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.
First of all, note that there are a great many men who can sing notes who's fundamental frequency is in the subwoofer range. Most Baritone/bass men can sing down to E2 which is 82 Hz, and a great many basses can sing two octaves below middle C, which is 65 Hz. Most men with low speaking voices are producing fundmentals in the 100 Hz range, and the booming professionals with radio voices can can easily speak in the 60-80 Hz range. For purposes of optimizing for human voice reproduction, however, the subwoofer crossover frequency is not critical.