Short answer: the Wonderboom 4 is the lighter, simpler floating speaker; the Bose SoundLink Flex 2nd gen is the fuller-sounding option if you accept a warmer balance. They rank 95 of 150 and 35 of 150.
Wonderboom 4 is compact, IP67 rated, buoyant, and finally charges through USB-C. Its bass lacks the depth of stronger small speakers, and it is not a major acoustic upgrade over Wonderboom 3.
The SoundLink Flex 2nd gen also floats and has a rugged build, but its bass-forward tuning can hide midrange detail. It can also lose charge while sitting unused, which matters for infrequent listeners.
Buy the Ultimate Ears Wonderboom 4 if you want the smallest floating IP67 speaker with USB-C charging.
Buy the Bose SoundLink Flex 2nd gen if a warmer, bigger presentation is more important than the lowest weight.
Want more options? Browse the full Portable Bluetooth rankings.
Specifications Side By Side
| Ultimate Ears Wonderboom 4 | Bose Soundlink Flex 2nd gen | |
|---|---|---|
| Price | $59.99 | $159.00 |
| Ranked | #95 of 150 in Medium Size Portable Bluetooth Speakers | #35 of 150 in Medium Size Portable Bluetooth Speakers |
| Battery Life | 14 hours (Manufacturer specified) | 12 hours (Manufacturer specified) |
| Maximum SPL | 87dB (Manufacturer specified) | - |
| Power Input | USB-C | USB-C |
| Stereo | No | No |
| Omnidirectional | Yes | No |
| Weight | 0.9 lbs (420 g) | 1.3 lbs (586 g) |
| IP Rating | IP67 | IP67 |
| Bluetooth | Yes | Yes |
| Bluetooth Version | 5.2 | 5.3 |
| Dimensions | 4.1” x 3.8” (104 x 95.3 mm) | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) |
| Drivers | 2x 40mm active drivers + 2x passive radiators (46.1 x 65.2mm) | 60mm full-range driver with passive radiators |
| TWS | Yes | Yes |
| Party Mode | No | Yes (Bose Party mode) |
| App | No | Yes |
| EQ | No | Yes (3 band) |
| Built-in Microphone | No | Yes |
| Power Bank | No | - |
| Aux Input | No | No |
| Digital Aux Input | No | No |
| Bluetooth Codecs | SBC | SBC, AAC, aptX Adaptive |
| Strap | Yes (built-in loop) | Yes (built-in loop) |
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Prices on this page were last checked September 30, 2026 at 2:57 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
Ultimate Ears Wonderboom 4: $59.99 Amazon eBay
Older models: the Ultimate Ears Wonderboom 3 (ranked lower, rated 2.9/5), the Ultimate Ears Wonderboom 2 (ranked lower, rated 2.9/5) and the Ultimate Ears Wonderboom (ranked lower, rated 2.9/5).
Pros: Small size.
Cons: Bass isn’t as deep as the top-ranked speakers and is a little thuddy. Not much improvement over the previous Ultimate Ears Wonderboom 3 besides the USB-C charging port.
Full Ultimate Ears Wonderboom 4 review and specifications →
| App | No |
|---|---|
| Aux Input | No |
| Battery Life | 14 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 5.2 |
| Built-in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 4.1” x 3.8” (104 x 95.3 mm) |
| Drivers | 2x 40mm active drivers + 2x passive radiators (46.1 x 65.2mm) |
| EQ | No |
| IP Rating | IP67 |
| Maximum SPL | 87dB (Manufacturer specified) |
| Omnidirectional | Yes |
| Party Mode | No |
| Power Bank | No |
| Power Input | USB-C |
| Stereo | No |
| Strap | Yes (built-in loop) |
| TWS | Yes |
| Weight | 0.9 lbs (420 g) |
- Links
- Reviews, Comparisons and Sound Samples
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Bose Soundlink Flex 2nd gen: $159.00 Amazon eBay
Older model: the Bose Soundlink Flex (ranked lower, 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 | Yes |
| 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 →
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- 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!
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