Short answer: the KEF LS50 Meta. It ranks #4 of 87 bookshelf speakers by sound quality at $1599; the PMC twenty.21 ranks #86 and costs $2000, so there is not much of a tradeoff to weigh.
What the KEF LS50 Meta offers: Uni-Q concentric driver mounts a 1” vented aluminum dome tweeter at the center of a 5.25” aluminum cone woofer, rated 79Hz-20kHz+. Speaker-to-speaker matching measured tight at roughly 0.5dB deviation between the pair tested, versus 2-3dB seen on some other speakers - likely why imaging stayed so precise. Imaging stays tight and focused even toed out, unlike most coincident designs where toe-out typically diffuses the image, giving more of an oval-shaped soundstage than a hard rectangular boundary. Horizontal and vertical directivity both hold to about ±50° at the -6dB point, so tonality stays consistent across roughly a 100° listening cone. The extended bass shelf is deliberately tuned for near-wall/boundary placement rather than the usual “pull it 3 feet into the room” advice, playing lower without excess boominess when placed close to a wall. At $1,000 (a frequent sale price versus $1,600 list), called a no-brainer for a compact stand-mount speaker. Independent ASR Klippel measurements corroborate this: very good directivity with the on- and off-axis curves tracking closely, and a predicted in-room response the reviewer called “very close to ideal.” Watch for: F3 of 67Hz and F10 of 42Hz mean it doesn’t get much below 50Hz in-room; a subwoofer is recommended for real bass. A 2-3dB scoop around 2-4kHz shows up in both the listening window and sound power measurements, matching a subjectively noticed lack of attack and vocal clarity that the reviewer wanted to correct with about 2dB of EQ. An on-axis diffraction dip around 8kHz smooths out with about 15° of toe-out (typical for concentric designs, but still present at 0°). Distortion is elevated at low frequencies since the single 5.25” cone shares surface area with the tweeter housing, reducing effective radiating area; multitone distortion crosses the 3% threshold at 96dB/1m, making roughly 88dB or below the safer output ceiling. Moderate sensitivity (~83dB average) needed 2-3dB more amplifier gain than typical in testing. Adding a subwoofer at an 80Hz crossover only helps lower-midrange distortion, not the elevated distortion in the 1-2kHz and above-5kHz regions. ASR’s own Klippel testing found the same pattern in starker terms: THD is very good at 86dB SPL/1m but climbs past 100% in the bass at 96dB SPL/1m, confirming this is not a near-field speaker for high-output bass-heavy material. Cumulative spectral decay (waterfall) also shows a couple of resonances lingering in the 1-2kHz region.
What the PMC twenty.21 offers: Transmission-line loaded design with a proprietary PMC/SEAS SONOLEX soft dome tweeter and doped mid/bass driver, reflecting PMC’s high-end British studio-monitor pedigree. Watch for: Amir was blunt: “The PMC Twenty.21 is a failure in design,” asking, “Did different people design different parts of the speaker and never talked to each other?” On-axis response is highly problematic, and the lack of a tweeter waveguide causes severe beamwidth compression that makes the speaker highly room-sensitive. Dual bass peaks indicate improper port tuning, with the port bump at 100Hz compounding rather than compensating for existing woofer peaks. Distortion is elevated throughout, spiking further at 96dB SPL near 200Hz from port noise. Initial listening was “screechy bright” enough to trigger the reviewer’s tinnitus, with harsh, lispy vocals and tubby, unnatural bass; only heavy manual EQ made it acceptable. At $2,000, Amir suspects the tuning was done “by ear” rather than with measurements.
Buy the KEF LS50 Meta. It ranks higher for sound quality than the PMC twenty.21 and costs less, so there is no real case for the other one.
If sound quality matters at all to you, skip the PMC twenty.21. It ranks near the bottom of the 87 bookshelf speakers, so look higher up the list instead.
