Subwoofer

A subwoofer is one driver in one box, built to cover the bottom two octaves of the audible range and nothing above them. Home units run roughly 20 Hz to 200 Hz and almost always arrive self-powered, with the amplifier and a low-pass filter sitting inside the cabinet next to an 8, 10, 12 or 15 inch cone. That onboard amplifier is why a sub needs only a thin line-level cable from the receiver instead of speaker wire. The enclosure comes sealed or ported, and that single choice shapes how the box behaves far more than the driver diameter everyone fixates on. What it buys you is the register you feel through the floor rather than hear as a pitch. THX built its home certification around an 80 Hz crossover because human directional hearing collapses below roughly that point, so one cabinet can carry the low end for an entire five or seven speaker system without the ear ever locating it. That is why the sub can live in a corner while the mains stay in their arc, and why a single well placed box does more for a small media room than another few hundred dollars spent on the front three. Budget models with 10 inch drivers start around 150 to 300 dollars, mid tier sealed and ported units run roughly 400 to 900, and the flagship end runs well past 1,000. A subwoofer is not a bass volume knob, and it does not overrule the room it sits in. Small rooms build standing waves at exactly the frequencies a sub produces, so the same box sounds thunderous in one seat and hollow in the next, and no amount of gain fills a null. That is bass trap territory rather than a sub problem. It is also a different component from the woofer inside a tower speaker, though the two words get swapped constantly in product listings.

Setting the crossover and finding the spot

Crossover comes first, because it decides which speakers do what. Eighty hertz is the THX default and a sound starting point for most systems, but the honest number comes from the main speakers' own low-frequency limit: small satellites usually need to hand off at 150 to 200 Hz, bookshelf pairs around 100 to 120 Hz, and large towers can run down to 60 or 80 Hz before the sub takes over. Set it in the bass management menu of the AV receiver, leave the sub's own dial wide open, and the two filters will not stack on top of each other. Enclosure type is the next fork. A sealed box rolls off gently below its cutoff, holds a flatter response and rings less, which suits music and small rooms. A ported box tunes a vent to reinforce output near a chosen frequency, so it plays louder on the same amplifier, then falls away below tuning at roughly twice the rate a sealed design does. Larger cones help for a plainly geometric reason: a 12 inch driver has about 113 square inches of cone area against a 10 inch driver's 78.5, some 44 percent more air moved per inch of travel. Placement is the last variable and the cheapest one. Corners maximize room gain and maximize peaks and nulls at the same time, so the reliable method is the subwoofer crawl. Put the sub on the main seat, play something with sustained bass, then crawl the floor perimeter and mark the spot where the low end sounds evenest, and move the sub there. Once the bass is settled, the speaker placement calculator sorts out the main channels around it.

Subwoofer vs. woofer

The one-line distinction: a woofer is a driver inside a speaker, and a subwoofer is a speaker of its own. A woofer handles the lower part of a full-range cabinet's job, typically from about 40 Hz up to 2 kHz, sharing an enclosure with a midrange and a tweeter and running off whatever amplifier drives the rest of the pair. It has to reproduce the body of a voice and the weight of a guitar as well as the bottom notes, so it is a compromise driver in a compromise box. A subwoofer gives up everything above roughly 200 Hz in exchange for excursion. The cone is larger, the suspension is built for long travel, the cabinet is braced against pressure rather than tuned for imaging, and the amplifier is matched to that one driver. The practical consequence is headroom. A tower speaker asked to produce 30 Hz at reference level distorts long before a dedicated sub does, and the midrange it is simultaneously trying to reproduce gets smeared by the same cone movement. Splitting the job is why surround sound formats give the low-frequency effects channel its own box, and why bass management exists at all.

Where the self-powered bass box came from

Ken Kreisel gets the credit for the first one, built in the 1960s at Jonas Miller Sounds in Los Angeles after customers complained that electrostatic panels had no bottom end. In 1973 he assembled a tri-amped monitor and bass rig used on the mixdown of Steely Dan's Pretzel Logic, and in 1974 Miller and Kreisel launched the Volkswoofer, described as the first self-powered subwoofer sold as a product. That launch also established the satellite-plus-sub architecture every soundbar package still copies. Cinema pushed the same idea on a different scale. Universal's Earthquake, also from 1974, ran the Sensurround system: up to twenty folded-horn low-frequency speakers reaching down near 16 Hz at levels as high as 120 dB, loud enough to rattle the building around the audience. Only five films ever used the format, and it collected a Scientific and Engineering Academy Award before discrete low-frequency channels in Dolby and DTS made a wall of horns unnecessary. The dedicated bass channel outlived the hardware that introduced it.

Common mistakes

The first mistake is jamming the sub into a corner and calling it done. Corner loading adds output, which sounds like an upgrade for about a week, until you notice the boom on some notes and the disappearing act on others. Run the crawl before committing, and if the corner genuinely wins, at least it won on merit rather than convenience. The second is leaving the crossover wherever it shipped. A generic 80 Hz setting starves small satellites that cannot reproduce 90 Hz cleanly, and it hands too much work to the sub when the mains are large towers with real low-frequency reach. Match the number to where the mains roll off, then confirm the receiver is not applying a second filter inside the sub on top of its own. The third is trusting a rule of thumb instead of your ears. The familiar advice to place a sub one-third of the way along a wall assumes a rectangular, sparsely furnished room, and every sofa, doorway and stairwell shifts the standing wave pattern. Verify by crawling or with a measurement sweep. And treat a second subwoofer as a real option rather than an extravagance, because two moderate boxes in different positions even out room modes in a way one large box in a home theater never manages.