Short answer: the Earfun Uboom Slim. It ranks #41 of 144 medium speakers by sound quality, rated 3.7/5, at $79; the Sony ULT Field 3 ranks #61, rated 3.4/5, and costs $138, 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 tradeoff: Not as deep bass as others.
Why pick the Sony ULT Field 3: IP67 rated, dustproof and water resistant. The catch: Sounds a bit hollow, a bit boosted in the treble.
Buy the Earfun Uboom Slim. It is rated higher for sound quality than the Sony ULT Field 3 and costs less, which makes it the one to get unless you need something the other one does better.
There is a real battery-life gap here: the Sony ULT Field 3 is rated for 24 hours, the Earfun Uboom Slim only 16 hours.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Earfun Uboom Slim | Sony ULT Field 3 | |
|---|---|---|
| Price | $79 | $138.00 |
| Ranked | #41 of 144 in Medium Size Portable Bluetooth Speakers | #61 of 144 in Medium Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | ~63Hz | - |
| Battery Life | 16 hours (Manufacturer specified) | 24 hours (Manufacturer specified) |
| Power Input | USB-C | USB-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| Weight | 1.2 lbs (560 g) | 2.6 lbs (1.2 kg) |
| Bluetooth Codecs | SBC | SBC, AAC, LDAC |
| Bluetooth Version | 5.2 | 5.2 |
| Built-in Microphone | Yes | Yes |
| Drivers | 45mm speaker drivers | 1x 20mm tweeter + 1x 86mm x 46mm woofer |
| Amplifier Power | 20W | 27W |
| 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) | 10.1” x 4.4” x 3.1” (256 x 113 x 79 mm) |
| App | No | Yes |
| Aux Input | Yes | No |
| EQ | No | Yes (App + ULT button) |
| TWS | Yes | Yes |
| Party Mode | - | Yes (Party Connect up to 100 speakers) |
| Power Bank | - | Yes (USB-C, 5V/1.5A) |
| Strap | - | Yes (detachable shoulder strap) |
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
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- JBL Flip 7 vs Earfun Uboom Slim
Prices on this page were last checked September 26, 2026 at 11:14 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 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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Sony ULT Field 3: $138.00 Amazon eBay
Older models: the Sony XB33 (rated 3.4/5), the Sony SRS-XE300 (rated 2.8/5) and the Sony SRS-XB30 (rated 2.6/5).
Pros: IP67 rated, dustproof and water resistant. 24 hour battery life. App with 10-band EQ. Party Connect with up to 100 speakers. USB-C in/out for charging your phone.
Cons: Sounds a bit hollow, a bit boosted in the treble. Custom EQ and the ULT bass-boost button can’t be used together - turning on ULT disables the EQ. Bass is very weak with ULT off. Lost to the JBL Charge 6 in a side-by-side comparison despite being the larger speaker.
Full Sony ULT Field 3 review and specifications →
| Amplifier Power | 27W |
|---|---|
| App | Yes |
| Aux Input | No |
| Battery Life | 24 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC, AAC, LDAC |
| Bluetooth Version | 5.2 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 10.1” x 4.4” x 3.1” (256 x 113 x 79 mm) |
| Drivers | 1x 20mm tweeter + 1x 86mm x 46mm woofer |
| EQ | Yes (App + ULT button) |
| IP Rating | IP67 |
| Omnidirectional | No |
| Party Mode | Yes (Party Connect up to 100 speakers) |
| Power Bank | Yes (USB-C, 5V/1.5A) |
| Power Input | USB-C |
| Stereo | Yes |
| Strap | Yes (detachable shoulder strap) |
| TWS | Yes |
| Weight | 2.6 lbs (1.2 kg) |
- Links
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- Head-to-Head Comparisons
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