I feel that subwoofers get a bad rap. Teenagers tossing the cheapest Walmart Boss Audio 12" in a generic ported box in the trunk of their Cobalt and rattling their trunk all over town in search of tite beatz yo have given a certain stigma to one of the most important parts of a quality audio setup. But first, some background.
Many cars with cheaper audio systems have a simple 4-speaker setup. Two in the front, two in the back. Each speaker is in charge of delivering the full range of frequencies to you: low, mids, and highs. The problem with this is that there is only one speaker cone doing all this. Typically these setups have overpowering mids, dim highs, and next to no bass. This can be rectified to an extent with a “smile curve” which consists of turning up the bass and treble on an equalizer, but that will only sound good at low levels because as the volume gets higher the speaker begins to distort. Even if it doesn’t necessarily sound bad you still aren’t getting the full quality of sound because the cone has to convey the small vibrations of the higher frequencies on top of the large, slow vibrations of the low frequencies. It’s like Clarkson’s description of a powerful FWD car. It’s just going to go wrong.
Adding a sub to your system allows one to set up a “high pass filter” on the rest of their speakers. This filter does exactly what it says on the tin by only letting high frequencies “pass through” to the speakers and be reproduced, preventing any bass from getting to your standard four speakers. A “low pass filter” is then set up for a subwoofer, which does the exact opposite and prevents any highs from distorting the bass. Clear bass, clear mids/highs, happy ears.
Of course, having a sub in your trunk doesn’t mean that you have to devote yourself to a life of dubstep and hip-hop. If tuned properly the subwoofer will become invisible. The bass will blend into the mids and highs smoothly and your passengers won’t even realize that big-ass speaker is back there.
Still unconvinced? Take a look at any hi-fi speakers and tell me what you see.
A pair of tweeters, mid range speakers, and a large subwoofer cone in a ported enclosure. A set like these Kenwood bookcase speakers will have crossovers (high-pass, low-pass, and band-pass filters) built into it so the proper speakers only get the right frequencies, something you’ll have to tune yourself in your car with the settings on your head unit (aftermarket head units are a must, I prefer Pioneer or Sony).