Perhaps I'm the only one who hasn't seen these photos showing the assembly of an Acoustat panel, but I couldn't find any diyAudio references to them. I really can't figure out how they escaped my attention until just now. Anyway, those who haven't already seen them and who spend time dreaming up ESL design and construction ideas may find them of interest.
http://www.audiocircuit.com/A-HTML/AA-Brands/A/Acoustat-ACO/941-ACO-GEN-Factory_-P-A01.htm
Few
http://www.audiocircuit.com/A-HTML/AA-Brands/A/Acoustat-ACO/941-ACO-GEN-Factory_-P-A01.htm
Few
Few: you can make up a couple of jigs with some plywood and a some 1/4 - 20 threaded rod. One at each end of a length of louvre and you can wind 30 gage heavy build magnet wire and have 20 wires per inch rather than the poor 5-6 that Acoustat used. If you want more wires then use a 1/4 - 32 threaded rod and bingo you have 32 wires per inch. You can buy large rolls of magnet wire from motor rebuilding shops amongst other sources. Note that this method requires that you solder all of the wires together at the ends so a small solder pot would be a good investment then you can dip solder an inch worth of stator wires at a time and then connect them all together with a small iron.
Note also that the horizontal piece of threaded rod is simply a guide/spacer for the wire. You will need to fit your jig base plate with some small hooks or screws at about one per inch across the back side of the threaded rod so you can bring your wire off the threaded rod then around the hook and back to the next thread on the rod. This is simple fast and easy to tension by hand. You then need to use your imagination to decide how you want to fix the wires to the louvre. There are lots of options. Acoustat's solvent and louvre scrap is straight ahead and works with a proven track record. I think that there are simpler ways but everybody has their own ideas. Regards Moray James.
Note also that the horizontal piece of threaded rod is simply a guide/spacer for the wire. You will need to fit your jig base plate with some small hooks or screws at about one per inch across the back side of the threaded rod so you can bring your wire off the threaded rod then around the hook and back to the next thread on the rod. This is simple fast and easy to tension by hand. You then need to use your imagination to decide how you want to fix the wires to the louvre. There are lots of options. Acoustat's solvent and louvre scrap is straight ahead and works with a proven track record. I think that there are simpler ways but everybody has their own ideas. Regards Moray James.
Moray, could you post some pics or drawings of your wire stator building method?
Also, could you post your simpler ideas of glueing the wires?
Thanks.
Also, could you post your simpler ideas of glueing the wires?
Thanks.
Wolf...
Wolf this is a pretty simple jig. Lets assume that you are wanting to wind a stator the same size as an Acoustat panel to start. You will need two identical jigs one for each narrow end of the louvre panel. The jig needs to consist of a base plate (say plywood) and a block that holds a length of 1/4 - 20 theraded rod the width of the stator panel and at the same height as the louvre panel. The block holding the threaded rod needs to have a groove or slot (horizontal) in its top to act as a seat to hold the rod. The depth of the slot needs to be about half to two thirds the thickness of the rod. The rod needs to be epoxy glued into this slot. You need the block with the slot to hold the rod and keep it from deforming under the stress of all the wires that you will be winding. The block is mounted to the base plate and butts up against the end of the louvre panel. To the back side of the block (away from the louvre) you will need a horizontal row of small hooks spaced about one every inch. These need to be screwed into the base plate. That's the whole design. The purpose of this jig is to hold the section of threaded rod in a horizontal position at the end of the louvre panel at the same height as the louvre and to provide hooks to act as anchors for the stator wire. Remember that the threads of the threaded rod are only acting as guide spacers for the stator wire, simply a series of small grooves at each end of the louvre panel. To wind a stator first anchor your stator wire to the first hook at one jig and line your wire up with the first thread of the rod. Run the wire down to the opposite end of the lovre and onto the first thread groove of that jig and then off and around the first hook and then back to the second thread on the rod. This process of serpentining back and forth between jigs goes on until the stator is wound. Hope that this helps. Regards Moray James.
