Hallie_Mae
I am doing a school project. I was wondering how to build speakers from scratch. Will you guys give me any ideas?
Answer
Well as it is a school project I assume that you are going to attempt to build a driver - the actual transducer from scratch, to understand the electromagnetic principles involved. Not a finished speaker system that one would put into use in their living room.
You should do some of the research yourself for a better learning experience. Here is the Wikipedia site for loudspeakers:
http://en.wikipedia.org/wiki/Loudspeaker
There is a lot there but the basic concept is well explained in "Driver Design."
Given that, your main concern is what materials to use and how to find them.
First you will need a magnet. A refrigerator magnet will not do. It's just too weak. If you can take apart an old hard drive you will find an extremely powerful rare Earth magnet. Barring that you can purchase inexpensive ceramic magnets at Radio Shack. If you can find a strong magnet laying around the house or if you teacher can provide one, so much the better.
The diaphragm or "cone" is the business end. It need not be cone shaped - we aren't building a high fidelity speaker here. The key factors are rigidity - stiffness - and light weight. The stiffer and lighter it is, the better it will perform. You need not use paper. Thin Styrofoam makes a good flat plate diaphragm. Craft stores sometimes stock it. The larger it is the more sound it will transfer to the air.
The voice coil is the electrical part. In a conventional speaker it is a coil of thin wire wound on a bobbin. The bobbin is cylindrical and surrounds the core of the magnet separated by a tiny space. This space is called the "magnetic gap" and is the area where the magnetic field is strongest. However you need not do it that way. If you get a coil of wire within the magnet's field it will respond. However the stronger the field the better. You can make a flat coil of wire and get it as close as possible without touching. Important things to consider are the thickness and length of the wire. The type of wire commonly used is called "armature wire." It is copper (usually) and is covered with enamel insulation. If you can get some that is the best stuff to use. Radio Shack may sell it as well. However any thin gauge insulated wire (I'd recommend no thicker than 26 gauge) will work. The total length of the coiled up wire is important because that will determine the speaker's electrical impedance. This is important because you will have to drive that speaker with some kind of amplifier. Amplifiers are designed to drive speakers within a given impedance range, usually between 4 Ohms and 16 Ohms. Connecting a speaker of 2 Ohms, for example, will cause such an amplifier to overheat and destroy itself or trigger a protection circuit. You will need to measure the coil's impedance with an Ohm meter. Your teacher should provide one. If he / she doesn't, inexpensive multi-meters (which will measure impedance) can be had at home improvement stores and radio Shack. They are really handy to have around and are a good investment. Given this, you will need to know what kind of amplifier the speaker will be driven by and what impedance it will tolerate. Between 6 and 10 Ohms is usually a safe bet.
The speaker will need some kind of frame to hold the diaphragm - voice coil - magnet assembly in their proper positions. This can be made, for your purposes, out of virtually anything that is strong enough. You may be able to cobble something together out of wood, plastic, metal and glue it together with hot glue, epoxy or any appropriate glue. If you have a parent or someone who has tools like drills, saws and possibly even welding equipment it would be of great advantage. The frame must hold the diaphragm only by it's edges. In conventional speakers the intermediate structure between the diaphragm and frame is called the "surround" and is flexible while holding the diaphragm centered. You really don't need a surround for your purposes as they are really only used to allow the diaphragm to move around a lot for bass response. I'm guessing that you aren't too concerned about that.
Last but not least is the enclosure. This is gone over in AVDADDY's link. However for your purposes you can get by by mounting your finished speaker on a flat panel or even in a shoe box. Again we aren't going for hi-fi here. The enclosure will give the sound it produces a little more fullness by containing the sound wave coming off the back of the diaphragm which, without some kind of enclosure, will cancel the wave coming from the front. This cancellation is more pronounced at lower frequencies.
Good luck. Hope you get an A.
Well as it is a school project I assume that you are going to attempt to build a driver - the actual transducer from scratch, to understand the electromagnetic principles involved. Not a finished speaker system that one would put into use in their living room.
You should do some of the research yourself for a better learning experience. Here is the Wikipedia site for loudspeakers:
http://en.wikipedia.org/wiki/Loudspeaker
There is a lot there but the basic concept is well explained in "Driver Design."
Given that, your main concern is what materials to use and how to find them.
First you will need a magnet. A refrigerator magnet will not do. It's just too weak. If you can take apart an old hard drive you will find an extremely powerful rare Earth magnet. Barring that you can purchase inexpensive ceramic magnets at Radio Shack. If you can find a strong magnet laying around the house or if you teacher can provide one, so much the better.
