Short answer: the Devialet Phantom II 98 dB on measured sound quality, the KEF LSX II LT on price. The Devialet ranks #10 of 100 medium powered bookshelf speakers at $2,998. The KEF LSX II LT ranks #35 at $699.99, $2,298.01 cheaper. The Devialet Phantom II 98 dB is discontinued; its replacement is the Devialet Phantom Ultimate 98dB, rated 4.4/5. If you are buying new, get the Devialet Phantom Ultimate 98dB.
The Devialet measures exceptionally deep bass for its size. Its sealed enclosure reaches -3dB at 30Hz, -6dB at 25.8Hz, and -12dB at 22.4Hz with a well-damped 0.302 low-frequency Q, and its preference scores reach 6.87 standalone and 7.95 with an ideal subwoofer, showing its appeal is not just bass quantity. It integrates amplification, WiFi, AirPlay 2, Spotify Connect, Roon, Bluetooth, Ethernet, and an analog/optical combo jack in each unit. The tradeoffs: stereo requires two individually powered speakers at $2,998, max output is rated at 98dB per speaker, and the integrated architecture offers less serviceability than conventional monitors.
The KEF LSX II LT trades outright bass extension for placement flexibility and connectivity. Its coincident Uni-Q-style driver keeps dispersion wide and consistent both horizontally and vertically, and the KEF Connect app provides real DSP control over boundary compensation, bass contour, treble trim, and subwoofer integration. Erin’s Audio Corner measured -3dB bass extension at 55Hz, well short of the Devialet, with bass compression appearing around 88 to 92dB per speaker and distortion crossing 3 percent around 96dB, meaning it suits close listening rather than a large room. This LT variant also drops the analog input found on the standard LSX II, so a turntable can’t connect directly.
What the KEF adds that the Devialet doesn’t: HDMI and USB-C connectivity, making it a strong option for a small TV or desktop setup, plus a subwoofer output for building out the low end later.
Buy the Devialet Phantom II 98 dB if measured bass extension and preference score matter most and the price is not a barrier.
Buy the KEF LSX II LT if you want HDMI-based TV integration and DSP-driven room adjustment at a fraction of the price, and plan to add a subwoofer for real bass extension.
Want more options? Browse the full Powered Home rankings.
Specifications Side By Side
| KEF LSX II LT | Devialet Phantom II 98 dB | |
|---|---|---|
| Price | $699.99 per pair | $2,998 per pair Discontinued |
| Ranked | #35 of 100 in Medium Size Powered Bookshelf Speakers | #10 of 100 in Medium Size Powered Bookshelf Speakers |
| Dimensions | 9.5”H x 6.1”W x 7.1”D (241.3 x 154.9 x 180.3 mm) | 6.6 x 6.2 x 8.6 in each |
| Inputs | Wifi, USB-C, HDMI, Optical, Bluetooth | Wi-Fi, Ethernet, Bluetooth, AirPlay 2, Spotify Connect, UPnP, Roon Ready, analog/optical combo jack |
| Outputs | RCA Subwoofer | - |
| Drivers | 115mm (4.5in.) magnesium/aluminium alloy cone woofer, 19mm (0.75in.) aluminium dome tweeter | One aluminum full-range driver; two aluminum bass drivers |
| Weight | 15 lbs (6.8 kg) | 9.5 lbs (4.3 kg) each |
| App | No | - |
| Bluetooth | Yes | Yes |
| EQ | No | - |
| Amplifier Power | 100w RMS Per Speaker | 400W RMS each |
| Bass Extension (-3dB) | 55Hz (measured, Erin’s Audio Corner) | 30Hz (measured, spinorama.org) |
| Bass Extension (-10dB) | 46Hz (measured, Erin’s Audio Corner) | approximately 22.6Hz (measured, spinorama.org) |
| Sensitivity | 84dB (measured at 0.3V/1m, Erin’s Audio Corner) | - |
| Spinorama Preference Score | 4.81 | 6.87 |
| Spinorama Preference Score with Perfect Sub | 7.03 | 7.95 |
| Subwoofer Output | Yes | - |
| XLR Input | No | No |
| RCA Input | No | No |
| TRS Input | No | No |
| Optical Input | Yes | Yes |
| Coaxial Input | No | No |
| USB Input | Yes | No |
| HDMI Input | Yes | No |
| AES Input | No | No |
| Aux Input | No | No |
| Frequency Response | 54Hz - 28kHz (±3dB) (Manufacturer specified) | 18Hz - 21kHz (-6dB) (Manufacturer specified) |
| Bluetooth Codecs | - | SBC, AAC |
| Maximum SPL | - | 98dB at 1m each (manufacturer specified) |
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Prices on this page were last checked October 9, 2026 at 8:01 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
KEF LSX II LT: $699.99 per pair Amazon eBay
Same family: the KEF LSX II (larger bookshelf, estimated 4.1/5), the KEF LS50 Wireless II (larger bookshelf, ranked higher, rated 4.3/5) and the KEF LS60 (floorstanding, rated 4.8/5).
