Hi audiophiles,
I need some clarifications to the result from my restauration of ML Sequel panels.
The original membranes didn't builld up enough charge (I guess), sound was dull and boomy.
I think ML coated their older models with graphite and it seems this stuff looses the abillity to be charged in a (long) period of time (mine are the first sequel 2 models ).
So I got 6my of mylar and EC Coating and repaired the panels (really not so easy to get wrinkle free :-() and still not perfect, I will do again.
But it's allready noteable how the sound balance got much better. Highs are there with shiny sparkling (cymbals, hihats etc.) And also mids have a nice resolution.
Only two things I'm not clear about: One speaker is louder. The foil of the one with less efficiency wasn't masked before coating and I applied the liquid everywhere.
This was not so clever, because discharging occurs somewhere at the border of the panel (this my theory) Could this be the reason for the reduced efficiency?
Second, both speakers sometimes produce a high frequency whistling sound. It beeps for some seconds and then is gone. What could be the reason for this? Could it be the tension of the mylar (not enough tensioning)??
I hope somebody can tell me
Bye
Olaf
I need some clarifications to the result from my restauration of ML Sequel panels.
The original membranes didn't builld up enough charge (I guess), sound was dull and boomy.
I think ML coated their older models with graphite and it seems this stuff looses the abillity to be charged in a (long) period of time (mine are the first sequel 2 models ).
So I got 6my of mylar and EC Coating and repaired the panels (really not so easy to get wrinkle free :-() and still not perfect, I will do again.
But it's allready noteable how the sound balance got much better. Highs are there with shiny sparkling (cymbals, hihats etc.) And also mids have a nice resolution.
Only two things I'm not clear about: One speaker is louder. The foil of the one with less efficiency wasn't masked before coating and I applied the liquid everywhere.
This was not so clever, because discharging occurs somewhere at the border of the panel (this my theory) Could this be the reason for the reduced efficiency?
Second, both speakers sometimes produce a high frequency whistling sound. It beeps for some seconds and then is gone. What could be the reason for this? Could it be the tension of the mylar (not enough tensioning)??
I hope somebody can tell me
Bye
Olaf
Hi Olaf
(sorry anyone else for answering in german)
die Beschichtung solltest Du wenn möglich schon mittels Maske aufbringen, da alle Punkte, wo eine direkte Verbindung zwischen Membran und Stator besteht -also auch unter den horizontalen Abstandhaltern- anfällig sind für Leckagen und Überschläge. Bei den Beschichtungen der älteren MLs kann man deutlich erkennen, daß die Beschichtung innerhalb der einzelnen Segmente nie die horizontalen Spacer berührt. Zur Kontaktierung der Beschichtung allerdings musst Du bis auf die seitlichen Abstandhalter beschichten. Der wenige Millimeter breite Kontaktstreifen sollte halbwegs mittig auf den Abstandhaltern positioniert sein und die Beschichtung nicht bis zum Aussenrand der Folie aufgetragen werden. Es ist auch vorteilhaft, den Kontaktstreifen in U-Form, bzw. als zwei links-rechts auf der Membran befindliche Streifen auszuführen.
Wichtig bei den MLs ist die mechanische Spannung, da die daraus folgende Lage der Grundresonanz in die Weichenabstimmung reinspielt!
beeping: Es ist nicht einfach Ferndiagnosen zu stellen, wenn die Membranspannung allerdings zu niedrig ist gibt es zwei mögliche Phänomene.
- Die Membran wird an einen der Statoren gezogen und bleibt dort kleben (bei kunststoffbeschichteten Satoren fast immer der Fall). Dabei wird dann ein leises andauerndes Knistern bis Prasseln hörbar, je nach Höhe der Polarisationsspannung. Nach Abschalten der Polarisation dauert es in der Regel einige Minuten bis sich die Folie unter Popp-Geräuschen vollständig wieder löst
- Die Membran wird an den Stator gezogen, klatscht deutlich hörbar dagegen, es gibt eine Entladung, die Membran löst sich und klatscht bei der nächsten Signalwelle wieder gegen den Stator. Ein lautes knatterndes Geräusch wird so erzeugt.
Ein Pfeifen deutet dagegen eher auf einen elektrischen Effekt hin und weniger auf einen mechanischen.
jauu
Calvin
(sorry anyone else for answering in german)
die Beschichtung solltest Du wenn möglich schon mittels Maske aufbringen, da alle Punkte, wo eine direkte Verbindung zwischen Membran und Stator besteht -also auch unter den horizontalen Abstandhaltern- anfällig sind für Leckagen und Überschläge. Bei den Beschichtungen der älteren MLs kann man deutlich erkennen, daß die Beschichtung innerhalb der einzelnen Segmente nie die horizontalen Spacer berührt. Zur Kontaktierung der Beschichtung allerdings musst Du bis auf die seitlichen Abstandhalter beschichten. Der wenige Millimeter breite Kontaktstreifen sollte halbwegs mittig auf den Abstandhaltern positioniert sein und die Beschichtung nicht bis zum Aussenrand der Folie aufgetragen werden. Es ist auch vorteilhaft, den Kontaktstreifen in U-Form, bzw. als zwei links-rechts auf der Membran befindliche Streifen auszuführen.
Wichtig bei den MLs ist die mechanische Spannung, da die daraus folgende Lage der Grundresonanz in die Weichenabstimmung reinspielt!
beeping: Es ist nicht einfach Ferndiagnosen zu stellen, wenn die Membranspannung allerdings zu niedrig ist gibt es zwei mögliche Phänomene.
- Die Membran wird an einen der Statoren gezogen und bleibt dort kleben (bei kunststoffbeschichteten Satoren fast immer der Fall). Dabei wird dann ein leises andauerndes Knistern bis Prasseln hörbar, je nach Höhe der Polarisationsspannung. Nach Abschalten der Polarisation dauert es in der Regel einige Minuten bis sich die Folie unter Popp-Geräuschen vollständig wieder löst
- Die Membran wird an den Stator gezogen, klatscht deutlich hörbar dagegen, es gibt eine Entladung, die Membran löst sich und klatscht bei der nächsten Signalwelle wieder gegen den Stator. Ein lautes knatterndes Geräusch wird so erzeugt.
Ein Pfeifen deutet dagegen eher auf einen elektrischen Effekt hin und weniger auf einen mechanischen.
jauu
Calvin
Hallo Calvin, vielen Dank.
Das mit der verschobenen Reso muß ich vielleicht auch noch ausgleichen.
For all:
I understand;
There are at least two factores, I've got to consider. The thinner mylar and the lower tensioning lead to a different resonance frequency.
In this case I guess the thinner foil counts less than the tensioning.
My expectations would be, that the frequency should be lower than the original Panels (maybe 60 Hz vs. 95 Hz). Is this right?
This won't influence the response at the 6db baffle step slope so much, but more the range at crossover frequency. As a result I expect a bump in lower response region of the panel.
I think redesign of the crossover is a must in this case . Maybe the bump is not so worse and I can live with it. (I'm not so shure if this is audible)
I realy should get a mike to messure acustical output.
Next foils will be masked and better tensioned
)
bye
P.S. What's the thickness of the original ML SL2 membranes? Can somebody tell me? I read somewhere it's 12 my.
Das mit der verschobenen Reso muß ich vielleicht auch noch ausgleichen.
For all:
I understand;
There are at least two factores, I've got to consider. The thinner mylar and the lower tensioning lead to a different resonance frequency.
In this case I guess the thinner foil counts less than the tensioning.
My expectations would be, that the frequency should be lower than the original Panels (maybe 60 Hz vs. 95 Hz). Is this right?
This won't influence the response at the 6db baffle step slope so much, but more the range at crossover frequency. As a result I expect a bump in lower response region of the panel.
I think redesign of the crossover is a must in this case . Maybe the bump is not so worse and I can live with it. (I'm not so shure if this is audible)
I realy should get a mike to messure acustical output.
Next foils will be masked and better tensioned
)bye
P.S. What's the thickness of the original ML SL2 membranes? Can somebody tell me? I read somewhere it's 12 my.
Hi,
@mims:
You won´t be able to disassemble the stators without destroying the membrane. Since You can´t use it again anyway, You can immedialtly install a new one!
@MJ
ML used the VHB-Tapes of 3M. As I remembrer they took 1.5/1.55mm or 1.0/1,1mm. For crossover-fregs as high as in the MLs -and the corresponding high mechanical tension- 1.0/1.1mm is sufficient for all instances.
I use 1.0/1.1 in my stators (which are of Sequel size)
jauu
Calvin
@mims:
You won´t be able to disassemble the stators without destroying the membrane. Since You can´t use it again anyway, You can immedialtly install a new one!
@MJ
ML used the VHB-Tapes of 3M. As I remembrer they took 1.5/1.55mm or 1.0/1,1mm. For crossover-fregs as high as in the MLs -and the corresponding high mechanical tension- 1.0/1.1mm is sufficient for all instances.
I use 1.0/1.1 in my stators (which are of Sequel size)
jauu
Calvin
Calvin said:
Hi Calvin,
Won't the capacitance increase too much if you use as small as 1,0 mm as a spacer?
In my curved wire esl I used around 1,0 mm (both sides) spacing and in my opnion the Mylar in the middle parts had somewhat less spacing because it is quite impossible to maintain the perfect curvature of the mylar. However because of the high mechanical tension, the deviation was acceptable. Since you mention 1,5 mm as spacing I will use that instead of the 1,0 mm.
The spacers will be put closer together to allow thinner films of Mylar. The sequel2 has cells as high as 12 cm but I will try around 7 cm and 5 alternately to distribute resonance.
BTW you're right about output. With 1,0 mm spacing even a small unit with a 1:50 step-up makes a lot of sound
Yeah, MartinJan
Calvin,
Thanks a lot for the reply. How can I install a new membrane? I know there's lot of information regading ELS DIY and I have to search but your direction will be really helpful.
I heard that I can use "tape residue remover" to soften the glue between stators. Where do I get the 6 mm mylar and EC coating? How do I install membrane? I do I make the connections between membrane and wire to the hv?
Thank you in advance.
soonmo
Thanks a lot for the reply. How can I install a new membrane? I know there's lot of information regading ELS DIY and I have to search but your direction will be really helpful.
I heard that I can use "tape residue remover" to soften the glue between stators. Where do I get the 6 mm mylar and EC coating? How do I install membrane? I do I make the connections between membrane and wire to the hv?
Thank you in advance.
soonmo
mimsguru said:
Hi,
I am the producer/supplier of the EC-coating. I've got genuine (custom made) mylar as well.
The EC-coating offers the best chemical and physical properties currently available. Because of its chemical composition it has to be used within 5 to 6 months (exact date is on the bottle).
For more information: please contact me, mj-dijkstra@zonnet.nl
Hi,
to get rid of the old tapes is really a problem. Even 3M themselves have no procedure how to do this. Using a heatgun softens the foamtapes and the glue and rubbing the tape off mechanically will work, but its a pain in the xxx. A solution could be to leave the old tape stick on and just try to pull the membrane off of the tape and to glue a very thin (0.05-0.1mm) new tape on top of the old one.
Then You´ll have to build a curved stretching frame for the new membrane.
Tape a membrane to the stretcher and stretch nearly as hard as the membrane could stand (~2% elongation is ok and of course only in the long direction).
Lay the membrane with stretcher very gently on the stator and rub the membrane onto the tape. If possible let the thing rest for some hours (the glue joint stabilizes).
Cut the membrane free from the stretcher, leaving some material left.
Turn the membrane to the opposite side (backside) and glue several cm of the overlap to the stator´s backside (Just as ML does it. You need to do this only in the long direction where high mechanical tension exists)
Use thin copper-tape as a diaphragm contact. Use one stripe on each of the long sides. Solder a wire to the end of the tape, isolate the last cms of the copper (clear selfadhesing tape like Tesa) and tape it on the backside of the stator.
Coat the diaphragm (leaving ~5mm asides the horizontal spacers free, because those joints are prone to flashovers)
Use a bit more of the coating over the copper-tape to have a good solid connection.
jauu
Calvin
to get rid of the old tapes is really a problem. Even 3M themselves have no procedure how to do this. Using a heatgun softens the foamtapes and the glue and rubbing the tape off mechanically will work, but its a pain in the xxx. A solution could be to leave the old tape stick on and just try to pull the membrane off of the tape and to glue a very thin (0.05-0.1mm) new tape on top of the old one.
Then You´ll have to build a curved stretching frame for the new membrane.
Tape a membrane to the stretcher and stretch nearly as hard as the membrane could stand (~2% elongation is ok and of course only in the long direction).
Lay the membrane with stretcher very gently on the stator and rub the membrane onto the tape. If possible let the thing rest for some hours (the glue joint stabilizes).
Cut the membrane free from the stretcher, leaving some material left.
Turn the membrane to the opposite side (backside) and glue several cm of the overlap to the stator´s backside (Just as ML does it. You need to do this only in the long direction where high mechanical tension exists)
Use thin copper-tape as a diaphragm contact. Use one stripe on each of the long sides. Solder a wire to the end of the tape, isolate the last cms of the copper (clear selfadhesing tape like Tesa) and tape it on the backside of the stator.
Coat the diaphragm (leaving ~5mm asides the horizontal spacers free, because those joints are prone to flashovers)
Use a bit more of the coating over the copper-tape to have a good solid connection.
jauu
Calvin
Thank you for the replies.
Building the curved stretcher seems to be a challenge. Any reference on this?
The problem of my bad panel is when the diaphragm is connected to power supply, the bias voltage drops to 10 volt. The power supply is ok because when the diaphragm is disconnected, it gives around 300 volt (this seems to be low too but another power supply also give the same volateg). I tried to switch the power supply and the problem remains.
My guess is the voltage drop is due to "leakage current" between stator and diapgragm, the thing that we see in a old capacitor. How can this happen in ESL panel?
Soonmo
Building the curved stretcher seems to be a challenge. Any reference on this?
The problem of my bad panel is when the diaphragm is connected to power supply, the bias voltage drops to 10 volt. The power supply is ok because when the diaphragm is disconnected, it gives around 300 volt (this seems to be low too but another power supply also give the same volateg). I tried to switch the power supply and the problem remains.
My guess is the voltage drop is due to "leakage current" between stator and diapgragm, the thing that we see in a old capacitor. How can this happen in ESL panel?
Soonmo
Hi,
if there´d be only a leakage the voltage wouldn´t drop that far down.
Sounds more like a shortcut somewhere. Maybe one of the diodes in the supply has an defect. Let the supply discharge thoroughly and measure all diodes on function.
You can´t seriously measure the output voltage wirth a standard multimeter. It´s inner resistance of typical 10meg is far too low and loads the supply too much.
You need to have an HV-probe or a measuring resistance.
You can easily built such one from a chain of resistances.
I use 100 pieces of 10meg. You then measure the voltage about just the last 1...5 resistors before the ground connection and recalculate the voltage at the input of the R-chain. (measuring just the last resistor will give a voltage of app. 200times the multimeter´s reading)
With such a measurement-setup the sequel-supplies should read 16V-19V (depending on the switches position in the supply) which calculates to 3.2kV....3.8kV. This reading nearly doesn´t change with connected panels. If it changes considerably, then there is massive leakage within the panel. Reasons for such a leakage can be carbon tracks from serious flashovers (seldom with ML), polluted panels (dust, smoke, insects, moistorous dirt films etc). Take care when opening or rebuilding the panel, because already one sweaty fingerprint can form an invisble leakage path.
jauu
Calvin
if there´d be only a leakage the voltage wouldn´t drop that far down.
Sounds more like a shortcut somewhere. Maybe one of the diodes in the supply has an defect. Let the supply discharge thoroughly and measure all diodes on function.
You can´t seriously measure the output voltage wirth a standard multimeter. It´s inner resistance of typical 10meg is far too low and loads the supply too much.
You need to have an HV-probe or a measuring resistance.
You can easily built such one from a chain of resistances.
I use 100 pieces of 10meg. You then measure the voltage about just the last 1...5 resistors before the ground connection and recalculate the voltage at the input of the R-chain. (measuring just the last resistor will give a voltage of app. 200times the multimeter´s reading)
With such a measurement-setup the sequel-supplies should read 16V-19V (depending on the switches position in the supply) which calculates to 3.2kV....3.8kV. This reading nearly doesn´t change with connected panels. If it changes considerably, then there is massive leakage within the panel. Reasons for such a leakage can be carbon tracks from serious flashovers (seldom with ML), polluted panels (dust, smoke, insects, moistorous dirt films etc). Take care when opening or rebuilding the panel, because already one sweaty fingerprint can form an invisble leakage path.
jauu
Calvin
I'm probably going to sound like a quitter here but here goes:
I got a pair of Martin Logan panels a few years ago for a song. They apparently needed to be rebuilt. I tore one of them apart and worked for hours to try to clean off the three different foam tape types off the metal. After a few hours, I was about 3% of the way through one panel.
I've never seen such fine foam used in foam tape, or such insanely good adhesive. I'd love to get my hands on some.
I lost interest in the weeks worth of work to tear them apart, and eventually I tossed them out when I moved.
I tried heat guns chemical action, etc. The stuff was amazing. I'm impressed.
The stuff would come off, but it wasn't easy.
Sheldon
I got a pair of Martin Logan panels a few years ago for a song. They apparently needed to be rebuilt. I tore one of them apart and worked for hours to try to clean off the three different foam tape types off the metal. After a few hours, I was about 3% of the way through one panel.
I've never seen such fine foam used in foam tape, or such insanely good adhesive. I'd love to get my hands on some.
I lost interest in the weeks worth of work to tear them apart, and eventually I tossed them out when I moved.
I tried heat guns chemical action, etc. The stuff was amazing. I'm impressed.
The stuff would come off, but it wasn't easy.
Sheldon
Hi,
@mims
building a stretching frame for a curved stator is very easy. You just need at least one (better two) moveable parts within the frame, so that You can stretch the membrane by taping it to the moveable parts and turning the threaded rods. Looks like this:
You can use wood for all parts, but sticky tape should really stick to the surface of the moveable parts and the long sides. Especially the surfaces of the moveable parts have to hold serious mechanical tensioning forces!
When the membrane is stretched (~2% elongation) tape the long sides of the membrane to the long fixed side-parts. But just pull very slightly to get rid of any wrinkles that built up (You can use more tension in horizontal direction close to the moveable parts).
jauu
Calvin
@mims
building a stretching frame for a curved stator is very easy. You just need at least one (better two) moveable parts within the frame, so that You can stretch the membrane by taping it to the moveable parts and turning the threaded rods. Looks like this:
You can use wood for all parts, but sticky tape should really stick to the surface of the moveable parts and the long sides.
Especially the surfaces of the moveable parts have to hold serious mechanical tensioning forces!An externally hosted image should be here but it was not working when we last tested it.
When the membrane is stretched (~2% elongation) tape the long sides of the membrane to the long fixed side-parts. But just pull very slightly to get rid of any wrinkles that built up (You can use more tension in horizontal direction close to the moveable parts).
jauu
Calvin
Thaks to Calvins's assistant, I managed to take apart the stators and diaphragm. I guess I removed the tape pretty well with the help of tape remover.
I will build the stretcher and try to build the new diaphragm. In Korea, I found following PET film that I can get in reasonable price.
http://www.skc.co.kr/skhp/en/prod/pf/03_06.jsp
Should this work for diaphragm(6 micron)? I will try white glue (PVA) with graphite as a coating material.
I already got 3M VHB tape but I noticed that in Sequel panel, there's another tape (black color, more like a rubber rather than foam). What is this? Can I use VHB instead?
Thnak you in advance.
I will build the stretcher and try to build the new diaphragm. In Korea, I found following PET film that I can get in reasonable price.
http://www.skc.co.kr/skhp/en/prod/pf/03_06.jsp
Should this work for diaphragm(6 micron)? I will try white glue (PVA) with graphite as a coating material.
I already got 3M VHB tape but I noticed that in Sequel panel, there's another tape (black color, more like a rubber rather than foam). What is this? Can I use VHB instead?
Thnak you in advance.
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