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Homemade speakers/Headphones
- Thread starter R6MGS
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PC
Obi Wan
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Oatmeal commonly comes cylindrical cartons down here.R6MGS said:
You could use a coffee can too but it's easier to work cardboard than steel.
If he can use his own stereo that makes it easier to match the electronics to the device. Even a small receiver's output it going to way more capable than a portable's.
It also opens up the possibility of leaving out the permanent magnet. By using only coils, one attached to the diaphragm and one fixed, you can drive them with both channels of a stereo amplifier (connected out of phase) and get a summed mono sound output.
PC.
Keoke
Great Pumpkin
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Well that approach seems a likely way to go PC. However, it might be beneficial [simpler] to get the coils from old loud speakers themselves. This would insure that the coil impedance's and the driving source output impedance would produce the minimum power loss. Just a thought.--Keoke
PC said:Oatmeal commonly comes cylindrical cartons down here.R6MGS said:
You could use a coffee can too but it's easier to work cardboard than steel.
If he can use his own stereo that makes it easier to match the electronics to the device. Even a small receiver's output it going to way more capable than a portable's.
It also opens up the possibility of leaving out the permanent magnet. By using only coils, one attached to the diaphragm and one fixed, you can drive them with both channels of a stereo amplifier (connected out of phase) and get a summed mono sound output.
PC.
the ease of working with a cardboard tube was exactly why I originally suggested the oatmeal box. Also for some reason I recall building some sort of project with an oatmeal box in my youth.
Using a coil from an existing radio is probably the best way to go, however, for most loudspeakers, the size/weight of the coil make it unlikely that it will be attached to the diaphragm. Using a small rare earth magnet will keep the weight on the diaphragm low which is needed to get response in the acoustic range, and will provide a good reaction to the magnetic field created by the coil.
On headphones (or at least the ones I have taken apart) the coil is attached to the diaphragm, however those coils are so small that the weight is almost irrelevant, and without really advance construction techniques, I don't think it is likely that this could be done at home.
Yisrael
OP
R6MGS
Yoda
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What are the dimensions of said oatmeal box....It looks alot like our salt boxes....i am just not sure about the height....The salt box is about 5.5 inches tall and the diameter is about 3.25 inches. The coil has to be almost touching the magnet, so I assume depending on the height of the coil used the box might have to be cut down?
Thanks again for all the help.
Thanks again for all the help.
it is the diameter that you need, not the height, the oatmeal box was just an example of something that was easy to work with, which should be about right in terms of diameter. somewhat smaller should work. If it is to small, I think you will have a problem getting the diaphragm to be "springy" enough to vibrate. Remember, you are trying to build a drum, and them make it vibrate. If you have a bit of large diameter 4" or more plastic drain pipe that would work also.
In a "real" speaker there speaker itself is usually very stiff, but supported by a flexible mount, which will allow it to move. my suggestion is to simplify it a bit by making something more like a drum, which will resonate and then with the magnet / coil make it vibrate.
In a "real" speaker there speaker itself is usually very stiff, but supported by a flexible mount, which will allow it to move. my suggestion is to simplify it a bit by making something more like a drum, which will resonate and then with the magnet / coil make it vibrate.
PC
Obi Wan
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Oatmeal cans make good pinhole cameras but aircraft hangars are really cool.
You can certainly use a salt box for the speaker. Whatever size you find easy to work with will be fine. The "drum head" style drivers, with a skin stretched tight on a frame allowing only small deflections, are often called called diaphragm or planar drivers. They're often mounted openly, without an enclosure. The enclosure should make them louder however.
There have been many excellent planar drivers sold over the years, from small (about an inch) sized diaphragms like Infinity's EMIT tweeters to full size, full range planar panels like Magnaplanars:
PC.
You can certainly use a salt box for the speaker. Whatever size you find easy to work with will be fine. The "drum head" style drivers, with a skin stretched tight on a frame allowing only small deflections, are often called called diaphragm or planar drivers. They're often mounted openly, without an enclosure. The enclosure should make them louder however.
There have been many excellent planar drivers sold over the years, from small (about an inch) sized diaphragms like Infinity's EMIT tweeters to full size, full range planar panels like Magnaplanars:
PC.
GregW
Yoda
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Glad to see it is coming together. You want to use the speaker level outputs from a receiver or radio and attach the + wire to one end of the voice coil and the - to the other end of the voice coil. The music comes out of the receiver as a varying voltage. That voltage turns the voice coil into an electromagnet which reacts to the field of the permanent magnet.
When you test it, remember to start at a low volume and work your way up. Don’t want to blow the speaker up before it is graded. /bcforum/images/%%GRAEMLIN_URL%%/frown.gif
When you test it, remember to start at a low volume and work your way up. Don’t want to blow the speaker up before it is graded. /bcforum/images/%%GRAEMLIN_URL%%/frown.gif
OP
R6MGS
Yoda
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ok...we got it vibrating....and even with the volume right up...it still isn't enough vibration to make any noise(we're using Mylar....the hellium balloon stuff)....we also spent a few hours driving around looking for an "earth magnet" with no luck....any ideas where we'd get one(tried radio shack)because I think part of our problem is that the magnet isn't strong enough. Also how could we boost the current thats going to the coil
GregW
Yoda
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If you happen to have an old hard drive from a computer, those have very powerful magnets. They aren't cylindrical like a traditional speaker magnet, just a thought.. There should be 2. Watch your fingers handling them. They can pinch and make you bleed.
