Sound advice:
The human hearing range is from 20 Hz to 20,000 Hz. "O.K...So what does that mean?" Well, 1 Hz is one cycle per second. So, if a speaker could produce a 1 Hz signal you would see the cone move out, back to the rest position, continue to move back (negative direction) and once again move forward to the rest position -all in one second. This motion of moving; first to a maximum position in one direction, then, back through the rest position to a maximum in the opposite direction and once again forward to the rest position, mirrors the action of a sine wave. Musical notes are made up from sine waves which are pure tones. When these pure sine waves are mixed with other sine waves of different frequencies and amplitudes various musical sounds are created. This is how a synthesizer keyboard can closely approximate the sound of a piano or violin. Any complex wave form can be made up from pure sine waves through this combination process. For example, a square wave can be made from a fundamental frequency sine wave and a number of subsequent harmonic sine waves each with a decreasing amplitude and increasing frequency. Note: you would likely never want to listen to a square wave, it's just for demonstration purposes. The higher the number of harmonic sine waves used the closer the final wave form will look like a square wave. This series of waves is called a Fourier series. O.K enough of the technotalk!! You are probably asking yourself ; " What does all this have to do with speakers?" The answer?' A speaker is a transducer. "O.K, so what's a transducer?" Transducers convert one form of energy to another. In this case the transducer (speaker) converts electrical energy to mechanical energy. It's the job of the speaker (transducer) to vibrate the air and recreate the musical signal you are listening to. The musical signal is made up from all those sine waves of different amplitudes and frequencies mentioned earlier. Sounds easy enough right? The problem is not all speakers can do this over the entire range of 20 Hz to 20 KHz very well. Lower frequencies need bigger surface area speakers and higher frequencies need smaller ones. It's for that reason most house speakers are constructed as; two way (tweeter and woofer) and three way (tweeter, mid range and woofer). The same applies to the automotive world. So why can't a SINGLE speaker perform over the entire range??? Speakers do exist that try to perform this task but they fall very short on performance. Known as "full range" speakers they are often found in very inexpensive systems. If you have ever heard the sound from these "things" you would know what I mean! The bass is really more of a mid range and distorted and the treble is very screechy. That's because the speaker is trying to vibrate slowly to reproduce bass and also try to move fast to reproduce treble and it can't do both WELL at the same time. The solution is to divide the entire audible bandwidth up into smaller bands so that speakers of different sizes can perform better i.e bigger speakers produce the lower frequencies and smaller speakers reproduce the higher ones. The traditional cone type speakers are constructed the same, independent of their size. A woofer is big, has a large magnet and a heavy cone so that it can vibrate large amounts of air at relatively low frequencies. A tweeter, on the other hand, needs to move very fast to vibrate at 20K Hz therefore the cone is very light and small and the magnet size required is much smaller.