Specifications Side By Side
| KEF LS50 Meta | PMC twenty.21 | |
|---|---|---|
| Price | $1,599.00 | $2,000 discontinued, superseded by twenty5.21 |
| Ranked | #4 of 87 in Medium Size Bookshelf Speakers | #86 of 87 in Medium Size Bookshelf Speakers |
| Bass Extension (-10dB) | 43Hz (measured, Erin’s Audio Corner) | 48.7Hz (measured, Audio Science Review) |
| Bass Extension (-3dB) | 68Hz (measured, Erin’s Audio Corner) | 68.8Hz (measured, Audio Science Review) |
| Dimensions | 11.9"H x 7.9"W x 11"D (302 x 200 x 280.5 mm) | 12.8"H x 6"W x 10.9"D (325 x 152 x 277 mm) (+6mm grille) |
| Impedance | 8 ohms nominal (3.7 ohms minimum above 80Hz, measured by Erin’s Audio Corner) | 8 ohms |
| Sensitivity | 83dB (measured average, Erin’s Audio Corner; 85dB manufacturer specified) | 83dB (1W/1m, manufacturer specified) |
| Drivers | 130 mm (5.25 in.) aluminium cone woofer, 25 mm (1 in.) vented aluminium dome with Metamaterial Absorption tweeter | 5.5" (140mm) doped mid/bass driver with cast alloy chassis, 27mm PMC/SEAS SONOLEX soft dome tweeter (ferrofluid cooled) |
| Weight | 17.2 lbs / 7.8 kg each | 11 lbs / 5 kg each |
| Woofer Cabinet | ported, rear | transmission line, 1.72m effective length |
| Frequency Response | - | 50Hz - 25kHz, +/-4.4dB (Manufacturer specified) |
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More useful head-to-heads from the same speaker class:
- Ascend Sierra 1 v2 vs Radiant Acoustics Clarity 4.2
- Ascend Sierra 1 v2 vs Revel M105
- Dynaudio X14 vs Ascend Sierra 1 v2
- Ascend Sierra Luna Duo vs PMC twenty.21
- KEF LS50 Meta vs Ascend Sierra Luna Duo
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The Two Speakers In Full
KEF LS50 Meta: $1,599.00 Amazon Crutchfield eBay
Pros: Uni-Q concentric driver mounts a 1” vented aluminum dome tweeter at the center of a 5.25” aluminum cone woofer, rated 79Hz-20kHz+. Speaker-to-speaker matching measured tight at roughly 0.5dB deviation between the pair tested, versus 2-3dB seen on some other speakers - likely why imaging stayed so precise. Imaging stays tight and focused even toed out, unlike most coincident designs where toe-out typically diffuses the image, giving more of an oval-shaped soundstage than a hard rectangular boundary. Horizontal and vertical directivity both hold to about ±50° at the -6dB point, so tonality stays consistent across roughly a 100° listening cone. The extended bass shelf is deliberately tuned for near-wall/boundary placement rather than the usual “pull it 3 feet into the room” advice, playing lower without excess boominess when placed close to a wall. At $1,000 (a frequent sale price versus $1,600 list), called a no-brainer for a compact stand-mount speaker. Independent ASR Klippel measurements corroborate this: very good directivity with the on- and off-axis curves tracking closely, and a predicted in-room response the reviewer called “very close to ideal.”
Cons: F3 of 67Hz and F10 of 42Hz mean it doesn’t get much below 50Hz in-room; a subwoofer is recommended for real bass. A 2-3dB scoop around 2-4kHz shows up in both the listening window and sound power measurements, matching a subjectively noticed lack of attack and vocal clarity that the reviewer wanted to correct with about 2dB of EQ. An on-axis diffraction dip around 8kHz smooths out with about 15° of toe-out (typical for concentric designs, but still present at 0°). Distortion is elevated at low frequencies since the single 5.25” cone shares surface area with the tweeter housing, reducing effective radiating area; multitone distortion crosses the 3% threshold at 96dB/1m, making roughly 88dB or below the safer output ceiling. Moderate sensitivity (~83dB average) needed 2-3dB more amplifier gain than typical in testing. Adding a subwoofer at an 80Hz crossover only helps lower-midrange distortion, not the elevated distortion in the 1-2kHz and above-5kHz regions. ASR’s own Klippel testing found the same pattern in starker terms: THD is very good at 86dB SPL/1m but climbs past 100% in the bass at 96dB SPL/1m, confirming this is not a near-field speaker for high-output bass-heavy material. Cumulative spectral decay (waterfall) also shows a couple of resonances lingering in the 1-2kHz region.
