In typical listening environments, speakers are designed to disappear. Good speakers are often described as “transparent” and “faithful”. There are specific conventions that help to standardize sound across different systems (stereo, 5.1 surround, etc). These standards are great for musicians and sound designers who make music in one place that will be heard in many different situations.
There are musical genres and artistic avenues that don’t subscribe to these sound standards. The Soundsystems of 1960s Jamaica, the Acousmonium of 1970s France, and the 40 part motet by Janet Cardiff are examples where the speaker design (including visual & sculptural aspects) plays a large role in the experience.
Technical standards are useful in many situations, but what value systems are embedded in these standards? What types of expressivity are foregrounded and what types are subverted? We listen to speakers all the time, but what is a speaker actually doing? Like many other technologies, speakers rarely announce themselves unless they are broken or distorted — “what’s wrong with the speaker!”
What if we shift the focus and foreground the speaker as an aesthetic object? What can speakers tell us about sound? about listening? How does a speaker work? What are the different kinds of speakers? How do speakers respond to and articulate spaces? This project asks you to experiment with speakers as visual, sonic, kinetic, and expressive objects.
The project has two main parts:
- Make a speaker! Build a single-channel speaker enclosure/sculpture/object/system. The physical form is up to you — you could have multiple tiny speakers tied together, one giant speaker cone, an architectural element with a well placed audio transducer, etc. It could be giant or tiny, tinny or full, distorted or clean. The only concrete constraint is to have a speaker cable and an amplification system. You can decide to build an amplifier into your speaker, or use an off-the-shelf amplifier.
- Make “sound” for your speaker! This can be a prerecorded track or live input. Is your system mono or stereo (or multichannel)? What kind of voice does your speaker have? Think about your sounds to in relation to the visual and sonic characteristics of your speaker.
Total project cost: $0-40
The basic parts we will be using:
- TDA7297 Amplifier (included with class)
- Talentcell 12V Lithium Ion Battery (included with class)
- You have a choice of speakers–you also can choose mono, double mono, stereo, mono/stereo, or stereo extended (I’ll explain in class)
- Hardware and Components (free within limits)
- Includes a 1/4 inch mono jack, an 1/8 stereo jack, power/charge jack, mounting hardware, wood, wire, a fuse, etc.
- switching mono jack to get mono/stereo (note: need two speakers)
So what is a Speaker? How do they work?
When things collide or move quickly, they displace air and make the sound. If you hit a drum with a stick, you can see the skin of the drum vibrate for a bit afterward. That movement displaces air particles which displaces other air particles which forms a wave that eventually reaches our ears. Loudspeakers work in a similar way.
Instead of a drum head, there is paper cone (sometimes called a diaphragm) that is attached to the rim of the loudspeaker. The inner part of the cone is attached to a voice coil that is positioned just in front of a permanent magnet. When you connect an audio signal to the loudspeaker, electrical signals change the polarity of the voice coil, creating an electromagnet. As the voltage flows back and forth in the cables, the electromagnet either attracts or repels the permanent magnet. This moves the coil back and forth, pulling and pushing the loudspeaker cone, which moves air like the drum skin!
In order to make a speaker work properly, it needs the right kind of signal, a “speaker level signal”. In order to condition your audio signal for a speaker, you first run in through an amplifier. There are two main types of speakers, passive speakers (which are simply speaker cones) and active speakers (that have a built in amplifier).
This animagraff by Jacob O’Neal gives an excellent overview.
You need an amplifier to connect your phone or your computer to a passive speaker. A powered speaker includes an amplifier as part of the speaker enclosure. There are a lot of amplification options that range in cost from around $2 to $2000. Note that bigger speakers generally require more power than smaller speakers, but some small amplifiers work well with larger speakers.
If you don’t have much experience with audio signal flow, take a look at this diagram:
Speaker cable is wire designed to connect speakersand amplifier sources. Typical speaker cable has two connections, positive (+) and negative (-). While speakers will work if you reverse the positive and negative wires, it is a good idea to match the positive terminal from the amplifier with the positive terminal on your speaker driver.
In the image above, the side with the blue line is positive (+) and would connect to the red terminal on your amplifier. The wire with the writing is negative (-) and connects to the black terminal.
Some amplifier options…
Embedding an amplifier or amplifiers into your sculpture/system will let you connect a phone or computer directly to your project. By using a battery powered amplifier you can even create a piece that is not connected to any external devices. There are a variety of amplifier options, depending on the form of and power requirements of your speaker. You will each get a tiny little amplifier and I have a few of the medium sized amps on hand, but if you’d like to permanently fix an amplifier into your project, you should purchase one. Here are some options… all of them are available both at Lee’s Electronics and online.
(a few dollars)
These tiny amplifier boards use
These tiny little thumb-sized amplifier boards require a power input between 5-12 volts (a 9v battery works well) and output about 2-4 watts of sound. In order to use this amp, you will need to connect an input jack and power like so…
These amplifiers are a bit larger due to the heat sink (the grill looking thing), but they have a built in barrel connector for power and can output an impressive 15W per channel (two audio channels, or stereo).
These amplifiers output a lot of power and are great if you are using larger speaker drivers or exciters. Unlike the smaller options, they can easily produce very loud sounds and will be helpful in producing bass frequencies.
These amplifiers are big and way beyond budget, but they are special in one way or another.
Multi-channel amplifiers like this Pyle Pro allow for the a multiple simultaneous channels of audio playback. This kind of amplifier is often used in basic surround sound setups like 5.1 or quad. It could also be used in multi-room situations to control different speaker combinations from a single computer, or to activate different audio drivers on a sound sculpture.
Both of these setup represent “audio standards” byt these multichannel amplifiers can be used in all kinds of ways, and with speakers that have no business speaker together! Make strange 8-channel monstrosities or drone music for 6 subwoofers. If you are in Vancouver, I have a couple of these amplifiers that you can borrow.
This amplifier, the d:16 made by Sonible, can output 16 separate channels of audio playback. It also has a digital processing and routing layer that makes this amplifier useful for complex surround sound setups for sonic arts and science research.
This idea is not new (try an image search for “Suitcase Speakers“) but making your own amplifier is an affordable way to create portable, battery powered, personalized speakers to compose with. You can find a broad range of tutorials online discussing how to make suitcase speakers, from simple to advanced projects. We’ll start with a simple design and you can expand on it as you see fit. In making your speaker you will learn about soldering and electronics, basic signal processing, and woodworking.
First, buy, find, or salvage a suitcase or another portable case! Instrument cases also work well. Garage sales, estate sales, second hand stores, dumpsters, and ebay are all good places to start. The easiest type of suitcase to work with has a sturdy wood frame and flat sides–like this or this. The common old samsonite suitcases will work too, but we might have to reinforce the plastic sides and deal with the slightly curved surface.
cymatics and animation
Read the Wikipedia article on Cymatics.