A subwoofer handles the bass frequencies that smaller speakers cannot reproduce effectively. Connecting one correctly depends on what type of subwoofer you have and what outputs your amplifier or AV receiver provides.
Types of subwoofer
Active (powered) subwoofers contain their own amplifier. They connect to a line-level output — either a dedicated subwoofer output on an AV receiver, or a pair of RCA outputs from a stereo amplifier. This is the most common type for home use.
Passive subwoofers have no built-in amplifier and connect to a speaker output, like any other speaker. They require the amplifier to drive them directly. Less common in home setups.
Connection from an AV receiver
Most AV receivers have a dedicated subwoofer output, labelled “SUB OUT” or “LFE” (Low Frequency Effects). Connect this to the “LFE IN” or single RCA input on an active subwoofer using a single RCA cable. The receiver manages bass management — directing low frequencies to the subwoofer and higher frequencies to the satellite speakers.
Connection from a stereo amplifier
Stereo amplifiers without a dedicated subwoofer output can connect an active subwoofer in several ways:
- Pre-out to subwoofer line in: if the amplifier has RCA pre-outputs (line-level outputs before the power amplifier stage), connect these to the subwoofer. The subwoofer's built-in crossover filters the signal.
- Subwoofer high-level inputs: some active subwoofers include speaker-level inputs, which connect to the amplifier's speaker binding posts alongside the main speakers. This is useful when no line-level output is available. The subwoofer draws the signal from the speaker terminals but takes a very small amount of current — it does not load the amplifier the way a second pair of speakers would.
Crossover setting
Most active subwoofers have a crossover frequency control. This sets the upper limit of what the subwoofer plays. Set it so the subwoofer hands off to your main speakers at a frequency they can reproduce comfortably. For small bookshelf speakers, typically 80–100 Hz. For larger floor-standing speakers, 60–80 Hz. If the AV receiver handles bass management, set the subwoofer's crossover to its maximum so the receiver's settings take effect instead.
Phase adjustment
The phase control (0° or 180°, sometimes variable) aligns the subwoofer's output with the main speakers. An incorrect phase setting causes bass frequencies to cancel rather than reinforce, resulting in thin sound. Set it by playing bass-heavy music and switching between 0° and 180°, choosing whichever position sounds fuller.
Frequently asked questions
Do I need one subwoofer or two?
One subwoofer is standard for home use. Two subwoofers placed at different positions in the room produce more even bass distribution, reducing room-mode peaks and nulls at the listening position. This is a refinement rather than a necessity.
Where should I place the subwoofer?
Bass is largely non-directional at low frequencies, so exact position matters less than for other speakers. However, room acoustics create standing waves — frequencies that are louder or quieter at specific positions. Placing a subwoofer in a corner maximises output but often emphasises room modes. A common starting point is near one of the main speakers. If you have the option, the “subwoofer crawl” — temporarily placing the subwoofer at the listening position and moving around the room to find where bass sounds most even — identifies a good placement.