Wolf this is a pretty simple jig. Lets assume that you are wanting to wind a stator the same size as an Acoustat panel to start. You will need two identical jigs one for each narrow end of the louvre panel. The jig needs to consist of a base plate (say plywood) and a block that holds a length of 1/4 - 20 theraded rod the width of the stator panel and at the same height as the louvre panel. The block holding the threaded rod needs to have a groove or slot (horizontal) in its top to act as a seat to hold the rod. The depth of the slot needs to be about half to two thirds the thickness of the rod. The rod needs to be epoxy glued into this slot. You need the block with the slot to hold the rod and keep it from deforming under the stress of all the wires that you will be winding. The block is mounted to the base plate and butts up against the end of the louvre panel. To the back side of the block (away from the louvre) you will need a horizontal row of small hooks spaced about one every inch. These need to be screwed into the base plate. That's the whole design. The purpose of this jig is to hold the section of threaded rod in a horizontal position at the end of the louvre panel at the same height as the louvre and to provide hooks to act as anchors for the stator wire. Remember that the threads of the threaded rod are only acting as guide spacers for the stator wire, simply a series of small grooves at each end of the louvre panel. To wind a stator first anchor your stator wire to the first hook at one jig and line your wire up with the first thread of the rod. Run the wire down to the opposite end of the lovre and onto the first thread groove of that jig and then off and around the first hook and then back to the second thread on the rod. This process of serpentining back and forth between jigs goes on until the stator is wound. Hope that this helps. Regards Moray James.
nothin like a good hard pull...
you got it Sy remember this is only 3o gage wire and hand pressure is lots to keep it tight and firmly pressed against the stator. Regards Moray James.
you got it Sy remember this is only 3o gage wire and hand pressure is lots to keep it tight and firmly pressed against the stator. Regards Moray James.
Hi,
Since i have no digital camera now , i'd like to explain the method i use.
The jig is very simple - it contains two wooden balks with threaded rods at ends. One threaded rod is fixed , while the other is made moveable.The moveable rod can be pulled with two large screws with hooks.
Two light louvers are placed on the jig , with few wooden sticks between them so that louvers would bend slightly. Then the wire is wound on both stators at once , and additionally stretched with screws.
One note : the threaded rods must be thick enough , or they must have additional steel support.The tension force becomes very high when there are so many wires.
Regards,
Lukas.
Since i have no digital camera now , i'd like to explain the method i use.
The jig is very simple - it contains two wooden balks with threaded rods at ends. One threaded rod is fixed , while the other is made moveable.The moveable rod can be pulled with two large screws with hooks.
Two light louvers are placed on the jig , with few wooden sticks between them so that louvers would bend slightly. Then the wire is wound on both stators at once , and additionally stretched with screws.
One note : the threaded rods must be thick enough , or they must have additional steel support.The tension force becomes very high when there are so many wires.
Regards,
Lukas.
Instead of hooks and threaded rods, I've been wondering if 40-pin headers could serve as the "comb" shown in the first of the Acoustat photos. Their dimensions (0.025" diameter with 0.10" spacing) seem just right, and they're not overly expensive. Some way would have to be devised to hold the set of pins firmly so that they could withstand the wire tension, but they could serve as both hook and wire guide at the same time. If 23 gauge double build magnet wire with an outside diameter of about 0.025" were used, you'd have a stator with 50% open area (wire insulation included) and 20 wires per inch. Seems pretty reasonable.
Hi,
Your idea may be quite good , if you find a way to fix the pin headers , and they prove to be strong enough.
Threaded rods work well . I chosen this method because the jig is very simple to build ( construction took about half a day , including buying parts , assembling and painting). Disadvantage of this method is that each wire must be cut at the end and soldered.
Your idea may be quite good , if you find a way to fix the pin headers , and they prove to be strong enough.
Threaded rods work well . I chosen this method because the jig is very simple to build ( construction took about half a day , including buying parts , assembling and painting). Disadvantage of this method is that each wire must be cut at the end and soldered.
lower open may well be better....
I dont have the time to reference the details so take this for what it's worth to you. Lower open area for a stator may well pove to be more effective. Somewhere in the 35 - 40 percent open area for a stator will most likely yield the highest output and best damped diaphragm. The kicker is that you are also going to have to use a finer gage wire to achieve this which means more work and wire. Just using larger wire will get you the open area you want but the field will not be as uniform as with smaller wires. 28 to 30 gage would seem about best and they are much easier to work with by hand than heavier gages.
Regarding the header idea do a little mock up and give it a try for yourself. I tried this method and found that the pins were not strong enough and they needed to either be at an angle to hold the wires on or to have a bend to hook the wire over. Even with 30 gage wire and only hand tension the amount of pressure the multiple wire can generate is substantial as it adds up with volume of wire used. The work involved in bonding them (the headers) to either styrene or acrylic was far more than simply knocking up a simple jig. Further you have to repeat the process with each and every panel that you build and you only need build the jigs once. Having the solder pot takes away all the soldering issues when terminating the stator wires. Regards Moray James.
I dont have the time to reference the details so take this for what it's worth to you. Lower open area for a stator may well pove to be more effective. Somewhere in the 35 - 40 percent open area for a stator will most likely yield the highest output and best damped diaphragm. The kicker is that you are also going to have to use a finer gage wire to achieve this which means more work and wire. Just using larger wire will get you the open area you want but the field will not be as uniform as with smaller wires. 28 to 30 gage would seem about best and they are much easier to work with by hand than heavier gages.
Regarding the header idea do a little mock up and give it a try for yourself. I tried this method and found that the pins were not strong enough and they needed to either be at an angle to hold the wires on or to have a bend to hook the wire over. Even with 30 gage wire and only hand tension the amount of pressure the multiple wire can generate is substantial as it adds up with volume of wire used. The work involved in bonding them (the headers) to either styrene or acrylic was far more than simply knocking up a simple jig. Further you have to repeat the process with each and every panel that you build and you only need build the jigs once. Having the solder pot takes away all the soldering issues when terminating the stator wires. Regards Moray James.
Good points regarding the header pins. I probably will give them a try to see what I can come up with, but it may turn out other approaches are easier.
Regarding the open area: I don't have measurements to back this up, but I understood that an ESL panel's sensitivity scales with its capacitance. If that's true, and if it's also true that once the wire spacing becomes small compared to the stator-diaphragm distance the capacitance becomes essentially equal to that of a solid stator, it would seem that a point of diminishing returns ought to be reached. The idea I proposed would yield a wire-to-wire distance of 0.025" which is fairly small compared to the 0.0625" stator-to-diaphragm distance I'm likely to use. There may be several reasons to go to finer wire and closer wire-to-wire spacing, but if this reasoning is correct (it certainly may not be!) increased sensitivity wouldn't be a major one. Do measurements show that I'm off base? I'd certainly like to know before I purchase wire!
Regarding the open area: I don't have measurements to back this up, but I understood that an ESL panel's sensitivity scales with its capacitance. If that's true, and if it's also true that once the wire spacing becomes small compared to the stator-diaphragm distance the capacitance becomes essentially equal to that of a solid stator, it would seem that a point of diminishing returns ought to be reached. The idea I proposed would yield a wire-to-wire distance of 0.025" which is fairly small compared to the 0.0625" stator-to-diaphragm distance I'm likely to use. There may be several reasons to go to finer wire and closer wire-to-wire spacing, but if this reasoning is correct (it certainly may not be!) increased sensitivity wouldn't be a major one. Do measurements show that I'm off base? I'd certainly like to know before I purchase wire!
Hi,
an idea for a wire stretching jig.
It consists of a threaded rod and a straight rod connected together via two faceplates. The faceplates are connected to two long rods in such a way that at one end the faceplates are fixed to the rods and on the other side they can move. The wire is wound such that it always lays on top of the threaded rods and turns round the straight rods. After winding the moveable part kan be pulled apart thereby stretching the wires. This could be done by means of some weight or by a screwing mechanism.
jauu
Calvin
an idea for a wire stretching jig.
