What Is Subwoofer Phase? How to Choose a Setting

Choose the approach that fits your setup

If you're looking at that control while preparing your receiver, we'd establish the calibration starting point first, because room calibration comes before fine tuning in SVS's setup sequence. If you're choosing a JBL SUB80P switch position by ear, we'd focus on familiar percussion because it gives you a specific musical cue to judge.

The useful question is how your subwoofer and speakers sound together. Phase affects that relationship, and the result depends partly on the speakers' positions in your room. Your next move therefore depends on whether you're preparing a connected home-theater system for calibration or comparing the available settings on the JBL.

Why bass can lose its punch

A powered subwoofer's variable phase control can add electrical delay to the incoming signal. Changing that delay can sometimes help its output blend better with the other loudspeakers. You're adjusting the relationship between sounds that play together, which is why the other speakers matter to the result.

When the subwoofer plays out of phase with the satellite speakers, their sound waves can cancel some of the subwoofer's sound waves. The audible result is reduced bass performance and less impact. Both parts of the system can be playing while their combined bass sounds weaker.

In the 0° to 180° control described by SVS, the 180° setting reverses the subwoofer's polarity. With that reversal, the subwoofer driver moves inward while the other speaker drivers move outward. This gives the number a physical meaning, while the listening result still depends on how the system is arranged.

In some systems where the subwoofer is on a wall opposite the speakers, reversing polarity can improve low-frequency response in the room. That's a possible benefit for that arrangement, not a universal rule that 180° gives stronger or weaker bass. Judge the setting by how the outputs combine in your installation.

A switch and a variable control offer different choices

Look at the choices your control actually offers. A simple 0/180 switch gives you a polarity choice between two positions. A continuously variable control also offers settings between those endpoints, letting you make smaller adjustments instead of choosing only one end or the other.

SVS describes its subwoofers in its phase glossary as having continuously variable 0° to 180° controls, while other brands may offer only a simple 0/180 polarity switch. That product distinction matters when you're following setup advice: a direction to choose a switch position and a direction to adjust through a range describe different controls.

For the JBL SUB80P comparison below, use the available Phase switch positions and its Normal starting recommendation. The listening task is to select a position. You can follow that task using the labels on the JBL itself, without translating Normal into a numerical setting.

Your room is part of the result

Your subwoofer's position relative to the other speakers affects its performance. A setting that suits one arrangement can therefore be a poor guide to another. Include the speakers and their positions when thinking about phase, because cancellation depends partly on the placement of the whole system.

Reflections, standing waves and absorption within the room also strongly influence subwoofer performance. The specific location affects both the amount and quality of bass. Although our ears generally don't hear direction at the low frequencies where subwoofers operate, the cabinet's location still matters to what you hear.

That separates two useful questions: how the subwoofer combines with your speakers, and how its location interacts with the room. If you're still deciding where the cabinet belongs, our guide to where to place a subwoofer takes you into that placement decision.

Use 0° before receiver calibration

SVS's home-theater starting recommendation applies to a powered subwoofer, meaning one with a built-in amplifier. The AV receiver or preamp/processor has a dedicated subwoofer or LFE output connected to the subwoofer's input. The subwoofer is already in the location where it will remain.

For that configuration, set phase to 0° before the receiver's auto-calibration. Put room calibration ahead of fine tuning. During calibration, the receiver or processor plays test tones through each speaker and the subwoofer and adjusts their levels.

The practical distinction is between choosing an initial phase setting and completing the system's setup. The zero setting belongs to the preparation for calibration. Use SVS's full calibration steps (opens in a new tab) when you're ready to work through that broader job.

If your receiver-to-subwoofer connection is still the decision in front of you, use our guide to connecting a subwoofer before applying this starting recommendation, which assumes the dedicated sub/LFE path is already connected.

Compare the JBL SUB80P settings with familiar music

On the JBL SUB80P, begin with the Phase switch in Normal. That's the usual recommendation, and you can experiment with the available switch positions to find the best bass response and impact. Have the JBL SUB80P instructions (opens in a new tab) beside you if you want the product's setup guidance while you listen.

1. Play music you know well that includes drums or other percussive sounds. Pick out those sounds so you have something familiar to follow.
2. Compare the available Phase switch positions while the music plays. Listen for the position where those percussive sounds have the greatest impact.
3. Leave the switch in the position that gives drums and other percussion maximum impact. That's the selected setting for your installation.

Normal being the usual recommendation and there being no absolutely correct setting fit together. Normal gives you a starting position, while the listening comparison accounts for your particular subwoofer, speakers and placement. The final choice follows the sound of that combination.

Listen for clearer, more lifelike percussion

Pay attention to the character of the percussion as well as its strength. JBL's listening criteria for the SUB80P are clearer audio, maximum impact and more lifelike drums, piano and plucked strings when the subwoofer is properly in phase with the satellite speakers.

Those examples give you something more specific to listen for than an overall impression of extra bass. Follow the drum hits, then the piano or plucked strings when they're present in your familiar music. Check the selected position for the clarity, impact and lifelike percussion that make the subwoofer and speakers sound convincing together.