Pros: The coincident driver provides useful consistency across listening positions, and the app offers placement and subwoofer adjustments. Erin’s measurements give preference scores of 4.81 standalone and 7.03 with an ideal subwoofer, with -3dB bass around 56Hz. HDMI and USB connectivity make it convenient for a small TV or desktop system. Horizontal and vertical dispersion both reach about ±60°, giving a broad sweet spot for more than one seat. Measured bass extension of 55Hz (-3dB), with a measured sensitivity of 84dB.
Cons: The 3.4dB midrange response span and treble-region dips keep it below more neutral monitors. The existing review finds bass compression around 88-92dB/1m and rising distortion at higher levels, so the small drivers suit close listening rather than a large room. This LT version has no analog input; a turntable cannot plug straight into it.
Full KEF LSX II LT review and specifications →
| AES Input | No |
|---|---|
| Amplifier Power | 100w RMS Per Speaker |
| App | No |
| Aux Input | No |
| Bass Extension (-10dB) | 46Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-3dB) | 55Hz (measured, Erin’s Audio Corner) |
| Bluetooth | Yes |
| Coaxial Input | No |
| Dimensions | 9.5”H x 6.1”W x 7.1”D (241.3 x 154.9 x 180.3 mm) |
| Drivers | 115mm (4.5in.) magnesium/aluminium alloy cone woofer, 19mm (0.75in.) aluminium dome tweeter |
| EQ | No |
| Frequency Response | 54Hz - 28kHz (±3dB) (Manufacturer specified) |
| HDMI Input | Yes |
| Inputs | Wifi, USB-C, HDMI, Optical, Bluetooth |
| Optical Input | Yes |
| Outputs | RCA Subwoofer |
| RCA Input | No |
| Sensitivity | 84dB (measured at 0.3V/1m, Erin’s Audio Corner) |
| Spinorama Preference Score | 4.81 |
| Spinorama Preference Score with Perfect Sub | 7.03 |
| Subwoofer Output | Yes |
| TRS Input | No |
| USB Input | Yes |
| Weight | 15 lbs (6.8 kg) |
| XLR Input | No |
- Links
- Reviews, Comparisons and Sound Samples
- Erin’s Audio Corner: Transform Your Sound System with the KEF LSX II LT Speaker More from Erin’s Audio Corner →
- Erin’s Audio Corner Website: KEF LSX II LT
- Erin’s Audio Corner Measurements (spinorama.org)
- Jasper Tech: Best Desktop Computer Speakers for Every Budget – 2026 More from Jasper Tech →
- Jasper Tech: Best Bookshelf Speakers For TV & Gaming - 2025
- Jasper Tech: Best Powered Bookshelf Speakers for Every Budget - 2025
- Head-to-Head Comparisons
Devialet Phantom II 98 dB: $2,998 per pair Discontinued Devialet eBay
Newer model: the Devialet Phantom Ultimate 98dB, ranked lower, estimated 4.4/5.
Pros: The manufacturer-supplied measurement shows unusually deep bass for the enclosure size: -3dB at 30Hz. Scores of 6.87 standalone and 7.95 with an ideal subwoofer suggest that its appeal is not limited to bass quantity. Integrated amplification and network playback can replace several components, and its 2.3dB midrange response span is reasonably even. Measured bass extension of 30Hz (-3dB).
Cons: Small-enclosure bass extension at the measurement level does not guarantee the same response at high volume. Stereo requires two units, and the integrated architecture offers less system flexibility than conventional monitors. Discontinued.
Full Devialet Phantom II 98 dB review and specifications →
| AES Input | No |
|---|---|
| Amplifier Power | 400W RMS each |
| Aux Input | No |
| Bass Extension (-10dB) | approximately 22.6Hz (measured, spinorama.org) |
| Bass Extension (-3dB) | 30Hz (measured, spinorama.org) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC, AAC |
| Coaxial Input | No |
| Dimensions | 6.6 x 6.2 x 8.6 in each |
| Drivers | One aluminum full-range driver; two aluminum bass drivers |
| Frequency Response | 18Hz - 21kHz (-6dB) (Manufacturer specified) |
| HDMI Input | No |
| Inputs | Wi-Fi, Ethernet, Bluetooth, AirPlay 2, Spotify Connect, UPnP, Roon Ready, analog/optical combo jack |
| Maximum SPL | 98dB at 1m each (manufacturer specified) |
| Optical Input | Yes |
| RCA Input | No |
| Spinorama Preference Score | 6.87 |
| Spinorama Preference Score with Perfect Sub | 7.95 |
| TRS Input | No |
| USB Input | No |
| Weight | 9.5 lbs (4.3 kg) each |
| XLR Input | No |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Devialet Phantom II 98 dB vs Genelec 8020D
- Devialet Phantom II 98 dB vs Genelec 8320A
- Devialet Phantom II 98 dB vs Genelec 8330A
- Devialet Phantom II 98 dB vs Dynaudio LYD 5
- Devialet Phantom II 98 dB vs Neumann KH80 DSP
- Devialet Phantom II 98 dB vs Klipsch The Fives
- Devialet Phantom II 98 dB vs JBL 305P MKII
- Devialet Phantom II 98 dB vs Genelec 8030C
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