Subwoofer Not Working or Not Hitting? How to Fix It
A subwoofer that's gone silent — or that's connected but 'not hitting' — is usually a setup problem, not a blown driver: a loose LFE cable, an auto-standby that never wakes, speakers set to 'large' so the receiver keeps the bass, or a room null swallowing the output. Work through these in order with a bass sweep, and you'll find it without pulling the sub apart.
Step 1 — Confirm the sub is producing bass at all
First establish whether the sub is truly silent or just weak. Play the bass test and sweep down through the low frequencies with your ear (or hand) near the sub's driver/port. If it moves air on the sweep, the sub works and you have a routing/level problem — jump to the receiver steps. If it's dead silent through the whole sweep, start with power and cabling. Also run the surround test's LFE channel to confirm the source is actually sending anything to the .1 channel.
Run the check now: sweep the lows in the bass test at the sub. Air moving = a level/routing fix; total silence = check power and the LFE cable first.
Step 2 — LFE cable seating and power/auto-standby
The dull basics catch most "dead sub" cases:
- Reseat the LFE cable. The single RCA sub cable works loose easily. Push it firmly into the sub's LFE / Sub In jack and the receiver's Subwoofer Pre-Out at both ends. If the sub has both L and R line inputs and only one LFE, use the LFE input.
- Power and auto-standby. Confirm the sub is switched on and the rear power LED is lit. Most subs have an Auto / On / Standby switch — in Auto mode the sub sleeps until it detects a signal, and a weak signal or a high wake-threshold means it never turns on. Set it to On to rule this out, and turn the sub's gain/volume up to at least halfway; if it was near zero, the signal that's supposed to wake it never arrives.
Step 3 — Receiver speaker config ("Large" steals the bass)
This is the classic AV-receiver mistake. In the receiver's speaker setup, each speaker is set to Small or Large. "Large" tells the receiver the speaker can handle deep bass itself, so it sends the low frequencies to that speaker instead of the subwoofer. If your fronts are set to Large, the receiver keeps the bass in the mains and your sub sits nearly silent.
- Set all speakers to Small (nearly always correct for real-world speakers), which routes their bass to the sub.
- Make sure the Subwoofer is set to Yes/Present, and if there's an LFE + Main vs LFE option, start with plain LFE.
Step 4 — Crossover setting
The crossover is the frequency below which bass is redirected to the sub — typically 80 Hz for most setups (the THX standard). If it's set too low (say 40 Hz), only the very deepest bass reaches the sub and it feels like it "isn't hitting." Set the receiver crossover to around 80 Hz, and if your sub also has its own low-pass filter knob, turn it to maximum (or to "LFE/Bypass") so the receiver — not the sub — controls the crossover. Two crossovers fighting each other is a common cause of thin, hole-in-the-middle bass.
Step 5 — Phase
If the sub plays but bass sounds thin or vanishes at the listening position, try the phase switch (0° / 180°, or a continuous dial). When the sub is out of phase with the main speakers, their bass waves partially cancel and you lose output right where you sit. Play steady bass from the bass test, flip the phase, and keep whichever setting sounds louder and fuller at your seat.
Step 6 — Room nulls (the subwoofer crawl)
Bass interacts violently with the room. At certain spots, reflected waves cancel the direct sound and create a null — a dead zone where the sub sounds absent even though it's working perfectly. If the sub tests fine up close but disappears at your couch, it's placement. Use the subwoofer crawl: put the sub on your couch, play steady bass, then crawl around the room on your hands and knees to where the bass sounds strongest and most even — that spot is where the sub should go. Corners boost output but can worsen boominess; the crawl finds the real sweet spot.
Step 7 — Amp protection mode
If the sub thumps once at power-on then goes dead, or cuts out under load, its internal amp may be in protection mode — triggered by a shorted speaker wire, an overheated amp, or a fault. Power it off for a few minutes, check the cabling for shorts, ensure it has ventilation, and power back on. A sub that immediately re-enters protection, clicks a relay repeatedly, or stays dead after a reset likely has a failed plate amplifier.
| Symptom | Most likely cause |
|---|---|
| Totally silent, no LED | Power off, or auto-standby not waking |
| Silent, powered, LFE test sends nothing | Sub set to "No" / no signal / cable |
| Weak, mains have plenty of bass | Fronts set to "Large" — set to Small |
| Only deepest notes reach it | Crossover set too low — raise to ~80 Hz |
| Fine up close, gone at the couch | Phase or a room null — flip phase, do the crawl |
| Thumps once then dies | Amp protection — likely a failed plate amp |
When it's the plate amp
Powered subs fail at the plate amplifier far more often than at the driver — the driver is a simple, robust cone, while the amp is packed with electronics and heat. If the sub is dead with the gain up, a known-good LFE signal confirmed by the surround test, and it won't wake in "On" mode, the amp has likely failed. Replacement plate amps are available for many models and are a straightforward swap (four screws and a couple of connectors), which is usually far cheaper than a new sub — check your model before writing the whole thing off.