We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-18 · 6 min read · Independent comparison
If you want an open-ear pair that keeps you aware of your surroundings while you run, commute or take calls, choose Monster Open Ear AC520; if you need to block the world out so you can actually sleep, focus or fly in peace, choose Kinglucky 50dB. These two earbuds sit at opposite ends of the same problem — one lets sound in on purpose, the other shuts it out on purpose — so the right pick comes down to what you're trying to do with your ears, not which one is "better."
• Monster Open Ear AC520 — biggest strength: an open-ear hook design with Bluetooth 6.0, IPX6 water resistance and up to 24 hours of total playtime, so your ears stay unplugged and you stay aware.
• Monster Open Ear AC520 — biggest trade-off: there's no active noise cancellation at all, and the open-ear fit means bass and isolation will always be modest compared to a sealed in-ear bud.
• Kinglucky 50dB — biggest strength: hybrid noise cancellation rated to a 50dB peak, a 3.0g ultra-light in-ear fit built for side sleepers, and 60+ app-based sleep sounds with up to 50 hours total playtime.
• Kinglucky 50dB — biggest trade-off: it's an in-ear bud that seals your ear canal, so you lose the awareness an open-ear design gives you, and the whole experience leans toward rest and focus rather than workouts or calls.
• Who the Monster is for: runners, cyclists, office workers and anyone who needs to hear traffic, coworkers or announcements while listening.
• Who the Kinglucky is for: side sleepers, light sleepers, shift workers, students and travelers who want a quiet bubble on demand.
The AC520 is built around one idea: your ears stay open. Instead of pushing a tip into your canal, it hangs on a hook over your ear, so ambient sound flows in freely. Monster pairs that with a dynamic driver and its HiFi tuning, which is the sensible way to compensate — open-ear designs leak bass, so the tuning has to work harder to sound full. If you've used open-ear buds before, you know the trade: you give up thump and isolation, and you get situational awareness you can't fake with a transparency mode.
Buy it if you run, bike, walk busy streets, or work somewhere you need to hear what's happening around you — and you want a case that doesn't look like every other case. Skip it if you need silence. With no noise cancellation and an open fit, this is the wrong tool for sleeping on a plane or drowning out a snoring partner.
Kinglucky 50dB: Who It's For
The Kinglucky 50dB is the mirror image. It's an in-ear bud with silicone tips that physically plug your canal like a traditional earplug, then layers hybrid ANC on top for a rated 50dB peak of noise reduction. That combination — passive silicone sealing plus active cancellation — is why it can make a loud room feel library-quiet. It's the kind of thing you'd want on a red-eye flight, in a dorm, or next to a partner who snores.
The sleep angle is where the design earns its keep. The buds weigh just 3.0g and use a contoured, polished silicone contact surface, which is the specific reason side sleepers can lie on their ear without the usual ache. Three modes cover your whole day: Sleep Mode mutes notifications entirely, ANC Focus Mode locks you in for work or study, and Transparency Mode lets the outside back in without removing the buds — you switch with a triple tap. The Kinglucky app adds 60+ tuned sleep sounds like rain, ocean and wind, plus a playback timer so audio doesn't run all night.
Battery is set up for exactly that use case: about 7 hours per charge (the sheet lists 7 hours average life with 7–10 hours claimed in the feature text), up to 50 hours with the case, a 1.5-hour USB-C charge, and an LED display on the case so you're not guessing at 2 a.m. Bluetooth 6.0 keeps the connection steady. Buy it if sleep, focus or travel quiet is your priority. Skip it if you want to hear traffic while running — a sealed, noise-cancelling bud is the last thing you want on a bike.
Side-by-Side: Which Should You Choose?
• Best for hearing your surroundings → Monster Open Ear AC520. Open-ear by design; nothing blocks your canal.
• Best for sleep → Kinglucky 50dB. 3.0g weight, side-sleeper-focused silicone fit, Sleep Mode and 60+ sleep sounds. The Monster has no sleep features at all.
• Best for running, cycling and sweaty workouts → Monster Open Ear AC520. IPX6 water resistance and a hook fit that won't seal you off from traffic.
• Best for total battery → Kinglucky 50dB on paper, with up to 50 hours via the case versus 24 hours on the Monster — though the Monster wins on per-charge time, at roughly 8 hours versus 7.
• Best for calls and everyday listening → Monster Open Ear AC520. ENC clear-call processing and HiFi tuning aimed at music and voice, not sleep.
• Best for a distinctive, wearable case → Monster Open Ear AC520. The slide-open handbag-style case with a removable lanyard is genuinely unusual.
• Best for app control and customization → Kinglucky 50dB. The Kinglucky app handles soundscapes, saved favorites and mode switching; the Monster runs on touch controls alone.
In my opinion, these aren't competitors so much as two different jobs. If I had to pick one for the average person's day — commuting, working, walking, taking calls — I'd buy the Monster Open Ear AC520, because staying aware of your surroundings is useful more hours of the day than total silence is, and the IPX6 rating plus 24-hour case make it the more versatile everyday bud. But if your problem is that you can't sleep, can't focus in a noisy room, or dread long flights, the Kinglucky 50dB is the one I'd recommend, and the Monster simply can't do that job. Decide which problem is actually yours, and the choice makes itself.
No. It's an open-ear design with no noise cancellation and no sleep-specific features, so it won't block sound or suit lying on your side. For sleep, the Kinglucky 50dB is the appropriate pick.
It's water resistant, but it's a sealed, noise-cancelling in-ear bud, which means you lose awareness of traffic and surroundings — a real safety downside outdoors. For workouts and outdoor use, I'd point you to the Monster AC520 instead.
Per charge, the Monster edges ahead at roughly 8 hours versus about 7 for the Kinglucky. Across the charging case, the Kinglucky goes further, at up to 50 hours compared to the Monster's 24. The Kinglucky also charges faster, at about 1.5 hours versus 2 hours.
The Monster Open Ear AC520. Its open-ear fit keeps you aware of your surroundings, and it includes ENC call processing plus Bluetooth 6.0. The Kinglucky is built for the opposite situation — shutting the world out.
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