Planar Options

[kctess5]

I've been planing on making some planar speakers to cover the >1000 Hz range, actively crossed over, but I'm a bit worried about the cost, safety (well not that much...) and difficulty of working with the tesla coil status voltage.

I'm not that familiar with all of the different planar speaker options and I was wondering if there are any types that can work with a standard amplifier, or one with minimal modification that I could make, preferably something that doesn't require super expensive components

[john65b]

I think you mean Electrostatic speakers?

[jefftrax]

There are some ribbon style planars on ebay that extend down to below 1000 hz.
TSG PA106 by tsgaudio And they are very efficient - around 100 db at 1 watt

[gootee]

Originally Posted by kctess5

I've been planing on making some planar speakers to cover the >1000 Hz range, actively crossed over, but I'm a bit worried about the cost, safety (well not that much...) and difficulty of working with the tesla coil status voltage.

I'm not that familiar with all of the different planar speaker options and I was wondering if there are any types that can work with a standard amplifier, or one with minimal modification that I could make, preferably something that doesn't require super expensive components

kctess5,

Rather than electrostatic types, why not make some much-simpler "planar magnetic" speakers, more or less like Magnepan makes them? All you need is a bunch of magnets, some mylar, and some foil or wire (and a frame, and a perforated piece of thin steel). Their sound can be truly exquisite! (And that might be an understatement.)

There are lots of threads here that show how to build them.

Basically, the magnets are "bar" types, usually about 1/2-inch wide and 1/8-inch thick (and as long as possible but if shorter you just need more of them). BUT, and this is the key, the N and S poles have to be on the large faces of the magnets. (Lots for sale on ebay, and websites.)

You just line the magnets up in columns, on a piece of thin perforated steel, with alternating columns with N up or S up. The mylar is stretched over the magnets, usually a few mm from them.

If a conductor is glued to the mylar, between two columns of magnets, then a current through that conductor (which is in the magnetic field that goes from the N magnets to the S magnets, which is roughly parallel to the mylar in the gaps between the N and S columns) will have a force induced on it that is perpendicular to the mylar, which will push it toward or away from the magnets, depending on the direction of the current.

So you could snake a single conductor up and down so it goes between all of the columns of magnets in the right sequence and then connect the two ends of the conductor to your amplifier's speaker terminals, and voila!

You can easily calculate what the resistance of the conductor would be, from its cross-sectional area and length. So then you can work out the conductor size and layout so it will be 4 Ohms or whatever you need, or somewhat close hopefully. Usually either aluminum foil or aluminum wire is used. The smaller the cross-sectional area the higher the resistance per unit of length. (Search for my posts here in the Exotics forum and you'll find almost all of the equations you need, for that, if you even need them at all.)

You could make a narrow section at the edge of a mylar panel, with lighter conductors and closer spacing to the magnets, say 4 inches wide, that could act as a ribbon-like tweeter, and use the rest of the panel, or a separate panel, as mid/bass, or have separate panels for each. Find some pictures of Magnepans with their socks removed and you'll see what I mean. Some people here also just make one panel and run it full range and claim the response is good for 30 Hz to 22 kHz. But I imagine that separate panels could have less distortion at very high volumes (which is the only place there should be anything like distortion, with these types of speakers).

If you really just want a tweeter, or mid+tweeter, you could probably get by with very low cost, by making them relatively narrow. However, you could probably also just make them small in both dimensions, and still get perfect sound, above 1 kHz. But bigger would probably be better, if you need high output levels. Here's a thread with a guy who's making some right now: Mini planar magnetic using neos . Also check out this thread: analysis epsilon .

Maybe you already are doing this but if not, I would also consider not using any crossover at the speakers and just using a separate amplifier for each frequency range, with a line-level crossover between the preamp and the multiple power amps. That is way better with ALL kinds of speakers (if they use crossovers). (Look for used power amplifiers on ebay, like Adcom GFA-545 or 535, or Hafler DH-220. They can be very cheap, like less than $100 to $200+, and are utterly fantastic for the price.)

The magnets can get expensive, if you use neodymiums, especially if you want large panels (like 2 feet wide by 6 feet tall). But Magnepan uses "regular" magnets and their sound is exquisite!

If you have never heard Magnepans, you might really be shocked at how good the sound quality can be, from these types of speakers.

Cheers,

Tom

[kctess5]

Thanks that was exactly what I was looking for. I didn't know if you needed special circuitry to drive those too but now I see you don't. I have an active line level crossover which makes things easier.

I have a way to get the highest grade neodymium for pretty cheap so this could work out

[brian t]

Gootee,what an excellent reply very informative we need more people like you on this forum, makes undertaking projects a bit easier when we can fall back on your experience.cheers

[gootee]

Thanks for the kind words, brian! And you're welcome, kctess5!

Maybe it's just one of my many character flaws <smile>. But I do tend to believe that one of the main ways that civilization and culture (and the Universe as a whole) can be advanced is by the sharing of any specialized or hard-won knowledge and any benefits of experience. I also just enjoy helping people. Or maybe it just makes me feel slightly worthwhile. Either way, it's a win-win situation.

Edit: When you are trying to glue the conductors to the mylar (unless you use peel&stick foil), a DC voltage of the proper polarity might be able to be used to help hold the conductors in place.


Regards,

Tom

[kctess5]

Originally Posted by gootee

Thanks for the kind words, brian! And you're welcome, kctess5!

Maybe it's just one of my many character flaws <smile>. But I do tend to believe that one of the main ways that civilization and culture (and the Universe as a whole) can be advanced is by the sharing of any specialized or hard-won knowledge and any benefits of experience. I also just enjoy helping people. Or maybe it just makes me feel slightly worthwhile. Either way, it's a win-win situation.

Edit: When you are trying to glue the conductors to the mylar (unless you use peel&stick foil), a DC voltage of the proper polarity might be able to be used to help hold the conductors in place.


Regards,

Tom

I must say I like this forum a lot more than others, so many fall into the trap of excessive group think and a lack of diversity in opinion, this one seems to not have this problem. I would guess this is because of the more mature group here and the huge amount of experience so many members have and are willing to share.

And about the dc thing how would that work? Would you stretch it out over the magnets and then apply the foil with the charge to interact with the magnetic field?

[gootee]

Applying DC (possibly with a suitable series resistor) of the proper polarity could be used to induce a force that would pull the conductor toward the magnets, which should also tend to hold the conductor in the center of the gap between magnet columns. So it could hold the conductor in place, against the mylar, in the correct position, while the glue cures, for example.

On second thought, if you use the Epsilon layout, which you probably should, it might not be very useful, since not all of the conductors should be centered in the gap.

Yes, this forum is great. There are even quite a few "famous industry greats" who are regulars, here, along with lots of other gifted and inspired people. It is, in a truly-profound sense, an interactive knowledge base, and a wonderful community resource.

The moderators deserve a lot of credit, too.