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Music Media Hardware

Building Your Own Drivers? 34

Posted by Cliff
from the speakers!-not-hardware-interface-code dept.
students asks: "I want to cheaply demonstrate how speaker 'drivers' (the part that makes the noise, not software...also known as a cone) work, not to produce ideal sound. Some quick research has made it clear that it's easy to find directions on how to build a fancy speaker box, but not much on how to make a driver. Unfortunately, I can't use Sake. I also can't get the thin wood. Does anyone know how to build a driver out of home materials?"
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Building Your Own Drivers?

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  • by n1ywb (555767) on Tuesday April 27, 2004 @12:35PM (#8985410) Homepage Journal
    http://www.andrew.cmu.edu/~hsakr/hdspeakers/hdspea kers.htm
    • Seriously tho (Score:3, Informative)

      by n1ywb (555767)
      A driver is just a solonoid connected to a paper cone. Look up how solonoids are constructed and you should get a pretty good idea of how to procede.

      • A solenoid is just a coil of wire. It produces a magnetic field inside the coil. This field can be made to change strength and direction by altering the flow of current in the wire. This field can result in a force that will accordingly push or pull magnetic materials. Unfortunately, most materials won't really react to this field, so I am guessing something ferromagnetic is coupled to any moving bits if solenoids are used.
        • After a bit of research, I guess you are right. Technically "solenoid" is synonymous with "inductor". This seems odd since I've never heard "solenoid" used except in the context of an electromagnetic actuator. Oh well, learn something new every day.
          • Well, if you really want to be technical, solenoid is synonymous with "cylindrical wound inductor", as you can have inductors of any shape you like. Toroids are the most common after solenoids, but any bit of wire has *some* stray inductance, just like it has some stray capacitance and resistance.
  • Sure. Here you go. (Score:5, Informative)

    by FreeLinux (555387) on Tuesday April 27, 2004 @12:53PM (#8985667)
    Here are the instructions you need to make a speaker. [cranbrook.edu]
  • by Cthefuture (665326) on Tuesday April 27, 2004 @12:56PM (#8985700)
    Hmmm, there really isn't much to a driver. It's basically just a coil of wire attached to a suspended structure (the cone) that sits inside a permanent magnet. The energy is fed to the coil which makes it move inside the magnet which in turn moves the cone structure to create air pressure waves (sound).

    Simple science-type experiments are super easy to do. No more complex than an electric motor experiment.

    Although I haven't read it, this [howstuffworks.com] probably has everything you need.
    • by unitron (5733)
      The permanent magnet and the coil *are* an electric motor, (or generator, depending upon whether they drive or are driven, that is, in audio, whether they are part of a speaker or part of a microphone), and are commonly known as a voice coil due to most early development being done as part of the development of the telephone.

      Voice coil motors are not limited to audio work, however. One notable example is the replacement of stepper motors in hard drive head positioning systems.

      Not all voice coil operated lo

  • by sweede (563231) on Tuesday April 27, 2004 @01:01PM (#8985772)
    http://www.silcom.com/~aludwig/images/driver.gif [silcom.com]

    You will have to create your own motor (magnet + former), your own cone and your own suspension (spider and suround)

    get a few donut shaped magnets amd glue them together, a paper tube wrap some thin magnet wire around it secure it with epoxy. get a hunk of round steel and a thin plate. attach the steel to the center of the plate, put the magenets around the pole peice and attach to the plate. add another steel plate to the top with a hole big enough that the former fits in.
    thats your motor

    make a spider from something. get a paper cone and attach it to the spider to the former to the surround to the frame. and your done !

    Or, you can get a cheap $10 speaker from partsexpress.com and use that as an example with good drawings

    • I made one once back in grade school as a science fair type of project. We used a glass jar as the frame, and some cloths hanger to suspend it so it was all visible. It sounded.... interesting. The jar directed the sound quite well, but it sounded like the whole thing was in a deep hole in the ground. Great for demonstration purposes though. using the jar ring (it was a ball style jam jar) and hanger made it so you don't need all that stuff about the metal plates.
  • EASY! (Score:3, Interesting)

    by arfonrg (81735) on Tuesday April 27, 2004 @01:57PM (#8986531)
    Get a thin peice of steel sheet metal (thinner the better) and mount it close (closer the better) to an electro-magnet (a coil of wire) but not touching.

