Sennheiser HD 505 headphones review: Open back, open mind

In the audio wars between on-ear and over-ear headphones, the latter is the clear winner with the former a much rarer product, at least for adult ears. But within the over-ear headphones victory, there’s still a raging debate, particularly for audiophiles: open-back vs closed-back.

Closed-back headphones are all the rage these days whose design lends itself to a wider range of use cases, with baked-in passive noise cancellation as a foundational starter. Open-back headphones are more situational, built mainly for at-home use in a controlled environment, but they’re designed to offer a natural soundstage, better comfort and greater awareness of the noises happening around you.

With its HD 505 headphones, Sennheiser isn’t just pushing a pricey pair of open-back cans, it’s also shunning contemporary wireless trends in lieu of exclusively wired connectivity. So, how exactly does a pair of open-back headphones fare when placed on the noggin of someone who’s very, very accustomed to closed-back wireless headphones? Let’s find out.

At $449.95 RRP, the Sennheiser HD 505 headphones are firmly targeted at audiophiles who don’t want to pay two to six times more for studio-grade open-back playback. In terms of closer open-back competitors, there’s the HiFiMan Sundara 2020, the Audio-Technica ATH-AD900X and the Fostex T60RP.

For a similar price bracket, there are premium closed-back wireless alternatives like the Bose QuietComfort, Sony WH-1000XM4 or, for $50 more, the Sony WH-1000XM5 headphones. After dozens of hours of testing and comparisons between the HD 505, XM4s and XM5s, I still prefer the Sony closed-backs for the price.

The design logic for the Sennheiser HD 505 seems to be ‘keep it simple’. You’ll get the wired open-back headphones in a single ‘copper’ colour with a screw-off detachable 6.5mm-to-3.5mm adaptor and a carry bag. That’s about it.

While the carry bag is a welcome inclusion, the HD 505s follow the open-back trend of not being foldable, so they’re not particularly transportable despite their lightweight design. In fairness, that’s a subtle reminder that these open-back cans are really only meant for at-home use, ideally in quiet (or at least quieter) environments.

There aren’t any physical controls on the earcups or cable, and the reasonably sized 1.8m wired cable isn’t removable. Pop the HD 505s on your noggin and adjust the headband through incremental notches to find the right fit. From there, enjoy the all-day comfort care of a padded headband and soft cushion earcups that wrap around 38mm drivers.

The fact that you only have 3.5mm or 6.5mm physical connectors seriously limits your connectivity choices in the modern world. My older smartphone and tablet—the Google Pixel 7 Pro and Samsung Galaxy Tab S7 Plus—don’t have audio jacks and nor do most devices in my home. That limited my playback testing to a desktop PC—via front audio connectors because the 1.8m cable isn’t a great length for back of a computer case on the floor—an HP OmniBook Ultra Flip 14 and a Steam Deck OLED, all of which work as plug-and-play devices.

As you’d hope from $450 open-back headphones, the Sennheiser HD 505s sound great, more so under the right conditions. For me, that meant maxing out the frequency response to 38.5kHz on my desktop PC or laptop and listening to hours of FLAC music files to fully appreciate the natural soundstage.

Whether gaming, watching TV shows and movies, or listening to dozens of hours of FLAC or lower-quality streaming music, the HD 505s offer great sound, most notably in terms of mids and highs. Even without virtual surround sound, I was still able to locate tucked-away chests in Avowed with audio cues, so these Sennheiser headphones are a good fit for gaming, though the lack of a microphone and the audio leakage means I wouldn’t use them online.

As you might expect from open-back headphones, lows aren’t as big as they should be, and deeper bass tracks in particular aren’t the best showcase for the HD 505s. A lot of my cons for the Reviews.org Audio Testing Playlist were around timid bass, as heard in Carly Rae Jepsen’s ‘I Didn't Just Come Here to Dance’, Childish Gambino’s ‘3005’, Opeth’s ‘The Funeral Portrait’ and The Weeknd’s ‘Blinding Lights’.

Tracks less reliant on booming bass fared better, particularly songs with a heavier emphasis on natural-sounding real-world instruments. Nina Simone’s ‘Feeling Good’ was the first well-balanced highlight, The Beatles’ ‘While My Guitar Gently Weeps’ was the best of the bunch, while Steely Dan’s ‘Do It Again’ showcased how easy it is to distinguish between and appreciate different instruments.

While the HD 505s did a great job of balancing the cacophony of Radiohead’s ‘The National Anthem’, the rhythm guitar was tricky to pinpoint in Deftones’ ‘Swerve City’ at times and the static was a smidge too prominent in Portishead’s ‘Humming’. Finally, Pink Floyd’s ‘Comfortably Numb’ was a solid balance albeit without anything standout about its playback.

Ultimately, the biggest con of the HD 505s comes from its open-back design, which is part and parcel of the form factor. Sound leaks prominently even at 30% volume, so much so that my partner was singing along to what I was listening to while she was watching TV on the couch next to me. Similarly, outside sounds are hardly diminished at all, meaning you either need to isolate to a very quiet space or crank the volume to counteract intruding external noises.

You really have to want a pair of open-back headphones—accepting all the cons of the form factor—to consider the Sennheiser HD 505s. If that’s you, you’ll enjoy great comfort and well-balanced audio at a cheap price compared to open-back alternatives, whose biggest con is a lack of oomphy bass. For anyone after all-rounder headphones, though, grab a pair of wireless closed-back cans for greater versatility.