An externally hosted image should be here but it was not working when we last tested it.
It consists of a threaded rod and a straight rod connected together via two faceplates. The faceplates are connected to two long rods in such a way that at one end the faceplates are fixed to the rods and on the other side they can move. The wire is wound such that it always lays on top of the threaded rods and turns round the straight rods. After winding the moveable part kan be pulled apart thereby stretching the wires. This could be done by means of some weight or by a screwing mechanism.
jauu
Calvin
that's what it looks like!
Calvin: greqt rendering. Thats essentially what the jig I was trying to discribe looks like short of the hooks to the back side of the threaded rod. As I mentioned with light gage wire hand pressure is enough to stretch it straight so with a little practice one can wind a stator with excellent consistancy and all the wire flat and flush to the louvre surface. Causing the louvre to bow upwards in the middle a small amount also helps insure that the wires conform to the louvre surface.
Few: as far as I know you are correct regarding efficiency. If you double up to 12 wires per inch (twice that of Acoustat) you should see a 3 db increase in sensitivity and if you then double again up to 24 wires per inch you should pick up an additional 3 db. That should in theory have you 6 db up over a stock Acoustat panel of the same size. The nice part is that all your extra wire and winding work will also yield you a better damped diaphragm as well.
The method that I plan to experiment with regarding bonding of stator wires is this. Auto body paint manufacturers make special primers for plastic parts. You can buy spray cans of clear plastic primer which comes in two versions. These are known as light and heavy build primers. This name refers to the thickness of build (and solid content) you can apply in a single wet coat. The intent here is to give the body shop repair man the ability to quickly fill in scratches and dents with the heavy build and then feather in and smooth out the surface with the light build spray.
Ok now that you know what the product is you are ready to give it a try. You will want to buy the light build clear spray plastic primer. Clean and lightly sand the louvre surface and apply a single coat of the light build primer. These primers set very quickly so you can now install the louvre into your winding jig. Wind the stator wires and when done spray two or three coats of the light build primer (allow each coat to set the prescribed time between coats). That should be enough to encapsulate your wires firmly and perminently onto the frame. Don't forget to prime the louver surface properly as this is what will provide the base adhassion for the top coats holding the sire in place. Some of you may be wondering if this will be strong enough to bond the wires as the coating is thin compared to applied epoxy beads and the like. You need to remember that with methods like that used bu Acoustat the wires are only held down as the point where the horizontal beads are applied. With this methos the wires are fully bonded 100 percent of the area where they make contact to the louvre. Further because this method uses such a thin film thickness to hold the wires in place you lose far less valuable stator to diaphragm space which means far more available peak to peak travel. Remember too that primer's are designed to bond to substrates not look good which is the job of the top coat. Further this kind of primer is designed to not only bond but also to fill and build up which means that it has a very high solid content (far greater than any top coat paint) and that translates into strength. The last significant advantage of this method is the speed at which it can be done (necessary in the body repair industry) this is litterally a several shot deal compared to solvent welds and glues. Best regards Moray James.
So give this a try and let us know how it works
Calvin: greqt rendering. Thats essentially what the jig I was trying to discribe looks like short of the hooks to the back side of the threaded rod. As I mentioned with light gage wire hand pressure is enough to stretch it straight so with a little practice one can wind a stator with excellent consistancy and all the wire flat and flush to the louvre surface. Causing the louvre to bow upwards in the middle a small amount also helps insure that the wires conform to the louvre surface.
Few: as far as I know you are correct regarding efficiency. If you double up to 12 wires per inch (twice that of Acoustat) you should see a 3 db increase in sensitivity and if you then double again up to 24 wires per inch you should pick up an additional 3 db. That should in theory have you 6 db up over a stock Acoustat panel of the same size. The nice part is that all your extra wire and winding work will also yield you a better damped diaphragm as well.
