Short answer: the KEF Muo gen2 for better sound quality, the Ultimate Ears Boom 4 for the lower price. The KEF Muo gen2 ranks #73 of 136 medium speakers at $249.99. The Ultimate Ears Boom 4 ranks #88 at $105, $144.99 cheaper.
What the KEF Muo gen2 offers: KEF seemed to have fixed the rolled off treble and overall balance Watch for: Lacking deeper bass. Very thuddy bass. Appears to be the exact same hardware but with updated tuning. Bass distorts as volume increases, and the claimed 43Hz extension is really only audible at low listening volumes, with a few seconds of lag after volume changes. Loses most of its bass off-axis. Customer reviews are mixed, ranging from praise for detail at low volume to complaints of a boxy, hollow sound.
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 KEF Muo gen2 when sound quality outweighs the price for you, and the Ultimate Ears Boom 4 when the price outweighs sound quality instead.
If battery life is a priority, the KEF Muo gen2 is rated for 24 hours versus 15 hours for the Ultimate Ears Boom 4.
Specifications Side By Side
| KEF Muo gen2 | Ultimate Ears Boom 4 | |
|---|---|---|
| Price | $249.99 | $105 |
| Ranked | #73 of 136 in Medium Size Portable Bluetooth Speakers | #88 of 136 in Medium Size Portable Bluetooth Speakers |
| App | Yes | Yes |
| Battery Life | 24 hours (Manufacturer specified) | 15 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC, aptX Adaptive up to 48 KHz 24 bit | - |
| IP Rating | IP67 | IP67 |
| Party Mode | Yes (Auracast) | - |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Digital Aux Input | Yes (USB-C) | No |
| Weight | 1.6 lbs / 740 g | 1.4 lbs / 620 g |
| Bluetooth Version | 5.4 | 5.1 |
| Drivers | 1x 58x117mm racetrack woofer, 1x 20mm tweeter | 2x 1.57" (40mm) active drivers + 2x 1.81" x 2.57" (46.1 x 65.2mm) passive radiators |
| Dimensions | 8.5" x 3.2" x 2.3" (216 x 82 x 59 mm) | 7.2" x 2.9" x 2.9" (184 x 73 x 73 mm) |
| Frequency Response | 43Hz - 20kHz (Manufacturer specified) | - |
| Output Power | 40W | - |
| Max Volume | 90dB | 85dBC |
| Power Input | - | USB-C |
| EQ | - | Yes (via app) |
| Built in Microphone | - | No |
| Power Bank | - | No |
| Aux Input | - | No |
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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
KEF Muo gen2: $249.99 Amazon eBay
Pros: KEF seemed to have fixed the rolled off treble and overall balance
Cons: Lacking deeper bass. Very thuddy bass. Appears to be the exact same hardware but with updated tuning. Bass distorts as volume increases, and the claimed 43Hz extension is really only audible at low listening volumes, with a few seconds of lag after volume changes. Loses most of its bass off-axis. Customer reviews are mixed, ranging from praise for detail at low volume to complaints of a boxy, hollow sound.
Full KEF Muo gen2 review and specifications →
| App | Yes |
|---|---|
| Battery Life | 24 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC, aptX Adaptive up to 48 KHz 24 bit |
| Bluetooth Version | 5.4 |
| Digital Aux Input | Yes (USB-C) |
| Dimensions | 8.5" x 3.2" x 2.3" (216 x 82 x 59 mm) |
| Drivers | 1x 58x117mm racetrack woofer, 1x 20mm tweeter |
| Frequency Response | 43Hz - 20kHz (Manufacturer specified) |
| IP Rating | IP67 |
| Max Volume | 90dB |
| Omnidirectional | No |
| Output Power | 40W |
| Party Mode | Yes (Auracast) |
| Stereo | Yes |
| TWS | Yes |
| Weight | 1.6 lbs / 740 g |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head 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
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