Short answer: both are discontinued, so this only matters if you are buying used. Used, the Harman Kardon Onyx Studio 8 is the better pick: it ranks #12 of 112 boombox speakers by sound quality (rated 4.1/5), against #76 (rated 2.8/5) for the Diamondboxx M3. If you want one new, the Harman Kardon Onyx Studio 9 replaces the Harman Kardon Onyx Studio 8 and is rated 4.1/5 at $184.99.
The Harman Kardon Onyx Studio 8 is the better-sounding, lighter choice. A stylish room-to-room speaker with warm, full sound, deep bass, and app EQ in a light, easy to carry body. At 7.3 lbs (3.3 kg) it weighs noticeably less than the Diamondboxx M3 at 11 lbs (5 kg). It has an adjustable EQ, which the Diamondboxx M3 lacks. The tradeoff: Warm tuning with boosted bass, not as loud as others, and no water resistance rating.
The Diamondboxx M3 is the longer-running choice. 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 8. 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 8 only if you find one used in good condition; both are discontinued, and it is the better rated of the two. For a new speaker, buy the Harman Kardon Onyx Studio 9, which replaces the Harman Kardon Onyx Studio 8.
Want more options? Browse the full Portable Bluetooth rankings.
A stylish room-to-room speaker with warm, full sound, deep bass, and app EQ in a light, easy to carry body.
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 8 | Diamondboxx M3 | |
|---|---|---|
| Price | $199.00 Discontinued | $700 Discontinued |
| Ranked | #12 of 112 in Boombox Size Portable Bluetooth Speakers | #76 of 112 in Boombox Size Portable Bluetooth Speakers |
| Aux Input | Yes | Yes |
| Aux Latency | 42ms | - |
| Bass Extension (-10dB) | 35Hz | - |
| Battery Life | 8 hours (Manufacturer specified) | 40 hours (Manufacturer specified) |
| Built-in Microphone | Yes | No |
| IP Rating | None | None |
| Bluetooth Latency | 175ms | - |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) | - |
| Power Input | DC Barrel Connector (19V/2.1A) | USB-C |
| Stereo | Partially (1 woofer) | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 7.3 lbs (3.3 kg) | 11 lbs (5 kg) |
| App | Yes (Harman Kardon One app) | No |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| Power Bank | No | No |
| EQ | Yes (App EQ) | No |
| Party Mode | No | No |
| USB Playback | No | No |
| Bluetooth Version | 5.2 | 5.0 |
| Amplifier Power | 50W RMS | 200W RMS / 400W peak |
| Dimensions | 10.6” x 11.9” x 6.3” (268 x 302.5 x 159.5 mm) | 14.7” x 9” x 8” (373.4 x 228.6 x 203.2 mm) |
| Drivers | 120mm woofer + 2x 20mm tweeters | 3” woofer + tweeter array |
| Digital Aux Input | No | No |
| Strap | No | - |
| FM Tuner | - | No |
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