[LaPierre]

My highschool has a senior project, what that means is you can choose a topic to research and whether the presentation you make passes or fails can determine whether or not you graduate. Sounds rough, but the requirements for passing are laughably low. I decided to raise the bar for myself and to create speakers from scratch to present as my project.


 
that's the basic look of two potential speaker concepts, they're like a pseudo-planar dynamic hybrid speaker design. I have several 1" Neodynmium N42 magnets for the driver and plan to make the voice coil 4 or 8 ohms. the diaphragm material will be HDPE (high density polyethylene) with a thickness of 0.06" (that might be thick, I can shave it down if needed which is likely).

I'm kind of unsure what to use as suspension, but I think I'm going to use rubber bands at each corner (vertical only). That's the best I can think of, probably is somewhat impractical. Does anyone know of an adhesive I could use for attaching the voicecoil to the diaphragm?

I'd appreciate any general advice, I plan to test a few different designs.

 

[khbaur330162]

Maybe use plastic window sealer (can be tensioned with a hair dryer, even thinner stock of Mylar can be found on eBay for pretty cheap), paper, or even thin foam as the diaphragm? Something light weight and thin enough that it could be glued to your baffles at their perimeter and still allow for flex, no suspension needed. I've read that 3M contact cement is good for gluing voice coils. If using Mylar as your diaphragm I've read that 3M 4693 Scotch-Grip Plastic Adhesive is good for gluing it down to your baffle.
 
Having difficulty imagining how you'd wrap the voice coil by hand. My mind immediately goes to Magnepan, using bar magnets and running lines of wire. It just seems easier to me, but you've already got the 1" disc magnets so perhaps a bit of time and patience is all that's needed.
 
Have you checked out diyAudio? There's lots of good reading material there. I'd suggest the Planars and Exotics forum.

 

[Alan1954]

Looks like you're building a 'distributed mode loudspeaker' (do a search). NXT is the company thats done most of the development and has the patents. Plenty of diy examples around, most use the little drivers or 'exciters' from parts express. Even if you're going to build your own drivers you could order some to see how they're built, they're pretty inexpensive. Search for 'nxt' on audiocircle and diyaudio for more info.
 
Have fun with it!

 

[Alaska Skier]

Great to know I'm not the only one who did this for a science fair, I did it in middle school, I vacuformed some of my cones out of that horrible plastic packaging that we always cut ourselves on and developed a modular system where I could switch out the cone, and voice coil that consisted of having a paper tube on the bottom of each cone so I could slide the voice coils on and off of each cone I wanted to test, the spider and stack of magnets were stuck together and the spider had a paper tube that I could slide the cone/voice coil into, your key to having a good presentation here is to have an overwhelming amount of data. Use a microphone and voltage sensor in conjunction to see how accurately the speaker outputs sound and also be sure to include the impedance of each voice coil. I'll send you photos if I can find them, also, be sure when testing to use a frequency generator to test response and also a piece of music you like to just personalize it, if your school has soundproof rooms great, do the testing in there, eliminating all variables and getting accurit data is the most important thing here. Good luck and if you need any help just let me know

 

[Alaska Skier]

Also, for wrapping voice coils, put a pinhole in a dish or cup that is not plastic and put some rubber cement in the dish. As the wire runs through the pinhole it will be coated with rubber cement and will adhere to itself gluing the coil together, also, a sewing machine thread tensioner works great for keeping the wire tight, rubber cement works great for this but be sure to not use a plastic dish for holdin it, the cement is also a solvent and will melt the dish resulting in a auful mess that is a pain to clean up

 

[LaPierre]

  Maybe use plastic window sealer (can be tensioned with a hair dryer, even thinner stock of Mylar can be found on eBay for pretty cheap), paper, or even thin foam as the diaphragm? Something light weight and thin enough that it could be glued to your baffles at their perimeter and still allow for flex, no suspension needed. I've read that 3M contact cement is good for gluing voice coils. If using Mylar as your diaphragm I've read that 3M 4693 Scotch-Grip Plastic Adhesive is good for gluing it down to your baffle.
 
Having difficulty imagining how you'd wrap the voice coil by hand. My mind immediately goes to Magnepan, using bar magnets and running lines of wire. It just seems easier to me, but you've already got the 1" disc magnets so perhaps a bit of time and patience is all that's needed.
 
Have you checked out diyAudio? There's lots of good reading material there. I'd suggest the Planars and Exotics forum.

Well, the HDPE I bought could probably be shaved much thinner, annoying but probably worth it for reduced weight. I'm not sure how I'd use material as flexible as mylar, i'm very to DIY audio -- or rather, other than dampening mods for headphones I haven't been introduced.

 

[LaPierre]

Great to know I'm not the only one who did this for a science fair, I did it in middle school, I vacuformed some of my cones out of that horrible plastic packaging that we always cut ourselves on and developed a modular system where I could switch out the cone, and voice coil that consisted of having a paper tube on the bottom of each cone so I could slide the voice coils on and off of each cone I wanted to test, the spider and stack of magnets were stuck together and the spider had a paper tube that I could slide the cone/voice coil into, your key to having a good presentation here is to have an overwhelming amount of data. Use a microphone and voltage sensor in conjunction to see how accurately the speaker outputs sound and also be sure to include the impedance of each voice coil. I'll send you photos if I can find them, also, be sure when testing to use a frequency generator to test response and also a piece of music you like to just personalize it, if your school has soundproof rooms great, do the testing in there, eliminating all variables and getting accurit data is the most important thing here. Good luck and if you need any help just let me know

I'm trying to avoid the normal spider + rubber suspension normal speakers use, I want to make something with a flat surface to function similarly to planars but still act like dynamics. I'll probably experiment around with different designs, though.

