I'm thinking about building my first set of hybrid ESL's. Not sure if this project will really take place but I'm gathering some info and getting into the theory.
If I would build these speakers, the ESL's would cover the range from about 300Hz and up. The rest will be reproduced by an 8" driver. They will be used in a very small listening room.
My first question is about the stators.
I can think of some advantages and disadvantages of using plate stator instead of a wired stator.
- It's hard to segment a plate stator
- finding the right material with the optimal hole-configuration
- Easy to get the right tension in the stator
- Less tension in the construction (easy construction)
- I can paint it any color I like
- I can cut it any shape I like
Did I forget any important issues with plate stators?
About the segmentation: Do I need segmentation when I can aim the speakers at the listening position (which is fixed in this room)? I do not care if the sweet spot is really small.
What size panel am I looking at when I want it to play down to 300Hz?
Welcome to the "DIY ESL club"! Insulating a perforated metal stator is the trickiest part of their construction; doing it well is not trivial. Wire stators solve the insulation problem quite directly, as long as appropriate wire is used, but the construction process is often more involved.
I've been living with very wide perforated metal stator ESLs for several years, without any segmentation, and I've enjoyed them very much. However, I'm currently in the process of building wire stator ESLs primarily because I'd like to solve the ultra-narrow sweet spot problem. If that's not an issue for you, then going with the simple construction of a metal plate stator---especially for your first ESL attempt---is a reasonable approach. Using 3M adhesive foam tape can make the construction quite straightforward, once the insulation is worked out. For what it's worth, I used epoxy paint intended to touch up kitchen appliances in order to paint my perforated metal stators.
My perforated metal panels are about 50 cm wide and I run them down to about 200 Hz. I'm going to make my new wire stators roughly has as wide, cross them over an octave higher, and supplement them with a vertical array of 8" woofers (run with open baffles, no enclosures). You can certainly get away with panels significantly narrower than the ones I now have and run them down to 300 Hz. Take a look at Roger Sanders' book on ESL construction if you haven't already. It contains some useful rules of thumb, even though some of his "scientific" explanations are wrong. Also take a look at Sheldon's DIY ESL video here. It will help clarify the construction process. I also like his method of using dot spacers instead of long strips.
Should you be interested, you are welcome to listen to my hybride ESL's.
I think you know my building description from the dutch "zelfbouwaudioforum" section "showcase"?
I did not segment the wirestators, so you could hear the influence of a narrow sweet spot.
I know you have the NSS03 set (same set I used to build my 4 ESL's)
Maybe listening can help you decide wether to build a pair of ESL's or sell your trafo's. After all it takes some time to build a good pair.
I live in Oosterzele near Gent (Belgium)
So I can't use any paint I like?
What's the trick to keep sufficient tension in the metal plate stator? I can imagine that with temperature the tension in a plate stator varies, as much or even more then in a wire stator.
A very small sweet spot isn't an issue.
I'll have a look at that link later. Dot-spacers ... sounds interesting.
How do you like the transformers from the NSS03?
Is it right that they can be used from 250Hz and up? I can find the transformation ratio (1:128) but no other specs. :confused:
I really like to come and listen to your hybrids. I don't have a lot of time this month but I think we can work something out for February, if that suites you.
If your goal is just to prevent the stator from rusting and make it a nice color, you have a wide range of paints to choose from. If you want to insulate the stator life is considerably trickier. Having someone powder coat the stators is probably the best bet, but as you'll find by searching this site, it isn't trivial to find a place willing or able to coat in ways that prevent arcing. I used epoxy spray paint, available in spray cans, to paint mine. I certainly wouldn't claim the results approach a good nylon powder coating, but I've been enjoying music through the panels for many years now.
I'm afraid I didn't chronicle my project; I'm hoping to do that with my next project but it's taking me FOREVER to find time free to get serious about putting things together. I've had most of the materials for months, including the woofers for the arrays, but just can't find the blocks of time necessary to make progress.
