Bose Soundlink Flex 2nd gen vs Ultimate Ears Boom 4

Last updated: October 12, 2026

Short answer: the Bose SoundLink Flex 2nd gen is the more polished compact speaker, while the UE Boom 4 is the tougher floating alternative. The Flex sits at 37 of 175 and the Boom 4 at 113 of 175, but their priorities are different: Bose aims for a warm, full presentation and UE emphasizes all-weather convenience.

Bose Soundlink Flex 2nd gen vs Ultimate Ears Boom 4

The Flex sounds much like its predecessor, with bass that can obscure midrange detail, and it is a mono speaker. Its idle battery drain is also worth considering if it will spend long periods unused. The Boom 4 brings IP67 protection, USB-C charging, app EQ, speaker pairing, and a 15-hour claim, but its bass is light and thuddy and distortion rises at high volume.

Buy the Bose SoundLink Flex 2nd gen if you value the fuller sound and do not need a floating speaker or stereo pairing.

Buy the Ultimate Ears Boom 4 if IP67 protection, flotation, app controls, and a more outdoor-oriented design matter most.

Looking for alternatives? See the complete Portable Bluetooth rankings.

Check Bose Soundlink Flex 2nd gen price at Amazon ($99.99) →Check Ultimate Ears Boom 4 price at Amazon ($129.99) →

Specifications Side By Side

Bose Soundlink Flex 2nd gen Ultimate Ears Boom 4
Price$99.99$129.99
Ranked#37 of 175 in Medium Size Portable Bluetooth Speakers#113 of 175 in Medium Size Portable Bluetooth Speakers
AppYesYes
Battery Life12 hours (Manufacturer specified)15 hours (Manufacturer specified)
Built-in MicrophoneYesNo
EQYes (3 band)Yes (via app)
IP RatingIP67IP67
Party ModeYes (Bose Party mode)-
Power InputUSB-CUSB-C
StereoNoYes
OmnidirectionalNoNo
TWSYesYes
Weight1.3 lbs (586 g)1.4 lbs (620 g)
BluetoothYesYes
Bluetooth Version5.35.1
Dimensions7.9” 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)
Aux InputNoNo
Drivers60mm full-range driver with passive radiators2x 1.57” (40mm) active drivers + 2x 1.81” x 2.57” (46.1 x 65.2mm) passive radiators
Bluetooth CodecsSBC, AAC, aptX AdaptiveSBC
Digital Aux InputNoNo
StrapYes (built-in loop)Yes (built-in loop)
Power Bank-No
Maximum SPL-85dBC (Manufacturer specified)
Check Bose Soundlink Flex 2nd gen price at Amazon ($99.99) →Check Ultimate Ears Boom 4 price at Amazon ($129.99) →

More worthwhile head-to-heads for Bose Soundlink Flex 2nd gen:

Prices on this page were last checked October 12, 2026 at 4:13 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 ranking card

Older model: the Bose Soundlink Flex (ranked lower, rated 3.8/5). See every Bose SoundLink Flex, Micro, Max and Plus generation.

Same family: the Bose SoundLink Max (larger model, rated 4.3/5), the Bose Soundlink Micro 2 (larger model, rated 3.6/5) and the Bose SoundLink Plus (larger model, rated 4.2/5).

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.

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Full Bose Soundlink Flex 2nd gen review and specifications →

ReleasedSep 2024 (2 years ago)
AppYes
Aux InputNo
Battery Life12 hours (Manufacturer specified)
BluetoothYes
Bluetooth CodecsSBC, AAC, aptX Adaptive
Bluetooth Version5.3
Built-in MicrophoneYes
Digital Aux InputNo
Dimensions7.9” x 3.5” x 2” (201 x 90 x 52 mm)
Drivers60mm full-range driver with passive radiators
EQYes (3 band)
IP RatingIP67
OmnidirectionalNo
Party ModeYes (Bose Party mode)
Power InputUSB-C
StereoNo
StrapYes (built-in loop)
TWSYes
Weight1.3 lbs (586 g)
Check current price at Amazon ($99.99) →Search eBay for Bose Soundlink Flex 2nd gen →

Ultimate Ears Boom 4: $129.99 Amazon $129.99 eBay

Ultimate Ears Boom 4 ranking card

Older model: the Ultimate Ears Boom 3 (ranked lower, rated 2.9/5). See every Ultimate Ears Wonderboom, Boom and Megaboom generation.

Same family: the Ultimate Ears Wonderboom 4 (smaller model, ranked higher, rated 2.9/5) and the Ultimate Ears Megaboom 4 (larger model, ranked lower, rated 2.1/5).

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 →

ReleasedJun 2024 (2 years ago)
AppYes
Aux InputNo
Battery Life15 hours (Manufacturer specified)
BluetoothYes
Bluetooth CodecsSBC
Bluetooth Version5.1
Built-in MicrophoneNo
Digital Aux InputNo
Dimensions7.2” x 2.9” x 2.9” (184 x 73 x 73 mm)
Drivers2x 1.57” (40mm) active drivers + 2x 1.81” x 2.57” (46.1 x 65.2mm) passive radiators
EQYes (via app)
IP RatingIP67
Maximum SPL85dBC (Manufacturer specified)
OmnidirectionalNo
Power BankNo
Power InputUSB-C
StereoYes
StrapYes (built-in loop)
TWSYes
Weight1.4 lbs (620 g)
Check current price at Amazon ($129.99) →Search eBay for Ultimate Ears Boom 4 →