How to connect a subwoofer to a stereo amplifier

Identify both ends before connecting

This guide covers powered subwoofers, which contain their own amplifier. Start with the exact amplifier and subwoofer models, their rear-panel labels and the corresponding manuals. Switch equipment off and disconnect it as those instructions require before changing cables. Keep protective earth connections intact.

Record a proposed route as named output → named input, including signal type. A subwoofer input designed for line level is different from a purpose-designed speaker-level input. The general connection guide explains why connector shape alone is insufficient.

Route 1: a documented subwoofer output

Path: amplifier's powered-subwoofer output → subwoofer's designated line input.

Use this when both manuals support the route. A mono sub output normally connects to the input identified for that use, which may carry an LFE or mono marking; follow the subwoofer's instructions rather than guessing which socket to use.

For a concrete label example, the Denon PMA-600NE rear-panel documentation identifies its PRE OUT connector as an output for a subwoofer with a built-in amplifier. That establishes its purpose. It does not, on its own, prove a particular crossover frequency or high-pass filtering of the main speakers.

Confirm whether the output follows the main volume control and whether the amplifier filters it. Do not bypass the subwoofer's low-pass filter just because the source socket says SUB. Bypass is appropriate only when the documented upstream arrangement provides the required filtering.

Route 2: variable stereo preamp outputs

Path: left and right variable pre-outs → the subwoofer's suitable left and right line inputs.

This route preserves both channels for a subwoofer designed to accept them. The SVS SB-1000 Pro manual describes stereo line-level connection and control settings; Focal's connection guide also distinguishes stereo pre-outs from a dedicated sub output.

Check that the pre-outs are available while the main speakers play and that their level tracks the volume control. A fixed recording output is not interchangeable with this arrangement: turning down the main system need not turn down that output.

If the sub has only one line input, use its manufacturer's supported stereo-to-mono solution. Do not join two amplifier outputs with an ordinary passive Y cable. Splitting one supported signal route and summing two outputs are different tasks.

Route 3: an explicitly compatible high-level input

Functional path: amplifier speaker output → subwoofer's purpose-designed high-level input.

Some powered subs accept a signal from speaker terminals through a dedicated input circuit. This is not permission to connect amplifier speaker outputs to ordinary RCA line inputs. It also does not establish a universal wiring recipe.

As a concrete amplifier counterexample, the NAD C 268 manual, printed page 5, prohibits grounding its blue speaker terminals, joining them together or connecting them to a common-ground device.

Speaker negative terminals are therefore not universally ground. Do not infer an electrical arrangement from terminal colour, and do not copy a high-level cable's wire-colour recipe from another model. If the two manuals do not establish a compatible connection, use a documented alternative or obtain manufacturer guidance before wiring. The NAD example does not certify a subwoofer pairing.

Complete a connection card

Fill in these fields before making the chosen connection:

• Equipment: exact amplifier and subwoofer models, manual revisions and relevant pages.
• Route: output label, input label, signal type and required cable.
• Volume: which control changes the subwoofer level during normal listening?
• Low-pass filter: which component supplies it, and which controls remain active?
• Main-speaker feed: full range or high-pass filtered, according to documentation?
• Restrictions: any high-level topology, grounding or operating requirements?

An unknown field remains unverified; a plausible label does not fill it in. Once the route is documented and connected, begin playback at a low level and follow the subwoofer integration guide to adjust placement, overlap, phase or polarity and level. A working connection is the start of integration, not proof that the settings are already right.