Tweeter Crossover Test

Tweeter Crossover Test: Check the Woofer to Tweeter Handoff Frequency

The crossover frequency is the point at which a speaker's crossover network hands audio signal from the woofer to the tweeter. At frequencies above the crossover point, the tweeter produces the majority of the sound; below it, the woofer handles the range. In a correctly working speaker, the handoff is smooth: the combined response through the crossover region is flat, with neither a dip (where both drivers are rolling off simultaneously) nor a peak (where both drivers add output simultaneously).

The frequency sweep through the crossover range reveals whether the transition is working correctly. A smooth, consistent sine tone through the crossover frequency is the goal. Any change in tonal character, level, or quality at the handoff frequency suggests a crossover problem that affects the speaker's overall accuracy.¹

How crossovers work acoustically

A passive crossover consists of capacitors, inductors, and resistors that create filter slopes: the low-pass filter rolls off the woofer's signal above the crossover frequency, and the high-pass filter rolls off the tweeter's signal below it. The rolloff slope (typically 6, 12, or 24 dB per octave) determines how quickly each driver's contribution decreases outside its intended range. Where the two filter curves cross (the crossover frequency), both drivers contribute simultaneously. The phase alignment between drivers at this point determines whether they add constructively (flat response) or partially cancel (a dip). The sine sweep crosses this transition and reveals where the woofer hands off to the tweeter, which tells you whether the integration is smooth at your listening position.²

Running the crossover integration test

Switch to Manual mode and sweep slowly from one octave below to one octave above the speaker's stated crossover frequency. For a speaker with a 2.5 kHz crossover, sweep from 1.2 kHz to 5 kHz. Listen for any change in the character of the sine tone as you pass through the crossover region. A clean integration produces a consistent, smooth tone throughout. A dip at the crossover frequency sounds like the tone briefly becoming quieter or thinner. A peak sounds like a slight hardening or boost at the handoff point. The sine sweep is the most reliable way to evaluate crossover integration because a pure fundamental tone at each frequency eliminates the masking effect of harmonics and broadband content, making even a subtle 1 dB dip or peak at the crossover frequency clearly audible as a change in level or tonal quality.

Repeating the sweep from multiple listening distances

Phase integration at the crossover frequency is sensitive to listening position because the tweeter and woofer acoustic centers are physically separated by several centimetres on the baffle. At some distances, the path length difference between the two drivers is small enough that the signals arrive in phase and sum constructively, producing a smooth transition. At other distances, the path length difference introduces a phase shift that produces partial cancellation and a dip at the crossover point. Repeat the sweep from at least three distances (60 cm, 90 cm, and 120 cm) to build a complete picture of how the phase integration changes with listening position relative to the driver spacing.³

Distinguishing crossover problems from room effects

Room reflections can create dips and peaks in the frequency response at the listening position that look identical to crossover integration problems. The key distinction: a room artifact changes with listening position; a crossover integration fault is consistent regardless of listening position. Sweep from three different positions: sitting, standing, and at 1 meter from the speaker. If the same dip or peak appears at the same frequency from all three positions, it is a speaker characteristic. If it appears in only one position, it is a room reflection or mode artifact. A consistent crossover integration fault visible at all positions may warrant opening the speaker to inspect crossover components.

Testing phase integration at the crossover from different distances

At the crossover frequency, the acoustic centres of the tweeter and woofer are physically separated by several centimetres. At some listening distances, the signals from both drivers arrive in phase and sum constructively; at other distances, path length differences shift the phase relationship and produce partial cancellation. Sweep from one octave below to one octave above the crossover frequency in Manual mode and note the character of the transition. Then move 30 cm closer to the speaker and repeat the sweep at the same volume, listening for whether the transition character at the crossover region changes.

A crossover that sounds smooth at 1 meter but shows a dip or step at 50 cm has a phase alignment designed for the normal listening distance. This is intentional in some speaker designs where the crossover is optimised for a specific distance. A crossover that produces a consistent dip or peak at all listening distances has a phase alignment fault independent of position, which may indicate a component failure or a wiring error in the crossover network.⁴

Reading phase integration change with distance

Repeat the test from 60 cm, 90 cm, and 120 cm to build a clear picture of which result is distance-dependent. A dip that is present at all distances is a speaker characteristic; a dip that appears only at one distance is a room reflection or a position-specific interference pattern. This distinction determines whether the next investigation step is opening the speaker or repositioning the listening seat.

Verifying tweeter polarity after driver replacement

Verifying that a replacement tweeter is wired in the correct polarity at the crossover network terminals requires only a brief sweep through the crossover region. A tweeter wired in reversed polarity combines out-of-phase with the woofer at the crossover frequency, producing a deep notch (typically 10–20 dB) rather than the shallow dip of a normal phase integration issue. Set Manual mode, advance to the crossover frequency, and hold the tone there. A notch from reversed polarity is unmistakably deep: the volume drops dramatically at the crossover frequency and returns to normal 200 Hz above and below it.

Reversed polarity is the single most likely cause of a severe notch after a driver replacement and the simplest fault to correct. Open the cabinet, identify the two terminals at the tweeter, and swap the positive and negative leads at the crossover output. Re-run the sweep through the crossover range to confirm the notch is resolved. After swapping polarity, the crossover region should produce a smooth, consistent sine tone, matching the character both above and below the handoff frequency.

Distinguishing polarity error from a component fault

A deep notch from reversed polarity disappears completely when you correct the wiring and is consistent at every listening position. A notch from a failed crossover component persists after correcting polarity and varies in depth with listening position. If the notch is still present after confirming correct polarity at the tweeter terminals, the issue is in the crossover network itself: a failed capacitor or inductor in the crossover section serving the tweeter. The sweep test reveals this definitively before any component-level investigation inside the crossover board is needed.⁵

Run the polarity check before reaching for a soldering iron, because a reversed lead is a two-minute fix and a failed component is not. If the notch survives a confirmed polarity swap and shifts with listening position, the fault lives in the crossover board rather than the wiring. That distinction tells you whether the repair is a lead swap or a capacitor replacement, so the sweep pays for itself before the cabinet is even open.

When to use this

Use this test when a speaker sounds harsh, hollow, or uneven in the upper midrange, particularly if the character changes at a specific pitch. It is also useful after speaker driver replacement or crossover component service to confirm the repaired crossover is integrating correctly.

Examples

Male vocals and acoustic guitar sounded slightly harsh and forward in one channel compared to the other

Identified a +2 dB peak at 2.8 kHz on sweep. Found a partially detached crossover capacitor lead on inspection. Resoldered the connection and the peak disappeared

Replaced a blown tweeter but the speaker sounded thin and recessed in the upper midrange after the repair

Sweep revealed a 3 dB dip at 2.2 kHz. The replacement tweeter sensitivity was 2 dB lower than the original. Added a small series resistor to the woofer circuit to match sensitivity levels