The United States, the world's biggest oil consuming country, consumed 18.5 million barrels of oil per day (mbd) in 2012, which accounted for nearly 20% of the world's total oil consumption per day. The highest level of oil consumption in US history was 20.8mbd, which occurred in 2005.
It is also important to be conscious of the speakerâs sensitivity rating, measured in decibels (dB). The higher the number, the less power a speaker requires in order to reach higher volumes without distortion. For most car speakers, this number typically ranges between 88 to 92 dB.
Drivers with such a wide frequency range capability are expensive and usually large, so a more common solution is the three-way system, typically with a woofer (for example, a 10 diameter cone), midrange speaker (4 cone) and tweeter (1 dome). A four-way system adds a super tweeter for the highest frequencies.