Interesting....well I guess one more thing for me to keep in mind when measuring transformers. Thanks for the info.
I am curious though, as to what audio transformers you were measuring that showed leakage inductance substantially changing with frequency. I haven't encountered this before.
Most audio amplifier and ESL transformers are either toroidal or EI core. In either case, all the windings share the same section of the core; ie there is no intentional magnetic leakage path built in to the core between the windings like in leakage transformer. So, the only flux leakage paths are thru air not core. This being the case, you can measure the leakage inductance of ESL transformers with or without the core in place and get essentially the same value.
Good point Steve. Since the windings are interleaved on top of each other with an ideal core all lines pass through both coils (theoretically). The core parameters are not supposed to effect leakage reactance. Since we are measuring apparent leakage inductance who knows the exact cause.
I may still have that set of transformers that were really bad. Since they are of no use to me, maybe I can take one apart and see how it was constructed. It was an EI core.
Later,
Jim
I may still have that set of transformers that were really bad. Since they are of no use to me, maybe I can take one apart and see how it was constructed. It was an EI core.
Later,
Jim
I revisited this test as the numbers don't compute for thickness. I think I was getting arcing to the insulation from air gaps rather than through the PVC jacket. Re-testing with a better method of securing the wire to the ground plane showed that the PVC insulation of .016" was good to 10kv+
Maybe Steve will share his AC test results. If nothing else, the visuals are far better 🙂
Jim
Maybe Steve will share his AC test results. If nothing else, the visuals are far better 🙂
Jim
For the short version, see attached pic showing results of 5kHz at 5kVrms applied for 15 seconds between wire and metal foil ground plane.
The slightly longer version is that I was a bit surprised to read Jim's test results of PVC wire insulation failing at 2.4kV DC.
Dieletric strength for PVC is around 550V/mil. With insulation thickness of 16 mil, it should easily withstand 2.4kV.
Looks like Jim's most recent testing confirms this.
I performed similar DC tests at 5kV and 10kV with no failures. I even applied 15kV without failure. I did include a series current monitoring resistor so I could observe any increase in current that might indicate failure. It was interesting to watch the current rise momentarily when switching to a higher voltage and then decline to a steady state value. The current rise was from charging the small capacitor made up of the wire and foil separated by PVC dielectric. The steady state value was from bulk resistivity of the PVC.
Researching insulation testing on line, it was mentioned many times that HV AC tests are much more stressful on the insulation. So, of course I had to give it a try. 😀
I was frustrated, though, to find no mention of what the "working voltage" ratings for PVC wire represent.
Starting with 1kHz @ 2kV. With lights out, could just see some corona glow around the wire.
Stepping up to 5kV, more corona and starting to smell a bit of ozone.
With 2kHz @ 5kV the corona was visible with the lights on. Very cool blue-purple glow.
So I had to call the wife in to have a look see. She was oohing and aahing at the pretty blue glow so I cranked up the frequency..3kHz..4kHz..5kHz...more and more intense corona, and then....
CRACK!!! and little wisps of smoke.
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Told you!!!
Welcome to barrier discharge world. Sometimes the distance (low capacitance) is more important than type of dielectric.
YouTube - High voltage dielectric barrier discharge
Sincerely,
Alex
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Thanks everyone for your help with this. I'll have to postpone this project for a couple of months due to financial constaints.
When I do this, I think I have all the info I need except:
When applying the coating to the membrane, how close do you go to the spacers, and do the wires go just past this point, or is the first/last wire directly over the edge of the coating.
Thanks,
Paul
When I do this, I think I have all the info I need except:
When applying the coating to the membrane, how close do you go to the spacers, and do the wires go just past this point, or is the first/last wire directly over the edge of the coating.
Thanks,
Paul
In case anybody is interested in the Terman handbook Jim mentioned, there is currently one up for auction on ebay. As luck would have it, I found one in good condition at a local used book store.
3 VINTAGE RADIO ENGINEERING BOOKS REFERENCE REPAIR+++++ - eBay (item 330439932773 end time Jun-13-10 19:17:43 PDT)
Thanks Steve,I'm still here.
And just reading.
Dealing with everyday life things latey,so sorry I havn't been fluent.
Paul, as Bolserst put it ,I(too) don't have any exprience with an original panel from acuostat.
But,if you double the area this will make more load on the amplifier.
Also by doubling the surface area increases the acuostic level of the speaker system(more than one speaker).
This shows an increase of speaker effeicency,I call this a phenomenom ,as I have yet to mearsure this.
