M50x Upgrade Guide: Best Headphones Beyond Audio-Technica

The Audio-Technica ATH-M50x is a common first step into the hobby. It’s a capable closed-back that earns its reputation as a starter headphone. The question isn’t whether to upgrade; it’s which direction makes sense for your listening habits.

This guide covers three headphones worth considering as your next step: the M50x itself as a reference point, the Sennheiser HD 600, and the HiFiMan Sundara. All three earn a place in the Buyer Guides section because the decision between them is genuinely non-obvious.

What to Look For in an M50x Upgrade

Tuning: Neutral vs. Colored

The M50x has a recognizable sound, elevated bass, a mid-bass hump, and a treble peak around 9 kHz. For many buyers, that tuning is fun and forgiving. But it also means you’re not hearing recordings as they were mixed. If your goal is critical listening, evaluating mixes, catching sibilance, identifying mastering decisions, a flatter response is more useful than an exciting one.

The two standard upgrade benchmarks are a neutral-warm tuning (HD 600’s territory) and a flat-extended planar response (Sundara’s territory). Neither is more correct in the abstract; the right answer depends on what you want to do with the headphone.

Open-Back vs. Closed-Back

The M50x is closed-back. That matters for portability, shared spaces, and late-night listening without disturbing others. Both upgrade options covered here are open-back, which means sound leaks in both directions. Open-back headphones generally produce a more natural, spacious soundstage because the driver isn’t working against a sealed chamber. The trade-off is real isolation for none.

Before committing to an open-back, think honestly about where you listen. A dedicated listening space, a home office, a bedroom with the door closed, is the right environment for either the HD 600 or the Sundara. If you need a closed-back for commuting or shared offices, neither of these is the right upgrade, and exploring Buyer Guides for closed-back alternatives is worth the time before you spend.

Amplification Requirements

The M50x runs comfortably off a phone or laptop. Most open-back planar magnetics and many open-back dynamics do not. The HD 600 has an 300-ohm impedance and benefits from a proper amp, though the gap between a decent DAC/amp stack and a laptop headphone out is real, but not transformative in the way planar amplification tends to be.

The Sundara is a planar magnetic. Underpowering it doesn’t just reduce volume; it affects dynamics and bass extension. A mediocre source makes the Sundara sound thin. If you don’t already have a DAC/amp or aren’t willing to invest in one, the HD 600 is the more forgiving upgrade path. The Sundara rewards the stack investment clearly and measurably.

Build, Comfort, and Long-Term Ownership

Comfort differs between the three. The M50x’s clamping force can tire some listeners in longer sessions, while the HD 600 and the Sundara are open-back designs with replaceable earpads. Both support long-term ownership: the HD 600’s cable and earpads are fully replaceable. The Sundara’s 2020 revision addressed the original’s earpad and headband comfort shortcomings specifically.

Build quality isn’t just about durability, it’s about whether a headphone stays in rotation five years from now or ends up replaced. The HD 600 has been in production for decades and its parts are replaceable. For gear at this tier, repairability is a meaningful purchase criterion.

Top Picks

Audio-Technica ATH-M50x

The M50x folds flat and includes three detachable cables in the box. For a first closed-back, that utility still holds.

Where they fall short is on the measurement data that matters most for critical listening. The mid-bass hump, prominent around 200 Hz in published measurements, adds warmth that reads as “bassy” rather than accurate. The 9 kHz treble peak creates a brightness that some listeners find fatiguing over long sessions. These aren’t catastrophic flaws; they’re the expected compromises of a consumer-friendly closed-back designed before the current generation of neutral reference standards. Buyers expecting flat studio-monitor performance should look elsewhere.

The case for keeping the M50x alongside an upgrade is real, closed-back utility doesn’t disappear just because you own something better. But if the question is “what should I buy next,” the answer is almost never another M50x.

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Sennheiser HD 600

The Sennheiser HD 600 is a neutral-warm open-back with a midrange-focused tuning, a natural soundstage and a build designed for long service.

