Subwoofer Placement: Where to Put One or Two Subs

The subwoofer's position in the room determines how the bass sounds at your seat more than the subwoofer itself does. Moving a sub three feet can change the response at the listening position by 10 dB or more at some frequencies. This guide covers how to find the right spot, why two subs beat one, and how to set the crossover, phase, and room correction once the sub is placed.

Why placement dominates

Below about 200 Hz in a home-sized room, wavelengths are long (a 40 Hz wave is 28 feet) and the room behaves as a resonant box. Its dimensions dictate a set of standing waves called room modes, each with peaks and nulls at fixed locations. Where the sub sits determines which modes it excites; where you sit determines which peaks and nulls you hear.

A null cannot be equalized away. If the seat sits in a null at 50 Hz, boosting 50 Hz makes the sub work harder and the null stays. Only moving the sub or the seat fixes it. Enter your dimensions in the room modes calculator to see which frequencies are likely to cause trouble.

Corner loading vs. mid-wall placement

Corners

A subwoofer in a corner couples to all three boundary surfaces (two walls and the floor) and excites every room mode. The result is the most output per watt, typically 6 dB or more over a mid-room position, and the deepest extension. The trade-off is that it excites every mode fully, so the response at the seat is often the most uneven, with big peaks that make the bass sound boomy or one-note.

Corners suit a sub that needs the free gain, a large room where extension matters more than smoothness, or a system with room correction ready to knock down the peaks.

Mid-wall

A sub at the midpoint of a wall sits in the null of that wall's odd-order modes. It does not excite the first-order mode along that dimension, which is often the worst offender. Output is lower than in a corner, but the response is frequently smoother. Front-wall center (under or beside the screen) is the most common mid-wall spot and has the benefit of being near the front speakers, which helps with blending at the crossover.

Mid-wall suits a sub with output to spare, a corner that sounds boomy, or a single-sub system where flatness matters more than maximum output.

The subwoofer crawl

The crawl is the practical method for finding the best single-sub spot in a specific room. It takes 20 minutes and requires no measuring equipment.

1. Put the subwoofer at the main listening position, on the seat itself or on the floor right in front of it. Ears and sub trade places, so what you hear at candidate positions is what you would hear at the seat with the sub there.
2. Play a bass-heavy track on repeat, or a bass sweep from 20 to 120 Hz. Sweeps are better because they expose nulls at specific frequencies rather than averaging them out.
3. Crawl along the walls with your head at roughly the height the sub's driver would be. Listen at corners, mid-walls, and a third of the way along walls for the spot where bass is loudest across the whole sweep with the fewest dips. Loud and even beats loud and lumpy.
4. Mark the two or three best spots. Put the sub in the best one, sit down, and confirm with the same track.

A measurement microphone and free software do the same job with a graph, which is more reliable than ears for spotting nulls. Either way, the goal is even response at the seat from about 20 Hz through the crossover.

Two subwoofers

Two subs are not primarily about more output, although you get 6 dB of that. The real advantage is that two sources placed strategically cancel each other's modal excitations, smoothing the response across multiple seats. One sub can be tuned for one seat; two subs can be good at several seats at once.

The layouts below were established by published multi-subwoofer research and are widely reproduced. In order of typical effectiveness:

Opposing mid-walls

One sub at the center of the front wall, one at the center of the rear wall. Or one at the center of each side wall. This cancels the first- and third-order modes along that axis and gives the flattest average response across a row of seats. It requires cable runs to two walls, and the rear sub may be in the way of seating.

Front corners

One sub in each front corner. This cancels width modes (the two subs are symmetric across the room), keeps both subs near the front speakers for easy blending, and keeps cabling simple. It does nothing for length modes, but for most rooms it is a large improvement over a single sub. This is the most common two-sub layout in practice.

Diagonal corners (one front, one opposite rear) is a workable third option. Four subs, one per corner or per mid-wall, gives the smoothest response across a large seating area but is overkill for one row.

Whichever layout you use, the two subs should be the same model, or at least have similar extension and output, and be fed the same signal. Most receivers offer two subwoofer outputs; if yours has one, a Y-splitter works.

