Short answer: the Zealot S89 for value, the Onyx Studio 9 for connectivity. The S89 is a great value for bass performance, play time and max volume in the boombox class, though it is on the heavy side. The Onyx Studio 9 adds Auracast multi-speaker connection alongside classic stereo pairing, but has slightly recessed mids, a boost in the upper mids and rolled off upper treble.
The case for the Harman Kardon Onyx Studio 9: Auracast multi-speaker connection alongside classic stereo pairing. The catch: Slight recessed mids, boost in the upper mids, rolled off upper treble.
What the Zealot S89 gets right: A great value for the bass performance, play time and max volume in the boombox class. The catch: On the heavy side.
Buy the Harman Kardon Onyx Studio 9. It is rated higher for sound quality than the Zealot S89 and costs less, so there is no real case for the other one.
If battery life is a priority, the Zealot S89 is rated for 40 hours versus 8 hours for the Harman Kardon Onyx Studio 9.
Water resistance is not close: the Zealot S89 is rated at IPX6 (powerful water jets), well ahead of the Harman Kardon Onyx Studio 9 at no water resistance.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Harman Kardon Onyx Studio 9 | Zealot S89 | |
|---|---|---|
| Price | $189.99 | $246.99 |
| Ranked | #14 of 75 in Boombox Size Portable Bluetooth Speakers | #18 of 75 in Boombox Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | 41Hz | 36Hz |
| Maximum SPL | 101dB (measured by Alan Ross Reviews) | - |
| IP Rating | None | IPX6 |
| 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) | 16.1 lbs (7.3 kg) |
| App | Yes (Harman Kardon One app) | No |
| Bluetooth Codecs | SBC | SBC |
| EQ | Yes (App EQ) | Yes (multiple modes) |
| Party Mode | Yes (Auracast) | Yes (PartyAdd up to 100 speakers) |
| USB Playback | No | Yes |
| Bluetooth Version | 5.3 | 5.3 |
| Battery Life | 8 hours (Manufacturer specified) | 40 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) | 21.2" x 10.4" x 9.4" (538 x 265 x 240 mm) |
| Drivers | 120mm woofer + 3x 20mm tweeters | 130W subwoofer + 2x 40mm drivers + 2x tweeters |
| Digital Aux Input | No | No |
| Aux Input | No | Yes |
| MicroSD Playback | - | Yes |
| Power Bank | - | Yes (USB-A + USB-C) |
| Built-in Microphone | - | No |
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- Harman Kardon Onyx Studio 9 vs JBL Partybox Encore Essential 2
Prices on this page were last checked September 23, 2026 at 11:24 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
Harman Kardon Onyx Studio 9: $189.99 Amazon eBay
Pros: An elegant 4.2kg living-room portable with a measured 41Hz -10dB bass point, 101dB maximum level, three tweeters, app EQ, stereo pairing and Auracast multi-speaker linking. Reviews praise its balanced, smooth presentation and non-fatiguing treble, making it a more music-focused choice than most party speakers. Measured bass extension of 41Hz (-10dB).
Cons: It has no water resistance, aux input or USB playback, and its eight-hour claimed battery life is short for an outdoor portable. Bass is less deep than some earlier Onyx Studio models, while the slightly recessed mids and rolled-off top end mean it is not the most open or detailed option; it still charges from an AC power cable rather than USB-C.
Full Harman Kardon Onyx Studio 9 review and specifications →
| Amplifier Power | 50W RMS |
|---|---|
| App | Yes (Harman Kardon One app) |
| Aux Input | No |
| Bass Extension (-10dB) | 41Hz |
| Battery Life | 8 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 5.3 |
| Digital Aux Input | No |
| Dimensions | 11.4" x 11.3" x 5.1" (289.2 x 287.5 x 130 mm) |
| Drivers | 120mm woofer + 3x 20mm tweeters |
| EQ | Yes (App EQ) |
| IP Rating | None |
| Maximum SPL | 101dB (measured by Alan Ross Reviews) |
| Omnidirectional | No |
| Party Mode | Yes (Auracast) |
| Power Input | AC Power Cable (2-Prong) |
| Stereo | Yes |
| TWS | Yes |
| USB Playback | No |
| Weight | 9.3 lbs (4.2 kg) |
- Links
- Reviews, Comparisons and Sound Samples
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Zealot S89: $246.99 Amazon Aliexpress eBay
Pros: A 7.3kg boombox with a claimed 36Hz bass extension, 40-hour battery life, IPX6 protection, USB-C charging, aux, USB and microSD playback, TWS and multi-speaker PartyAdd. Listener comparisons find it capable of very high output and substantial bass for outdoor use. Measured bass extension of 36Hz (-10dB).
Cons: At high volume, listener reports describe the bass as loose or muddy and the overall balance as less clear than better boombox speakers. The heavy cabinet and basic finish also make it less polished for daily portability, while its multiple EQ modes cannot substitute for a genuinely neutral tuning.
Full Zealot S89 review and specifications →
| Amplifier Power | 250W |
|---|---|
| App | No |
| Aux Input | Yes |
| Bass Extension (-10dB) | 36Hz |
| Battery Life | 40 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 5.3 |
| Built-in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 21.2" x 10.4" x 9.4" (538 x 265 x 240 mm) |
| Drivers | 130W subwoofer + 2x 40mm drivers + 2x tweeters |
| EQ | Yes (multiple modes) |
| IP Rating | IPX6 |
| MicroSD Playback | Yes |
| Omnidirectional | No |
| Party Mode | Yes (PartyAdd up to 100 speakers) |
| Power Bank | Yes (USB-A + USB-C) |
| Power Input | USB-C |
| Stereo | Yes |
| TWS | Yes |
| USB Playback | Yes |
| Weight | 16.1 lbs (7.3 kg) |
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- Reviews, Comparisons and Sound Samples
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