Short answer: the Harman Kardon Onyx Studio 6. It ranks #12 of 75 boombox speakers by sound quality at $130; the Diamondboxx M3 ranks #53 and costs $700, so there is little reason to consider the other one.
What the Harman Kardon Onyx Studio 6 offers: Harman Kardon Onyx Studio 6 uses 2x 75mm woofers + 2x 20mm tweeters. Its 2.94 kg, claimed 8 hours (Manufacturer specified) battery life, IPX7 protection, aux input, up to 96dB and stereo playback make it a practical option for its intended room or portable use. Watch for: Bass is limited by its 37Hz specification. There is no companion app. No EQ adjustment.
What the Diamondboxx M3 offers: An unusually compact 5kg high-output boombox, with a claimed 200W RMS Class A/B amplifier, 114dB maximum level, active crossovers and a choice of large battery packs. It has aux input, USB-C power and TWS pairing, while the aluminum heat sink is designed to sustain loud playback without thermal shutdown. Watch for: Despite its output, bass does not reach as deep as the best large portables and can distort when pushed hard. The treble-forward tuning can sound aggressive, there is no app or EQ to correct it, and the lack of a water rating makes it a poor match for poolside or rough-weather use.
Buy the Harman Kardon Onyx Studio 6. It ranks higher for sound quality than the Diamondboxx M3 and costs less, so there is no real case for the other one.
Battery life favors the Diamondboxx M3: rated for 40 hours against 8 hours for the Harman Kardon Onyx Studio 6.
Water resistance is not close: the Harman Kardon Onyx Studio 6 is rated at IPX7 (brief submersion), well ahead of the Diamondboxx M3 at no water resistance.
Still deciding? The full Portable Bluetooth rankings cover every ranked option.
Specifications Side By Side
| Harman Kardon Onyx Studio 6 | Diamondboxx M3 | |
|---|---|---|
| Price | $130 | $700 |
| Ranked | #12 of 75 in Boombox Size Portable Bluetooth Speakers | #53 of 75 in Boombox Size Portable Bluetooth Speakers |
| Aux Input | Yes | Yes |
| Bass Extension (-10dB) | 37Hz | - |
| Battery Life | 8 hours (Manufacturer specified) | 40 hours (Manufacturer specified) |
| Built-in Microphone | Yes | No |
| IP Rating | IPX7 | None |
| Bluetooth Latency | 180ms | - |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) | - |
| Party Mode | Yes (Wireless Dual Sound) | No |
| Power Input | DC Barrel Connector (19V/2A) | USB-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| TWS | Yes (see https://www.reddit.com/r/Bluetooth_Speakers/comments/w339x5/how_to_harman_kardon_onyx_studio_5_6_dual_sound/) | Yes |
| Weight | 6.5 lbs (2.94 kg) | 11 lbs (5 kg) |
| Bluetooth Codecs | SBC | SBC |
| App | No | No |
| EQ | No | No |
| Power Bank | No | No |
| USB Playback | No | No |
| Bluetooth Version | 4.2 | - |
| Amplifier Power | 50W RMS | 200W RMS / 400W peak |
| Dimensions | 5" x 11.5" x 11.2" (128 x 291 x 284 mm) | 14.7" x 9" x 8" (373.4 x 228.6 x 203.2 mm) |
| Drivers | 2x 75mm woofers + 2x 20mm tweeters | 3" woofer + tweeter array |
| Digital Aux Input | No | No |
| FM Tuner | - | No |
Related Speaker Comparisons
How Harman Kardon Onyx Studio 6 compares with other leading options:
- Tribit Stormbox Blast vs Harman Kardon Onyx Studio 6
- Harman Kardon Go + Play 3 vs Harman Kardon Onyx Studio 6
- JBL Partybox Encore 2 vs Harman Kardon Onyx Studio 6
- JBL Partybox Encore Essential 2 vs Harman Kardon Onyx Studio 6
- JBL Partybox Encore vs Harman Kardon Onyx Studio 6
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.
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The Two Speakers In Full
Harman Kardon Onyx Studio 6: $130 Amazon eBay
Pros: Harman Kardon Onyx Studio 6 uses 2x 75mm woofers + 2x 20mm tweeters. Its 2.94 kg, claimed 8 hours (Manufacturer specified) battery life, IPX7 protection, aux input, up to 96dB and stereo playback make it a practical option for its intended room or portable use. Measured bass extension of 37Hz (-10dB).
Cons: Bass is limited by its 37Hz specification. There is no companion app. No EQ adjustment.
Full Harman Kardon Onyx Studio 6 review and specifications →
| Amplifier Power | 50W RMS |
|---|---|
| App | No |
| Aux Input | Yes |
| Bass Extension (-10dB) | 37Hz |
| Battery Life | 8 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Bluetooth Latency | 180ms |
| Bluetooth Version | 4.2 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 5" x 11.5" x 11.2" (128 x 291 x 284 mm) |
| Drivers | 2x 75mm woofers + 2x 20mm tweeters |
| EQ | No |
| IP Rating | IPX7 |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) |
| Omnidirectional | No |
| Party Mode | Yes (Wireless Dual Sound) |
| Power Bank | No |
| Power Input | DC Barrel Connector (19V/2A) |
| Stereo | Yes |
| 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 | 6.5 lbs (2.94 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Alan Ross Reviews: Onyx Studio 7 vs Onyx Studio 6 - massive deep bass battle 😁 More from alanrossreviews →
- That Speaker Guy: Harman Kardon Onyx Studio 6 vs Devialet Mania
- Ezekielo: Citation 200 vs Onyx Studio 6 vs Bose Portable Speaker Sound Comparison
- Alan Ross Reviews: Harman Kardon Go+ Play 2 mini or Onyx Studio 6 - best speaker for bass?
- Alan Ross Reviews: Ultimate HK Onyx Studio speaker review and comparison! 8 speakers!
- Head-to-Head Comparisons
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- Harman Kardon Onyx Studio 6 vs Zealot ZE51
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- Harman Kardon Onyx Studio 6 vs JBL Partybox Encore Essential
- See all 57 comparisons
Diamondboxx M3: $700 eBay
Pros: An unusually compact 5kg high-output boombox, with a claimed 200W RMS Class A/B amplifier, 114dB maximum level, active crossovers and a choice of large battery packs. It has aux input, USB-C power and TWS pairing, while the aluminum heat sink is designed to sustain loud playback without thermal shutdown.
Cons: Despite its output, bass does not reach as deep as the best large portables and can distort when pushed hard. The treble-forward tuning can sound aggressive, there is no app or EQ to correct it, and the lack of a water rating makes it a poor match for poolside or rough-weather use.
Full Diamondboxx M3 review and specifications →
| Amplifier Power | 200W RMS / 400W peak |
|---|---|
| App | No |
| Aux Input | Yes |
| Battery Life | 40 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Built-in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 14.7" x 9" x 8" (373.4 x 228.6 x 203.2 mm) |
| Drivers | 3" woofer + tweeter array |
| EQ | No |
| FM Tuner | No |
| IP Rating | None |
| Omnidirectional | No |
| Party Mode | No |
| Power Bank | No |
| Power Input | USB-C |
| Stereo | Yes |
| TWS | Yes |
| USB Playback | No |
| Weight | 11 lbs (5 kg) |
- Reviews, Comparisons and Sound Samples
- No independent measurement review is linked for this model; it is ranked from hands-on listening and comparison against similarly priced speakers.
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