The factory that makes headphones costing more than a luxury vehicle
Tullamore, County Offaly, sits 22km from the geographical center of Ireland. It’s not exactly a survey mark, but it’s still a Midlands landmark if you judge by heart and not GPS. Whiskey lovers may recognize the town by its bottle. It shares its name as the Tullamore D.E.W. distillery. Many travelers don’t even notice it because they just take another exit from the motorway. For me, however, this is the center of sights and sounds that defines my brief time in Ireland. Sennheiser, one of the most recognized brands in audiophile-quality audio and now celebrating its 80th birthday, invited me to Ireland. If you are into headphones like I am, then you will find something even more intoxicating in the reclaimed toilets. Here, just outside of this small community, which is humming quietly, and about an hour’s drive west of Dublin, lies the Sennheiser Audiophile Experience Center. Here, icons are assembled, and we assembled–journalists from multiple countries and multiple channels here to observe automation and human interaction produce some of the most lauded personal audio accessories of the last 30 years. It’s not about following trends, but rather chasing the truth. You can invite a fellow forum user with the handle “DACDaddy76” to join us. Here are my impressions of what goes into building a pair headphones. The HE 1, the world’s most expensive cans for critical listening, is also the first to be heard. Fritz Sennheiser established his company, which bears his name, in a farmhouse near Hanover in Germany in 1945. Sennheiser didn’t add a headphone to its professional microphones, or other broadcasting and recording products, until 1968. The HD 414, with its iconic yellow foam pads, was the first. This pivotal move, however, set the stage – and soundstage – for decades with its groundbreaking open-back (“Open Aire”) style. Tullamore became a member of the Teutonic Team in 1991. The facility began making transducers, the full-range speakers that are inside headphones. These were used to create the HD 580 Precision and HD 580 Jubilee, which are known for their balanced but warm voicing. The HD 600 was released in 1997, and became the quintessential Sennheiser headphones due to their resolving but not fatigued nature. It’s a headphone with a natural voice and a solid build that will show off your source over long listening sessions. In 2003, HD 650 headphones were introduced with a sound that was thicker than faster. The HD 800 was Sennheiser’s flagship in 2009, a benchmark for forensic clarity, costing $1,399 at the time (a quaint price today, considering the 800 S revision costs $1,799). Product management team members were in Wedemark throughout these launches, and many more. The Tullamore Factory would manufacture the drivers, and then ship them to Germany for the final assembly. In 2021, Sennheiser acquired the consumer portfolio of Swiss hearing care solutions firm Sonova Holding AG. Sennheiser had been manufacturing transducers in Tullamore for many years. Within a year of that, the assembly and packaging lines of the 600 Series and 800 Series as well as other lines were moved to Tullamore. This was done to optimize production and streamline operations. The Tullamore facility will renovate its lobby in 2023 to create an exclusive area where guests can hear headphones made there. This brings us to the present. This brings us to the gate. The secret to building these transparent playback conduits is still hidden behind opaque doors. It’s a recording-free zone, with dozens of proprietary machines performing upwards of 80 different processes.
Pat Fulton, our Willy Wonka, is behind the entrance gate (and yes, the golden tickets used for invitations). Fulton is the plant manager at this facility and has worked there for more than 30 years. Tullamore’s systems and workforce have grown under his watch. He is there as we walk past plasma nozzles and pneumatic conveyors on our way to audio inception. The first step in creating a Sennheiser headphones begins with selecting the material and mould that will enhance the acoustical quality of the transducer. In the model that we are monitoring, a 0.03mm cable is attached to the membrane. This bond is kept within surgical tolerances, which is thinner than a hair strand. Next, it’s on to the next station. It is kinetic, but not chaotic. The diaphragm oscillation is checked between each strand bonding, each composite bonding and any electromechanical adjustments. This ensures that each ripple behaves in a consistent manner across the surface of the sound spectrum. Whether it’s a 7mm TrueResponse Transducer for the IE 900, or a 56mm Ring Radiator for the HD 820, QC is regarded as indisputably important. It’s a complex routing, with a flexible flow. Fulton claims the line can be adapted and scaled if necessary. Give the factory one hour and a check-list. Sennheiser is adding SKUs to its line-up in 2025. The company introduced two new models since I was in Ireland: the HD 550 and HD 550. The latter, in particular, is a new mainstay for articulate, budget-conscious fidelity.
