How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
If you want the longest battery life and the most advanced wireless spec, choose OpenRock S2; if you need a simpler, touch-controlled open-ear pair with strong water resistance for everyday workouts, choose Monster AC317.
• OpenRock S2 – biggest strength: A 7 g hook-clip design with LDAC hi-res audio, 32 hours of total playtime, and a triple-layer sweat defense system.
• OpenRock S2 – biggest trade-off: It leans on button controls rather than touch, and the spec sheet is packed with features that a casual listener may never touch.
• Monster AC317 – biggest strength: IPX6 water and sweat resistance paired with a compact, lightweight open-ear hook and full touch control at a simple, no-fuss feature set.
• Monster AC317 – biggest trade-off: Bluetooth 5.4 and a 24-hour battery ceiling put it a generation and 8 hours behind the OpenRock S2 on paper.
• Pick OpenRock S2 if you want marathon battery, hi-res codec support, and remote camera control for hiking and long training blocks.
• Pick Monster AC317 if you want a straightforward open-ear hook with touch controls and the confidence of IPX6 against heavy sweat and rain.
The OpenRock S2 is built around one idea: stay light and stay put. At just 7 g, with 0.6 mm titanium filaments and soft liquid silicone, it's designed to flex to different ear shapes rather than clamp down on one. In my opinion, that's the single most important thing in an open-ear sport bud, because a hook that pinches kills the whole "forget you're wearing it" promise. This one is aimed at people who wear buds for the entire session — runners, hikers, gym regulars — not just for a 30-minute walk.
Where it really separates itself is the audio chain. A 12 mm dynamic driver feeds what OpenRock calls BassDirect, which channels low-frequency energy toward the ear canal while keeping leakage down. On top of that you get LDAC and Hi-Res certification, so if you stream from a service and a phone that support the higher-bitrate codec, you're getting more detail than a standard SBC/AAC connection can carry. The frequency range is quoted at 20 Hz to 40,000 Hz with a 22-ohm impedance — an easy load for a phone to drive.
The durability story is unusually specific. Instead of just quoting a waterproof rating, OpenRock layers three defenses: an angled ear-hook fit that lets sweat slide off, a sealed BassDirect cavity that shields the PCBA, and a nano-coating over the internal components. It's rated IPX5, so it handles sweat and splashes but is not meant for swimming or full submersion.
Skip it if you want touch gestures, or if you mostly listen indoors and don't need hi-res codecs or 32 hours. You'd be paying for sport engineering you won't use.
Monster AC317: Who It's For
The Monster AC317 takes the opposite approach: keep it simple and keep it comfortable. It's a compact open-ear hook with an ultra-soft silicone cushion and a balanced earbud weight distribution, so the grip stays soft rather than tight. The design keeps your ear canal open, which means you hear traffic, a training partner, or a gym announcement without pulling a bud out. For city runners and cyclists, that situational awareness is the whole point.
Monster leans on "Pure Monster Sound" — a digital audio processor and professional drivers tuned to lift the mid and high frequencies. Translation: vocals, cymbals, and podcast dialogue come through clearly, and the nozzle design redirects sound waves toward the ear while limiting leakage. Don't expect a bass-forward tuning; the frequency range is described as mid to high, so this is a clarity-first signature rather than a thump-first one.
Calls run through an AI noise reduction algorithm with a hands-free focus. Water resistance is IPX6 — a step above splash-only, rated to withstand sweat and rain splashes, which is the realistic threat for most outdoor sessions. Battery is 7 hours per charge and 24 hours with the case, and the case fully recharges in about an hour over the included Type-C cable.
Connectivity is Bluetooth 5.4 with a low-latency focus, so audio and video stay in sync for shows and gaming on your phone. Controls are full touch — play/pause, volume, calls, voice assistant — which many people find faster than hunting for a physical button. It ships in gray white with a plastic hook enclosure and a 180-day warranty.
Skip it if you want the longest possible runtime, hi-res codec support, multipoint, or a two-year warranty. This is a solid everyday bud, not a spec-sheet champion.
• Best for battery life → OpenRock S2. 8 hours per charge and 32 hours total beat 7 and 24.
• Best for quick top-ups → OpenRock S2. A 5-minute charge buys an hour of listening; Monster's case needs about an hour to fill.
• Best for hi-res audio → OpenRock S2. LDAC and Hi-Res certification with a 20 Hz–40 kHz range versus a mid-to-high tuning.
• Best for bass → OpenRock S2. BassDirect funnels a 12 mm driver's low end toward your ear canal; Monster tunes for mids and highs.
• Best for water and sweat → Monster AC317. IPX6 outranks the S2's IPX5 on paper for rain and heavy sweat.
• Best for touch controls → Monster AC317. Tap gestures instead of push buttons.
• Best for calls in wind → OpenRock S2. Four mics, beamforming, AI noise cancellation, and a wind-resistant structure.
• Best for multi-device users → OpenRock S2. Multipoint Bluetooth 6.0 keeps two devices connected at once.
• Best for low-latency video → Monster AC317. Bluetooth 5.4 with an explicit low-latency, synced-audio focus.
• Best for peace of mind → OpenRock S2. A 2-year warranty versus 180 days.
I'd buy the OpenRock S2. The 32-hour total runtime, LDAC support, multipoint, and the layered sweat defense are exactly what I'd want from an open-ear sport bud — and the remote camera button is a small touch I'd actually use. The Monster AC317 is a genuinely good alternative if IPX6 and touch controls matter more to you than raw specs, and it's the simpler pair to live with day to day. But if I'm picking one, the OpenRock S2 covers more ground for the same job. Check the current price on Amazon before you decide, since that's the one thing that can flip this call.
On paper, yes for battery (32 vs 24 hours), audio codecs (LDAC/Hi-Res vs a mid-to-high tuning), Bluetooth version (6.0 vs 5.4), and warranty (2 years vs 180 days). The Monster AC317 wins on water resistance (IPX6 vs IPX5) and touch controls. "Better" depends on which of those you value most.
The Monster AC317 is rated IPX6, which covers sweat and rain splashes. The OpenRock S2 is IPX5 with a triple-layer internal defense system. For heavy rain or drenching workouts, IPX6 gives you more headroom.
The OpenRock S2 lists active noise cancellation plus 4-mic AI call noise cancellation with a wind-resistant structure. The Monster AC317 lists AI noise reduction for calls only. Neither is a sealed design, so don't expect the isolation of an in-ear bud.
Pricing shifts constantly and isn't something this comparison tracks — use the price button on this page to check the current price on Amazon for both before you buy.
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