Short answer: the Bose Soundlink Flex 2nd gen on measured sound quality, the Earfun Uboom Slim on price. The Bose Soundlink Flex 2nd gen ranks #35 of 144 medium speakers, rated 3.8/5, at $159. The Earfun Uboom Slim ranks #41, rated 3.7/5, at $79, $80 cheaper.
What the Bose Soundlink Flex 2nd gen does well: A very portable 586g, IP67-rated speaker with a clear, well-balanced midrange that keeps voices and instruments intelligible. Watch for: One Flex remains mono and cannot deliver genuine low-bass rumble; RTINGS also found the elevated treble can turn hi-hats and other high-frequency detail piercing.
The case for the Earfun Uboom Slim: Excellent pricing, strong waterproof build (IPX7), good battery life (16 hours), smooth sound with volume compensation, speakerphone capability. The tradeoff: Not as deep bass as others.
Buy the Bose Soundlink Flex 2nd gen if sound quality matters more than the price. Buy the Earfun Uboom Slim if the price matters more than sound quality.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Bose Soundlink Flex 2nd gen | Earfun Uboom Slim | |
|---|---|---|
| Price | $159.00 | $79 |
| Ranked | #35 of 144 in Medium Size Portable Bluetooth Speakers | #41 of 144 in Medium Size Portable Bluetooth Speakers |
| App | Yes | No |
| Battery Life | 12 hours (Manufacturer specified) | 16 hours (Manufacturer specified) |
| Built-in Microphone | Yes | Yes |
| EQ | Yes (3 band) | No |
| IP Rating | IP67 | IPX7 |
| Party Mode | Yes (Bose Party mode) | - |
| Power Input | USB-C | USB-C |
| Stereo | No | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 1.3 lbs (586 g) | 1.2 lbs (560 g) |
| Bluetooth Version | 5.3 | 5.2 |
| Dimensions | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) | 2.6”H x 7.1”W x 2.6”D (65 x 180 x 65 mm) |
| Aux Input | No | Yes |
| Drivers | 60mm full-range driver with passive radiators | 45mm speaker drivers |
| Bluetooth Codecs | SBC, AAC, aptX Adaptive | SBC |
| Digital Aux Input | No | No |
| Strap | Yes (built-in loop) | - |
| Bass Extension (-10dB) | - | ~63Hz |
| Amplifier Power | - | 20W |
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More worthwhile head-to-heads for Bose Soundlink Flex 2nd gen:
- Bose Soundlink Flex 2nd gen vs Earfun Uboom L
- Bose Soundlink Flex 2nd gen vs Soundcore Motion 300
- Bose Soundlink Flex 2nd gen vs Soundcore Motion+
- Bose Soundlink Flex 2nd gen vs Soundcore Boost “upgraded” 2021
- Bose Soundlink Flex 2nd gen vs Minirig 4
Prices on this page were last checked September 26, 2026 at 11:14 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Speakers In Full
Bose Soundlink Flex 2nd gen: $159.00 Amazon eBay
Older model: the Bose Soundlink Flex (rated 3.8/5).
Pros: A very portable 586g, IP67-rated speaker with a clear, well-balanced midrange that keeps voices and instruments intelligible. The second generation adds a Bose app with 3-band EQ, better-placed controls and stereo pairing with another Bose Soundlink Flex 2nd gen. It supports AAC and aptX Adaptive in addition to SBC, making it a stronger wireless option than most small rivals.
Cons: One Flex remains mono and cannot deliver genuine low-bass rumble; RTINGS also found the elevated treble can turn hi-hats and other high-frequency detail piercing. The claimed battery life is only 12 hours, and some owners report accelerated standby drain after firmware updates. It is expensive for its size, so the added app and codec support, not a transformational sound upgrade over the original, are the main reasons to choose it.
Full Bose Soundlink Flex 2nd gen review and specifications →
| App | Yes |
|---|---|
| Aux Input | No |
| Battery Life | 12 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC, AAC, aptX Adaptive |
| Bluetooth Version | 5.3 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) |
| Drivers | 60mm full-range driver with passive radiators |
| EQ | Yes (3 band) |
| IP Rating | IP67 |
| Omnidirectional | No |
| Party Mode | Yes (Bose Party mode) |
| Power Input | USB-C |
| Stereo | No |
| Strap | Yes (built-in loop) |
| TWS | Yes |
| Weight | 1.3 lbs (586 g) |
- Links
- Reviews, Comparisons and Sound Samples
- Joy & Oluv’Sone: Bose Soundlink Flex 2nd gen vs Flex More from Oluv’Sone →
- Oluv Patreon: Bose Soundlink Flex 2nd gen - sound demo
- Tô Thái Trí Hùng: Unbox & Sound Test - Bose Soundlink Flex 2
- Joy & Oluv’Sone: Bose Soundlink Flex 2nd gen & Soundcore Motion 300 sound test
- Alan Ross: Hall of Fame classic vs latest Bose tech! More from alanrossreviews →
- CEONTHEMAKING: Bose Soundlink Flex 2nd Gen VS Marshall Emberton III - What’s NEW?? More from CEONTHEMAKING →
- Alan Ross - The Anti Shill!: Small speaker, mighty sound, The Flex gen 2 shatters physics!
- Head-to-Head Comparisons
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Earfun Uboom Slim: $79 eBay
Pros: Excellent pricing, strong waterproof build (IPX7), good battery life (16 hours), smooth sound with volume compensation, speakerphone capability. Measured bass extension of ~63Hz (-10dB).
Cons: Not as deep bass as others. Warm tuned, peaks in the mids and lower treble, rolled off upper treble
Full Earfun Uboom Slim review and specifications →
| Amplifier Power | 20W |
|---|---|
| App | No |
| Aux Input | Yes |
| Bass Extension (-10dB) | ~63Hz |
| Battery Life | 16 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 5.2 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 2.6”H x 7.1”W x 2.6”D (65 x 180 x 65 mm) |
| Drivers | 45mm speaker drivers |
| EQ | No |
| IP Rating | IPX7 |
| Omnidirectional | No |
| Power Input | USB-C |
| Stereo | Yes |
| TWS | Yes |
| Weight | 1.2 lbs (560 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Earfun Uboom Slim vs Xiaomi Sound Outdoor
- Earfun Uboom Slim vs Bose Soundlink Flex
- Earfun Uboom Slim vs Bose Soundlink Revolve+ II
- Earfun Uboom Slim vs Tribit Xsound Plus 2
- Earfun Uboom Slim vs Soundcore Boom 3i
- Earfun Uboom Slim vs Soundcore 3/Soundcore Select 2
- Earfun Uboom Slim vs Sony ULT Field 3
- Earfun Uboom Slim vs Xiaomi Sound Party
- See all 16 comparisons