A look inside: the assembly process of a Sunship crossover
A passive crossover is the quiet control center of a high-efficiency horn loudspeaker. It divides the musical signal between the woofer and compression driver, shapes their acoustic balance, and helps the two sources behave as a coherent system. In a Sunship design, that work takes place alongside the geometry of the wooden horn, the cabinet volume, and the mechanical alignment of the drivers.
The assembly process therefore involves more than placing capacitors and coils into a box. Component values, physical orientation, cable routing, solder joints, damping, and service access all influence the finished network. The aim is a crossover that preserves the immediacy and dynamic ease associated with TAD-Pioneer drivers while maintaining tonal control across the audible range.
Because every custom loudspeaker is treated as a complete system, the crossover is developed around the intended drivers and enclosure rather than selected as a generic accessory. That system-level approach gives the builder room to refine the handoff between the bi-radial horn and the woofer, with time alignment and efficient signal transfer kept in view from the beginning.
From driver data to a working network
The process starts with the electrical and acoustic behavior of the selected drivers. Sensitivity, impedance, usable bandwidth, phase response, and the way each unit interacts with its horn all matter. A compression driver may produce high output from a small amplifier, but it still needs careful filtering and level matching to integrate naturally with a large-format woofer.
The relationship between efficiency and amplifier power is explained in Sunship’s guide to horn loudspeaker sensitivity. That context is useful when considering the crossover: a small change in attenuation or filter design can have an audible effect in a system where the drivers respond readily to modest input.
A passive network may include low-pass and high-pass sections, impedance compensation, attenuation components, and protection elements where appropriate. The exact topology depends on the acoustic targets. Rather than chasing a textbook electrical slope in isolation, the designer has to consider the combined acoustic output of the horn, driver, woofer, and enclosure.
Selecting the crossover architecture
A time-aligned passive crossover is intended to support consistent arrival of the main wavefronts from the different drivers. Physical driver position, horn depth, diaphragm location, and crossover phase all contribute to this relationship. Correct alignment can make transients sound more focused and can improve the sense that the music comes from a single source.
Component selection is part of the voicing strategy. Air-core inductors, film capacitors, non-inductive resistors, and robust terminals may be chosen for their electrical behavior, current handling, stability, and practical reliability. The goal is not to fill the network with expensive parts without purpose; each component must suit its position in the circuit and the demands placed on it.
The network layout is then planned around short signal paths and sensible separation. Inductors can interact magnetically when placed too close or aligned carelessly, while long parallel runs can increase unwanted coupling. A deliberate arrangement helps the schematic remain predictable once it becomes a physical assembly.
Preparing the board and components
Sunship’s heavily braced birch plywood cabinets provide a rigid environment for the loudspeaker system, and the crossover needs a similarly considered mounting solution. A solid board or panel supports the components, keeps solder joints from carrying mechanical stress, and allows the finished network to be inspected before it is installed inside the cabinet.
Each part is checked against the intended value and position. Inductors are measured for resistance, capacitors are verified for capacitance, and resistors are selected with suitable power ratings. Marking the board before soldering reduces errors when several visually similar parts appear in different sections of the circuit.
| Assembly stage | Main focus | Desired result |
|---|---|---|
| Component preparation | Values, ratings, polarity, and condition | Every part matches the design |
| Board layout | Spacing, orientation, and service access | Low interaction and secure mounting |
| Point-to-point wiring | Short, clear signal paths | Stable electrical behavior |
| Soldering | Heat control and joint quality | Reliable, low-resistance connections |
| System fitting | Driver terminals and cabinet routing | Correct polarity and clean installation |
| Listening verification | Level, integration, and imaging | A balanced, coherent loudspeaker |
Mounting methods must hold the components firmly without damaging their bodies. Large capacitors and inductors may need additional ties, clamps, or adhesive support. Mechanical security is especially important in a substantial cabinet that can transmit vibration into the crossover area.
Wiring, soldering, and mechanical discipline
During wiring, the builder follows the circuit from input terminal through the individual filter branches and onward to the driver outputs. Cable lengths are kept practical, and high-current woofer paths are given appropriate conductors. Polarity markings remain visible so that a later inspection can confirm the intended phase relationships.
A good solder joint is clean, fully wetted, and mechanically stable. Excess solder does not compensate for poor contact, and excessive heat can stress a component or insulation. After each group of connections is completed, continuity and resistance checks provide an early opportunity to find a misplaced wire or an accidental bridge between terminals.
The crossover is commonly assembled so that its internal logic can be understood during servicing. Clear labeling is valuable in a custom loudspeaker because future adjustments may involve driver replacement, system upgrades, or a change in room-specific voicing. Neat construction is therefore functional rather than merely cosmetic.
Fitting the network into the loudspeaker
Once the passive network has passed bench checks, it is connected to the cabinet and drivers. Cable routing must avoid interference with the woofer’s moving assembly, ventilation openings, and cabinet bracing. The network also needs to remain accessible enough for inspection while being protected from accidental contact and unnecessary vibration.
The woofer and compression driver are connected with polarity verified against the crossover design. A reversal at one terminal can produce a serious cancellation around the crossover region, even when every component on the board is correct. This is one reason why electrical testing is followed by listening rather than treated as a substitute for it.
The cabinet’s internal volume, horn geometry, damping, and mounting hardware all affect the final result. A crossover that measures correctly on a bench still has to operate in its intended enclosure. Installation is therefore the point where the electrical design becomes part of the complete acoustic instrument.
Voicing through measurement and listening
Verification combines technical checks with focused listening. Frequency response, impedance, phase behavior, and unwanted noise can reveal problems that are difficult to identify by ear. Listening then helps assess qualities such as vocal presence, bass integration, transient clarity, and the stability of the stereo image.
In a custom-built system, small refinements may be evaluated in the context of the room and the listener’s preferred balance. Sunship’s Berlin listening room provides a setting where the complete loudspeaker, amplifier, source, and room interaction can be experienced together rather than judged from a loose crossover board.
Useful listening tests include low-level detail, sudden dynamic contrasts, piano attacks, male and female voices, and dense orchestral passages. A well-integrated network should let the system move from quiet expression to high output without making the crossover region call attention to itself.
Practical checks before final approval
The final inspection confirms that the crossover is electrically sound, mechanically secure, and clearly documented. Measurements are repeated after installation, terminals are tightened, and internal wiring is checked for strain. Any change made during voicing should be recorded so that the completed speaker has a traceable configuration.
For anyone studying or commissioning a custom passive network, the most useful principles are:
- Match every component to its circuit position and power requirement.
- Keep inductors physically separated and orient them deliberately.
- Verify driver polarity and continuity before critical listening.
- Support large components so vibration cannot fatigue their connections.
- Judge the crossover as part of the complete cabinet and horn system.
The finished network may remain hidden once the loudspeaker is closed, but its influence is present in every note. To hear how careful crossover assembly, horn loading, and cabinet construction come together, arrange a visit to the Sunship Audio listening room in Berlin and experience the completed system at full scale.