Compare Bose SoundLink Flex Portable Speaker, 2nd Gen vs Marshall Kilburn III Portable Bluetooth Speaker

Power references point to a strong 50W Class D amplifier setup, repeatedly tied to the speaker's loud, forceful output.

App impressions are mixed: one reviewer could not finalize the app connection, while others found the app clean, useful, and easy for EQ and settings.

Audio format support is supported by SBC, AAC, aptX and higher-quality Android streaming references.

Audio format support is adequate but limited, with reviewers noting SBC, AAC, and LC3 while calling out the lack of higher-resolution codecs.

Backward compatibility is weak because multiple reviewers state the second-generation model cannot stereo-pair with the original Flex.

Battery life is adequate but not a highlight, with reviewers citing up to 12 hours and much shorter runtime at high volume or in tests.

Battery life is one of the clearest strengths, with reviewers repeatedly citing about 50 hours or real-world multi-day use.

Codec support is a meaningful Gen 2 upgrade, with reviewers citing Snapdragon Sound, aptX, SBC and AAC support.

Bluetooth codec support covers standard lossy codecs, but reviewers consistently noted the absence of hi-res options such as LDAC or aptX Adaptive.

Bluetooth connection stability is praised by several reviewers, with notes on Bluetooth 5.3, Snapdragon Sound, no hiccups and no disconnections.

Bluetooth connection stability tested well in direct use, with one reviewer reporting easy pairing, a solid connection, and no signal weirdness.

Bluetooth range is only lightly covered, with one spec citing 30 feet and another reviewer saying they could walk a good distance before issues.

Bluetooth range is viewed positively, with reviewers citing a 10-meter range and one test exceeding that distance around the house.

Cabinet construction is praised through metal or steel grille references plus rubberized, silicone or aluminum casing materials.

Build and cabinet quality are praised as solid, premium, and durable-feeling, with sturdy materials and a serviceable battery access door.

Charging is a recurring weakness: reviewers repeatedly cite about four hours to recharge, which some call slow or disappointing.

Charging is generally strong with USB-C PD and quick-charge claims, though reviewers warn that weaker chargers or playback while charging can slow things down.

Cohesive presentation is strong overall, with reviewers describing the sound as balanced, full, clear or unexpectedly capable for the size.

The speaker presents a cohesive Marshall package, combining warm sound, loud output, physical controls, and retro styling into a unified experience.

Controls are mixed: some found them easy, but SoundGuys called the buttons mushy and Android Police found touch operation confusing.

Physical control feel is a major strength, with reviewers praising tactile switches, knobs, and playback controls.

Design and aesthetics are a major consensus strength, with repeated praise for the premium feel, colors, slim body and attractive grille.

Design is one of the most widely praised traits, with reviewers repeatedly calling out the amp-inspired retro look, premium finishes, and statement-piece character.

Detail retrieval is a strength for the size, with reviewers hearing crisp detail, nuance and separated musical layers.

Detail retrieval is generally strong, especially in vocals, cymbals, bass texture, and layered tracks, though one reviewer heard some upper-mid detail loss.

High-volume behavior is mixed: some reviewers say Bose processing keeps distortion controlled, while others heard clarity drop or distortion at higher volumes.

High-volume distortion control is excellent across reviews, with repeated reports of loud playback without cracking, hissing, peaking, muddiness, or obvious distortion.

Durability is strong, with reviewers citing rugged construction, drop-proof claims, solid feel and protection against outdoor abuse.

Dust resistance is strongly supported by repeated IP67 and dustproof references across the reviews.

Dust resistance improved over the prior model, with reviewers consistently citing IP54 protection as useful but not fully rugged.

Dynamic headroom is supported by TechRadar's bass comments, though the broader evidence suggests dynamics are good for size rather than huge.

Dynamic behavior is a strength, with reviewers crediting dynamic loudness and placement compensation for preserving balance and detail as volume changes.

Energy efficiency is only lightly supported, with one reviewer noting effective sleep behavior that avoids unnecessary battery drain.

Energy efficiency is supported by the unusually long runtime from only a modest battery-capacity increase, which one reviewer attributes to major efficiency gains.

EQ customization is one of the clearest upgrades, but reviewers generally describe it as useful while limited to basic bands or presets.

EQ customization is broad for a Bluetooth speaker, with physical bass and treble knobs plus app presets, custom EQ, placement compensation, and M-button shortcuts.

Everyday usability is strong for desks, bedrooms, travel, poolside use and small gatherings thanks to the compact design and easy operation.

Everyday usability is strong thanks to straightforward controls, easy living-room use, and the ability to move the speaker around without losing useful sound coverage.

Float capability is directly praised by multiple reviewers, who note the speaker floats if dropped in water.

Most reviewers describe the sound as balanced, clear or full, with punchy bass for the size but not true party-speaker low end.

Frequency balance is broadly praised for tight bass, clear mids, and crisp highs, though a few reviewers heard extra bass or mids in some contexts.

Google support is limited to Fast Pair, which reviewers describe as a useful setup convenience rather than a full smart ecosystem feature.

The fabric loop or strap is useful for bags and hooks, though one reviewer wanted a more flexible loop or included carabiner.

The carry strap is praised for comfort, style, and usefulness, especially its velvet lining and secure feel despite the speaker's weight.

Home theater integration is limited but present through Bose SimpleSync with compatible Bose smart speakers or soundbars.

Home theater integration is limited today, but one reviewer notes future Auracast surround use with Marshall soundbars as a possible path.

