Dynamic speakers are remarkable devices. They work on principles that haven't fundamentally changed in a century. And they carry a limitation baked into their basic physics.
The voice coil they depend upon for movement.
The voice coil sits in a gap in the magnetic circuit. When current flows through it, the interaction with the magnetic field produces force — that force moves the cone. In theory, the force produced should be exactly proportional to the current applied, across the coil's entire range of travel.
But that's not what happens.
The magnetic field isn't perfectly uniform throughout the gap. As the coil moves outward or inward, it enters regions of slightly different flux density, and the relationship between current and force changes. That deviation from linearity is distortion — and it increases the further the coil travels from its rest position.
This is why bass requires the most excursion and produces the most distortion in a dynamic driver. The cone travels further, spending more time in the non-linear regions of the magnetic field. Minimizing that non-linearity has been one of the central engineering challenges in loudspeaker design for decades.
Chris Brunhaver, who designs our Aspen loudspeakers, has spent a significant part of his career focused on exactly this problem. His work on woofer motor geometry has reduced distortion by a full order of magnitude compared to many conventional woofer designs — not a marginal improvement but a fundamental reduction in the mechanism that limits dynamic speaker performance. The gap between what a well-designed modern woofer can do and what the same driver would have produced twenty years ago is real and clearly audible.
He's not alone in this pursuit. Companies serious about bringing the full truth of music into a room have made substantial progress on voice-coil linearity — through improved motor geometries, better-matched suspension systems, and correction approaches that compensate for residual non-linearity. The cumulative effect is speakers that distort less, track more faithfully, and get out of the way of the music in ways previous generations simply couldn't manage.
Can voice-coil distortion be truly eliminated? Probably not to absolute zero. But "not zero" and "not audible" are very different things.
The distance between where we were and where we are now is remarkable.
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