Short answer: the Harman Kardon Onyx Studio 9 if sound quality matters most, the Zealot S78 if price matters most. The Harman Kardon Onyx Studio 9 ranks #13 of 73 boombox speakers at $186.99. The Zealot S78 ranks #73 at $159.68, $27.31 cheaper.
What the Harman Kardon Onyx Studio 9 offers: Auracast multi-speaker connection alongside classic stereo pairing. Harman Kardon One app with EQ. USB-C charging, up from the previous generation’s AC power brick. Watch for: Slight recessed mids, boost in the upper mids, rolled off upper treble. Not as deep bass as previous Onyx Studio speakers.
What the Zealot S78 offers: 120W RMS output with 150W peak power, exceptional 40-hour battery life, power bank function, IP67 waterproof, EQ with multiple modes, dual woofers with tweeters and passive radiators, MicroSD and USB playback, AUX input, TWS stereo pairing, USB-C charging Watch for: Gets distorted above 50%. Not much bass. Volume level fluctuates at high volume.
Buy the Harman Kardon Onyx Studio 9 if sound quality is the priority over the price, or the Zealot S78 if the price is the priority over sound quality.
The Zealot S78 is not a sound-quality pick. It sits near the bottom of the 73 boombox speakers; there are better options higher up.
If battery life is a priority, the Zealot S78 is rated for 40 hours versus 8 hours for the Harman Kardon Onyx Studio 9.
There is a real gap in water resistance: the Zealot S78 at IP67 (brief submersion) against the Harman Kardon Onyx Studio 9, which has no water resistance.
Specifications Side By Side
| Harman Kardon Onyx Studio 9 | Zealot S78 | |
|---|---|---|
| Price | $186.99 | $159.68 |
| Ranked | #13 of 73 in Boombox Size Portable Bluetooth Speakers | #73 of 73 in Boombox Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | 41Hz | - |
| Max Volume | 101dB | - |
| IP Rating | None | IP67 |
| 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 | 9.7 lbs / 4.4 kg |
| App | Yes (Harman Kardon One app) | No |
| Bluetooth Codecs | SBC | SBC |
| EQ | Yes (App EQ) | Yes (multiple modes) |
| Party Mode | Yes (Auracast) | No |
| USB Playback | No | Yes |
| Bluetooth Version | 5.3 | - |
| Battery Life | 8 hours (Manufacturer specified) | 40 hours (Manufacturer specified) |
| Output Power | 50W RMS | 120W RMS / 150W peak |
| Dimensions | 11.4" x 11.3" x 5.1" (289.2 x 287.5 x 130 mm) | 16.1" x 6.6" x 7.3" (410 x 167 x 185 mm) |
| Drivers | 120mm woofer + 3x 20mm tweeters | 2x ~120mm (4.72") woofers + 2x ~42mm tweeters + 2x passive radiators |
| Digital Aux Input | No | No |
| Aux Input | - | Yes |
| MicroSD Playback | - | Yes |
| Power Bank | - | Yes (USB-A) |
| Built in Microphone | - | No |
Related Speaker Comparisons
Other pairings from the same speaker class worth checking:
- Zealot ZE41 vs ZZA K8
- Zealot ZE41 vs W-King X10
- Harman Kardon Onyx Studio 7 vs W-King X10
- Harman Kardon Onyx Studio 9 vs Zealot S95
- Harman Kardon Onyx Studio 8 vs Harman Kardon Onyx Studio 9
Prices on this page were last checked August 27, 2026 at 10:09 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: $186.99 Amazon eBay
Pros: Auracast multi-speaker connection alongside classic stereo pairing. Harman Kardon One app with EQ. USB-C charging, up from the previous generation’s AC power brick.
Cons: Slight recessed mids, boost in the upper mids, rolled off upper treble. Not as deep bass as previous Onyx Studio speakers.
Full Harman Kardon Onyx Studio 9 review and specifications →
| App | Yes (Harman Kardon One app) |
|---|---|
| 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 |
| Max Volume | 101dB |
| Omnidirectional | No |
| Output Power | 50W RMS |
| 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
- Head-to-Head Comparisons
- Harman Kardon Onyx Studio 9 vs Zealot ZE41
- Harman Kardon Onyx Studio 9 vs Harman Kardon Onyx Studio 7
- Harman Kardon Onyx Studio 9 vs Zealot ZE21
- Harman Kardon Onyx Studio 9 vs Harman Kardon Onyx Studio 6
- Harman Kardon Onyx Studio 9 vs Zealot S89
- Harman Kardon Onyx Studio 9 vs Harman Kardon Onyx Studio 8
- Harman Kardon Onyx Studio 9 vs JBL Boombox 4
- Harman Kardon Onyx Studio 9 vs Vifa Copenhagen 2.0
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Zealot S78: $159.68 Amazon Aliexpress eBay
Pros: 120W RMS output with 150W peak power, exceptional 40-hour battery life, power bank function, IP67 waterproof, EQ with multiple modes, dual woofers with tweeters and passive radiators, MicroSD and USB playback, AUX input, TWS stereo pairing, USB-C charging
Cons: Gets distorted above 50%. Not much bass. Volume level fluctuates at high volume.
Full Zealot S78 review and specifications →
| App | No |
|---|---|
| Aux Input | Yes |
| Battery Life | 40 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Built in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 16.1" x 6.6" x 7.3" (410 x 167 x 185 mm) |
| Drivers | 2x ~120mm (4.72") woofers + 2x ~42mm tweeters + 2x passive radiators |
| EQ | Yes (multiple modes) |
| IP Rating | IP67 |
| MicroSD Playback | Yes |
| Omnidirectional | No |
| Output Power | 120W RMS / 150W peak |
| Party Mode | No |
| Power Bank | Yes (USB-A) |
| Power Input | USB-C |
| Stereo | Yes |
| TWS | Yes |
| USB Playback | Yes |
| Weight | 9.7 lbs / 4.4 kg |
- Reviews, Comparisons and Sound Samples
- Jay’s Straight Up Reviews & More: W-King X20 vs Zealot S78 Bluetooth Boombox Battle Outdoor Tailgater Special 🚗 Let the Whoopin’ Begin More from JaysStraightUpReviews →
- Jay’s Straight Up Reviews & More: DBSOARS F29 Max vs Zealot S78 🛜 (5B) Budget Bluetooth Boombox Basement Battle 🔊 Bass Modes Enabled
- Reddit Search for Zealot S78 Review
- Head-to-Head Comparisons