Short answer: the Radiant Acoustics Clarity 4.2 for better sound quality, the KEF Q100 for the lower price. The Radiant Acoustics Clarity 4.2 ranks #23 of 87 bookshelf speakers at $2998. The KEF Q100 ranks #68 at $550, $2448 cheaper.
What the KEF Q100 offers: 5.25” Uni-Q coaxial driver keeps the tweeter and woofer point-source aligned for consistent imaging. 86dB sensitivity is reasonably easy to drive. Watch for: CEA2034 spinorama shows broad, audible deviations from flat rather than narrow peaks: a lift from 700Hz-1.5kHz and again from 5kHz up, plus a cancellation notch around 1.4kHz from port/cabinet interaction. Bass sensitivity drops to about 80dB and impedance falls below 4 ohms in the bass, demanding a capable amplifier. The reviewer heard boomy, buzzing bass that improved somewhat with the port plugged, and could not recommend it, calling the famous reputation more about looks than sound.
What the Radiant Acoustics Clarity 4.2 offers: Compact bookshelf design using a 4” Purifi mid-woofer with matching Purifi passive radiators and an AMT tweeter on a purpose-designed waveguide, built with genuine heft - aluminum baffle, extensive internal bracing and damping. Surprisingly wide horizontal dispersion (about ±70° through the midrange and into the treble), more enveloping than its larger 6.2 sibling despite the smaller cabinet. More linear on-axis than the bigger Clarity 6.2, which needs 15-20° of toe-out to tame a rising treble; the 4.2 can be listened to closer to on-axis without that same correction. Wider-than-typical vertical dispersion (roughly +30°/-20°) for a two-way design, since its smaller woofer keeps the tweeter-to-woofer distance short. Genuinely deep bass extension for its size (F3 44Hz, reaching about 40Hz in-room), though it comes at a real cost to sensitivity. No resonance issues visible in impedance measurements. Watch for: Low sensitivity (rated 78dB, measured 78.5dB) is the trade-off for its bass extension - needs a fair amount of amplifier power, around 100W recommended for small-to-medium rooms versus the manufacturer’s own 60W baseline. Designed specifically for smaller rooms; the reviewer had to move testing out of his open-plan living room and into a smaller bedroom to avoid running into compression. A dip in the upper midrange gives a mild lack of attack and clarity, and a peak around 5kHz occasionally added a touch of extra sibilance. Multitone distortion crosses the reviewer’s 3% threshold at 96dB, making about 88dB a better average listening level; a slight upper-midrange bump persists even with an 80Hz high-pass filter applied. Dynamic range is limited: fine at 86dB, but the woofer starts giving up headroom by 96dB and drops off significantly by 102dB. Compared to its pricier sibling Clarity 6.2, has notably less dynamic range and higher multitone distortion, reflecting the smaller driver complement. A niche product size-wise - the reviewer couldn’t identify a clear direct competitor in the same size/price/SPL class.
Buy the KEF Q100 if the price matters more than sound quality. Buy the Radiant Acoustics Clarity 4.2 if sound quality matters more than the price.
If sound quality matters at all to you, skip the KEF Q100. It ranks near the bottom of the 87 bookshelf speakers, so look higher up the list instead.
