Short answer: the Harman Kardon Onyx Studio 9. Both are rated 4.1/5 for sound quality (#15 and #16 of 112 boombox speakers), and the Harman Kardon Onyx Studio 9 costs $184.99 against $235.33 for the Zealot ZE51, and with sound quality even, the cheaper one is the better buy.
The Harman Kardon Onyx Studio 9 is the longer-running, lighter choice. An elegant living room portable with balanced, smooth, non-fatiguing sound, app EQ, and stereo pairing for music lovers. It is rated for 8 hours of battery against 4 for the Zealot ZE51. At 9.3 lbs (4.2 kg) it weighs much less than the Zealot ZE51 at 26 lbs (11.81 kg). The tradeoff: It has no water resistance, aux input or USB playback, and its eight-hour claimed battery life is short for an outdoor portable.
The Zealot ZE51 is the tougher choice. A big stereo boombox with clean, wide sound and low distortion at high volume for outdoor parties. It is rated IPX5, while the Harman Kardon Onyx Studio 9 has no water resistance. It keeps a wired aux input, which the Harman Kardon Onyx Studio 9 lacks. The catch: The Zealot ZE41 still wins on raw bass depth and price.
Buy the Harman Kardon Onyx Studio 9. Both are rated the same for sound quality, and it costs $50.34 less than the Zealot ZE51.
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 big stereo boombox with clean, wide sound and low distortion at high volume for outdoor parties.
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Specifications Side By Side
| Harman Kardon Onyx Studio 9 | Zealot ZE51 | |
|---|---|---|
| Price | $184.99 | $235.33 after coupon |
| Ranked | #15 of 112 in Boombox Size Portable Bluetooth Speakers | #16 of 112 in Boombox Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | 41Hz | - |
| Maximum SPL | 101dB (measured by Alan Ross Reviews) | - |
| IP Rating | None | IPX5 |
| Power Input | AC Power Cable (2-Prong) | Type-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 9.3 lbs (4.2 kg) | 26 lbs (11.81 kg) |
| App | Yes (Harman Kardon One app) | Yes |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC (inferred; additional codecs unverified) |
| EQ | Yes (App EQ) | Yes (Hi-Res, 3D Surround, Extra Bass, Vocal and other sound modes) |
| Party Mode | Yes (Auracast) | - |
| USB Playback | No | Yes |
| Bluetooth Version | 5.3 | 5.3 |
| Battery Life | 8 hours (Manufacturer specified) | 4 hours (Manufacturer specified) |
| Amplifier Power | 50W RMS | 250W |
| Dimensions | 11.4” x 11.3” x 5.1” (289.2 x 287.5 x 130 mm) | 22.1” x 9.4” x 13” (562 x 238 x 331 mm) |
| Drivers | 120mm woofer + 3x 20mm tweeters | 1x 133mm + 2x 93mm + 2x 45mm |
| Digital Aux Input | No | No |
| Aux Input | No | Yes |
| Strap | No | Yes (strap) |
| Battery Capacity | - | 48000mAh (12x4000mAh) |
| Frequency Response | - | 20Hz - 20kHz (Manufacturer specified) |
| Microphone Input | - | Yes (Karaoke mode) |
| MicroSD Playback | - | Yes |
| Power Bank | - | Yes (USB-A + USB-C) |
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