Published measurements show a response that tracks closely to the Harman target in the midrange, with a gentle bass shelf. The 300-ohm impedance means it needs amplification; an entry-level amp such as a Schiit Magni Heresy or JDS Atom can drive it without a major investment.

The open-back design is a genuine constraint. Sound leaks in both directions, meaningfully. For anyone in a shared space or needing isolation, this isn’t the right answer. But for a dedicated listening setup, the HD 600 is the clearest step up from the M50x that exists at the mid-tier, not because it’s dramatically better at everything, but because it’s genuinely more accurate at the things that matter for long-term critical listening development.

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HiFiMan Sundara

Planar magnetic drivers do something dynamic drivers don’t, and the HiFiMan Sundara is where most buyers first hear it. Planar drivers use a thin, light diaphragm, which is why they are associated with fast transient response and precise imaging, a different character from the HD 600’s dynamic driver.

The 2020 revision addressed the original’s most consistent criticism: earpad and headband comfort. The updated earpads are larger and softer. The headband distributes weight more evenly. For longer sessions, it’s a meaningful improvement. Aftermarket pads such as the ZMF Universe are available for further comfort.

HiFiMan’s quality control has been inconsistent enough that it warrants mention. The 2020 revision improved this, but checking both channels on arrival is a practical step rather than paranoia. The amplification requirement is not optional, running the Sundara off an underpowered source compresses dynamics and flattens the bass in ways that undermine its core strengths. On a proper stack, the Sundara’s flat, well-extended response and planar imaging make a compelling case for being the better technical upgrade from the M50x, even if the HD 600 is the more immediately accessible one.

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Buying Guide

Choosing Based on What You Want to Hear

The most useful frame for this decision is not price tier but listening goal. The HD 600 is tuned for music enjoyment, its neutral-warm character makes long sessions natural and non-fatiguing, and its midrange rendering rewards vocal and acoustic material. The Sundara is tuned for detail and accuracy, its flat extension and planar speed make it more revealing of recording quality, both in good ways and bad ones. If your library skews toward pop, electronic, or heavily produced music, the HD 600’s more forgiving presentation is the better daily driver. If you listen to jazz, classical, or acoustic genres where imaging and micro-detail are directly musical, the Sundara’s planar character pays dividends.

The Stack Question

Neither the HD 600 nor the Sundara is the right answer if you’re not willing to add a DAC/amp. The HD 600 can function off a decent integrated amp or a modest stack; the gap between that and a laptop is real but not transformative. Dedicated DAC/amp separates are worth the complexity specifically for planar magnetic headphones, and the Topping or JDS ecosystem provides solid entry-level options without significant outlay. If a stack isn’t currently in the budget, the HD 600 is the more practical upgrade choice until it is. Browsing the full headphone buying guides for stack recommendations before committing to the Sundara is a reasonable step.

Open-Back Is a Lifestyle Constraint

Open-back headphones are not simply “better” than closed-back, they’re suited to a specific use context. Both the HD 600 and Sundara require a private listening environment to function as intended. In a shared apartment, an open office, or a commute, open-back isolation is effectively zero, and sound leakage is significant enough to bother others nearby. A sealed alternative, the AKG K371 is a neutral-tuned closed-back at this tier, is the better fit.

HiFiMan QC and Long-Term Ownership Risk

The HD 600 has been in production for decades. Replacement cables, earpads, and grilles are available directly from Sennheiser and through aftermarket suppliers. The Sundara is a newer design with a shorter track record. HiFiMan’s QC variability is a real factor, not a reason to avoid the headphone, but a reason to purchase from a retailer with a clear return window, check both channels immediately on arrival, and consider it a slightly higher-risk purchase than the HD 600. The performance ceiling justifies the risk for buyers who are prepared for it.

Upgrade Path Thinking

The M50x upgrade decision has a longer arc than just the next headphone. The HD 600 works as a long-term reference purchase because it combines solid performance with genre versatility. The Sundara shows what planar magnetics do, which may lead to interest in higher-tier planars. Neither path is wrong, but they are different trajectories. If the goal is to find a headphone and stop thinking about gear, the HD 600’s long production run makes it a safe place to start.