    That's a simple speaker and how many of the really cheap ear-phones work.
  • you can hook a tiny motor to an amp and it will produce sound. lots of stuff will. I'm not responsible if wreck your amp.
  • by Mercenary_56 (622604) on Tuesday April 27, 2004 @02:25PM (#8986832)
    Here is a science lesson (meant for high school students) on how to make a speaker. You can download the doc here [prek-12engineering.org] or use Google's cache here. [66.102.7.104]
  • by itwerx (165526)
    Since the coil is really the only part that's difficult to see just take an existing speaker and bust the magnet in half. It'll sound like crap but you'll be able to see everything.
    Just be careful removing the bottom steel plate so you don't damage the coil. Easiest way is to use a nail or sharp knife to scrape away as much of the glue as possible then brace it in a vice and use a cold chisel or large standard screwdriver to pry/knock it loose.
    Once the bottom plate is off use that same chisel comi
  • by xoran99 (745620) on Tuesday April 27, 2004 @03:37PM (#8988035)
    ./configure
    make
    make install

    Someone had to do it :P
  • by cr0sh (43134) on Tuesday April 27, 2004 @04:04PM (#8988516) Homepage
    Once, when I was in high school, and 12 inch woofers were expensive (for a HS student), I set about building my own "sub". Now, don't get me wrong - it SUCKED! But I did learn how to build a real speaker.

    I started out with a largish cardboard box, and traced a large circle on the front, and cut it out with a steak knife. I then made a paper flattened "cone" out of construction paper (a little larger than the hole), made a bunch of radial slits along the edge, then bent, formed, and glued this to the hole. At the apex of the cone (inside the box), I had glued a piece of toilet paper tubing upon which I had wound a mess of wire I had gotten from the windings on a motor armature (as I remember, I didn't do a very neat job of winding it). On the backside of the cardboard, underneath the tube, I mounted (with a bunch of duct tape) a piece of speaker magnet I had (for some reason, when I was a kid, it was far easier to get speaker magnets than whole, large speakers - but I digress). I hooked the wires from the coil up to a radio - and it worked!

    Not much bass, but it was definitely a working "loudspeaker". You could probably take this same technique and apply it to build a much better speaker, perhaps even something to act as a demonstration model. With a little thought, you could even put together a bunch of "speaker kits", if you are teaching a class or something...

  • http://www.partsexpress.com/

    In particular: here [partsexpress.com]

    There seem to be howtos, free design software, parts, etc.
    I'm not associated with this site, other than as a customer. (Inexpensive optical audio cables!)
  • Just make an electromagnet (coil of wire) with a permanent magnet on a rod attached elastically within it. The rod will move in and out as different voltages are applied to the electromagnet. If you apply a crappy paper cone, you might even get it to make sound.
  • ...and you may just win this contest [bbspot.com].
  • Alright, (Score:2, Interesting)

    by Anonymous Coward
    First, follow the various links above on speakers. That gets you the basic design.

    Now, to get a decent shape, suspension, and spider for your speaker, you may want to make your own paper and mold it onto the shapes.

    Start with Play-Doh® or something similar. Shape out the cone and suspension nicely. Then, make a plaster (flour, if need be) cast of it. Then cast that, and seal the result. Now you have a mold to form your cone. Do the same with the design for the spider. The great thing about this proces
  • It sounds like you're doing something Mr. Wizard-ish, where you'll be showing younger kids "how stuff works". So maybe you don't need to build a speaker as we know it.

    Back in the day, when dinosaurs ruled the planet, we had these things called "LP"s and "45"s. And when we were young, we always used to fool around with them, doing things that would make our college audiophile friends scream. Including ...

    ... playing the records by rolling a sheet of paper into a cone, sticking a pin through the small en

  • by eggoeater (704775) on Wednesday April 28, 2004 @04:09AM (#8994222) Journal
    I use to run a pro-sound company and we would usually have blown drivers laying around. If I wanted to show someone how a driver works, I would take a blown driver, cut the surround and spider, take it apart, point to the different parts (cone, magnet, coil) and explain the theory. Then I'd take a good speaker and give a demonstration, starting with the fact that a constant current (i.e. DC) creates a magnetic field that pushes the cone in or out depending on the polarity. This is easily done with a 9v battery. (BE CAREFUL! If you do this with some cheap-o home or car speaker you could blow it!) When you apply the 9v battery to the driver, you can see the cone move up or down and it's easy to visualize the magnetic field being generated by the coil pushing or pulling on the magnet.
    Next I take a cheap sine wave generator (you can get kits that cost $10) and set the frequency to maybe 5Hz (you can find cheap multi-meters that measure Hz). The point here isn't to listen (you can't) but to see the cone moving in and out. This helps the student see that the signal going to a speaker is alternating current (AC) and it quickly moves the speaker back and forth. Higher frequencies move the cone so little or so fast that it's difficult for the student to understand what's happening. So starting with a low frequency and then turning up the frequency helps the student see exactly why the speaker is making sound. The bigger the speaker the better this demonstration works. I usually had 15" drivers to mess with and you can really see the cone move at frequencies below 20.
    Have fun.

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