The diaphragm or "cone" is the business end. It need not be cone shaped - we aren't building a high fidelity speaker here. The key factors are rigidity - stiffness - and light weight. The stiffer and lighter it is, the better it will perform. You need not use paper. Thin Styrofoam makes a good flat plate diaphragm. Craft stores sometimes stock it. The larger it is the more sound it will transfer to the air.
The voice coil is the electrical part. In a conventional speaker it is a coil of thin wire wound on a bobbin. The bobbin is cylindrical and surrounds the core of the magnet separated by a tiny space. This space is called the "magnetic gap" and is the area where the magnetic field is strongest. However you need not do it that way. If you get a coil of wire within the magnet's field it will respond. However the stronger the field the better. You can make a flat coil of wire and get it as close as possible without touching. Important things to consider are the thickness and length of the wire. The type of wire commonly used is called "armature wire." It is copper (usually) and is covered with enamel insulation. If you can get some that is the best stuff to use. Radio Shack may sell it as well. However any thin gauge insulated wire (I'd recommend no thicker than 26 gauge) will work. The total length of the coiled up wire is important because that will determine the speaker's electrical impedance. This is important because you will have to drive that speaker with some kind of amplifier. Amplifiers are designed to drive speakers within a given impedance range, usually between 4 Ohms and 16 Ohms. Connecting a speaker of 2 Ohms, for example, will cause such an amplifier to overheat and destroy itself or trigger a protection circuit. You will need to measure the coil's impedance with an Ohm meter. Your teacher should provide one. If he / she doesn't, inexpensive multi-meters (which will measure impedance) can be had at home improvement stores and radio Shack. They are really handy to have around and are a good investment. Given this, you will need to know what kind of amplifier the speaker will be driven by and what impedance it will tolerate. Between 6 and 10 Ohms is usually a safe bet.
The speaker will need some kind of frame to hold the diaphragm - voice coil - magnet assembly in their proper positions. This can be made, for your purposes, out of virtually anything that is strong enough. You may be able to cobble something together out of wood, plastic, metal and glue it together with hot glue, epoxy or any appropriate glue. If you have a parent or someone who has tools like drills, saws and possibly even welding equipment it would be of great advantage. The frame must hold the diaphragm only by it's edges. In conventional speakers the intermediate structure between the diaphragm and frame is called the "surround" and is flexible while holding the diaphragm centered. You really don't need a surround for your purposes as they are really only used to allow the diaphragm to move around a lot for bass response. I'm guessing that you aren't too concerned about that.
Last but not least is the enclosure. This is gone over in AVDADDY's link. However for your purposes you can get by by mounting your finished speaker on a flat panel or even in a shoe box. Again we aren't going for hi-fi here. The enclosure will give the sound it produces a little more fullness by containing the sound wave coming off the back of the diaphragm which, without some kind of enclosure, will cancel the wave coming from the front. This cancellation is more pronounced at lower frequencies.
Good luck. Hope you get an A.
Difference between active and passive speakers?
lwk362393
I'm a musician and just usually use amps, but as gigs get bigger I need to start adding monitors and speakers, but I don't know much about them.
Answer
Copied and pasted straight from WikiAnswers (http://wiki.answers.com/Q/What_is_the_difference_between_a_passive_and_active_speaker_system): "An active system has amplifiers and electronic crossover built in to the cabinet.
A passive system has just the speakers and possibly a passive crossover (made up of capacitors and inductors) inside the cabinet. A passive system requires external amplifier(s) to work."
From http://www.mediacollege.com/forum/showthread.php?t=1918: "Very simple, passive speakers need an amplifier for them to be useful, while active speakers have a built-in amplifier that requires electrical power and an audio signal."
And here is much more info that I don't understand (thought I didn't even try that hard): http://www.hometheaterhifi.com/volume_9_4/feature-article-active-speakers-12-2002.html
Good luck!
Copied and pasted straight from WikiAnswers (http://wiki.answers.com/Q/What_is_the_difference_between_a_passive_and_active_speaker_system): "An active system has amplifiers and electronic crossover built in to the cabinet.
A passive system has just the speakers and possibly a passive crossover (made up of capacitors and inductors) inside the cabinet. A passive system requires external amplifier(s) to work."
From http://www.mediacollege.com/forum/showthread.php?t=1918: "Very simple, passive speakers need an amplifier for them to be useful, while active speakers have a built-in amplifier that requires electrical power and an audio signal."
And here is much more info that I don't understand (thought I didn't even try that hard): http://www.hometheaterhifi.com/volume_9_4/feature-article-active-speakers-12-2002.html
Good luck!
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