Ack! What was I thinking. Hardware store! OSH (don’t know if that store is near you) has a lot of magnets. One that might work well is that telescoping tool grabber.
Ack! What was I thinking. Hardware store! OSH (don’t know if that store is near you) has a lot of magnets. One that might work well is that telescoping tool grabber.
PC
Obi Wan
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How much force is applied to the coil by the magnet is determined by the strength of the magnetic field crossing the wire and the current through it. The strength of the magnetic field is determined by the strength of the magnet and the physical geometry of the magnet and coil wires.
Using stronger magnets is one way to do it (like the rare earth magnets). But magnetic field strength drops off very rapidly with distance so geometry is very important. Commercial cone type drives maximize field strength buy burying a cylindrical coil in a donut shaped magnet
Commercial planar dynamic speakers don't use cylindrical coils. They flatten the coil over the surface of the diaphragm, usually in straight, parallel rows with the magnets also laid out in rows and mounted very close to the diaphragm.
Rather than trying to strengthen the magnets or raise current you could also try to rearrange the wires to be closer to the magnets and add more wires.
You can also examine your layout to see if you have any wires that are "fighting each other" rather than working together. If you run a current in a given direction within the magnetic field it will push in a certain direction. If you have two wires right next to each other with the current going in opposite directions (such as when you fold a wire back on itself) the force generated by each one will be opposite and cancel each other out.
PC.
Radio Shack's website shows catalog #64-1895, Rare Earth Super Magnets (2-Pack), $1.89, available at most stores.
.
Using stronger magnets is one way to do it (like the rare earth magnets). But magnetic field strength drops off very rapidly with distance so geometry is very important. Commercial cone type drives maximize field strength buy burying a cylindrical coil in a donut shaped magnet
Commercial planar dynamic speakers don't use cylindrical coils. They flatten the coil over the surface of the diaphragm, usually in straight, parallel rows with the magnets also laid out in rows and mounted very close to the diaphragm.
Rather than trying to strengthen the magnets or raise current you could also try to rearrange the wires to be closer to the magnets and add more wires.
You can also examine your layout to see if you have any wires that are "fighting each other" rather than working together. If you run a current in a given direction within the magnetic field it will push in a certain direction. If you have two wires right next to each other with the current going in opposite directions (such as when you fold a wire back on itself) the force generated by each one will be opposite and cancel each other out.
PC.
Radio Shack's website shows catalog #64-1895, Rare Earth Super Magnets (2-Pack), $1.89, available at most stores.
.
Hi
Since you said it wasn't quite working, I just "borrowed" some parts from an old radio one of my kids was playing with.
Here is what I came up with (stuff from around the house)
as a frame to hold the diaphragm - a roll of tape. the Diaphragm - I cut the top off of a regular rubber balloon and stretched it over the roll of tape.
magnet - a tiny round magnet which had been part of a spinning top at one point - I super glued it to the balloon / diaphragm in the center.
Coil - I ripped apart the speaker from previously mentioned radio.
I hooked the coil up to my HiFi receiver, and was rather careful not to short it out (the receiver!)
As I brought the coil close to the magnet, the speaker was clear enough to understand the news.
If anyone can explain how to cut and paste pictures into the message, I will send you pictures of the speaker.
(or PM me your E-mail)
Yisrael
Since you said it wasn't quite working, I just "borrowed" some parts from an old radio one of my kids was playing with.
Here is what I came up with (stuff from around the house)
as a frame to hold the diaphragm - a roll of tape. the Diaphragm - I cut the top off of a regular rubber balloon and stretched it over the roll of tape.
magnet - a tiny round magnet which had been part of a spinning top at one point - I super glued it to the balloon / diaphragm in the center.
Coil - I ripped apart the speaker from previously mentioned radio.
I hooked the coil up to my HiFi receiver, and was rather careful not to short it out (the receiver!)
As I brought the coil close to the magnet, the speaker was clear enough to understand the news.
If anyone can explain how to cut and paste pictures into the message, I will send you pictures of the speaker.
(or PM me your E-mail)
Yisrael
OP
R6MGS
Yoda
Offline
Wow, thanks! Man, I love this forum!
The coil I've been using is from an old Crystal Diode radio kit...But if we don't have luck with it we'll rip apart an old speaker.
PC, I think your right about the wires not being close enough to the magnet. We won't have time to play with it for a few days....but thats the first thing we'll try when we do.
BTW: Radioshack isn't technically radioshack here anymore....It was bought out by "The Source"
The coil I've been using is from an old Crystal Diode radio kit...But if we don't have luck with it we'll rip apart an old speaker.
PC, I think your right about the wires not being close enough to the magnet. We won't have time to play with it for a few days....but thats the first thing we'll try when we do.
BTW: Radioshack isn't technically radioshack here anymore....It was bought out by "The Source"