Subwoofer Test

This subwoofer test checks that your subwoofer plays, that it gets the right signal, and that it blends with your speakers. Play the subwoofer channel on its own, the LFE channel that films use for explosions, and confirm the low pulses come from the subwoofer and nowhere else. Then play an 80 Hz crossover tone through the speakers and the subwoofer together and flip the phase switch to the louder setting. Third-octave subwoofer test tones from 20 to 200 Hz, a slow sweep and a rattle finder show how deep and how cleanly it plays. It works as a subwoofer test online for home theater subwoofers, 2.1 PC speakers, soundbars with a wireless subwoofer and car audio.

How to test a subwoofer

1. Set the subwoofer's own volume knob to about the middle and its crossover or low pass knob to the highest setting, or to LFE if it has one.
2. Open Subwoofer setup and press Play subwoofer channel. With 6 or more outputs, the pulses go to the subwoofer channel only. With 2 outputs, they play on both speakers and a 2.1 subwoofer takes them through its crossover.
3. Press 80 Hz in step 2 and sit in your usual seat. Flip the phase switch on the subwoofer, or press Sub flipped here when it is offered, and keep the louder setting.
4. Open Tones and step down from 200 Hz. Every step should come from the subwoofer area, with no step much louder than its neighbours.
5. Open Rattle finder to catch anything that buzzes in the room.

What the results mean

The subwoofer makes no sound

• Power and standby. Subwoofers set to Auto go to standby after a spell of silence and wake when a signal arrives. A quiet test may not wake them, so set the power switch to On instead of Auto while you test.
• The cable. Use the receiver's SUB or LFE output to the subwoofer's LFE input. If the subwoofer has no LFE input, use its left or mono line input.
• The receiver thinks there is no subwoofer. In the speaker setup, set Subwoofer to Yes, then run the microphone calibration again.
• The computer sends stereo. Windows set to stereo sends no subwoofer channel. Set 5.1 or 7.1 with the Configure button in the Sound control panel, or let the receiver redirect bass from the front speakers by setting them to Small.
• A wireless subwoofer lost its link. Soundbar subwoofers pair by a button on the back. Press it, then follow the soundbar's pairing steps.

Bass seems to come from the subwoofer's corner

Below about 80 Hz, your ears cannot tell where bass comes from, so a well set subwoofer seems to vanish into the speakers. If you can point at it, it is playing too high. Lower the crossover in the receiver to 80 Hz, and check that the subwoofer's own crossover knob is not also filtering at a lower point, which leaves a gap. If you can hear voices from the subwoofer, it is getting frequencies far above its job.

Bass is thin at the crossover

When the speakers and the subwoofer play the same frequency a few milliseconds apart, they can cancel each other near the crossover. Play the 80 Hz tone and flip the phase: one setting should be clearly louder, and that is the one to keep. If the receiver has distance or delay settings, enter the real distance from your seat to the subwoofer, which lines up the timing. A subwoofer placed far from the front speakers needs more care here.

One note booms or the bass is uneven

Room modes make some notes far louder at your seat than others. Try the subwoofer crawl: put the subwoofer at your seat, play the slow sweep, and crawl along the front of the room listening for the spot where the bass sounds most even. Put the subwoofer there. Corners give the most output and the most boom. Two subwoofers in different places smooth the room better than one larger one. The bass test hz page explains how room size sets the booming notes.

The subwoofer hums or buzzes when idle

A 50 or 60 Hz hum with nothing playing comes from a ground loop. Plug the subwoofer and the receiver or computer into the same power strip, try a different cable, keep the cable away from power cables, and if it stays, a ground loop isolator on the subwoofer line fixes it. A buzz that comes and goes with the room lights points to a dimmer switch on the same circuit.

Setting crossover, level and phase step by step

1. Set the main speakers to Small in the receiver and the crossover to 80 Hz.
2. Turn the subwoofer's own crossover knob to maximum or LFE, and its phase to 0.
3. Run the receiver's microphone calibration with the subwoofer volume knob at the middle.
4. Play the 80 Hz tone here, flip the phase, and keep the louder setting.
5. Step through Tones from 125 Hz down to 31.5 Hz. The steps should sound roughly even. If they fall off sharply below the crossover, raise the subwoofer level a little.
6. Play music and films you know well, and adjust the subwoofer level by 1 or 2 dB to taste.

2.1 desk speakers, soundbars and car subwoofers

A 2.1 desk set sends bass to its subwoofer by itself, so the browser plays stereo and the subwoofer's volume knob sets the balance. Soundbars handle their subwoofer the same way: use the soundbar's bass setting, not the computer's. In a car, set the amplifier's low pass filter to about 80 Hz and use the rattle finder with the engine off. For testing all six or eight channels of a home theater, use the 5.1 surround sound test or the 7.1 surround sound test online.

What a subwoofer tester cannot do

A web page cannot hear your room, so it cannot measure the subwoofer's level, its frequency response or its timing. Your ears decide. For accurate level and phase matching, use the receiver's calibration microphone, or a measurement microphone with Room EQ Wizard. The subwoofer channel only reaches the subwoofer directly when your browser reaches 6 or more outputs.

Subwoofer test questions