Short answer: the Bose Soundlink Flex. It ranks #34 of 136 medium speakers by sound quality at $84.99; the Ultimate Ears Boom 4 ranks #88 and costs $105, so there is little reason to consider the other one.
What the Bose Soundlink Flex offers: IP67 rated; rugged enough to survive drops from several feet and floats. Around 12 hours of battery at moderate volume. Watch for: Not stereo. Warm sounding with overly boosted bass which drowns out midrange detail
What the Ultimate Ears Boom 4 offers: IP67 rated, floats, and finally charges via USB-C instead of the older Booms’ Micro-USB. 15 hour battery. Customizable EQ and speaker-pairing via the UE app. Watch for: Not much improvement over the old ones. Weak bass extension and thuddy bass. Gets distorted above 90%
Buy the Bose Soundlink Flex. It ranks higher for sound quality than the Ultimate Ears Boom 4 and costs less, so the other one has nothing left to offer.
Specifications Side By Side
| Bose Soundlink Flex | Ultimate Ears Boom 4 | |
|---|---|---|
| Price | $84.99 | $105 |
| Ranked | #34 of 136 in Medium Size Portable Bluetooth Speakers | #88 of 136 in Medium Size Portable Bluetooth Speakers |
| App | Yes | Yes |
| Bass Extension (-10dB) | 56Hz | - |
| Battery Life | 12 hours (Manufacturer specified) | 15 hours (Manufacturer specified) |
| Built in Microphone | Yes | No |
| EQ | No | Yes (via app) |
| IP Rating | IP67 | IP67 |
| Bluetooth Latency | 33ms | - |
| Max Volume | 96dB | 85dBC |
| 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 / 589 g | 1.4 lbs / 620 g |
| Bluetooth Version | 4.2 | 5.1 |
| Dimensions | 7.9" x 3.5" x 2" (201 x 90 x 52 mm) | 7.2" x 2.9" x 2.9" (184 x 73 x 73 mm) |
| Drivers | 1x 60mm full-range driver + 2x passive radiators | 2x 1.57" (40mm) active drivers + 2x 1.81" x 2.57" (46.1 x 65.2mm) passive radiators |
| Digital Aux Input | No | No |
| Power Bank | - | No |
| Aux Input | - | No |
Related Speaker Comparisons
Other pairings from the same speaker class worth checking:
- JBL Charge Essential 2 vs Ultimate Ears Wonderboom 4
- Soundcore Boost “upgraded” 2021 vs JBL Charge Essential 2
- Soundcore Boost “original model” pre-2021 vs JBL Charge Essential 2
- Bose Soundlink Flex vs Bose SoundLink Color II
- LG Xboom Grab vs Ultimate Ears Boom 4
Prices on this page were last checked August 27, 2026 at 10:09 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: $84.99 Amazon eBay
Pros: IP67 rated; rugged enough to survive drops from several feet and floats. Around 12 hours of battery at moderate volume.
Cons: Not stereo. Warm sounding with overly boosted bass which drowns out midrange detail
Full Bose Soundlink Flex review and specifications →
| App | Yes |
|---|---|
| Bass Extension (-10dB) | 56Hz |
| Battery Life | 12 hours (Manufacturer specified) |
| 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 |
| Max Volume | 96dB |
| Omnidirectional | No |
| Party Mode | Yes (Bose Party mode) |
| Power Input | USB-C |
| Stereo | No |
| TWS | Yes |
| Weight | 1.3 lbs / 589 g |
- Links
- Reviews, Comparisons and Sound Samples
- Joy & Oluv’Sone: Bose Soundlink Flex 2nd gen vs Flex More from Oluv’Sone →
- Alan Ross Reviews: Bose Soundlink Flex Review! vs JBL Flip 6 and JBL Charge 5. Travel heaven?? 🤞 More from alanrossreviews →
- Joy & Oluv’Sone: Bose Soundlink Flex 2nd gen vs Flex
- Alan Ross Reviews: Beats Pill vs Harman Luna vs Bose Flex vs Soundcore Motion Plus
- Alan Ross Reviews: Tribit Xsound Mega vs the world! (JBL Charge 5, Bose Flex, Sony XB33, LG PL7) 👍
- Alan Ross Reviews: Bose Soundlink Flex vs Soundcore Boost vs Bogasing M4 - cheap or Bose?
