Short answer: the Zealot ZE21 for value, the Harman Kardon Onyx Studio 5 for the design. The Onyx Studio 5 has an elegant circular design with a carrying handle, but its sound is warm with boosted bass. The ZE21 is a great value for bass performance, play time and max volume in the boombox class, though the ZE41 now beats it and it is a little rolled off up top.
Buy the Zealot ZE21. It is rated higher for sound quality, and the Harman Kardon Onyx Studio 5 is discontinued, so it is only available used.
If battery life is a priority, the Zealot ZE21 is rated for 40 hours versus 8 hours for the Harman Kardon Onyx Studio 5.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Zealot ZE21 | Harman Kardon Onyx Studio 5 | |
|---|---|---|
| Price | $247.41 | $499.99 Discontinued |
| Ranked | #18 of 90 in Boombox Size Portable Bluetooth Speakers | #24 of 90 in Boombox Size Portable Bluetooth Speakers |
| App | No | No |
| Aux Input | Yes | Yes |
| Bass Extension (-10dB) | 36Hz | - |
| Battery Life | 40 hours (Manufacturer specified) | 8 hours (Manufacturer specified) |
| EQ | Yes (multiple modes) | No |
| IP Rating | IPX6 | IPX7 |
| MicroSD Playback | Yes | - |
| Party Mode | Yes (PartyAdd up to 100 speakers) | Yes (Wireless Dual Sound) |
| Power Input | USB-C | DC Barrel Connector (19V/2.1A) |
| Stereo | Yes | Partially (1 woofer) |
| Omnidirectional | No | No |
| TWS | Yes | Yes (see https://www.reddit.com/r/Bluetooth_Speakers/comments/w339x5/how_to_harman_kardon_onyx_studio_5_6_dual_sound/) |
| Weight | 20.4 lbs (9.27 kg) | 6.6 lbs (3 kg) |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| Power Bank | Yes (USB-A + USB-C) | No |
| USB Playback | Yes | No |
| Built-in Microphone | No | Yes |
| Amplifier Power | 250W | 50W |
| Dimensions | 16.7” x 10.3” x 14.3” (424 x 262 x 363 mm) | 11.3” x 11.3” (285.8 x 285.8 mm) |
| Drivers | 130W subwoofer + 2x 50mm woofers + passive radiators | 120mm woofer + 25mm tweeter + 2x passive radiators |
| Maximum SPL | 116dB (Manufacturer specified) | - |
| Digital Aux Input | No | No |
| Bluetooth Version | 5.3 | 4.2 |
| Strap | - | No |
Related Speaker Comparisons
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- Harman Kardon Go + Play 3 vs Zealot ZE21
- JBL Partybox Encore 2 vs Zealot ZE21
- JBL PartyBox On-The-Go 2 Plus vs Zealot ZE21
- JBL Partybox Encore Essential 2 vs Zealot ZE21
Prices on this page were last checked October 2, 2026 at 10:18 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
Zealot ZE21: $247.41 Amazon AliExpress eBay
Pros: The ZE21’s main attraction is unusually deep bass for a battery boombox: owner testing finds real output in the 40-50Hz region and audibility down toward the low 30s. Its TWS button can form a stereo pair with another compatible Zealot, and its large, rugged chassis gives it credible party-speaker scale. Measured bass extension of 36Hz (-10dB).
Cons: That deep-bass emphasis comes with a pronounced 60-110Hz kick-bass dip and over-loud 250-600Hz lower mids, which can make rock and pop sound hollow or boxy. The supplied sound modes do not fully correct the tuning; the most positive independent report required source-side parametric EQ. Treble is also soft and clarity trails better-tuned rivals.
Full Zealot ZE21 review and specifications →
| Amplifier Power | 250W |
|---|---|
| App | No |
| Aux Input | Yes |
| Bass Extension (-10dB) | 36Hz |
| Battery Life | 40 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 5.3 |
| Built-in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 16.7” x 10.3” x 14.3” (424 x 262 x 363 mm) |
| Drivers | 130W subwoofer + 2x 50mm woofers + passive radiators |
| EQ | Yes (multiple modes) |
| IP Rating | IPX6 |
| Maximum SPL | 116dB (Manufacturer specified) |
| 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 | 20.4 lbs (9.27 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Jagist reviews: Jbl Boombox 4 Vs Zealot Ze21!!! More from Jagistreviews →
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- Techder Audios: JBL Boombox 4 VS Zealot ZE21 BATTLE OF THE BOOMBOXES! More from techderaudios →
- Jay’s Straight Up Reviews & More: Zealot ZE21 vs JBL Boombox 3 Tailgater Special @20ft. The Budget Beast Against the OG Boombox More from JaysStraightUpReviews →
- Head-to-Head Comparisons
Harman Kardon Onyx Studio 5: $499.99 Discontinued Amazon eBay
Newer model: the Harman Kardon Onyx Studio 9, ranked higher, rated 4.1/5.
Pros: The iconic circular cabinet and integrated handle make it an attractive room-to-room speaker. Reviews praise its generous bass, balanced mids and smooth top end at moderate levels, giving it a warm, relaxed presentation for casual indoor music.
Cons: The large bass boost can mask lower-mid detail and make dense mixes muddy. Battery life is only around eight hours at moderate volume, it is not especially loud, and it has no water resistance for outdoor use. Discontinued.
Full Harman Kardon Onyx Studio 5 review and specifications →
| Amplifier Power | 50W |
|---|---|
| App | No |
| Aux Input | Yes |
| Battery Life | 8 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 4.2 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 11.3” x 11.3” (285.8 x 285.8 mm) |
| Drivers | 120mm woofer + 25mm tweeter + 2x passive radiators |
| EQ | No |
| IP Rating | IPX7 |
| Omnidirectional | No |
| Party Mode | Yes (Wireless Dual Sound) |
| Power Bank | No |
| Power Input | DC Barrel Connector (19V/2.1A) |
| Stereo | Partially (1 woofer) |
| Strap | No |
| TWS | Yes (see https://www.reddit.com/r/Bluetooth_Speakers/comments/w339x5/how_to_harman_kardon_onyx_studio_5_6_dual_sound/) |
| USB Playback | No |
| Weight | 6.6 lbs (3 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Harman Kardon Onyx Studio 5 vs Harman Kardon Go + Play 2
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- Harman Kardon Onyx Studio 5 vs Zealot S89
- Harman Kardon Onyx Studio 5 vs Tribit Stormbox Blast 2
- Harman Kardon Onyx Studio 5 vs Zealot ZE41
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- See all 58 comparisons