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Rigging a Speaker

elementcollector1
in Engineering

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I have an 8-ohm, 0.5 watt speaker that is the perfect size for a project I am attempting. Is it possible to hook this up to an mp3, ipod, or Arduino Uno?

Yes, it is possible, feed it a signal not exceeding about a volt RMS AC, the source device should be capable of handling a low impedance load.

Just measure it with an AC voltmeter or oscilloscope at the volume setting you want, with the load (speaker) connected on one channel.

There may be dozens of different players with different output designs to answer your last question.

8 ohms is a nominal impedance @1khz. If you drive it down to 100hz your impedance will drop to 0.8 ohms impedance. Most portable listening devices output somewhere between 1 and 2 volts and are designed to drive loads around 16 - 32 ohms nominal impedance @1khz. Assuming that your portable listening device is capable of a clean .05 watts @ 1 volt you get ~.05 amps @ 16 ohms nominal impedance. Your 8 ohm speaker will probably have a much more linear range than headphones and you will be driving your device well outside of specification if you open it up completely. It's not that it won't drive it, it's just that you will shorten the life of your listening device!

Can I put something in between the two to control the impedance? I'll try to see how many amps / volts my ipod puts out.

An audio taper potentiometer will work.

What is described is a need for impedance matching.

 

Two common methods are (a) using a transformer. Which provides efficient transfer of power without being able to add power.

http://nuclearpowert.../h1011v4_46.htm

 

or (b) using a transistor as an emitter follower. As well as providing efficient transfer of power, this can add power as it amplifies current. (taken from the transistor supply)

http://www.carlomoze...iles/Unit_4.pdf

Edited by Joatmon

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