Full KEF LS50 Meta review and specifications →
| Bass Extension (-10dB) | 43Hz (measured, Erin's Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 68Hz (measured, Erin's Audio Corner) |
| Dimensions | 11.9"H x 7.9"W x 11"D (302 x 200 x 280.5 mm) |
| Drivers | 130 mm (5.25 in.) aluminium cone woofer, 25 mm (1 in.) vented aluminium dome with Metamaterial Absorption tweeter |
| Impedance | 8 ohms nominal (3.7 ohms minimum above 80Hz, measured by Erin's Audio Corner) |
| Sensitivity | 83dB (measured average, Erin's Audio Corner; 85dB manufacturer specified) |
| Weight | 17.2 lbs / 7.8 kg each |
| Woofer Cabinet | ported, rear |
- Links
- Reviews, Comparisons and Sound Samples
- Erin’s Audio Corner: Unveiling the KEF LS50 Meta: The Truth Behind the Hype More from Erin’s Audio Corner →
- Erin’s Audio Corner Website KEF LS50 Meta
- Audio Science Review KEF LS50 Meta More from Audio Science Review →
- GR-Research: KEF LS50 Meta! Worthy of HYPE? More from GR-Research →
- Erin’s Audio Corner: My Top Picks of 2023: Must-Haves Under $3000
- Erin’s Audio Corner Measurements (spinorama.org)
- Reddit Search for KEF LS50 Meta Review
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- See all 61 comparisons
PMC twenty.21: $2,000 discontinued, superseded by twenty5.21 eBay
Pros: Transmission-line loaded design with a proprietary PMC/SEAS SONOLEX soft dome tweeter and doped mid/bass driver, reflecting PMC’s high-end British studio-monitor pedigree.
Cons: Amir was blunt: “The PMC Twenty.21 is a failure in design,” asking, “Did different people design different parts of the speaker and never talked to each other?” On-axis response is highly problematic, and the lack of a tweeter waveguide causes severe beamwidth compression that makes the speaker highly room-sensitive. Dual bass peaks indicate improper port tuning, with the port bump at 100Hz compounding rather than compensating for existing woofer peaks. Distortion is elevated throughout, spiking further at 96dB SPL near 200Hz from port noise. Initial listening was “screechy bright” enough to trigger the reviewer’s tinnitus, with harsh, lispy vocals and tubby, unnatural bass; only heavy manual EQ made it acceptable. At $2,000, Amir suspects the tuning was done “by ear” rather than with measurements.
Full PMC twenty.21 review and specifications →
| Bass Extension (-10dB) | 48.7Hz (measured, Audio Science Review) |
|---|---|
| Bass Extension (-3dB) | 68.8Hz (measured, Audio Science Review) |
| Dimensions | 12.8"H x 6"W x 10.9"D (325 x 152 x 277 mm) (+6mm grille) |
| Drivers | 5.5" (140mm) doped mid/bass driver with cast alloy chassis, 27mm PMC/SEAS SONOLEX soft dome tweeter (ferrofluid cooled) |
| Frequency Response | 50Hz - 25kHz, +/-4.4dB (Manufacturer specified) |
| Impedance | 8 ohms |
| Sensitivity | 83dB (1W/1m, manufacturer specified) |
| Weight | 11 lbs / 5 kg each |
| Woofer Cabinet | transmission line, 1.72m effective length |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons