Stealth Magnets: what HIFIMAN changed in its planar drivers

Why the magnets sit in the sound's way

In a dynamic headphone the magnet sits behind the diaphragm, out of the path the sound takes to your ear. A planar magnetic driver is built the other way round: its film usually hangs between two rows of bar magnets, and the sound it makes has to leave through the gaps between those bars.

A conventional bar has a rectangular cross-section, so the sound coming off the film meets flat faces and sharp corners. Some of it reflects back toward the diaphragm, some bends around the corners, and the waves leaving neighboring gaps interfere with one another. How much that matters depends on the frequency. A bass wavelength is far larger than a bar a few millimeters wide and passes almost untouched, while the short wavelengths of the treble are the ones a bar can disturb.

The HIFIMAN Arya Unveiled review puts the problem in plain terms: rectangular magnets physically block the sound waves coming off the diaphragm and create turbulence.

What HIFIMAN changed in the bar

A Stealth Magnet does the same magnetic job with a rounded profile, shaped so the sound slides past it more cleanly. The review of the HIFIMAN HE1000 Stealth quotes HIFIMAN's own description of the aim: magnets "as acoustically transparent, or invisible as possible". The magnets still drive the film. What the shape is meant to change is how much of the sound they disturb on the way out.

The benefits HIFIMAN attaches to it are lower distortion, less turbulence and more transparency. Those are the maker's claims, and they describe the intent. None of the reviews here isolates the magnets' effect from everything else that changed in the headphone around them.

Which HIFIMAN headphones use them

Every HIFIMAN planar reviewed here but one uses them, from the $109 HE400se to the flagships. The HE400se review notes that the design used to be kept for expensive models and no longer is, and the Sundara Closed-back has them too.

The exception is the open-back HIFIMAN Sundara. As far as its reviewer knows, the current revision goes without Stealth Magnets, and the review lists that among its cons. It scores 9.0 all the same, higher than most of the models that have them.

What our reviews heard on them

If the magnets set the sound, the headphones that share them would share a character. They don't. The HIFIMAN Edition XS is the Stealth Magnets edition, the one meant to fix harsh, sibilant highs, and on some songs its treble still turns plasticky and sibilant. The HE400se has them at $109 and its review finds a narrow soundstage and muffled mids.

The Arya Stealth, the first Arya to get them, has a stage its review calls not super wide, and imaging it calls unbeatable. The reviewer mentions having heard that the magnets shrink the stage, but one headphone can't show whether they are the reason. For more on why stage size and placement come apart, see the soundstage explainer.

The Arya Unveiled takes the idea furthest. HIFIMAN removed the outer grille entirely, and with magnets meant to stay out of the sound's way, its review describes a driver close to floating in free air, with a dead-silent background and holographic imaging. The cost is a bare driver open to damage, which needs its magnetic covers on whenever it's put down.

Magnets, diaphragm and grille are separate parts

HIFIMAN usually ships several technologies together, and reviews and spec sheets list them in one breath. The magnet shape is one. A very thin diaphragm is another: NEO Supernano on some models, a nanometer-thickness film on others. The Window Shade grille on the outside of the cup is a third, meant to protect the driver while keeping the back open and cutting reflections there. The HE1000 Stealth adds a fourth, an uneven arrangement of magnets on either side of the film that HIFIMAN calls its Advanced Asymmetrical Magnetic Circuit.

They do different jobs, and only the diaphragm moves. The Sundara shows how separate they are: it has no Stealth Magnets, it does have the NEO Supernano diaphragm HIFIMAN says makes the response faster and more detailed, and its review ranks speed and micro-detail among its strengths. Since no review can hear the magnets apart from the rest, a sound credited to Stealth Magnets is a sound credited to the whole package.

How much they should count when you buy

Treat them as a line on the spec sheet. The HIFIMAN headphones reviewed here that use them run from 6.8 for the Sundara Closed-back, a Mixed verdict, to 9.3 for the HE1000se, and the one open-back HIFIMAN planar without them sits near the top of that range. What separates those headphones in their reviews is tuning, fit and price. The best planar magnetic headphones guide ranks the reviewed planars on their scores, magnets or not.