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We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-27 · 7 min read · Independent comparison
• Lenovo GM2 — biggest strength: true in-ear fit with Active Noise Cancellation, a 10 mm dynamic driver and a 30-hour battery average life in a compact black ABS case.
• Lenovo GM2 — biggest trade-off: with a sealed in-ear design and ANC, you block out the world, which is exactly what you don't want while cycling or crossing busy streets.
• Monster Open Free AC100 — biggest strength: an open-ear, earhook design with a 16 mm dynamic driver, AI noise-cancelling dual mics for calls, and ambient awareness so traffic and voices still reach you.
• Monster Open Free AC100 — biggest trade-off: open-ear means less isolation and less thump in the low end, and the 30-hour figure is a total across recharges, with roughly 6 hours per single session.
• Lenovo GM2 is for: gamers, commuters and call-heavy users who want immersion, low latency and ANC.
• Monster Open Free AC100 is for: runners, gym-goers and outdoor workers who want their ears open and their surroundings heard.
The Lenovo GM2 is built around one idea: keep the noise out and the audio in. It's a true in-ear design with a 10 mm dynamic driver, a 20 Hz – 20 kHz frequency range, 32 ohm impedance and 99 dB sensitivity, so it plays loud and full off a normal phone without needing a headphone amp. The spec that matters most for gamers is the low-latency Bluetooth 5.3 connection — Lenovo lists it as stable for gaming, music and calls, with a 10-meter wireless range that lets you leave the phone on the desk and walk the room.
Battery is where it punches above its size. Lenovo rates the average life at 30 hours with a 1.5-hour charge time, and the carrying case is the same black ABS shell the earbuds sit in. That's a full work week of commutes and evening sessions for a lot of people. The controls are push-button media controls rather than touch, which I actually consider a plus for gaming — no accidental taps mid-match — and the mic is positioned for HD calls across phones, tablets and consoles. The 70 g item weight is light enough to forget in a jacket pocket.
Who should buy it: anyone who wants Active Noise Cancellation in an in-ear shape, plays mobile or console games where latency matters, takes a lot of calls, or wants one pair that handles sports and long sessions without a recharge ritual. Who should skip it: if you hate the feeling of something sealed in your ear canal, or you need to hear traffic, coworkers or your surroundings while listening, the GM2's whole design works against you. In those cases the isolation is a bug, not a feature.
Monster Open Free AC100: Who It's For
Sound comes from a 16 mm dynamic driver — noticeably larger than the GM2's 10 mm — with a 20 Hz – 20 kHz range. A bigger driver in an open housing usually means a wider, more spacious presentation with decent bass rather than the tight, pressurized bass a sealed in-ear gives you. Monster leans into that "expansive soundstage" language, and the physics backs the general direction.
For calls, the AC100 pairs dual microphones with AI noise-cancelling that monitors your environment and produces an opposite signal to cut background noise — Monster describes it as filtering out up to 99% of ambient noise. That's the manufacturer's figure, not an independent measurement, but the dual-mic plus environmental-reduction approach is a real, sensible design for busy cafés and offices. Battery is rated at 6 hours per single use with a 30-hour total, and the nano-coating resists sweat and rain splash, which is why Monster positions this squarely at the gym and outdoor crowd. It ships in white, includes a user manual, and carries a 1-year manufacturer warranty.
Who should buy it: runners, cyclists, walkers, gym users and anyone who works in a busy space but still needs to hear a colleague or a siren. Who should skip it: if you want deep isolation on a plane, or you're chasing maximum bass impact and a sealed fit for competitive gaming, the open-ear design simply can't deliver that.
Side-by-Side: Which Should You Choose?
• Best for gaming and low latency → Lenovo GM2. Bluetooth 5.3 low-latency mode is the headline feature, and push-button controls avoid mis-taps mid-match.
• Best for noise cancellation while you listen → Lenovo GM2. It has Active Noise Cancellation built in; the AC100's noise-cancelling tech is aimed at your mic feed for calls, not at silencing your music.
• Best for call clarity in loud places → Monster Open Free AC100. Dual mics plus AI environmental noise reduction are purpose-built for conversations in cafés and offices.
• Best for all-day ear comfort → Monster Open Free AC100. Nothing sits in the canal, so there's no soreness or pressure buildup.
• Best for total battery life between charges of the case → tie on paper, but they work differently. Both claim 30 hours total; the GM2 charges in 1.5 hours, the AC100 runs about 6 hours per session before you top it up.
• Best for bass weight and isolation → Lenovo GM2. Sealed in-ear plus ANC gets you the punchier, more enclosed sound.
• Best for workouts and sweat → Monster Open Free AC100. The water-resistant nano-coating is explicitly there for sweat and rain splash.
• Best for a subtle, universal look → Lenovo GM2. A black in-ear set disappears; white earhooks are a statement.
If I had to pick one, I'd buy the Lenovo GM2 — for the way most people actually use earbuds. Active Noise Cancellation, low-latency Bluetooth 5.3, a 10 mm driver, push-button controls and a 30-hour rated battery in a black case cover gaming, commuting and calls in one pair, and the sealed fit is the safer default if you're not sure which camp you're in. I'd only steer you to the Monster Open Free AC100 if open-ear comfort and staying aware of your surroundings are non-negotiable — that's a runner's or outdoor worker's priority, and in that specific case it's the better tool. Check the current price on Amazon before deciding, since both sit in a range where a small difference can tip the balance.
For gaming, yes, in my opinion. The GM2 is explicitly built around a low-latency Bluetooth 5.3 mode and push-button media controls, which suits fast reaction games. The AC100's strength is awareness and comfort, not competitive latency.
Not the same kind. The GM2 has Active Noise Cancellation for what you hear. The AC100's AI noise-cancelling works on your microphone, reducing background noise so callers hear you clearly — it doesn't seal out the world around you.
Both are rated at 30 hours total, but they split it differently. The GM2 lists a 30-hour average life with a 1.5-hour charge time; the AC100 gives about 6 hours per single session with a 30-hour total across recharges.
Generally yes. The open-ear, earhook design won't plug your canal, the nano-coating resists sweat and rain splash, and you keep hearing your surroundings. Just expect less bass isolation than a sealed in-ear like the GM2.
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