Short answer: the Earfun Uboom Slim. It ranks #41 of 150 medium speakers by sound quality, rated 3.7/5, at $79; the Ultimate Ears Boom 4 ranks #99, rated 2.9/5, and costs $109.99, so there is little reason to consider the other one.
Why pick the Earfun Uboom Slim: Excellent pricing, strong waterproof build (IPX7), good battery life (16 hours), smooth sound with volume compensation, speakerphone capability. The catch: Not as deep bass as others.
What the Ultimate Ears Boom 4 does well: IP67 rated, floats, and finally charges via USB-C instead of the older Booms’ Micro-USB. The tradeoff: Not much improvement over the old ones.
Buy the Earfun Uboom Slim. It is rated higher for sound quality than the Ultimate Ears Boom 4 and costs less, which makes it the one to get unless you need something the other one does better.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Earfun Uboom Slim | Ultimate Ears Boom 4 | |
|---|---|---|
| Price | $79 | $109.99 |
| Ranked | #41 of 150 in Medium Size Portable Bluetooth Speakers | #99 of 150 in Medium Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | ~63Hz | - |
| Battery Life | 16 hours (Manufacturer specified) | 15 hours (Manufacturer specified) |
| Power Input | USB-C | USB-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| Weight | 1.2 lbs (560 g) | 1.4 lbs (620 g) |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| Bluetooth Version | 5.2 | 5.1 |
| Built-in Microphone | Yes | No |
| Drivers | 45mm speaker drivers | 2x 1.57” (40mm) active drivers + 2x 1.81” x 2.57” (46.1 x 65.2mm) passive radiators |
| Amplifier Power | 20W | - |
| IP Rating | IPX7 | IP67 |
| Digital Aux Input | No | No |
| Dimensions | 2.6”H x 7.1”W x 2.6”D (65 x 180 x 65 mm) | 7.2” x 2.9” x 2.9” (184 x 73 x 73 mm) |
| App | No | Yes |
| Aux Input | Yes | No |
| EQ | No | Yes (via app) |
| TWS | Yes | Yes |
| Power Bank | - | No |
| Maximum SPL | - | 85dBC (Manufacturer specified) |
| Strap | - | Yes (built-in loop) |
Related Speaker Comparisons
More top alternatives to Earfun Uboom Slim:
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- Soundcore Motion 300 vs Earfun Uboom Slim
- JBL Charge 6 vs Earfun Uboom Slim
- JBL Flip 6 vs Earfun Uboom Slim
- JBL Flip 7 vs Earfun Uboom Slim
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
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 | Yes |
| 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
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Ultimate Ears Boom 4: $109.99 Amazon eBay
Older model: the Ultimate Ears Boom 3 (ranked lower, rated 2.9/5).
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 →
| App | Yes |
|---|---|
| Aux Input | No |
| Battery Life | 15 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC |
| 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 |
| Maximum SPL | 85dBC (Manufacturer specified) |
| Omnidirectional | No |
| Power Bank | No |
| Power Input | USB-C |
| Stereo | Yes |
| Strap | Yes (built-in loop) |
| TWS | Yes |
| Weight | 1.4 lbs (620 g) |
- Links
- Reviews, Comparisons and Sound Samples
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