Inter-speaker connectivity is supported through Bose speaker linking, stereo mode and party mode, but compatibility limits reduce flexibility.

Inter-speaker connectivity is a weakness: reviewers repeatedly note no native stereo pairing or multi-speaker system, and one Auracast attempt was glitchy.

Latency is mostly described positively for video and streaming, though one reviewer still noticed a minor amount of video latency.

LED lighting is present as functional knob illumination and level indication, not as decorative party lighting.

Lighting is limited to useful LED indicators on the controls rather than immersive or decorative effects.

Reviewers say the Flex 2 gets loud enough for rooms, yards and small outdoor groups, but several note it is not the loudest or best for large spaces.

Maximum volume is a major strength, with reviewers describing serious, room-filling, or even unbelievable loudness for a single portable speaker.

Low-volume performance is only lightly supported, but TechRadar specifically heard clearer vocals at lower volume levels.

Low-volume performance is specifically praised for retaining richness, separation, and bass rather than thinning out in background listening.

The built-in microphone is confirmed for calls and assistant access, though call quality evidence is limited.

The microphone category is a clear weakness because multiple reviewers state there is no built-in mic.

Pairing reliability is generally positive when using compatible Bose speakers, though the ecosystem is limited and not backward-compatible with the original Flex.

Multi-speaker pairing reliability is weak because reviewers say the speaker lacks true wireless stereo or native multi-speaker pairing, with one failed Auracast attempt.

Multipoint is repeatedly confirmed, letting the speaker connect to two devices or manage multiple sources through the Bose app.

Multipoint connectivity is supported and described as letting two devices pair at the same time.

Omnidirectional sound is a weakness; Tom's Guide specifically describes strong directionality and a narrow soundstage.

Omnidirectional sound is a standout feature, with reviewers repeatedly praising the 360-degree, wide, room-filling presentation and minimal dead spots.

On-device controls are generally useful and complete, but touch-finding and button feel vary by reviewer.

On-device controls are a major strength, with reviewers repeatedly praising the knobs, switches, playback control, and simple no-learning-curve operation.

Power-bank support is absent; reviewers explicitly say it cannot charge a phone or other devices.

The power-bank function is repeatedly confirmed, letting the speaker charge phones or other devices through USB-C.

Value opinions are mixed: several reviewers say the quality justifies the price or sales help, while others call it expensive or a Bose tax.

Price and value are mixed-to-positive: reviewers call it pricey, but most say the sound, design, battery, and upgrades justify the cost.

Setup receives direct positive support from one reviewer who called it easy to set up and easy to use.

Setup is simple, helped by Bluetooth pairing and Google Fast Pair, with one reviewer calling the pairing process real simple.

The shortcut button can access a phone voice assistant, but reviewers frame this as basic phone-assistant access rather than a full built-in assistant.

Smart assistant integration is effectively absent, with reviewers repeatedly noting no voice assistant or voice control.

Smart features are limited: reviewers mention app controls, shortcuts, Spotify options and voice-assistant access, but repeatedly describe the feature set as lean.

Smart features are intentionally minimal, with no Wi-Fi, voice assistant, or smart-speaker behavior despite a useful app and EQ tools.

Speakerphone quality is only lightly supported, with one reviewer saying the microphone works fine for quick calls but does not sound amazing.

Speakerphone capability is absent because reviewers state there is no built-in microphone and that it cannot be used as a speakerphone.

Status indicators are only lightly covered, with SoundGuys noting a status light above the shortcut button.

Status indicators are useful, with reviewers highlighting the 10-bar battery gauge and illuminated control-level LEDs.

Stereo and imaging evidence is mixed: two-unit stereo mode can add separation, but the single speaker is directional and not especially wide.

Stereo imaging is wide and impressive, but not truly precise stereo separation; reviewers praise spaciousness while noting symmetry and separation limits.

Low-end hardware gets positive attention, with reviewers citing the built-in subwoofer or woofer as a source of strong bass.

Surround-like presentation is wide and immersive, but reviewers caution that it is not true full surround sound.

Sustainability is supported by the replaceable battery design and battery-preservation features that may extend useful life.

USB-C charging is consistently confirmed, though reviewers also note the port does not provide wired audio or power-bank output.

USB-C charging is a clear upgrade and strength, supporting charging the speaker and external devices with modern USB-C hardware.

Value for money is mixed but generally acceptable: reviewers praise quality for the price while noting cheaper rivals exist.

Overall value for money is mostly positive, with reviewers seeing worthwhile upgrades, strong sound, premium design, and long battery life despite the price.

Vocals are consistently described as clear, easy to hear or delicate, supporting strong voice clarity for music and spoken content.

Voice clarity is strong for music playback, with reviewers repeatedly reporting clear, forward, or crisp vocals.

Water resistance is a major strength: reviewers repeatedly cite IP67 protection or water immersion suitability.

Water resistance is useful but moderate: reviewers consistently cite IP54 splash protection while warning it is not full waterproofing or beach-rugged IP67.

The speaker is widely praised as slim, light and bag-friendly, with reviewers repeatedly saying it is easy to carry or pack.

Weight convenience is mixed: reviewers find it carryable with the strap, but repeatedly describe it as heavy, large, or better for home and gatherings than backpacking.

Wi-Fi streaming is a weakness because reviewers repeatedly note there is no Wi-Fi support, even at this price.

Wired playback is a clear weakness: reviewers repeatedly state there is no 3.5mm jack and USB-C is for charging, not audio.

Wired input is a useful fallback, with reviewers highlighting the 3.5mm AUX port for non-Bluetooth or higher-quality listening paths.