Short answer: the Harman Kardon Onyx Studio 7. It ranks #14 of 112 boombox speakers by sound quality (rated 4.1/5) at $248.90 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 7 is the better-sounding, lighter pick. An elegant home portable with warm, spacious sound, strong deep bass, and stereo pairing with a second unit. At 6.4 lbs (2.9 kg) it weighs much less than the Diamondboxx M3 at 11 lbs (5 kg). It links with other speakers (Wireless Dual Sound), which the Diamondboxx M3 cannot. Watch for: Consumer Reports finds the bass prominent and boomy, mids hazy, treble slightly smeared and the soundstage congested.
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 7. The catch: 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 7. It is rated higher for sound quality; the Diamondboxx M3 is no longer sold new.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
An elegant home portable with warm, spacious sound, strong deep bass, and stereo pairing with a second unit.
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 7 | Diamondboxx M3 | |
|---|---|---|
| Price | $248.90 | $700 Discontinued |
| Ranked | #14 of 112 in Boombox Size Portable Bluetooth Speakers | #76 of 112 in Boombox Size Portable Bluetooth Speakers |
| Aux Input | Yes | Yes |
| Aux Latency | 0ms | - |
| Bass Extension (-10dB) | 37Hz | - |
| Battery Life | 8 hours (Manufacturer specified) | 40 hours (Manufacturer specified) |
| Built-in Microphone | Yes | No |
| IP Rating | None | None |
| Bluetooth Latency | 266ms | - |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) | - |
| Party Mode | Yes (Wireless Dual Sound) | No |
| Power Input | DC Barrel Connector (19V/2.1A) | USB-C |
| Stereo | Partially (1 woofer) | Yes |
| Omnidirectional | No | No |
| TWS | No | Yes |
| Weight | 6.4 lbs (2.9 kg) | 11 lbs (5 kg) |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| App | No | No |
| EQ | No | No |
| Power Bank | No | No |
| USB Playback | No | No |
| Amplifier Power | 50W RMS | 200W RMS / 400W peak |
| Dimensions | 11.3” x 11.3” (285.8 x 285.8 mm) (round design) | 14.7” x 9” x 8” (373.4 x 228.6 x 203.2 mm) |
| Drivers | 120mm woofer + 2x 25mm tweeters | 3” woofer + tweeter array |
| Digital Aux Input | No | No |
| Bluetooth Version | 4.2 | 5.0 |
| Strap | No | - |
| FM Tuner | - | No |
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