Somewhere deep in these threads I read a discusion about using either one big amp and some surface area vs smaller surface area's (totalling the one big one) and several amps driving them instead of one big one.
This is supposed to yield a better speaker effeicency, a lesser load on each amplifier and use less power in the long run.
While like I said I personaly have yet to measure this,physics says you can't get something for nothing.
I have read this in other books and stuff on P.A systems,plus I have had much experience with very big and loud system's of such.
Some might call them small,but 5Kw to 15Kw in such a system is not small by no means.
And from that experience the more surface area the better it sounded and the louder it got,until the amplifiers could not do any more.
Anyway once I get some more things squared away I will start that part of my study.
Meanwhlie I my bench got too cluttered to have 7Kv+ flyin around ,chips don't like it ,you know what I mean?
And I have to fix my frequency counter in order to get those very acurate transformer specs done.
But at least I know round'abouts what they are and why It works the way it does,Thanks to you guys here at diyaudio.
So,I'm getting on it! jer
And just reading.
Dealing with everyday life things latey,so sorry I havn't been fluent.
Paul, as Bolserst put it ,I(too) don't have any exprience with an original panel from acuostat.
But,if you double the area this will make more load on the amplifier.
Also by doubling the surface area increases the acuostic level of the speaker system(more than one speaker).
This shows an increase of speaker effeicency,I call this a phenomenom ,as I have yet to mearsure this.
Somewhere deep in these threads I read a discusion about using either one big amp and some surface area vs smaller surface area's (totalling the one big one) and several amps driving them instead of one big one.
This is supposed to yield a better speaker effeicency, a lesser load on each amplifier and use less power in the long run.
While like I said I personaly have yet to measure this,physics says you can't get something for nothing.
I have read this in other books and stuff on P.A systems,plus I have had much experience with very big and loud system's of such.
Some might call them small,but 5Kw to 15Kw in such a system is not small by no means.
And from that experience the more surface area the better it sounded and the louder it got,until the amplifiers could not do any more.
Anyway once I get some more things squared away I will start that part of my study.
Meanwhlie I my bench got too cluttered to have 7Kv+ flyin around ,chips don't like it ,you know what I mean?
And I have to fix my frequency counter in order to get those very acurate transformer specs done.
But at least I know round'abouts what they are and why It works the way it does,Thanks to you guys here at diyaudio.
So,I'm getting on it! jer
On my 2+2's there are thick felt strips on the back side. This I assume was to help limit the panel esp at Fs. They are mounted vertically centerd on the louver.
One wider (but not doubled) panel would need this protection more, no?
Would it be possible to double the layers of stator wire on the back side?
My thinking is that this would increase efficiency, and restrict airflow thereby restricting membrane travel?
Thanks,
Paul
One wider (but not doubled) panel would need this protection more, no?
Would it be possible to double the layers of stator wire on the back side?
My thinking is that this would increase efficiency, and restrict airflow thereby restricting membrane travel?
Thanks,
Paul
Yes, the thick felt strips are there to dampen the diaphragm fundamental resonance (Fs). If you build a wider panel and want similar damping as the Acoustat panels you will most likely need to apply felt to the same percentage of panel area. I say most likely because the amount of damping required to achieve a particular LF response is dependent on the ratio of tension to air load. If you use higher tension you will need more damping.
I experimented with placing stator wires closer together leaving only 38% open area and did not notice any improvement in damping of Fs compared to the more typical 45%-50% open area.
The damping pads on the back if the Acoustat's are there to help keep the diaphragms stable under hard low frequency drive situations. The problem lies in the fact that they (Acoustat) used 65 gage HS Mylar and built the panels 9 inches wide. The Heat Shrink (HS) Mylar only just pulls enough tension over that width to stay stable if you don't play them too hard. So with a 0ne or a 0ne plus 0ne you will be pushing them to near their limit if you play loud and like bass. So the pads offer some resistive air load to stabilize the diaphragms. If you build a wider panel you should move up to the 80 gage HS Mylar, it is not likely that you will hear any difference between the two film thicknesses as far as high frequency goes but the heavier film will shrink a little tighter and so stay more stable. You will have to experiment to see if you still need the pads. If you build a narrower panel say six or seven inches wide then the 65 gage Mylar will be stable and you won't need the pads and you will get better stage and imaging than with a nine inch panel.
I might ask why you want to build a wider panel? Acoustat was there and did that and pushed things as far as they could with the nine inch panel (and still required the pads to keep it stable, most of the time) so why would you think that you could build a wider one and that it would work? This assumes that you will use the HS65.
If Bass is what you want simply build a set of six or seven inch wide panels in a 0ne plus 0ne configuration and get a couple of powered subs. If you really want great bass get yourself five inexpensive eight inch powered subs (small ones) and scatter them in a random fashion around your room placing just one of them in a corner (ala Ged's) and you will get fantastic bass from a very small amount of floor space. You will also control your room modes even better than with stereo subs and they only have to cost around $100 - $150 each. Building a larger panel is not the way to go. If you must make bass with a panel then build them the same size or slightly smaller than the stock nine inch versions and use more of them, so go to a model six configuration. A set of two plus two's with a really good amp can make a lot of high quality bass but you will require a really stable amp that is happy to drive a hard load (take a look a Sanders amps). Just my two cents but the 0ne plus 0nes with a number of dynamic sub is the best and least expensive way to get ESL sound with great bass. Remember that while adding additional panels does increase the capacitive load to the amp the system efficiency does go up with additional panels and so you end up not pushing your amp as hard as you would if you had a set of 0ne plus 0nes (only four panels total for stereo) and wanted to play loud.
I think that if you wanted to use your stators to provide a greater amount of resistive air load on your diaphragms (which I think is a very good idea) you would likely need to drop the open area down into the range of 25 - 30%. The easiest solution thought is to reduce the panel width accept the small reduction in bass output and use powered dynamic subs to make up the difference. If you decide to use film much lighter in gage than the stock 65 gage HS Mylar then then you are going to have to build a narrower panel any way as the thinner films will not remain stable if you choose to build even a standard width panel. There is no way to cheat on this one it just is what it is.
I might ask why you want to build a wider panel? Acoustat was there and did that and pushed things as far as they could with the nine inch panel (and still required the pads to keep it stable, most of the time) so why would you think that you could build a wider one and that it would work? This assumes that you will use the HS65.
If Bass is what you want simply build a set of six or seven inch wide panels in a 0ne plus 0ne configuration and get a couple of powered subs. If you really want great bass get yourself five inexpensive eight inch powered subs (small ones) and scatter them in a random fashion around your room placing just one of them in a corner (ala Ged's) and you will get fantastic bass from a very small amount of floor space. You will also control your room modes even better than with stereo subs and they only have to cost around $100 - $150 each. Building a larger panel is not the way to go. If you must make bass with a panel then build them the same size or slightly smaller than the stock nine inch versions and use more of them, so go to a model six configuration. A set of two plus two's with a really good amp can make a lot of high quality bass but you will require a really stable amp that is happy to drive a hard load (take a look a Sanders amps). Just my two cents but the 0ne plus 0nes with a number of dynamic sub is the best and least expensive way to get ESL sound with great bass. Remember that while adding additional panels does increase the capacitive load to the amp the system efficiency does go up with additional panels and so you end up not pushing your amp as hard as you would if you had a set of 0ne plus 0nes (only four panels total for stereo) and wanted to play loud.
I think that if you wanted to use your stators to provide a greater amount of resistive air load on your diaphragms (which I think is a very good idea) you would likely need to drop the open area down into the range of 25 - 30%. The easiest solution thought is to reduce the panel width accept the small reduction in bass output and use powered dynamic subs to make up the difference. If you decide to use film much lighter in gage than the stock 65 gage HS Mylar then then you are going to have to build a narrower panel any way as the thinner films will not remain stable if you choose to build even a standard width panel. There is no way to cheat on this one it just is what it is.
my plan (not set in stone) was to make a one plus one style speaker, but to have a wider panel than the single panels used by acoustat. Possibly 12" wide.
I was also considering doubling up (or more ) the stator wires on the back side only. In the center of the panel, one could even triple up the stator wires, such that in the center of the panel there is no open area.
I will be using the electronics from my 2+2's which I've done the Izzy Wizzy mods to.
I am using a capacitor to my amp input to cut the low freq. below 100 Hz. ( 6 dB/ octave ) and using a Vandersteen sub. Right now I have skads of bass, probably a little bottom heavy.
I understand that if I redid the speaker panels, I might have to move the crossover a little higher, and that would be fine, but I didn't want to make a wider section to get a bigger panel, actually a little narrower than what I've got.
Paul
I was also considering doubling up (or more ) the stator wires on the back side only. In the center of the panel, one could even triple up the stator wires, such that in the center of the panel there is no open area.
