Sennheiser released the world's first consumer open-backed headphones in 1968, around about the time The Beatles' eponymously named double album came out. It was a hugely significant moment for fans of cans – being super comfortable to wear while sounding vibrant and powerful. Fast forward six decades, and the company is on a roll with popular models of all types and prices. The HD 505 you see here is an entry-level product described by the manufacturer as "the gateway to audiophile excellence", no less.

UP CLOSE

Like the classic HD 414 that put Sennheiser on the open-back map all those years ago, this product is built down to a price yet still respectably robust. It is typically understated in style, with only discreet copper-coloured accents offering any sort of visual stimulation. Plastic is the order of the day, of course, but it's decent stuff, and all the parts of this product fit together nicely with no squeaking or creaking. I can't promise the HD 505 will last as well as the 414, but it's got a better chance than most headphones.

The adjustment mechanism that's concealed inside the headband moves positively and has sufficient travel to accommodate all but the most unusually sized heads. The outer part of the headband is covered with nicely applied synthetic leather – vinyl, in other words – and the contact point is padded with memory foam. The latter is also used for the circumaural earpads, this time covered with velour; the rears of the earcups are protected by lightweight steel mesh, which carries some branding.

Inside the earcups is a reworked version of the 38mm transducer that's been showing up in several of Sennheiser's more affordable designs over the last year or two. The company has tweaked it for this application, in a drive for greater low-frequency impact and weight – but without, it says, sacrificing any of its acknowledged and admired transparency. Sennheiser is claiming a frequency response of 12Hz to 39kHz, and a nominal impedance of 120 ohms – so only the weediest smartphone will have any trouble driving this design effectively.

The HD 505 comes with a single 1.8m length of cable, which connects to the left earcup via the classic 'twist and lock' method using a 2.5mm jack, and at the other end, there's a 3.5mm termination with a screw-on 6.3mm adapter. Sennheiser is happy to point out that longer cables, and/or cables with balanced terminations, are available – and similarly happy to charge for them, of course.

THE LISTENING

The most striking thing about the way the HD 505 sounds is the most predictable. This is an open-backed design, so if it didn't sound airy and expansive, then what would be the point? It's immediately apparent that Sennheiser makes good on everything that its non-closed configuration promises. Not only is the soundstage larger than what any comparably priced closed-back alternative can muster, but it's also quite rigorously defined and carefully controlled.

Listen to a recording with plenty going on – Woody and Dutch on the Slow Train to Peking by Rickie Lee Jones, for example – and the authority with which this design serves up the recorded acoustic is unarguable. Every element of the recording gets an appreciable pocket of space in which to do its thing, free of interference from any other. But at the same time, the Sennheiser is able to unify the recording into a singular event rather than present it as a series of discrete occurrences. The spaces on the stage are given just as much weighting as the events, and the result is a confident and convincing presentation.

The HD 505 is highly adept at peering into a recording and teasing out all sorts of fine details that lesser headphones are happy to overlook, too. The tiny harmonic variations in John Glacier's Money Shows are almost pounced upon, and having retrieved them, this pair of headphones has no problem putting them into context. At every stage of the frequency range, it is informative in the manner of a twenty-four-hour rolling news channel. Yet such a fanatical level of examination doesn't make this design a mere analytical tool. Sure, it's keen to give you the full picture, but not at the expense of entertainment. The HD 505 is an enthusiastic and perky listen, one which appears to enjoy your music almost as much as you do.

As you'd expect from this brand, tonality is carefully neutral, which allows the inherent flavour of a recording to take the spotlight. The HD 505 steps out of the way of the music so as not to become the story. It's a long way from some designs which simply embellish the bass or spice up the treble. Indeed its voicing from top to bottom is butter-smooth with no area spotlit or understated. The top end has bite and substance in equal measure, and the midrange is as open and eloquent as I've heard in a pair of headphones costing this sort of money. The insight into a vocalist's character and technique is remarkable and thoroughly invigorating. In short, it's a headphone for grown-ups.

It even displays commendable dynamic headroom, so the changes in intensity and sheer volume in Aphex Twin's Come On You Slags! are given plenty of expression. The sheer control the HD 505 exerts over the bass means that rhythmic positivity is never in short supply. All the same, some may be put off by this headphone's lack of bite at the bottom end – it is sinewy, taut and tight but simply lacks weight by the standards of some rivals. I wouldn't go so far as to call this its Achilles heel, but some might see it as a disappointment. On the other hand, others who are more interested in timing than physical weight will approve of how this headphone is voiced.

THE VERDICT

The new HD 505 is classic modern Sennheiser – open, expansive, rhythmically engaging and tonally pretty neutral. The subtle lack of bass weight will put some off, but those who prioritise accuracy may like it even more for this. So this design is an impressively realised and capable product, at least for the audience it is aimed at. Rivals such as Beyerdynamic and Grado give a more visceral but arguably less accurate sound – but to my ears can't match the all round ability of this. Well worth a listen then, and long may Sennheiser continue to make its beloved open-back headphones.

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