Click here to purchase the entire book in PDF format. Ribbon Loudspeakers As we have now seen many times, if you put current through a piece of wire, you generate a magnetic field around it. If that wire is suspended in another magnetic field, then the field that you generate will cause the wire to move. The direction of movement is determined by the polarity of the field that you created using the current in the wire. The velocity of the movement is determined by the strength of the magnetic fields, and therefore the amount of current in the wire. Ribbon loudspeakers use exactly this principle. We suspend a piece of corrugated aluminum in a magnetic field and connect a lead wire to each end of the ribbon as is shown in Figure 6.127. Figure 6.127: When you put current in the wire, a magnetic field is created around it and the ribbon. Therefore the ribbon moves. When we apply a current through the wire and ribbon, we generate a magnetic field, and the ribbon moves. If the current goes positive and negative, then the ribbon moves forwards and backwards. Therefore, we have a loudspeaker driver where the ribbon itself is the diaphragm of the loudspeaker. This ribbon has a low mass, so it's easy to move quickly (making it appropriate for high frequencies) but it doesn't create a large magnetic field, so it cannot play very loudly.. Also, if you thump the ribbon with your finger, you'll see that it has a very low resonant frequency, mainly because it's loosely suspended. As a result, this is a good driver to use for a tweeter, but it's difficult to make it behave for lower frequencies. There are advantages and disadvantages to using ribbon loudspeakers: