use flat panels and I only stretch the diaphragm just enough to get rid of all the wrinkles. I run my ESL fullrange and I really like them.
http://www.diyaudio.com/forums/plan...ut-stretch-your-full-range-esl-diaphragm.html
http://www.diyaudio.com/forums/plan...ut-stretch-your-full-range-esl-diaphragm.html
Hi Wachara,
Yes, I remember your thread, (I posted in it inquiring about the powder coating), I'm glad you are enjoying those speakers, they're very nice! 🙂
A few questions if you don't mind:
Does the relatively low tension you use ever cause the diaphragm to hit the stator(s)?
Do you play them very loud?
What type of music do you normally listen to?
And finally, do you use them to watch movies?
Thanks for any replies...
Yes, I remember your thread, (I posted in it inquiring about the powder coating), I'm glad you are enjoying those speakers, they're very nice! 🙂
A few questions if you don't mind:
Does the relatively low tension you use ever cause the diaphragm to hit the stator(s)?
Do you play them very loud?
What type of music do you normally listen to?
And finally, do you use them to watch movies?
Thanks for any replies...
Hi wreck,
I don't notice the diaphragm hitting the stators, and my panels can play music very loud.
I listen to classical, jazz, and temporary, popular vocal music.
No, I don't use them to watch movies. You need a good subwoofer to really enjoy action movies. 😉
Wachara C.
I wish I had the room bro...I really do...😉
Anyway, when I arc tested panel 1 of 4, I found around a dozen spots where direct wire contact produced small arcs... Seems my powder coater either didn't do his job, or maybe he really didn't understand the result I was seeking...
No use beating a dead horse though...🙄
I found out first-hand what Calvin and Jer were talking about as far as insulating these things is concerned...
The polyurethane primer I used to re-coat the edges was supposed to be 'non-conductive'...But it's clear to me now,, that that claim didn't take into account ESLs...
Thankfully I saw a post from Jer that mentioned that nail polish hardened as a nylon (i think that's correct)
Either way, the spot-touching I did with ordinary nail polish worked like a charm once hardened, no more arcs!
Tedious though...So far the process has taken me 2 hours to correct one half of one panel, so at this pace, all four is going to take me 16-plus hours...Ughhh! ...on the other hand, no-one said this build was going to be easy...
After I 'spot-check' these panels, I'm still going to go over them with some Minwax Urethane... double-checking can't hurt, I suppose...
Oh boy...I've went way beyond my quota...'scuze me ...while I...
Bye.
-wreck
I would just give them a good wet coat or two with some 2X clear acrylic!! 😉
It has about 2 to 4 times the dielectric strength of polyurethane and will cure much Faster.
jer 🙂
It has about 2 to 4 times the dielectric strength of polyurethane and will cure much Faster.
jer 🙂
Wow, really? I'll have to return the quart of urethane then, as it was expensive. Cool.
I got looking at the panel a little closer, and cannot place all the blame on the powder coat job, as there are some left over microscopic metal burrs (inside the holes) that I should have paid more attention to BEFORE the coating was done. I mean, I did use a very fine file and then an emery cloth flap wheel on them (for hours) but it might have not been enough, as I've heard that even powder coating doesn't like to cover sharp spots as well as smooth ones..
Oh well, the nail polish works for the trouble spots, 'sall good.
I got looking at the panel a little closer, and cannot place all the blame on the powder coat job, as there are some left over microscopic metal burrs (inside the holes) that I should have paid more attention to BEFORE the coating was done. I mean, I did use a very fine file and then an emery cloth flap wheel on them (for hours) but it might have not been enough, as I've heard that even powder coating doesn't like to cover sharp spots as well as smooth ones..
Oh well, the nail polish works for the trouble spots, 'sall good.
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Well, this spot checking for archs has been more of a PITA than I had expected.
There was 70-80 arch points per panel!
Jeez!
The good thing is that I am almost done, next is spray-coating with 2X clear.
Cheers...
There was 70-80 arch points per panel!
Jeez!
The good thing is that I am almost done, next is spray-coating with 2X clear.
Cheers...
AHHHHHHH!!!! 
:N:
Oh Man !!!!
Good thing you checked it !!!!
At least you have a good base coat to start with.
😴
jer 🙂
:N:Oh Man !!!!
Good thing you checked it !!!!
At least you have a good base coat to start with.
😴
jer 🙂
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Hi,
after so many bad experiences I don't trust a coater who claims he can do the job prior of a test run 🙄
They certainly all know how to paint as thin as possible, but hardly anyone has expertise in thick layer coating.
And what a coater thinks of a thick coat is still a thin coat for us.
Unfortunately the most promising way to achieve even and thick coatings -fluidized bed powdering- requires a elaborated process and alot of testing before.
The common Diyer with a low demand of device number count has to rely on spray coating which results in thinner coatings.
Here no more than 2 layers are practical.
Thicker coatings require multiple runs of additional wet coats.
Another possibility could be wet dipping.
At least in theory this would allow for thick layers.
The Q remains of how even such coatings woud be.
It probabely requires extensive testing, before process timing and -speeds fit.
In comparison using wire is like a kiddo's game.
jauu
Calvin
after so many bad experiences I don't trust a coater who claims he can do the job prior of a test run 🙄
They certainly all know how to paint as thin as possible, but hardly anyone has expertise in thick layer coating.
And what a coater thinks of a thick coat is still a thin coat for us.
Unfortunately the most promising way to achieve even and thick coatings -fluidized bed powdering- requires a elaborated process and alot of testing before.
The common Diyer with a low demand of device number count has to rely on spray coating which results in thinner coatings.
Here no more than 2 layers are practical.
Thicker coatings require multiple runs of additional wet coats.
Another possibility could be wet dipping.
At least in theory this would allow for thick layers.
The Q remains of how even such coatings woud be.
It probabely requires extensive testing, before process timing and -speeds fit.
In comparison using wire is like a kiddo's game.
jauu
Calvin
Plastidip is difficult to work with.
First it must be thinned....a lot.
The stuff in the spray can's is to thin and does not cover enough area produce a good buildup thickness for what it cost.
The clear acyrlic enamels are the most cost effective high performance coatings that I have found to date.
And easier to work with.
FWIW
jer 🙂
First it must be thinned....a lot.
The stuff in the spray can's is to thin and does not cover enough area produce a good buildup thickness for what it cost.
The clear acyrlic enamels are the most cost effective high performance coatings that I have found to date.
And easier to work with.
FWIW
jer 🙂
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