Automation, while invaluable, hasn’t fully replaced manual assemblage, however. After the transducers have been removed from the belts, the 100+ skilled employees of the plant will fine-tune them. Some are here since the 600 Series launched, while others are fresh out the technical college. This combination of callouses, newcomers and tribal knowledge ensures that the tribe’s knowledge is not only preserved but also evolving. This is good, because tuning involves more than the curve of an embossed sheet. The baffles, resonators and ear pads are all positioned differently. Other components, such as casings, can also be arranged differently. To ensure the attention to detail required, a combination of precision and passion is needed. We’re then given the chance to get our hands dirty, though at a lower level. The task is simpler and requires no soldering: assemble an HD 660S2-a model that was introduced in 2023. The parts are arranged under fluorescent lighting, followed by a demonstration. Next, it is our turn to go through each step. The mesh grilles on the chassis are placed, the foam cushions are clipped into place, the ear cups snapped to the headband and the detachable cable is plugged in. A robot may be able follow the cadence of the sequence. The satisfying physical feedback that confirms completion may be difficult for machines to register. The headphones are then placed in an anechoic room for frequency sweeps, which verify that everything is aligned within the margins of error. Our builds are then bagged and packaged, complete with Made in Ireland stickers and certification, in case there is a need to trace any defects back to a particular batch, or even the builder. After our shift is complete, we are led to the last showcase. Damian is behind a glass partition, responsible for hundreds of hours and 3,000 pieces that go into every HE 1, the $70,000 custom headphone system. Want one? Sennheiser asks for a deposit of $10,000 and you’ll have to wait 45 days if the component is available and Damian has enough bandwidth (four were in production simultaneously during our visit). You pay the rest once they are ready. But what you get for your five-figure investment is a testament to transcendence.
What goes into the HE 1 is improbable, impractical, and awe-inspiring. This is a middle-finger to compromise. This is not just another headphone, it’s the moonshot. The HE 1’s block of Carrara marble is not only beautiful, but also vibration-dampening. This spring-loaded design has a variety of routing options, including S/PDIF optical, USB and unbalanced or balanced RCA. There’s a physical input for any source, from DAPs to turntables. This interface feeds 8 ESS Sabre ES9018 Digital-to-Analog Converters (four DACs per channel in parallel) with resolutions of up to 32 bits/384 kHz. The use of gold-vaporized ceramics for the L/R channel paths reduces distortion. Those, in turn, feed the vacuum tube preamplifier–all in service of reproducing summit-fi technicalities.
The headset itself, found at the end of a specially tuned fabric-wrapped 99.9% silver-plated OFC cable, sits snugly thanks to luxurious, hand-sewn leather and reflection-absorbing microfiber cushions. The headset contains diaphragms with a platinum vaporized thickness of 2.4 micrometers, sandwiched between two conductive plates. Each one is powered by Cool Class A MOSFET amplifiers located in the “fin” on the precision-machined aluminium ear cup. The fully decoupled supply system helps to prevent electrical interference.
The results are a reproduction from 8 Hz up to 100 kHz with distortion of less than 0.01%, at 1 kHz and 100 dB. This means that everything is in the right place. Damian tests extensively before he approves an HE 1. The acoustics, and the apparatus should not buckle due to humidity or hubris. The last part of AEC is exactly what you need. Math doesn’t work for me. I don’t need to be told the details. In a section of the old lobby, now soundproofed, communion is taking place. This acoustically-treated alcove is where an HE 1 is released. In this curated, clean space, emotions are unlocked.
