Sennheiser 280 Pro headphones w/ Zu Audio Mobius


Longevity. Sennheiser’s 280 Pro has been in production since 2003. In headphones terms, this entry-level model is a pensioner working well beyond retirement age. At US$99 the Sennheiser 280 Pro sells for half as much as it did at launch.

What sets the 280 Pro apart from similarly affordable big box store rivals is their ability to deliver a very healthy dose of bass; not the bloated kind that seasoned head-fier’s like to point and laugh at on the majority of Beats headphones…but the DEEP kind. The 280 Pro go LOW.

Another of the 280 Pro’s strongest suits is (passive) noise isolation. A firmer than average clamping force – that eases over time – counterbalanced by large and amply padded leatherette ear cushions demonstrates that not all closed back models isolate the listener to the same degree. According to the German manufacturer the 280 Pro can attenuate external noise by up to 32db. That’s handy for use in busy office environments.

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The 280 Pro’s suitability to street life will largely depend on the wearer’s tolerance of two things:

  1. Cyberman effect. I’m not particularly fond of headphones that have me visually approximating the Doctor Who adversary.
  2. The coiled cable. It’s fine for DJ booths but too long and unwieldy for those listening on the go with portable players.

Plugged into an integrated amplifier or portable player at home, cabling and on-head appearance concerns dissolve to nothing. Either way, the design is lightweight and the construction quite rugged for an all-plastic affair. No wonder they’re popular with the DJ set.

A 3.5mm cable termination and 64 Ohm impedance make it a good fit for the PonoPlayer. The latter’s US$400 price tag and less overt bass handling returns the compliment.

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On headstage scale and detail dig there’s little to complain about, especially at their US$99 asking price. That said, the 280 Pro won’t be displacing the likes of Master&Dynamic’s MH40 or OPPO’s PM-3 in audiophile land any time soon. The Sennheiser just don’t have the transparency and dynamics of the more expensive rivals. To complain about that is to miss this headphone’s broader talents with micro-dynamic flicker and pant-seat kick. Not the most refined headphone in the world but boy, these are super fun to listen to. The midrange isn’t half bad either.

These are talents that Zu Audio’s Sean Casey sees and hears. You might know of Zu Audio as a loudspeaker manufacturer – that’s their bread and butter – but they also produce a full suite of cables, all of which are made on-site at their Ogden factory. Handling the wire side of the business is Casey’s wife, Stefanie.

On top of the usual array of power, digital and analogue cables, Casey and Casey already offer their Mobius wire for HD600 and HD650 owners. The 280 Pro predates the industry trend for detachable cables so shipping the cable direct to customers isn’t an option here. Instead, Stefanie Casey applies the cable modification at the factory, after which the Zu-modded 280 Pro sell for upwards of US$199 (depending on cable length and colour). Each pair comes with a two year warranty.

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Sean Casey details the Mobius cable with bullet-point precision: “Silver copper hybrid, Teflon dielectric, low capacitance, high inductance, developed for HD600/HD650 but tweaked for the 280 Pro. Left and right channels do not see each so there’s no crosstalk.”

Zu Audio’s complete rewire into the headphone’s earcups takes over an hour to complete. Even longer when you’re explaining each step to someone peering over your left shoulder – yours truly. I visited Zu Audio’s Ogden factory just prior to CES 2015 in January.

Once a fresh pair of 280 Pro are unboxed, the stock cable is immediately given the chop, after which the earpads are removed and the left cup’s casing unscrewed, thus exposing where the stock cable enters the headphone and travels through the headband to the right earcup. Casey disassembles the lot before clipping out the Sennheiser wire and ‘interfacing’ mini circuit board, all of which lands in the bin.

Before direct wiring the replacement Mobius cable into each earcup, a ‘Zu’ 3.5mm jack is soldered to one end so that left and right channels can be tested and assigned correctly at the other; first left, then right. Terminations inside each cup see the cable soldered directly to the voice coil.

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A full meter of Zu’s wire is required for internal routing alone. Heat shrink is applied at important routing junctions to ensure maximum durability. The headphone is then re-assembled and resealed.

So – how does the Mobius’ sound compared to the original? I listened right there and then at the factory via the PonoPlayer’s twin 3.5mm outputs and then again with the stock and Zu-modded versions back in Sydney.

That ten-thousand-league-deep bass? It’s still present; and it remains the biggest draw card of the 280 Pro, modded or not. Those that favour dub-inflected techno artists like The Orb, Deadbeat, Basic Channel or the Sly & Robbie-produced Grace Jones will find plenty of skull-rattling low frequency action to assist with their mental rump-shaking.

That said, the modified Sennheiser although airier than the standard version still sounds a little closed in up top. Its uppermost frequencies aren’t as incisive nor does as much ambient information spill forth as I hear via the aforementioned OPPO PM-3 or Master&Dynamic MH40. You can’t expect a cable switcheroo to transform a transducer’s personality, only refine it.

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The most obvious post-operative improvement is a lifting of the proverbial veil – that’s a cliché, I know. Flipping it over, the unaltered headphone is contrasted as comparatively murky and congealed. We’re not talking huge deltas but still, the changes are of sufficient magnitude not to be attributable to other factors. Case in point: the tape-hiss layers that click in and out of Four Tet’s “Morning” arrive with more midrange textural depth under Mobius.

Lastly, the Zu-cabled version presents with an marginally wider headstage but emphatically better internal layer separation. On Built to Spill’s epic cover of Neil Young & Crazy Horse’s “Cowgirl In The Sand” more space is cleared between midrange and upper bassline, allowing Doug Martsch’s treated vocals more room to drift. The low-reach of the 280 Pro gives the song a much needed anchoring; something that doesn’t present with lesser recordings played back through more neutral-sounding headphones.

If you find your existing headphones a little too intellectual, all brain and no brawn, then the Sennheiser 280 Pro’s downward-facing tonal balance could be for you. They’re eminently affordable but if you have the extra cash for a better version of this model, the Zu-modded variant is the way to go. Long may they run.

Further information: Zu Audio

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Written by John H. Darko

John lives in the NOW + HERE = NOWHERE. He derives an income from the ad revenues of DAR. John is also an occasional staff writer for Stereophile, 6moons and TONEAudio.

Twitter: DarkoAudio
Instagram: DarkoAudio
Facebook: DAR


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  1. I can see the retort now, Shock horror headphone cables make a difference, what will they think of next! . Well for most of us this has been known for decades now and it’s about time the manufacturers started to give us more options in this area. When I purchased my pair of Grado 325is a while ago I remember comments on their web site about how the cable was chosen to give, in their opinion’, a balanced presentation. That’s the point, their opinion maybe completely different to my preferred sound. Grado and others listen please give us a standard plug in cable option.

  2. John, I bought a pair of these bad boys from Zu a few months ago, and I think your review nails it quite eloquently.

  3. Most excellent article! I have been telling people this for ages, yes, cabling characteristics matter a lot. I love the richness of sound these headphones produce, but I am on my second pair with the same headband cracking problem. It is unfortunate that these are so poorly constructed.