Short answer: the Luna 2 for a more articulate, detailed sound, the Soundlink Flex if the price gap matters more. The Luna 2 ranks #25 and the Flex ranks #38 out of 172 medium portable speakers, for $119.96 more.
The two take opposite approaches to tuning. The Luna 2’s review praises an articulate, spacious midrange with precise imaging and instrument separation, and calls its bass tight and well-controlled from its 62mm x 82mm woofer and passive radiator, staying cleaner at volume than pricier rivals like the Sonos Play. The Flex goes the other direction: it’s warm sounding with overly boosted bass that drowns out midrange detail, the opposite tradeoff from the Luna 2’s more revealing character.
The Luna 2 isn’t without its own rough edges. Its treble can sound bright and edgy, it loses more output off-axis than some rivals, and some listeners hear mid-range rattling on certain tracks, similar to sibling JBL models. Both speakers share the same 12-hour battery rating, trailing category leaders like the JBL Charge 6 that roughly double it.
What the Luna 2 adds: true stereo sound when two units are paired via AirTouch, plus onboard EQ with four presets and a custom mode, both missing from the single-driver Flex.
What the Flex adds: a built-in microphone for calls and Bose Party Mode for linking multiple speakers, neither of which the Luna 2’s spec sheet lists.
Buy the Luna 2 for the more articulate, detailed sound and the option to pair two units for true stereo.
Buy the Soundlink Flex if the lower price matters more than midrange detail and you don’t mind its bass-forward, warmer signature.
Want more options? Browse the full Portable Bluetooth rankings.
Articulate, spacious midrange with precise imaging and instrument separation.
Amazon $199.95 B&H Photo Video $199.95 eBay
IP67 rated; rugged enough to survive drops from several feet and floats.
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Specifications Side By Side
| Harman Kardon Luna 2 | Bose Soundlink Flex | |
|---|---|---|
| Price | $199.95 | $79.99 |
| Ranked | #25 of 172 in Medium Size Portable Bluetooth Speakers | #38 of 172 in Medium Size Portable Bluetooth Speakers |
| App | Yes | Yes |
| Aux Input | No | No |
| Battery Life | 12 hours (Manufacturer specified) | 12 hours (Manufacturer specified) |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | SBC | SBC |
| EQ | Yes (4 presets + custom) | No |
| IP Rating | IP67 | IP67 |
| MicroSD Playback | No | - |
| Power Input | USB-C | USB-C |
| Stereo | No | No |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| USB Playback | No | - |
| Weight | 1.6 lbs (735 g) | 1.3 lbs (589 g) |
| Bluetooth Version | 5.4 | 4.2 |
| Dimensions | 8.5” x 3.3” x 3.2” (216 x 84 x 81 mm) | 7.9” x 3.5” x 2” (201 x 90 x 52 mm) |
| Drivers | 62mm x 82mm woofer with passive radiator, 20mm tweeter | 1x 60mm full-range driver + 2x passive radiators |
| Frequency Response | 58Hz - 20kHz (-6dB) (Manufacturer specified) | - |
| Amplifier Power | 40W (25W woofer + 15W tweeter) | - |
| Digital Aux Input | No | No |
| Strap | No | Yes (built-in loop) |
| Bass Extension (-10dB) | - | 56Hz |
| Built-in Microphone | - | Yes |
| Bluetooth Latency | - | 33ms |
| Maximum SPL | - | 96dB (measured by Alan Ross Reviews) |
| Party Mode | - | Yes (Bose Party mode) |
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