Make the sub disappear. Not the bass.

When the mains and sub overlap badly, the result may sound like bass follows the sub, swells around one note, or vanishes in the transition band. But room modes can produce similar symptoms. The goal is not “make a line perfectly flat”; it is a smoother, repeatable result for your actual seat and listening area.

A crossover is a handoff, not a brick wall

A crossover reduces the subwoofer’s output above a chosen region and, in a bass-managed system, may reduce the main speakers’ output below it. The filters have slopes rather than instant cutoffs; the main speakers and sub still overlap. Their acoustic output also depends on speaker roll-off, placement and room reflections. Genelec’s monitor-placement guide describes different crossover ranges for different product families, and warns that poor phase alignment can reduce the level at the handoff.

That is why one number cannot fit every speaker/sub/receiver combination. Many AV receivers offer a common starting setting, but follow the equipment’s manual and check the resulting acoustic response. Do not claim that an “80 Hz” setting is automatically right—or that the knob marking is the exact point where acoustic output crosses.

Find out who owns the crossover

For speaker-size, sub-output and room-correction checks, use the AV receiver bass-management guide.

In an AV receiver or a streamer with bass management, the processor may already high-pass the main speakers and low-pass the sub output. In a simple two-channel system, the mains may run full range while a subwoofer’s own low-pass control shapes only the sub. Those are different arrangements; neither should be “fixed” by blindly stacking another filter.

Read your receiver and sub manuals to determine which controls are active on the actual input. On some subs an LFE/bypass input disables the onboard low-pass; on others it does not. Verify speaker size, sub output, polarity/phase controls and whether any automatic room correction changed the settings. Note the baseline before changing anything.

Place the sub before you fine-tune the crossover

The subwoofer location changes which room modes are excited and what reaches the seat. A phase setting that works in one corner may not work after moving it across the room. Genelec recommends trial and measurement to find smooth low-frequency extension through its system-specific crossover. Start with Subwoofer Placement 101 to compare practical locations, or use our subwoofer-crawl guide to make a shortlist.

When comparing sub spots, keep the same speakers, input, volume, crossover and seat. A smooth average around the seats you use is more useful than the deepest output in a corner. If bass disappears only at one seat, read the listening-seat null guide before forcing a crossover change.

Set level for blend, not spectacle

With position fixed, begin with the manufacturer’s level-calibration procedure if available. A sub set much too high can call attention to itself and exaggerate a modal peak; too low can leave the system thin. Listen to familiar material and compare the same measurement region at the same main volume. Do not turn a louder setting into evidence that it is smoother.

The acoustic level at the seat is not the dial value. Moving the sub closer to boundaries may increase output, so repeat level calibration after a placement change. Room Tuner’s relative response is suitable for controlled A/B comparison, not an absolute calibrated SPL target.

Test phase at the crossover after placement

Where main and sub output overlap, their relative timing and polarity determine whether they reinforce or partially cancel at the seat. A simple 0°/180° phase switch changes polarity; it is not a universal “correct side” selector. The preferred setting can change with placement, speaker distance, processing and crossover. Genelec’s guidance explicitly says to adjust phase at the crossover after the speakers and sub are placed.

Some systems have a variable phase or delay control, others only a two-position switch, and some room-correction processors handle alignment internally. If the equipment permits manual adjustment, compare the available settings at fixed position and volume. A setting that makes one frequency louder could still create a problem elsewhere, so inspect the neighbourhood around the crossover and several useful seats.

A repeatable “one change” experiment

1. 1 · Save the baseline

   Write down routing, crossover, sub level, phase and listening location.

2. 2 · Measure the handoff

   Use the same phone ear-height position and playback path. Make a baseline reading, including the lower mid-bass region.

3. 3 · Move only the sub

   Try one practical location at a time, with all controls unchanged. Pick the most promising position.

4. 4 · Recheck level

   Adjust level only after the location is fixed; compare at the same main-system volume.

5. 5 · Compare phase

   If your system offers a phase switch, test A/B at the seat; restore the better setting before any crossover experiment.

6. 6 · Change crossover last

   Test a nearby manual-supported setting if a transition problem persists; keep everything else fixed.

Room Tuner Pro includes a guided Find the best sub spot test that plays the same quick test from each sub location you try and scores the response at the seat. A guided phase-switch comparison is available only where the saved subwoofer profile and system controls support it. The app asks you to change hardware settings yourself; it does not set phase or crossover automatically. Measurements may be inconclusive if playback paths or levels vary.