1 Output Transducers (Loudspeakers)

2 Loudspeakers  Transducers that convert electrical signals into sound waves  The current flow in the coil causes the diaphragm to move, thus causing changes in sound pressure

3 Loudspeakers  Loudspeakers usually consist of multiple speakers (drivers) to cover the full frequency range Tweeter Mid-range Woofer

4  Produces Low Frequencies Cone diaphragm Surround Basket Spider Magnet Voice Coil

5 Woofer Frequency Response

6 Tweeter  Produces high frequencies  Uses only one suspension medium.

7 Tweeter Frequency Response

8 Crossover  D ivides and routes the appropriate portions of the signal to each of the speakers in the system

9 Crossover High-Pass

10 Crossover Low-Pass

11 Crossover Band-Pass

12 Passive Crossover  A passive filter is placed after the amplifier  It cannot raise the gain on the signal

13 Active Filter  An active filter is so called because it requires electric power for its operation and can raise the gain of the signal  enables adjustment of the frequency ranges  In active filtering the signal splitting occurs before it is amplified

14 Passive Speakers  These do not contain an in-built amplifier and so must be powered by an external amp  Used in most home Hi-Fi systems  Do not require power leads  May require fairly thick cables to carry the signal

15 Active Speakers  Have a built in amplifier and so can be used with small output signals  Most PC speakers are active to boost the weak output (~4W) from most sound cards  Require only thin signal cables  Increased weight  Overall performance my be restricted by a poor amplifier

16 Distortion  Distortion is an unwanted change introduced in the original sound when it is reproduced through a loudspeaker system  Intermodulation distortion the interaction of two or more frequencies contained in the original sound which produces a third frequency not present in the original sound

17 Distortion  Harmonic distortion similar to intermodulation distortion, except it is a reaction involving one frequency  Transient distortion the inability of a loudspeaker system to properly reproduce transients, short, temporary sounds of less than a second  Loudness distortion caused by overdriving the loudspeaker system, producing a loudness level higher than that of the original studio production

18 Enclosures  The loudspeaker enclosure serves as a passive processor of the sound, collecting and directing it to the desired location  Without a baffle or enclosure low frequency sound from the front and back of the speaker will cancel each other out

19 Infinite Baffle  By completely enclosing the back of the speaker we get an infinite degree of blocking  Stops low frequency cancellation  Wastes energy produced by rear of speaker

20 Vented Enclosure (Bass-reflex)  The rear wave from the loudspeaker is delayed so that it emerges from the port in phase with the wave motion from the front  Relies on strict relationship  Enclosure size  Size of opening (port)  Resonance of loudspeaker

21 Fin