What frequency should I use for a subwoofer test tone?

Start with a sweep from 20 Hz to 200 Hz. That covers the full subwoofer range. Single tones at 80 Hz and 40 Hz are also useful for checking crossover and room modes.

Why is 80 Hz the recommended crossover?

80 Hz is the THX recommended value. Bass below about 80 Hz is hard to localize, so the subwoofer can be placed for best bass response without being heard as a separate source.

How can I tell if a bass peak is a room mode?

Play a slow sweep and listen for a frequency that is much louder than neighboring frequencies. For a 5 m room, expect a mode near 34 Hz. Moving the subwoofer or your seat can reduce the peak.

Can I damage my subwoofer with test tones?

Yes. Low tones can damage drivers if played loud. Always start at low volume and stop if you hear distortion. Increase volume slowly and only to a moderate level.

Subwoofer Test Tones: Checking Bass From 20 to 200 Hz

Run a bass sweep from 20 Hz up to 200 Hz to check how your subwoofer handles the low end. Human hearing runs from 20 Hz to 20,000 Hz, and subwoofers cover roughly 20 to 200 Hz. A controlled sweep reveals where your subwoofer starts to roll off, where room modes cause peaks or dips, and whether the crossover point is set correctly. Start at low volume to protect the driver.

What a Subwoofer Test Tone Does

A subwoofer test tone is a pure tone at a specific frequency. Play tones across the bass range and listen to how your subwoofer and room respond at each frequency. Use a slow sweep from 20 Hz up to 200 Hz. As the tone rises, listen for changes in loudness. A smooth, even response is the goal. Some notes will be much louder or quieter, and that points to a room mode or a crossover issue.

Below 80 Hz, low frequency test signals are hard to localize by ear. That is why one subwoofer can sit off center without drawing attention. Judge the overall bass balance by ear; do not worry about pinpointing the subwoofer's location.

Understanding the Crossover

The crossover splits the audio signal so low frequencies go to the subwoofer and higher frequencies go to the main speakers. Set it to 80 Hz. That is the THX recommended value, and it sends everything below 80 Hz to the subwoofer while the main speakers handle everything above. It works because bass below about 80 Hz is hard to localize, so the subwoofer can go where the bass response is best without sounding like it is stuck in a corner.

Testing Your Crossover Setting

Play a bass test frequency at 80 Hz, then at a higher frequency. You want a smooth transition between subwoofer and main speakers. If the 80 Hz tone sounds much louder than the higher tone, the crossover is set too high or the subwoofer level is too high. If the 80 Hz tone is weak, the crossover is too low or the subwoofer is not getting enough signal. Adjust the crossover knob or the subwoofer volume until the levels match.

Room Modes and Bass Peaks

Room modes are resonances caused by sound waves reflecting between walls. They make certain bass notes sound much louder or quieter than others. Calculate the first axial mode for a room dimension using f = c / (2L), with c the speed of sound, about 343 m/s at 20 °C, and L a room dimension. For a 5 m room, the first axial mode is about 34 Hz. That means a 34 Hz tone will boom in that room.

Finding Your Room Modes

Play a slow sweep from 20 Hz to 200 Hz. Listen for frequencies that jump out as much louder. These are likely room modes. A strong peak at 34 Hz matches the 5 m dimension. Move the subwoofer or your listening position to reduce the effect. Because bass below 80 Hz is hard to localize, you have freedom to place the subwoofer where it avoids the worst modes.

Sweeping Bass Tones Step by Step

A controlled low frequency test using a sweep tone is the most reliable way to check your entire bass range. Follow these steps:

Set your subwoofer crossover to 80 Hz or your preferred point.
Set the subwoofer volume to a moderate level. Start low to avoid damaging the driver.
Play a slow sweep from 20 Hz to 200 Hz. Give it at least 10 seconds so you can hear changes.
Listen for sudden jumps in volume. Note the frequencies where they occur.
If you hear a dip or peak, move the subwoofer to a different spot and repeat the test.
Adjust the crossover and subwoofer level until the sweep sounds as even as possible.

Protecting Your Subwoofer During Testing

Low tones can damage drivers if played loud. Always start at low volume. A 20 Hz test tone demands far more power than an 80 Hz tone for the same perceived loudness. If you hear distortion or the driver sounds like it is struggling, stop immediately and reduce the volume. This matters most when testing the lowest bass notes. Damage from overexcursion is permanent and not covered by warranty.

Using the Results to Improve Your Setup

Once you have identified room modes and confirmed your subwoofer crossover at 80 Hz is smooth, make adjustments. A strong room mode at 34 Hz means you should try placing the subwoofer in a different corner or along a different wall. Because bass below 80 Hz is hard to localize, put the subwoofer in a spot that minimizes the mode without harming the stereo image. A gradual drop in the lowest part of the sweep means your subwoofer may be reaching its limit. That is normal for many subwoofers. Aim for the flattest response you can get in your room.