- Alan Ross Reviews: Tribit Stormbox Flow has deeper bass than the Bose Flex but………..
- Jay’s Straight Up Reviews & More: Tribit Stormbox Flow vs Soundcore Motion 300 (LDAC) 😵 Budget Bose Soundlink Flex “Inspired” Speakers More from JaysStraightUpReviews →
- Oluv Patreon: Soundcore Motion 300 = Bose Soundlink Flex = Earfun UBoom L?
- Alan Ross Reviews: Bose Soundlink Flex or JBL Flip 6 (eq adjusted) or Denon Envaya - best speaker for travel!
- Alan Ross Reviews: Bose Soundlink Flex or Beosound A1 (1st gen) - ultimate compact speaker 😇
- Alan Ross Reviews: Bose Soundlink Flex or JBL Flip 6 (eq adjusted) or Denon Envaya - best speaker for travel!
- Jay’s Straight Up Reviews & More: Tribit Stormbox Flow vs Soundcore Motion 300 (LDAC) 😵 Budget Bose Soundlink Flex “Inspired” Speakers
- Patricio Benadon: Bose SoundLink Flex vs. Mini 2 SE. Music audio quality sound test. Listen 4 different genres!
- Patricio Benadon: Bose SoundLink Flex vs. Mini 2 SE. Music audio quality sound test. Listen 4 different genres!
- Danny Pops: BEST Bose Speaker?? Bose Soundlink Flex vs micro, Color II, and revolve + More from DannyPops →
- Alan Ross Reviews: Bose Soundlink Flex vs Minirig MK3 and Marshall Emberton - best bluetooth speaker?
- Joy & Oluv’Sone: JBL, Bose, B&O, Sonos, Earfun, SoundCore… which portable speaker sounds best?
- Alan Ross - The Anti Shill!: Small speaker, mighty sound, The Flex gen 2 shatters physics!
- Reddit Search for Bose Soundlink Flex Review
- Head-to-Head Comparisons
- Bose Soundlink Flex vs Bose Soundlink Flex 2nd gen
- Bose Soundlink Flex vs JBL Charge Essential 2
- Bose Soundlink Flex vs Tribit Xsound Plus 2
- Bose Soundlink Flex vs Teufel Rockster XS
- Bose Soundlink Flex vs Soundcore Motion 100
- Bose Soundlink Flex vs Tribit Stormbox Pro
- Bose Soundlink Flex vs Soundcore Boom 3i
- Bose Soundlink Flex vs Xiaomi Sound Outdoor
- See all 77 comparisons
Ultimate Ears Boom 4: $105 Amazon eBay
Pros: IP67 rated, floats, and finally charges via USB-C instead of the older Booms’ Micro-USB. 15 hour battery. Customizable EQ and speaker-pairing via the UE app.
Cons: Not much improvement over the old ones. Weak bass extension and thuddy bass. Gets distorted above 90%
Full Ultimate Ears Boom 4 review and specifications →
| App | Yes |
|---|---|
| Aux Input | No |
| Battery Life | 15 hours (Manufacturer specified) |
| Bluetooth Version | 5.1 |
| Built in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 7.2" x 2.9" x 2.9" (184 x 73 x 73 mm) |
| Drivers | 2x 1.57" (40mm) active drivers + 2x 1.81" x 2.57" (46.1 x 65.2mm) passive radiators |
| EQ | Yes (via app) |
| IP Rating | IP67 |
| Max Volume | 85dBC |
| Omnidirectional | No |
| Power Bank | No |
| Power Input | USB-C |
| Stereo | Yes |
| TWS | Yes |
| Weight | 1.4 lbs / 620 g |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Ultimate Ears Boom 4 vs Ultimate Ears Boom 3
- Ultimate Ears Boom 4 vs Ultimate Ears Wonderboom
- Ultimate Ears Boom 4 vs Klipsch Groove/Heritage Groove
- Ultimate Ears Boom 4 vs Ultimate Ears Wonderboom 2
- Ultimate Ears Boom 4 vs Ultimate Ears Wonderboom 3
- Ultimate Ears Boom 4 vs Ultimate Ears Wonderboom 4
- Ultimate Ears Boom 4 vs Sony SRS-XE300
- Ultimate Ears Boom 4 vs Tribit Stormbox
- See all 74 comparisons