 

[LaPierre]

  Maybe use plastic window sealer (can be tensioned with a hair dryer, even thinner stock of Mylar can be found on eBay for pretty cheap), paper, or even thin foam as the diaphragm? Something light weight and thin enough that it could be glued to your baffles at their perimeter and still allow for flex, no suspension needed. I've read that 3M contact cement is good for gluing voice coils. If using Mylar as your diaphragm I've read that 3M 4693 Scotch-Grip Plastic Adhesive is good for gluing it down to your baffle.
 
Having difficulty imagining how you'd wrap the voice coil by hand. My mind immediately goes to Magnepan, using bar magnets and running lines of wire. It just seems easier to me, but you've already got the 1" disc magnets so perhaps a bit of time and patience is all that's needed.
 
Have you checked out diyAudio? There's lots of good reading material there. I'd suggest the Planars and Exotics forum.

Planars seem difficult to design, but I do really like them. Never heard a planar loudspeaker, but my HE-400i sound pretty good and so did my (sold) T50rp IIs.

 

[khbaur330162]

  Planars seem difficult to design, but I do really like them. Never heard a planar loudspeaker, but my HE-400i sound pretty good and so did my (sold) T50rp IIs.

No idea how difficult it would be to design a planar magnetic loudspeaker that sounded "good" -and of course that's what we're aiming for here- nor have I ever heard one myself, but since you said all we really have to accomplish with this project is something that more or less makes sound for a day or two, to that end I don't think it should be all that difficult.
 
Seeing as you want the driving force to be planar, yet some type of surround so it acts as a dynamic, the diaphragm needs to be pretty stiff in my mind, but.06" seems really thick to me. I'd probably consider buying a much thinner piece of plastic, it seems easier than shaving that one down.
 
Here's a great thread on how to build a simple planar magnetic loudspeaker and he says they sound pretty darn good, too.
http://www.diyaudio.com/forums/planars-exotics/95541-full-range-planar-speaker-using-neo-magnets.html
I'm not sure how he connects the Aluminum tape pieces to be quite honest, I never found anything on how he gets the audio signal to jump through the adhesive layer from one piece of tape to another. Maybe you'll have better luck finding this piece of information, perhaps you could create a diyAudio account and ask him yourself as I believe he's still active to the forum, or you could maybe just scrape the adhesive off and glue the corners of the Aluminum tape together with conductive epoxy. That, or you could glue runs of wire to the diaphragm as your voice coil like they did with the Magnepan speakers. 

 

[LaPierre]

Update: I've figured out quite a few things through trial and error. I ended up making my speakers cones and using 36awg wire. I ditched the polyethylene (it's way too heavy) and am using normal paper/thin cardboard from folders (25 cents each at walmart, so pretty economical). It's not very difficult to make a coil with 4 ohms impedance (about 80 wraps around a cylinder with a diameter slightly more than 1".  I currently have two problems.

1. I'd like to buy foam surrounds since I'm currently just using tape to suspend my cones and it isn't the worst but isn't ideal. I want to buy them in bulk with an inner diameter or 5.5 - 8" but even on ebay they're pretty expensive. 

2. I'm using thick paper folders and was wondering if I could get the material thinner? I might try sanding it a little but I think that might be hard to do consistently with multiple cones, and also I feel like I'd need to 'seal' the cones after and couldn't think of something that wouldn't dampen their vibration.

On a side note, this project has been really fun and a good learning experience. I wouldn't mind sharing my story and posting pictures when I'm finally done.

 

[Muinarc]

You could make surrounds by buying foam or rubber (soft stuff is out there) and cutting it in half, making it a U or cut it in half again and make it a 1/4 arc shaped piece then glue 2 ends together. Not much surface to mount the cone too, but it could for sure be done depending of the materials. I have seen bicycle innertubes used this way before.

 

[khbaur330162]

1. I agree with Muinarc. That, or maybe Plastidip. (I had to mention it)
2. Perhaps an art supply store has funky kinds of paper in different gsm ratings that you could use? Not really sure. Why do you like the paper so much? Because the fibers are sort of loosely woven? Also -just to throw this out there- my mind immediately went to transparency sheets. I'm guessing they could be formed into cones that would be relatively rigid. Have you seen those youtube videos on DIY thermoforming? You could make a thermoforming box, make a mold for your diaphragm, heat the thin plastic and then vacuum seal it around the mold while it cools; diaphragm and surround all in one.

 

[LaPierre]

I never got back to people to report my progress. I've tried many things, but my best results have been with regular masking tape and printer paper. They sound surprisingly good. I'll take pictures later this week. I tried foam surrounds and they're highly incompatible to my design for various reasons. With a bit of thorough explanations / a picture tutorial I think anyone on here could make a speaker like I have without having to spend much more than 20$ (you could actually build multiple, that's just the base approximation for the price).