Short answer: the Harman Kardon Onyx Studio 9. It ranks #15 of 112 boombox speakers by sound quality (rated 4.1/5) at $184.99 and is still sold new; the Diamondboxx M3 ranks #76 (rated 2.8/5) and is discontinued, so it is only an option used.
The Harman Kardon Onyx Studio 9 is the better-sounding choice. An elegant living room portable with balanced, smooth, non-fatiguing sound, app EQ, and stereo pairing for music lovers. It links with other speakers (Auracast), which the Diamondboxx M3 cannot. It has an adjustable EQ, which the Diamondboxx M3 lacks. The catch: It has no water resistance, aux input or USB playback, and its eight-hour claimed battery life is short for an outdoor portable.
The Diamondboxx M3 is the longer-running pick. A compact, very loud boombox with a powerful amplifier and a choice of large battery packs. It is rated for 40 hours of battery against 8 for the Harman Kardon Onyx Studio 9. It keeps a wired aux input, which the Harman Kardon Onyx Studio 9 lacks. Watch for: Despite its output, bass does not reach as deep as the best large portables and can distort when pushed hard.
Buy the Harman Kardon Onyx Studio 9. It is rated higher for sound quality, and the Diamondboxx M3 is discontinued, so it is only available used.
Want more options? Browse the full Portable Bluetooth rankings.
An elegant living room portable with balanced, smooth, non-fatiguing sound, app EQ, and stereo pairing for music lovers.
A compact, very loud boombox with a powerful amplifier and a choice of large battery packs.
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Specifications Side By Side
| Harman Kardon Onyx Studio 9 | Diamondboxx M3 | |
|---|---|---|
| Price | $184.99 | $700 Discontinued |
| Ranked | #15 of 112 in Boombox Size Portable Bluetooth Speakers | #76 of 112 in Boombox Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | 41Hz | - |
| Maximum SPL | 101dB (measured by Alan Ross Reviews) | - |
| IP Rating | None | None |
| Power Input | AC Power Cable (2-Prong) | USB-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 9.3 lbs (4.2 kg) | 11 lbs (5 kg) |
| App | Yes (Harman Kardon One app) | No |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| EQ | Yes (App EQ) | No |
| Party Mode | Yes (Auracast) | No |
| USB Playback | No | No |
| Bluetooth Version | 5.3 | 5.0 |
| Battery Life | 8 hours (Manufacturer specified) | 40 hours (Manufacturer specified) |
| Amplifier Power | 50W RMS | 200W RMS / 400W peak |
| Dimensions | 11.4” x 11.3” x 5.1” (289.2 x 287.5 x 130 mm) | 14.7” x 9” x 8” (373.4 x 228.6 x 203.2 mm) |
| Drivers | 120mm woofer + 3x 20mm tweeters | 3” woofer + tweeter array |
| Digital Aux Input | No | No |
| Aux Input | No | Yes |
| Strap | No | - |
| Power Bank | - | No |
| Built-in Microphone | - | No |
| FM Tuner | - | No |
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