We flip through CDs and LPs in pairs until we find tracks that we like. Then we push a button and the transformation is triggered. The HE 1’s presentation is equal parts dramatic and mechanics. The HE 1 is presented in equal parts mechanics and drama. As the motorized glass cover opens, and brushed metal buttons extend, eight quartz tubes rise up like precious artifacts. They are amber idols, glowing and growing, and electrons waiting to be excited. The headsets are surprisingly lightweight for something that is responsible for so many engineers’ and executives’ reputations. We then settle into matching lounge chair. The HE 1 is fed from a Rega Turntable and renders each grain as the needle traces grooves. A lysergic, ritualistic whisper emerges out of the claustrophobic grime. You are wrapped in a billowing sparseness and engulfed in constricting echo. This is a possession personified.
Next, we try a cut from CD: “The Chain” off Fleetwood Mac’s 1977 stone classic Rumours. The physical interaction between instruments and the atmosphere is highlighted, uncovered. From the taut basses to the cymbal splashes, to the hi-hat breaks to the scrapes of nylon guitar string, everything is uncovered. The voice of Lindsey Buckingham and Stevie Nicks, with their increased aggression and whispered remorse, are upscaled to a harmonious level. This is 4K HDR, a leap in resolution that is exponential. This is unsettling detail. This is real-time devastation.
Throughout our session, the desire to analyze the method is challenged by the allure of the means. The separation is superb, and the imaging is flawless. The HE 1 is the closest I’ve heard to a floor-standing speaker. Transients are sometimes spicy, but they’re in service to authentic timbre. Low end isn’t so much about physical slam as it is about a surgically precise impact. The HE 1 offers an audiophile-like experience, with its effortlessness. It is adding a carefully crafted signal between source and destination in order to remove the distance between listener and artist. The HE 1 does not color the playback despite its thousands of components. Presentation is not flattering, but faithful. It’s beautiful. It’s brutal. The HE 1 will not tolerate songs that are poorly mastered, compressed, or oversaturated. The HE 1 is revealing, but it’s also exposed. The varnish is stripped away by a supernatural honesty, similar to that of a studio monitor. Prepare to lose all joy if the production is a flop. It’s not a sterile event. If you’re going to invest in a price-no-object personal sanctuary, this is the pinnacle of statement peace. This is the ultimate in statement peace if you are going to invest money into a personal sanctuary that has no price limit. It could be to protect an unsuspecting customer from our work. Perhaps it’s to relive happy memories with a pair of quality wired headphones. The 300-ohm, 660S2 has a vented magnet and retooled voice coil. It is harder to drive because of this. It’s still more driving when paired with an amp. The punchier bass adds to the musicality. The notes are not smeared and they’re not too bassy. The HD 660S2 is a refined version of Sennheiser’s midrange-centric line. It sounds great for metal, but it doesn’t sound bassy. Sennheiser’s HD 660S2 offers a refined sound (especially good for metal). distillery. You can’t visit these reclaimed swamps without a drink. We need to cool down our ears, even if we’re using other senses. Both are exercises in observation–equally tactile and ephemeral impressions. Both are exercises in observation–equally tactile and ephemeral impressions.
Distilling is detail. It’s an orchestra of compounds. Layers are carefully nudged to work together. Adding a splash H2O can be used as a form EQ to sharpen microdynamics, transforming them from murky into melodic. The natural reverberation chamber is created by aging in casks and condensation. The subtleties of mouthfeel, mid-notes and nose bloom are revealed when you talk about them. Overtones and resonance, viscosity or attack, a long-lasting finish, are all factors to consider. Sounds familiar? Sound familiar? The magic of opening a bottle of whiskey is similar to listening to an impactful song. Different expressions are used for different anatomy.
From drivers, to drams — it’s the perfect coda. This is how a sip can become a story in the same way that transducers have become this tale. Stopping to breathe and marvel is what it’s all about. You don’t even have to drive through misty moors or whiskey warehouses to get some. More deals, reviews and buying guides
The PopSci Team has spent thousands of testing hours to find the best gadgets and gear you can buy. Tony Ware has been writing about music and how to break it since the mid-90s, when his college paper said that they already had a movie critic. But maybe he just wanted to check out the free promotional CDs. He was immediately hooked on outlining the intangibles and has covered everything audio for numerous alt. Since then, he has written for countless magazines, websites and weeklies. He also competes in bar trivia competitions.
