Harman Kardon Onyx Studio 9 vs Yeahbox Sonic Boom Ultra

Last updated: September 16, 2026

Short answer: the Yeahbox Sonic Boom Ultra for better sound quality, the Harman Kardon Onyx Studio 9 for the lower price. The Yeahbox Sonic Boom Ultra ranks #10 of 75 boombox speakers at $349.20. The Harman Kardon Onyx Studio 9 ranks #14 at $194.95, $154.25 cheaper.

Harman Kardon Onyx Studio 9 vs Yeahbox Sonic Boom Ultra

What the Harman Kardon Onyx Studio 9 offers: 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. Watch for: 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.

What the Yeahbox Sonic Boom Ultra offers: By far the loudest boombox tested against it, hitting 106-107dB, roughly 3-5dB louder than the JBL Boombox 4, Zealot ZE41, Tribit Stormbox Blast 2, W-King X20, and Hopestar A90/A95. The massive 6x9in racetrack woofer reaches audible bass down to around 30Hz on the Country EQ preset, and a teardown confirmed genuinely robust internals: a thick vented voice coil and a dedicated crossover output per driver. HDMI ARC input/output lets it double as a TV soundbar, a feature none of its direct competitors offer. 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 custom EQ in the app noticeably reduces bass output compared to the factory presets and doesn’t persist after the speaker powers off. No Auracast, no removable battery, a plastic handle with some flex, and heavy at 11kg (24lb) for $388. Most of the sound-quality coverage comes from enthusiast listening-test comparisons rather than independent measurement.

Buy the Harman Kardon Onyx Studio 9 if the price is the priority over sound quality, or the Yeahbox Sonic Boom Ultra if sound quality is the priority over the price.

There is a real gap in water resistance: the Yeahbox Sonic Boom Ultra at IPX6 (powerful water jets) against the Harman Kardon Onyx Studio 9, which has no water resistance.

Want more options? Browse the full Portable Bluetooth rankings.

Buy the Yeahbox Sonic Boom Ultra at Amazon ($349.20) →Buy the Harman Kardon Onyx Studio 9 at Amazon ($194.95) →

Specifications Side By Side

Harman Kardon Onyx Studio 9 Yeahbox Sonic Boom Ultra
Price$194.95$349.20
Ranked#14 of 75 in Boombox Size Portable Bluetooth Speakers#10 of 75 in Boombox Size Portable Bluetooth Speakers
Bass Extension (-10dB)41Hz-
Maximum SPL101dB (measured by Alan Ross Reviews)-
IP RatingNoneIPX6
Power InputAC Power Cable (2-Prong)USB-C (60W fast charging)
StereoYesYes
OmnidirectionalNoNo
TWSYesYes
Weight9.3 lbs (4.2 kg)24.3 lbs (11 kg)
AppYes (Harman Kardon One app)Yes
Bluetooth CodecsSBCSBC (inferred; additional codecs unverified)
EQYes (App EQ)Yes (Country, Classic, and custom app EQ; custom settings don't persist after the app closes)
Party ModeYes (Auracast)No (TWS stereo pairing of 2 units only, no Auracast)
USB PlaybackNoYes
Bluetooth Version5.36.0
Battery Life8 hours (Manufacturer specified)-
Amplifier Power50W RMS320W RMS / 500W Peak
Dimensions11.4" x 11.3" x 5.1" (289.2 x 287.5 x 130 mm)23.4" x 9.8" x 12.3" (595 x 248 x 313 mm)
Drivers120mm woofer + 3x 20mm tweeters6x9in racetrack woofer (200W) + 2x 4.5in midrange (40W each) + 2x tweeters (20W each), true 3-way
Digital Aux InputNoNo
Aux Input-Yes
Battery Capacity-45000mAh (Reviewer estimated)
Inputs-HDMI ARC (in/out, usable as a TV soundbar), AUX in/out, USB drive, microSD, optional wired mic
MicroSD Playback-Yes
Lights-Yes
Buy the Yeahbox Sonic Boom Ultra at Amazon ($349.20) →Buy the Harman Kardon Onyx Studio 9 at Amazon ($194.95) →

How Yeahbox Sonic Boom Ultra compares with other leading options:

Prices on this page were last checked September 16, 2026 at 12:41 AM 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.

As an eBay Partner, we may be compensated if you make a purchase.

The Two Speakers In Full

Harman Kardon Onyx Studio 9: $194.95 Amazon eBay

Harman Kardon Onyx Studio 9 ranking card

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 Power50W RMS
AppYes (Harman Kardon One app)
Bass Extension (-10dB)41Hz
Battery Life8 hours (Manufacturer specified)
Bluetooth CodecsSBC
Bluetooth Version5.3
Digital Aux InputNo
Dimensions11.4" x 11.3" x 5.1" (289.2 x 287.5 x 130 mm)
Drivers120mm woofer + 3x 20mm tweeters
EQYes (App EQ)
IP RatingNone
Maximum SPL101dB (measured by Alan Ross Reviews)
OmnidirectionalNo
Party ModeYes (Auracast)
Power InputAC Power Cable (2-Prong)
StereoYes
TWSYes
USB PlaybackNo
Weight9.3 lbs (4.2 kg)
Check current price at Amazon ($194.95) →Search eBay for Harman Kardon Onyx Studio 9 →

Yeahbox Sonic Boom Ultra: $349.20 Amazon eBay

Yeahbox Sonic Boom Ultra ranking card

Pros: By far the loudest boombox tested against it, hitting 106-107dB, roughly 3-5dB louder than the JBL Boombox 4, Zealot ZE41, Tribit Stormbox Blast 2, W-King X20, and Hopestar A90/A95. The massive 6x9in racetrack woofer reaches audible bass down to around 30Hz on the Country EQ preset, and a teardown confirmed genuinely robust internals: a thick vented voice coil and a dedicated crossover output per driver. HDMI ARC input/output lets it double as a TV soundbar, a feature none of its direct competitors offer.

Cons: 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 custom EQ in the app noticeably reduces bass output compared to the factory presets and doesn’t persist after the speaker powers off. No Auracast, no removable battery, a plastic handle with some flex, and heavy at 11kg (24lb) for $388. Most of the sound-quality coverage comes from enthusiast listening-test comparisons rather than independent measurement.

Full Yeahbox Sonic Boom Ultra review and specifications →

Amplifier Power320W RMS / 500W Peak
AppYes
Aux InputYes
Battery Capacity45000mAh (Reviewer estimated)
Bluetooth CodecsSBC (inferred; additional codecs unverified)
Bluetooth Version6.0
Digital Aux InputNo
Dimensions23.4" x 9.8" x 12.3" (595 x 248 x 313 mm)
Drivers6x9in racetrack woofer (200W) + 2x 4.5in midrange (40W each) + 2x tweeters (20W each), true 3-way
EQYes (Country, Classic, and custom app EQ; custom settings don't persist after the app closes)
IP RatingIPX6
InputsHDMI ARC (in/out, usable as a TV soundbar), AUX in/out, USB drive, microSD, optional wired mic
LightsYes
MicroSD PlaybackYes
OmnidirectionalNo
Party ModeNo (TWS stereo pairing of 2 units only, no Auracast)
Power InputUSB-C (60W fast charging)
StereoYes
TWSYes
USB PlaybackYes
Weight24.3 lbs (11 kg)
Check current price at Amazon ($349.20) →Search eBay for Yeahbox Sonic Boom Ultra →