Short answer: the Sony ULT Field 3, if you are buying new. The EarFun Uboom Slim ranks higher than it (#43 vs #71 of 179 medium speakers, 3.7/5 vs 3.4/5) but is discontinued, so only consider it used; the Sony ULT Field 3 is still sold new at $208.
The EarFun Uboom Slim is the better-sounding, lighter option. A slim, affordable waterproof stereo speaker with long battery life that doubles as a speakerphone. At 1.2 lbs (560 g) it weighs much less than the Sony ULT Field 3 at 2.6 lbs (1.2 kg). It keeps a wired aux input, which the Sony ULT Field 3 lacks. The catch: Not as deep bass as others.
The Sony ULT Field 3 is the longer-running option. A rugged waterproof stereo speaker with long battery life, a detailed app EQ, a shoulder strap and a phone charging port. It is rated for 24 hours of battery against 16 for the EarFun Uboom Slim. It supports LDAC Bluetooth, which the EarFun Uboom Slim lacks. It has an adjustable EQ, which the EarFun Uboom Slim lacks. The tradeoff: Sounds a bit hollow, a bit boosted in the treble.
Buy the Sony ULT Field 3 new; the EarFun Uboom Slim is no longer sold new, so it only makes sense as a used find.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
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Specifications Side By Side
| EarFun Uboom Slim | Sony ULT Field 3 | |
|---|---|---|
| Price | $79 Discontinued | $208.00 |
| Ranked | #43 of 179 in Medium Size Portable Bluetooth Speakers | #71 of 179 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 | Yes | Yes |
| 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) |
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