You only want the best, which is why you selected the BMW 325 or 325i. You bought it for the aerodynamic design, the fabulous kidney-shaped grilles and distinctive four headlights. There are a lot of features that are great about a BMW, but perhaps the best is the car's stereo system. There is nothing like cruising down the freeway on a summer day with your tunes making the drive more like a personal concert venue, especially when your vehicle of choice is the BMW 325 or 325i. Stereo sound can be improved or wrecked depending in large part on the speakers you choose to use in your vehicle's stereo system. High-quality 325 speakers or 325i speakers rely on woofers, tweeters and midrange drivers to bring you every level of sound frequency that your music requires for audio excellence.

As you might recall from your science classes in school, sound is transmitted through air waves, which are produced when there are fluctuations in air pressure. Those waves hit your ear drum, which works as a flexible diaphragm, causing the diaphragm to move. Those movements in the diaphragm are picked up by your brain and read as sound. The same theory also is at work in your car's speakers. The drivers all employ a diaphragm that is designed to pick up different types of air pressure frequencies that the driver reads as sound.

The very smallest drivers are called tweeters. These units are designed to pick up the high frequency sounds that are emitted from the electronic bits stored on the medium on which your song or audiobook is recorded. Higher-pitched sounds are made when the air pressure changes rapidly. These quick changes cause the diaphragm in the tweeter to vibrate rapidly, and those vibrations are translated by the speaker into high-pitched sounds.

The largest drivers are known as woofers. Low frequency sounds are easily picked up by the woofers. Their large size encourages the diaphragm in these drivers to move slowly, which is a similar motion that low-pitched sounds create in wave frequency. Woofers are not your best choice to pick up high frequency sounds because it is harder for the diaphragm to vibrate faster due to the mass of the cone impeding the movement. The cone is the structure that holds the diaphragm in place, upon which the polarity changes of electromagnetic and permanent magnets create the air movement and vibration. Midrange drivers are in between the sizes of the woofers and tweeters, and consequently are at the perfect size to easily pick up the sounds in the middle of the frequency range of sound.

Excellent-quality auto speakers will contain a woofer, tweeter, and midrange driver. These will pick up every nuance of sound on your favorite music that you play in your BMW 325.