Short answer: the Teufel Boomster 2021 for balance, the Onyx Studio 9 for connectivity. The Boomster 2021 is pretty balanced and slightly warm, though its bass is not as deep as above ranked speakers. 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.
Buy the Harman Kardon Onyx Studio 9. It is rated higher for sound quality and still sold new, while the Teufel Boomster 2021 is discontinued.
If battery life is a priority, the Teufel Boomster 2021 is rated for 18 hours versus 8 hours for the Harman Kardon Onyx Studio 9.
There is a real gap in water resistance: the Teufel Boomster 2021 at IPX7 (brief submersion) against the Harman Kardon Onyx Studio 9, which has no water resistance.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Harman Kardon Onyx Studio 9 | Teufel Boomster 2021 | |
|---|---|---|
| Price | $189.99 | €250 Discontinued |
| Ranked | #15 of 91 in Boombox Size Portable Bluetooth Speakers | #46 of 91 in Boombox Size Portable Bluetooth Speakers |
| Bass Extension (-10dB) | 41Hz | - |
| Maximum SPL | 101dB (measured by Alan Ross Reviews) | - |
| IP Rating | None | IPX7 |
| 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) | 8.3 lbs (3.75 kg) |
| App | Yes (Harman Kardon One app) | No |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| EQ | Yes (App EQ) | No |
| Party Mode | Yes (Auracast) | No |
| USB Playback | No | No |
| Bluetooth Version | 5.3 | 5.0 |
| Battery Life | 8 hours (Manufacturer specified) | 18 hours (Manufacturer specified) |
| Amplifier Power | 50W RMS | 42W RMS |
| Dimensions | 11.4” x 11.3” x 5.1” (289.2 x 287.5 x 130 mm) | 14.6” x 7.1” x 5.8” (370 x 180 x 148 mm) |
| Drivers | 120mm woofer + 3x 20mm tweeters | 1x 110mm (4.3”) woofer + 2x 65mm midrange drivers + 2x 20mm tweeters |
| Digital Aux Input | No | No |
| Aux Input | No | Yes |
| Strap | No | No |
| FM Tuner | - | Yes |
| Power Bank | - | No |
| Built-in Microphone | - | No |
Related Speaker Comparisons
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- Harman Kardon Go + Play 3 vs Harman Kardon Onyx Studio 9
- JBL Partybox Encore 2 vs Harman Kardon Onyx Studio 9
- JBL PartyBox On-The-Go 2 Plus vs Harman Kardon Onyx Studio 9
Prices on this page were last checked October 4, 2026 at 9:58 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
Older models: the Harman Kardon Onyx Studio 8 (ranked higher, rated 4.1/5), the Harman Kardon Onyx Studio 7 (ranked higher, rated 4.1/5), the Harman Kardon Onyx Studio 6 (ranked higher, rated 4.1/5), the Harman Kardon Onyx Studio 5 (ranked lower, rated 3.9/5) and the Harman Kardon Onyx Studio 4 (rated 3.3/5).
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 | Yes |
| 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 |
| Strap | No |
| TWS | Yes |
| USB Playback | No |
| Weight | 9.3 lbs (4.2 kg) |
- Links
- Reviews, Comparisons and Sound Samples
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Teufel Boomster 2021: €250 Discontinued eBay
Newer model: the Teufel Boomster 4, ranked higher, rated 3.4/5.
Pros: Teufel Boomster 2021 uses 1x 110mm (4.3”) woofer + 2x 65mm midrange drivers + 2x 20mm tweeters. Its 3.75 kg, claimed 18 hours (Manufacturer specified) battery life, IPX7 protection, aux input and stereo playback make it a practical option for its intended room or portable use.
Cons: There is no companion app. No EQ adjustment. Discontinued.
Full Teufel Boomster 2021 review and specifications →
| Amplifier Power | 42W RMS |
|---|---|
| App | No |
| Aux Input | Yes |
| Battery Life | 18 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC |
| Bluetooth Version | 5.0 |
| Built-in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 14.6” x 7.1” x 5.8” (370 x 180 x 148 mm) |
| Drivers | 1x 110mm (4.3”) woofer + 2x 65mm midrange drivers + 2x 20mm tweeters |
| EQ | No |
| FM Tuner | Yes |
| IP Rating | IPX7 |
| Omnidirectional | No |
| Party Mode | No |
| Power Bank | No |
| Power Input | USB-C |
| Stereo | Yes |
| Strap | No |
| TWS | Yes |
| USB Playback | No |
| Weight | 8.3 lbs (3.75 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
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