The method that I plan to experiment with regarding bonding of stator wires is this. Auto body paint manufacturers make special primers for plastic parts. You can buy spray cans of clear plastic primer which comes in two versions. These are known as light and heavy build primers. This name refers to the thickness of build (and solid content) you can apply in a single wet coat. The intent here is to give the body shop repair man the ability to quickly fill in scratches and dents with the heavy build and then feather in and smooth out the surface with the light build spray.
Ok now that you know what the product is you are ready to give it a try. You will want to buy the light build clear spray plastic primer. Clean and lightly sand the louvre surface and apply a single coat of the light build primer. These primers set very quickly so you can now install the louvre into your winding jig. Wind the stator wires and when done spray two or three coats of the light build primer (allow each coat to set the prescribed time between coats). That should be enough to encapsulate your wires firmly and perminently onto the frame. Don't forget to prime the louver surface properly as this is what will provide the base adhassion for the top coats holding the sire in place. Some of you may be wondering if this will be strong enough to bond the wires as the coating is thin compared to applied epoxy beads and the like. You need to remember that with methods like that used bu Acoustat the wires are only held down as the point where the horizontal beads are applied. With this methos the wires are fully bonded 100 percent of the area where they make contact to the louvre. Further because this method uses such a thin film thickness to hold the wires in place you lose far less valuable stator to diaphragm space which means far more available peak to peak travel. Remember too that primer's are designed to bond to substrates not look good which is the job of the top coat. Further this kind of primer is designed to not only bond but also to fill and build up which means that it has a very high solid content (far greater than any top coat paint) and that translates into strength. The last significant advantage of this method is the speed at which it can be done (necessary in the body repair industry) this is litterally a several shot deal compared to solvent welds and glues. Best regards Moray James.
So give this a try and let us know how it works
Moray James: Have you verified the 6 dB sensitivity increase of 24 wire/inch stators relative to the Acoustats? I'm curious about when, in practice, the point of diminishing returns is reached as you increase the number of wires per inch. For example, I would be surprised if another doubling to 48 wires/inch yielded yet another 3 dB increase (not that it would practical anyway).
Also, I can't quite tell from your interesting primer information whether this is something you've already tried and found to work, or whether it's as yet an untested idea. It's interesting either way.
Few
Also, I can't quite tell from your interesting primer information whether this is something you've already tried and found to work, or whether it's as yet an untested idea. It's interesting either way.
Few
have a look...
at the series of articles by Mathew Lattis in AudioXpress. Mathew confirmed to his surprise that tighter wire spacing actually generated more output that stators with 50 % or more open area. I have experimented with various laquer's to hold down stator wire in the past and found it promissing enough to move to the next step. I have the necessary materials in hand to do the technique discribed but have not the time at present to do so. I thought that there might be others out there who would be interested. I have built panels (using wire wrap wire with tefzel insulation 28 gage) and made versions with 12 and then 20 wires per inch and can confirm that compared to stock Acoustat panels the play louder and sound much better. That last experiment was about 16 years ago. Hope this helps. pleas let us know how your experiments turn out. Best regards Moray James.
at the series of articles by Mathew Lattis in AudioXpress. Mathew confirmed to his surprise that tighter wire spacing actually generated more output that stators with 50 % or more open area. I have experimented with various laquer's to hold down stator wire in the past and found it promissing enough to move to the next step. I have the necessary materials in hand to do the technique discribed but have not the time at present to do so. I thought that there might be others out there who would be interested. I have built panels (using wire wrap wire with tefzel insulation 28 gage) and made versions with 12 and then 20 wires per inch and can confirm that compared to stock Acoustat panels the play louder and sound much better. That last experiment was about 16 years ago. Hope this helps. pleas let us know how your experiments turn out. Best regards Moray James.
Moray,
Very interesting information. What I was asking myself, with very thin (28 gauge) and tightly spaced wire, would not the stator itself start to generate some output, as it becomes relatively flexible and *might* start to (partially) vibrate?
Jan Didden
Very interesting information. What I was asking myself, with very thin (28 gauge) and tightly spaced wire, would not the stator itself start to generate some output, as it becomes relatively flexible and *might* start to (partially) vibrate?