I will be using the electronics from my 2+2's which I've done the Izzy Wizzy mods to.
I am using a capacitor to my amp input to cut the low freq. below 100 Hz. ( 6 dB/ octave ) and using a Vandersteen sub. Right now I have skads of bass, probably a little bottom heavy.
I understand that if I redid the speaker panels, I might have to move the crossover a little higher, and that would be fine, but I didn't want to make a wider section to get a bigger panel, actually a little narrower than what I've got.
Paul
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Paul I don't understand, you said first that you wanted to make a wider panel then you finished by saying that you didn't want to make a wider section to get a bigger panel, I don't know what you mean by that. If you are cutting the panel off at 100 Hz then why do you need a bigger (wider) panel?
I have built panels with 24 wires per inch and posted pictures on several threads here. You could also build 32 wires per inch if you wanted. If you intend to keep your drive force symmetrical then you will have to have the same number of stator wires per inch on both the front and rear stators.
The wider you make a panel the more directional it will become (will beam more). A six or seven inch wide panel will give you a wider sweet spot for stereo and still play as loud as you want if you are rolling it off at 100 Hz.
If you wanted to make a 6-7 inch wide panel using say 3 micron film then you could divide the panel in half with a 1/2 inch wide clamp running vertically and that would probably remain stable. For that matter a three inch wide panel might get the job done if you are running a floor to ceiling vertical line source. Remember most good one inch dome tweeters only have a peak to peak linear excursion of about one sixteenth of an inch. While they don't go down to 100 Hz they can reach well below one K. A number of two way dynamic designs with a one inch domes crossover below fifteen hundred Hz.
I have built panels with 24 wires per inch and posted pictures on several threads here. You could also build 32 wires per inch if you wanted. If you intend to keep your drive force symmetrical then you will have to have the same number of stator wires per inch on both the front and rear stators.
The wider you make a panel the more directional it will become (will beam more). A six or seven inch wide panel will give you a wider sweet spot for stereo and still play as loud as you want if you are rolling it off at 100 Hz.
If you wanted to make a 6-7 inch wide panel using say 3 micron film then you could divide the panel in half with a 1/2 inch wide clamp running vertically and that would probably remain stable. For that matter a three inch wide panel might get the job done if you are running a floor to ceiling vertical line source. Remember most good one inch dome tweeters only have a peak to peak linear excursion of about one sixteenth of an inch. While they don't go down to 100 Hz they can reach well below one K. A number of two way dynamic designs with a one inch domes crossover below fifteen hundred Hz.
I seem to recall reading that flyscreen is a suitable stator material on the louvers somewhere in this thread...
Can anyone relate the pros and cons of flyscreen as a stator?
Thanks
WM
Can anyone relate the pros and cons of flyscreen as a stator?
Thanks
WM
amp considerations
If I was to use my acoustat transformers (medallion and C updates, izzy wizzy mods and new caps), build new panels one panel wide (diaphragm width) 8";
d/s 1mm; panel height <8 ft tall, kynar coated wire 28 guage using ~12 wires /inch
crossed over at 4-500 Hz (first order ((cap installed in amp at input)) ) and used my NYAL moscode for the bass/low midrange (driving open baffle woofers)
what would be the smallest tube amp I could use to drive these guys.
I built Tube labs simple se and love it.
I would be willing to try tubelabs push pull amp.
Just wondering if as a upper mid/ treble speaker, I will still need a gutsy amp.
~95dB peaks on rock will suffice for me
Paul Thanks
If I was to use my acoustat transformers (medallion and C updates, izzy wizzy mods and new caps), build new panels one panel wide (diaphragm width) 8";
d/s 1mm; panel height <8 ft tall, kynar coated wire 28 guage using ~12 wires /inch
crossed over at 4-500 Hz (first order ((cap installed in amp at input)) ) and used my NYAL moscode for the bass/low midrange (driving open baffle woofers)
what would be the smallest tube amp I could use to drive these guys.
I built Tube labs simple se and love it.
I would be willing to try tubelabs push pull amp.
Just wondering if as a upper mid/ treble speaker, I will still need a gutsy amp.
~95dB peaks on rock will suffice for me
Paul Thanks
WM,
There is another thread somewhere, where they talk about the pro/con issue of flyscreen.
Seems its hard to get it glued flat to the louver, also if it isn't extremely thin, some of the "bumps" will be closer to the mylar than the "recesses" limiting your excursion (bass).
Sorry this is so late
Paul