Short answer: the Yeahbox Sonic Boom Ultra. It ranks #11 of 112 boombox speakers by sound quality (rated 4.2/5) at $388 and is still sold new; the Harman Kardon Onyx Studio 6 ranks #13 (rated 4.1/5) and is discontinued, so it is only an option used. The Harman Kardon Onyx Studio 6’s replacement, the Harman Kardon Onyx Studio 9, is rated 4.1/5 at $184.99.
The Yeahbox Sonic Boom Ultra is the longer-running pick. A massively loud boombox with deep bass, long battery life, and HDMI ARC so it can double as a TV soundbar. It is rated for 24 hours of battery against 8 for the Harman Kardon Onyx Studio 6. It has an adjustable EQ, which the Harman Kardon Onyx Studio 6 lacks. It plays in stereo from a single unit, unlike the Harman Kardon Onyx Studio 6. Watch for: The 500W peak-power rating doesn’t fully hold up: it gets noisy above roughly 80-90% volume, and the midrange isn’t fully refined, sometimes sitting a touch too forward.
The Harman Kardon Onyx Studio 6 is the lighter option. A waterproof carry speaker with warm sound, deep bass for its size, and pairing with a second unit. At 6.5 lbs (2.94 kg) it weighs much less than the Yeahbox Sonic Boom Ultra at 24.3 lbs (11 kg). It links with other speakers (Wireless Dual Sound), which the Yeahbox Sonic Boom Ultra cannot. Watch for: Warm tuning with boosted bass, and not as loud as others.
Buy the Yeahbox Sonic Boom Ultra. It is rated higher for sound quality; the Harman Kardon Onyx Studio 6 is no longer sold new.
Want more options? Browse the full Portable Bluetooth rankings.
A massively loud boombox with deep bass, long battery life, and HDMI ARC so it can double as a TV soundbar.
A waterproof carry speaker with warm sound, deep bass for its size, and pairing with a second unit.
Prices on this page were last checked October 31, 2026 at 7:11 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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Specifications Side By Side
| Yeahbox Sonic Boom Ultra | Harman Kardon Onyx Studio 6 | |
|---|---|---|
| Price | $388.00 | $130 Discontinued |
| Ranked | #11 of 112 in Boombox Size Portable Bluetooth Speakers | #13 of 112 in Boombox Size Portable Bluetooth Speakers |
| App | Yes | No |
| Aux Input | Yes | Yes |
| Battery Capacity | 45000mAh (Reviewer estimated) | - |
| Bluetooth | Yes | Yes |
| Bluetooth Version | 6.0 | 4.2 |
| Dimensions | 23.4” x 9.8” x 12.3” (595 x 248 x 313 mm) | 5” x 11.5” x 11.2” (128 x 291 x 284 mm) |
| Drivers | 6x9in racetrack woofer (200W) + 2x 4.5in midrange (40W each) + 2x tweeters (20W each), true 3-way | 1x 120mm (4.7”) woofer + 1x 25mm (1”) tweeter + 1x passive radiator |
| EQ | Yes (Country, Classic, and custom app EQ; custom settings don’t persist after the app closes) | No |
| Inputs | HDMI ARC (in/out, usable as a TV soundbar), AUX in/out, USB drive, microSD, optional wired mic | - |
| IP Rating | IPX6 | IPX7 |
| MicroSD Playback | Yes | - |
| Amplifier Power | 320W RMS / 500W Peak | 50W RMS |
| Party Mode | No (TWS stereo pairing of 2 units only, no Auracast) | Yes (Wireless Dual Sound) |
| Power Input | USB-C (60W fast charging) | DC Barrel Connector (19V/2A) |
| Stereo | Yes | No |
| 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/) |
| USB Playback | Yes | No |
| Weight | 24.3 lbs (11 kg) | 6.5 lbs (2.94 kg) |
| Digital Aux Input | No | No |
| Bluetooth Codecs | SBC (inferred; additional codecs unverified) | SBC |
| Lights | Yes | - |
| Battery Life | 24 hours (Manufacturer specified) | 8 hours (Manufacturer specified) |
| Strap | No | No |
| Bass Extension (-10dB) | - | 37Hz |
| Built-in Microphone | - | Yes |
| Bluetooth Latency | - | 180ms |
| Maximum SPL | - | 96dB (measured by Alan Ross Reviews) |
| Power Bank | - | No |
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