Phase and polarity

The subwoofer and the front speakers both produce sound in the crossover region (roughly 60 to 120 Hz). If they arrive at the seat out of phase, they cancel and you get a hole in the response right where the sub is supposed to hand off to the mains.

• Polarity (0° / 180° switch). This inverts the sub's signal. Try both and pick whichever gives more bass in the crossover region at the seat. If the sub is near the front speakers, 0° is usually right. If the sub is at the rear of the room, 180° often sounds better.
• Variable phase (0° to 180° dial). A finer version of the same adjustment. Play an 80 Hz test tone, sit in the seat, and turn the dial until the tone is loudest. That is where sub and mains sum constructively.
• Distance in the receiver. Auto-setup often reports a longer sub distance than a tape measure would, because the sub's electronics add a few milliseconds of delay. Leave that number alone.

With two subs, set both to the same phase first, then adjust the pair against the mains.

Crossover and speaker size

Set every speaker in the receiver to Small and the crossover to 80 Hz. This is the THX reference and it works for almost every system, including full-range towers.

Why 80 Hz: below it, humans cannot easily localize sound, so bass from a single point does not seem to come from the wrong place. Above it, subwoofers start to reveal their location. And handing everything below 80 Hz to the sub relieves the receiver's amplifiers of the hardest work while letting the mains sit where they image best rather than where the bass is smoothest.

Small satellites that roll off above 80 Hz may need 100 or 120 Hz; set the crossover about an octave above the speaker's rated low-frequency limit if unsure. Set the subwoofer's own low-pass filter to its highest setting or to bypass, so the receiver's crossover is the only one in the chain.

LFE

The .1 channel is the Low Frequency Effects track: a dedicated bass-only channel, band-limited to 120 Hz, mixed to play 10 dB louder than the equivalent level in the main channels. That extra headroom is why explosions hit hard. The receiver sums LFE with the redirected bass from every Small speaker and sends it to the sub output.

Leave the LFE low-pass at 120 Hz, the standard; setting it lower discards content that is in the mix. Use the "LFE" subwoofer mode rather than "LFE + Main," which sends bass to both the sub and the mains and creates uneven summing.

Room gain

Below the room's lowest mode, a small room stops resonating and starts pressurizing, and sub output rises by roughly 3 dB per halving of frequency. A sub that measures flat to 30 Hz outdoors may reach 20 Hz in the room. It also means corner placement plus room gain can bloat the bottom octave. Room correction handles this; a gentle rising "house curve" of 3 to 6 dB from 100 Hz down to 20 Hz is what most people prefer for movies.

Avoiding nulls at the seat

The seat is as important as the sub. If the crawl still leaves a stubborn dip, the seat may be sitting in a null.

• Move the seat forward or back by 1 to 2 feet. Nulls are narrow in space; a small move often clears one.
• Avoid the exact center of the room lengthwise. The center is always a null for the first length mode. Around 38 percent of room length is a common starting point.
• Stay off the rear wall. Leave 3 feet or more, or as far as the room allows, to avoid boundary boost and a harsh reflection.
• Add a second sub. This is the real solution for seat-to-seat consistency.

Integrating with room correction

Room correction (the automated equalization built into most receivers) is the last step, not the first. It measures the response at several seats and applies filters to flatten it. It does well at cutting peaks; it cannot fill nulls; and it cannot fix a bad placement.

The sequence that works:

1. Place the sub or subs using the crawl or measurements.
2. Set the sub's gain knob to roughly its midpoint, low-pass to bypass, phase to 0°.
3. Run the receiver's automatic calibration with the mic at ear height, at the main seat and several positions around it.
4. Check the results: speakers Small, crossover 80 Hz. If the software set the sub trim near the limit of its range, adjust the gain knob and re-run.
5. Many people bump the sub's trim 2 to 5 dB above what the calibration chose; the software targets flat, and a little extra bass is how most people prefer movies.
6. Listen from every seat. If one seat is much worse, revisit placement before reaching for the equalizer.

Done in this order, a single subwoofer can sound good and two can sound excellent, in a room you did not have to rebuild.