|LFE: An acronym for Low Frequency Effects. The very term sub in the term subwoofer, means meaning sound below 50 Hz. A sub is typically capable of producing sound in the range of 35 Hz to 100 Hz. Some subs can go higher, though this is not really needed. A sub that can go lower than 35 Hz is good indeed, and the lower a sub can go, the more ideal it is for producing deep rumbles. Subs that go really low are also costlier.
Drivers: The driver is what produces the sound from your speakers. It consists of the enclosure (typically metal), a permanent magnet, and the diaphragm (often of paper). Speaker drivers are of three types, distinguished largely on the frequency spectrum they are built to reproduce. Tweeters are the smallest of the speaker drivers and can produce the highest-frequency sounds, like the tinkling of breaking glass. A good-quality tweeter can reproduce sounds up to 25,000 Hz. Squawkers are the mid-range drivers. They are typically 3- to 5-inch drivers with the ability to produce a wide spectrum of sound between the sub and the tweeters.
The subwoofer is the low-frequency sound producer, and is responsible for all the thuds and thumps. They are capable of playing sounds below 150 Hz. A sub also has the biggest driver, sizes range from 6.5 inches to 12 inches in diameter.
SNR: The Signal to Noise Ratio is a very important consideration for audiophiles and the discerning user. Very simply put, every sound channel carries, along with the actual audio content, a certain amount of signal interference or stray noise. This causes distortion in sound, and it is particularly noticeable at higher volumes, mainly because of the unit design imperfections. SNR is measured as a ratio. A typical good value for a speaker is 85 dB, with some higher end 5.1 sets having an SNR as high as 110dB. Speakers with an SNR of below 65 dB should be avoided at all costs!