Short answer: the Harman Kardon Onyx Studio 8. It ranks #11 of 75 boombox speakers by sound quality at $199; the Diamondboxx M3 ranks #53 and costs $700, so there is little reason to consider the other one.
What the Harman Kardon Onyx Studio 8 offers: At 3.3 kg, Harman Kardon Onyx Studio 8 combines 2x 75mm woofers + 2x 20mm tweeters with Bluetooth and aux. Claimed 8 hours (manufacturer specified) battery life, up to 96db and stereo playback make its feature set practical for its intended room or portable use. Watch for: Bass is limited by its 35Hz specification.
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 8. It ranks higher for sound quality than the Diamondboxx M3 and costs less, which settles it without a real tradeoff to make.
There is a real battery-life gap here: the Diamondboxx M3 is rated for 40 hours, the Harman Kardon Onyx Studio 8 only 8 hours.
Want more options? Browse the full Portable Bluetooth rankings.
Specifications Side By Side
| Harman Kardon Onyx Studio 8 | Diamondboxx M3 | |
|---|---|---|
| Price | $199.00 | $700 |
| Ranked | #11 of 75 in Boombox Size Portable Bluetooth Speakers | #53 of 75 in Boombox Size Portable Bluetooth Speakers |
| Aux Input | Yes | Yes |
| Aux Latency | 42ms | - |
| Bass Extension (-10dB) | 35Hz | - |
| Battery Life | 8 hours (Manufacturer specified) | 40 hours (Manufacturer specified) |
| Built-in Microphone | Yes | No |
| IP Rating | None | None |
| Bluetooth Latency | 175ms | - |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) | - |
| Power Input | DC Barrel Connector (19V/2.1A) | USB-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 7.3 lbs (3.3 kg) | 11 lbs (5 kg) |
| App | Yes (Harman Kardon One app) | No |
| Bluetooth Codecs | SBC | SBC |
| Power Bank | No | No |
| EQ | Yes (App EQ) | No |
| Party Mode | No | No |
| USB Playback | No | No |
| Bluetooth Version | 5.2 | - |
| Amplifier Power | 50W RMS | 200W RMS / 400W peak |
| Dimensions | 10.6" x 11.9" x 6.3" (268 x 302.5 x 159.5 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
More worthwhile head-to-heads for Harman Kardon Onyx Studio 8:
- Tribit Stormbox Blast vs Harman Kardon Onyx Studio 8
- Harman Kardon Go + Play 3 vs Harman Kardon Onyx Studio 8
- JBL Partybox Encore 2 vs Harman Kardon Onyx Studio 8
- JBL Partybox Encore Essential 2 vs Harman Kardon Onyx Studio 8
- JBL Partybox Encore vs Harman Kardon Onyx Studio 8
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 8: $199.00 Amazon eBay
Pros: At 3.3 kg, Harman Kardon Onyx Studio 8 combines 2x 75mm woofers + 2x 20mm tweeters with Bluetooth and aux. Claimed 8 hours (manufacturer specified) battery life, up to 96db and stereo playback make its feature set practical for its intended room or portable use. Measured bass extension of 35Hz (-10dB).
Cons: Bass is limited by its 35Hz specification.
Full Harman Kardon Onyx Studio 8 review and specifications →
| Amplifier Power | 50W RMS |
|---|---|
| App | Yes (Harman Kardon One app) |
| Aux Input | Yes |
| Aux Latency | 42ms |
| Bass Extension (-10dB) | 35Hz |
| Battery Life | 8 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC |
| Bluetooth Latency | 175ms |
| Bluetooth Version | 5.2 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 10.6" x 11.9" x 6.3" (268 x 302.5 x 159.5 mm) |
| Drivers | 2x 75mm woofers + 2x 20mm tweeters |
| EQ | Yes (App EQ) |
| IP Rating | None |
| Maximum SPL | 96dB (measured by Alan Ross Reviews) |
| Omnidirectional | No |
| Party Mode | No |
| Power Bank | No |
| Power Input | DC Barrel Connector (19V/2.1A) |
| Stereo | Yes |
| TWS | Yes |
| USB Playback | No |
| Weight | 7.3 lbs (3.3 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Alan Ross Reviews: Harman Kardon Onyx Studio 8 review - part 2 of 3 More from alanrossreviews →
- Alan Ross Reviews: Onyx Studio 8 vs HK Onyx 6, Xtreme 3, PartyBox Encore, Go+ Play, Bag of Riddim! part 3 of 3
- Alan Ross Reviews: Dead room vs Live room - Onyx studio 8 self tuning test! part 1 of 3
- Alan Ross Reviews: Ultimate HK Onyx Studio speaker review and comparison! 8 speakers!
- Head-to-Head Comparisons
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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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