Jan Didden
I guess that depends...
After I built my first panels with fine gage wire I switched from half inch thick louvre to the 3/8 inch version and liked it better. Acoustats use a 24 gage wire with a heavy build PVC dielectric so they are not stiff but they are heavy. I think that what you end up with is a balance of weight thing. The fine gage wire is light and you are placing it under tension when you wind it onto the louvre. At the end of the day I think that the 3/8 louvre with fine gage wire (over a grater surface area) makes for a better sounding unit probably because there is less energy stored in it due to the reduced mass and increased stator tension. This is just an assumption on my part as I have no measurements of any kind. I am going by what I hear. Those panels were all built with DuPont HS 65 gage diaphragm film (same stuff Acoustat used) and I am planning to build some new versions with 3 micron mylar. They ought to sound better by a mile than the old ones with HS 65. I think that it use to be that designers thought that 1/4 to 1 mil mylar was so light that the overall surface air load would damp the diaphragm effectively but I don't believe that is the case. Thinner films sound so much better. But there are a number of variables at work with thinner films allowing greater extension at both frequency extreems as well as being lighter and easier to drive and damp.
In Mathew Lattis's article he was surprised to find that 1/16 inch aluminum bug screen had lower sensitivity than perf metal with a less open ratio of solid to open area. Mathew's articles are an interesting read. Regards Moray James.
After I built my first panels with fine gage wire I switched from half inch thick louvre to the 3/8 inch version and liked it better. Acoustats use a 24 gage wire with a heavy build PVC dielectric so they are not stiff but they are heavy. I think that what you end up with is a balance of weight thing. The fine gage wire is light and you are placing it under tension when you wind it onto the louvre. At the end of the day I think that the 3/8 louvre with fine gage wire (over a grater surface area) makes for a better sounding unit probably because there is less energy stored in it due to the reduced mass and increased stator tension. This is just an assumption on my part as I have no measurements of any kind. I am going by what I hear. Those panels were all built with DuPont HS 65 gage diaphragm film (same stuff Acoustat used) and I am planning to build some new versions with 3 micron mylar. They ought to sound better by a mile than the old ones with HS 65. I think that it use to be that designers thought that 1/4 to 1 mil mylar was so light that the overall surface air load would damp the diaphragm effectively but I don't believe that is the case. Thinner films sound so much better. But there are a number of variables at work with thinner films allowing greater extension at both frequency extreems as well as being lighter and easier to drive and damp.
In Mathew Lattis's article he was surprised to find that 1/16 inch aluminum bug screen had lower sensitivity than perf metal with a less open ratio of solid to open area. Mathew's articles are an interesting read. Regards Moray James.
Moray, thanks. I have the AA issues and will re-read Lattis'es articles. Interesting stuff!
Jan Didden
Jan Didden
one last point...
my panels were designed with the same diaphragm to stator spacing as were the Acoustats however I have always split the panels down the centre with a 1/4 inch wide spacer. This is because the Acoustat stator to diaphragm distance and thier width left the diaphragm unstable under very hard drive conditions. Many have found that they can make Acoustat diaphragms colapse and stick to one of the stators if you push them hard enough. This problem can become worse over time as the diaphragms stretch. Periodic Rx by re heat shrinking the diaphragms help to reduce this problem from happening. One of the down sides to using heat shringing to tension a diaphragm. Stretching skins is the better way to go. Regards Moray James.
my panels were designed with the same diaphragm to stator spacing as were the Acoustats however I have always split the panels down the centre with a 1/4 inch wide spacer. This is because the Acoustat stator to diaphragm distance and thier width left the diaphragm unstable under very hard drive conditions. Many have found that they can make Acoustat diaphragms colapse and stick to one of the stators if you push them hard enough. This problem can become worse over time as the diaphragms stretch. Periodic Rx by re heat shrinking the diaphragms help to reduce this problem from happening. One of the down sides to using heat shringing to tension a diaphragm. Stretching skins is the better way to go. Regards Moray James.
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