Most loudspeaker projects fall short on the horn. A compression driver and its horn must be designed together — mixing and matching is illusory. We recently measured the dispersion characteristics of our custom bi-radial wooden horns using a turntable and microphone setup. Measuring Horn Directivity With A Turntable And Microphone The TAD TD-4001 has very specific requirements with next to zero leeway. Both must click acoustically and mechanically like two matching puzzle pieces.

The author discovered TAD on the Paris DIY scene in the late 1990s and started this project in 2013 with a clear goal: build an impeccable horn-loaded system addressing the two hardest challenges — the wood horn and the crossover. Inspiration also comes from Japanese Jazz Kissa culture, where dedicated listening spaces treat music with reverence.

Unlike commercial off-the-shelf designs, every Sunship loudspeaker pair represents hundreds of hours of iterative refinement. The crossovers alone are complex, high-order networks tuned for flat response to monitoring standards, with the low-frequency section controlling woofer impedance so even low-power tube amps can drive the bass with authority.

The heart of any great horn-loaded loudspeaker lies in the marriage between driver and horn. Too many projects treat these as separate components that can be freely combined, but the reality is far more demanding. A compression driver like the TAD TD-4001 has a specific acoustic signature, dispersion profile, and mechanical interface that must be matched precisely by its horn. When the two are designed together, the result is a coherent wavefront that projects music with startling clarity and presence. When they are mismatched, the listener hears coloration, uneven frequency response, and phase irregularities that undermine the entire system.

Horn construction is an art form in itself. While many manufacturers turn to injection molding or simple metal stamping, the most satisfying results come from hand-built wooden horns. Baltic birch plywood, cut on a CNC machine and then carefully sanded and finished by hand, offers a rigidity and internal damping that synthetic materials struggle to match. The double-layered construction with bracing creates a cabinet that is both massive and inert, allowing the driver to work without the cabinet adding its own voice. Each horn becomes a unique piece of craftsmanship, weighing in at a substantial figure that speaks to its solidity.

The crossover is often described as the most difficult part of any speaker build, and for good reason. A passive crossover must divide the frequency spectrum cleanly while preserving phase coherence across the crossover region. It must handle the specific impedance curves and efficiency of each driver without introducing coloration or distortion. Custom crossover design requires careful measurement, listening, and iteration. The parts quality matters enormously — high-grade capacitors, inductors, and resistors make a measurable difference in the final sound. This is where many projects succeed or fail, and where patient, methodical engineering pays off.

Japanese Jazz Kissa culture has long understood what serious listening is about. These dedicated jazz coffee houses are built around the idea that music deserves a room designed for it, equipment chosen for it, and time set aside for it. The inspiration drawn from this tradition shapes the entire philosophy behind a serious horn system. It is not merely about specifications or measurements, but about creating an emotional connection with the music. A properly designed horn-loaded system can recreate the scale, dynamics, and intimacy of a live jazz performance in ways that conventional speakers rarely approach.

The TAD driver lineage carries a remarkable pedigree. Originally developed for professional monitoring applications, these drivers were built to reveal truth — to expose every detail in a recording without flattering it. The TD-2001 and TD-4001 compression drivers, paired with woofers like the TL-1601, form the backbone of legendary systems that have become benchmarks in high-end audio. Their radial horns provide controlled dispersion, while the drivers themselves offer vanishingly low distortion and lightning-fast transient response. Owning and restoring these components is a pursuit that connects the listener to decades of professional audio history.

Wood selection and cabinet construction deserve obsessive attention. Solid, well-braced enclosures prevent energy storage and resonance that smear the music. The visible grain, the choice of finish, the precision of joints — these details matter both acoustically and aesthetically. A beautifully finished speaker in a listening room becomes furniture as much as instrument, and the visual pleasure of a handcrafted cabinet enhances the ritual of listening. Options for finish range from simple oiled wood to automotive-grade painted surfaces, each requiring different levels of skill and patience to execute well.

The journey from initial inspiration to a finished, singing system is long but deeply rewarding. It begins with research, moves through parts sourcing and cabinet construction, and culminates in hours of listening, measuring, and refining. Along the way, the builder develops a deeper understanding of acoustics, electronics, and materials. The online community of enthusiasts shares ideas, resources, and hard-won lessons, making the path easier for those who follow. Whether driven by nostalgia for classic designs or a desire for uncompromising sound, the horn-loaded path offers a destination worth the effort.