Short answer: the Bose Soundlink Flex, unless the price gap is a dealbreaker. The Flex ranks #95 and the Wonderboom 4 ranks #36 out of 150 medium portable speakers, for $20 more.
Neither speaker gets its bass tuning quite right, just in different ways. The Wonderboom 4’s review describes its bass as not as deep as the top-ranked speakers in its class and a little thuddy, and notes it isn’t much of an upgrade over the Wonderboom 3 beyond the switch to USB-C charging. The Flex’s bass goes the opposite direction: it’s warm and overly boosted to the point of drowning out midrange detail. Between the two complaints, the Flex’s larger single 60mm driver and dual passive radiators still deliver a higher 96dB max volume against the Wonderboom 4’s 87dB.
The Wonderboom 4’s real strength is its size and true 360-degree sound. It’s rated Omnidirectional, unlike the Flex, and at 0.9 lbs (420 g) it’s noticeably lighter and more pocketable than the Flex’s 1.3 lbs (589 g). Both are IP67 rated and float.
What the Flex adds: a companion app, Bose Party Mode for linking multiple speakers, and a built-in microphone for calls, none of which the Wonderboom 4 has.
What the Wonderboom 4 adds: true 360-degree omnidirectional sound and a smaller, lighter form factor at less than half the price.
Buy the Flex for the louder output, app support, and party-mode pairing, if the higher price is acceptable.
Buy the Wonderboom 4 if you want the smallest, lightest, true 360-degree speaker and don’t mind giving up some volume and app features.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Ultimate Ears Wonderboom 4 | Bose Soundlink Flex | |
|---|---|---|
| Price | $59.99 | $79.99 |
| Ranked | #95 of 150 in Medium Size Portable Bluetooth Speakers | #36 of 150 in Medium Size Portable Bluetooth Speakers |
| Battery Life | 14 hours (Manufacturer specified) | 12 hours (Manufacturer specified) |
| Maximum SPL | 87dB (Manufacturer specified) | 96dB (measured by Alan Ross Reviews) |
| Power Input | USB-C | USB-C |
| Stereo | No | No |
| Omnidirectional | Yes | No |
| Weight | 0.9 lbs (420 g) | 1.3 lbs (589 g) |
| IP Rating | IP67 | IP67 |
| Bluetooth | Yes | Yes |
| Bluetooth Version | 5.2 | 4.2 |
| 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) | 1x 60mm full-range driver + 2x passive radiators |
| TWS | Yes | Yes |
| Party Mode | No | Yes (Bose Party mode) |
| App | No | Yes |
| EQ | No | No |
| Built-in Microphone | No | Yes |
| Power Bank | No | - |
| Aux Input | No | No |
| Digital Aux Input | No | No |
| Bluetooth Codecs | SBC | SBC |
| Strap | Yes (built-in loop) | Yes (built-in loop) |
| Bass Extension (-10dB) | - | 56Hz |
| Bluetooth Latency | - | 33ms |
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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) |
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Bose Soundlink Flex: $79.99 Amazon eBay
Newer model: the Bose Soundlink Flex 2nd gen, ranked higher, rated 3.8/5.
Pros: IP67 rated; rugged enough to survive drops from several feet and floats. Around 12 hours of battery at moderate volume. Measured bass extension of 56Hz (-10dB).
Cons: Not stereo. Warm sounding with overly boosted bass which drowns out midrange detail
Full Bose Soundlink Flex review and specifications →
| App | Yes |
|---|---|
| Aux Input | No |
| Bass Extension (-10dB) | 56Hz |
| Battery Life | 12 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC |
| Bluetooth Latency | 33ms |
| Bluetooth Version | 4.2 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) |
| Drivers | 1x 60mm full-range driver + 2x passive radiators |
| EQ | No |
| IP Rating | IP67 |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) |
| 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 (589 g) |
- Links
- Reviews, Comparisons and Sound Samples
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