I haven't found serious tension variations resulting from changes in the dimensions of the perforated metal. Once a year or so I re-tension the diaphragm with a heat gun, but I think that's from the diaphragm and adhesive tape very slowly creeping. I would say, though, that using thicker perforated metal for the stators made construction much more reliable. My prototypes were made with lincaine style perforated aluminum, as suggested by Sanders, and I found it difficult to avoid minor dents, folds, and kinks in the material. Since the stator-diaphragm gap is small, it doesn't take much of a deviation from flatness to cause trouble. The steel stators I used in my final project were much easier to work with. Just don't get carried away. Overly thick stators will cause their own set of problems.
An ANNOYING problem with perforated stators which killed my project was that, not insulated, the edges of the perforation WILL LEAK. My ESL worked, but extremely quietly because it couldn't bias up high enough, the charge was being ripped away by the stators!
I still need to figure out how to round off EVERY PERFORATION :dead:
You can find it here
For hybrid use these toroids are ok.
Using the standard filter delivered with the NSS03 set , I can measure a crossover around 450 Hz , wich is rather high.
On the other hand ,I am sure that you can use these toroids from 250 Hz.
It depends on the panelconfiguration you are using.
It could give a better result.
Anyway, you are welcome here.
I think I can give you a lot of tips and information about building a good wire stator . I did build some over time.
You will not have any insulation problems using a wire stator.
You can build a rather efficient panel .
send me a mail, whenever it suits you.
Following up on (or perhaps needlessly repeating) bigwill's useful post: the problem is that just as the strength of a chain is determined by its weakest link, the bias voltage you can apply to your ESLs is determined by the breakdown voltage of the most vulnerable point on the pair of speakers. Even if 99.99% of the pair of speakers is very well insulated, if one tiny point is less well insulated, and it happens to be in a bad place, then it will limit your speakers' performance. The real bummer is that the sharp points on metal stators are the sources of the highest electric fields and are therefore the most vulnerable to arcing. Those same sharp points are exactly the same points that are hardest to insulate. Wet coatings, such as paint, tend to pull away from the sharp points because of the paint's surface tension. You end up with the worst insulation in the very locations that need the most protection.
Nonetheless, it's still possible to make things work. You must face the sharper edges of the perforated holes on each stator away from the diaphragm, not toward it. (Metal stators usually have one sharp side and one smooth side because of the way the holes are punched.) You also have to be careful to keep the metal stators flat, and inspect them before coating them to find any other spots that might lead to problems and smooth them out.
You can also search this site for the discussion on chemical approaches to smoothing the sharp edges, but electropolishing is really the best way to do that. By the time you employ professional electropolishing and professional powder coating you might start wondering why you didn't buy a pair of commercial panels, or at least kits! You just have to decide where you want to spend your time, your money, and your energy. Not everyone chooses the same set of compromises. The bottom line, at least from my perspective, it that it's possible to make a rewarding set of panels without doing everything the "best" way, but you do have to be careful about some important details. Experience is the best teacher, so I'd suggest making some small prototypes to test the waters. Smaller panels are much easier to put together and they needn't cost much. Once you hear your own sandwich of metal and mylar make music you can decide if you want to really dive in.
For all ESL problems I suggest anyone contact ER Audio who produce a full range ESL kit and who are extremely helpful in answering queries re same. I have built pseudo-copies of his speakers and am pleased with the result, although still "tweaking". Stators will work uninsulated, but once the humidity rises above 50% loss of output may start to occur. The ER kit comes with insulated stators but the insulation type is not devulged although it may be akin to powder coating. Bass is good and "sub wooferish" with surprising effect. The "sweet spot" on mine is wide although I am still looking at all aspects of these speakers. I am currently using 4' x 2' areas which are segmented and because of this, I believe, there is not such a demand on the amplifier requirements as presented by one large panel, and dispersion is better. Some of my panels are just bare metal and the only arcing/sparking that occurs seems to be the odd insect or two, or maybe dust, but this is rare, although high (80% and above) humidity can cause problems due to having to turn up the level to get sufficient sound out. Segmented speakers can be either planar or curved array arrangements to aid dispersion, but they certainly would guard against letting the smoke out of your amplifier in comparison with single stator types. It does cost some coin to pursue the DIY thing and on reflection it may have been simpler for me to buy his kit!
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