Specifications Side By Side
| KEF Q100 | Radiant Acoustics Clarity 4.2 | |
|---|---|---|
| Price | $550 Discontinued | $2,998 |
| Ranked | #68 of 87 in Medium Size Bookshelf Speakers | #23 of 87 in Medium Size Bookshelf Speakers |
| Bass Extension (-3dB) | 85Hz (measured, Audio Science Review) | 44 Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-10dB) | 65Hz (measured, Audio Science Review) | 35 Hz (measured, Erin’s Audio Corner) |
| Discontinued | Yes | - |
| Sensitivity | 85dB (2.83V/1m, measured, Audio Science Review) | 78 dB |
| Impedance | 8 ohms nominal | 4 ohms |
| Frequency Response | 49Hz - 40kHz (+/-3dB) (Manufacturer specified) | 40 Hz - 25 kHz |
| Drivers | 5.25" Uni-Q aluminum coaxial driver, 1" aluminum dome tweeter | (2) 4" (102mm) woofer + AMT tweeter |
| Weight | 13 lbs / 5.9 kg each | 28.7 lbs / 13 kg (per pair: 57.3 lbs / 26 kg) |
| Dimensions | 11.8"H x 7.1"W x 10.7"D (300 x 180 x 272 mm) | 9.5"H x 6.3"W x 9.4"D (241 x 160 x 239 mm) |
| Woofer Cabinet | ported, rear | passive radiator |
| Woofer | - | 4" (102mm) PURIFI USHINDI |
| Tweeter | - | AMT (Air Motion Transformer) |
| Amplifier Required | - | Yes |
| Recommended Power | - | 50-200W |
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The Two Speakers In Full
KEF Q100: $550 Discontinued eBay
Pros: 5.25” Uni-Q coaxial driver keeps the tweeter and woofer point-source aligned for consistent imaging. 86dB sensitivity is reasonably easy to drive.
Cons: CEA2034 spinorama shows broad, audible deviations from flat rather than narrow peaks: a lift from 700Hz-1.5kHz and again from 5kHz up, plus a cancellation notch around 1.4kHz from port/cabinet interaction. Bass sensitivity drops to about 80dB and impedance falls below 4 ohms in the bass, demanding a capable amplifier. The reviewer heard boomy, buzzing bass that improved somewhat with the port plugged, and could not recommend it, calling the famous reputation more about looks than sound. Discontinued.
Full KEF Q100 review and specifications →
| Bass Extension (-10dB) | 65Hz (measured, Audio Science Review) |
|---|---|
| Bass Extension (-3dB) | 85Hz (measured, Audio Science Review) |
| Dimensions | 11.8"H x 7.1"W x 10.7"D (300 x 180 x 272 mm) |
| Discontinued | Yes |
| Drivers | 5.25" Uni-Q aluminum coaxial driver, 1" aluminum dome tweeter |
| Frequency Response | 49Hz - 40kHz (+/-3dB) (Manufacturer specified) |
| Impedance | 8 ohms nominal |
| Sensitivity | 85dB (2.83V/1m, measured, Audio Science Review) |
| Weight | 13 lbs / 5.9 kg each |
| Woofer Cabinet | ported, rear |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Radiant Acoustics Clarity 4.2: $2,998 Radiant Acoustics eBay
Pros: Compact bookshelf design using a 4” Purifi mid-woofer with matching Purifi passive radiators and an AMT tweeter on a purpose-designed waveguide, built with genuine heft - aluminum baffle, extensive internal bracing and damping. Surprisingly wide horizontal dispersion (about ±70° through the midrange and into the treble), more enveloping than its larger 6.2 sibling despite the smaller cabinet. More linear on-axis than the bigger Clarity 6.2, which needs 15-20° of toe-out to tame a rising treble; the 4.2 can be listened to closer to on-axis without that same correction. Wider-than-typical vertical dispersion (roughly +30°/-20°) for a two-way design, since its smaller woofer keeps the tweeter-to-woofer distance short. Genuinely deep bass extension for its size (F3 44Hz, reaching about 40Hz in-room), though it comes at a real cost to sensitivity. No resonance issues visible in impedance measurements.
Cons: Low sensitivity (rated 78dB, measured 78.5dB) is the trade-off for its bass extension - needs a fair amount of amplifier power, around 100W recommended for small-to-medium rooms versus the manufacturer’s own 60W baseline. Designed specifically for smaller rooms; the reviewer had to move testing out of his open-plan living room and into a smaller bedroom to avoid running into compression. A dip in the upper midrange gives a mild lack of attack and clarity, and a peak around 5kHz occasionally added a touch of extra sibilance. Multitone distortion crosses the reviewer’s 3% threshold at 96dB, making about 88dB a better average listening level; a slight upper-midrange bump persists even with an 80Hz high-pass filter applied. Dynamic range is limited: fine at 86dB, but the woofer starts giving up headroom by 96dB and drops off significantly by 102dB. Compared to its pricier sibling Clarity 6.2, has notably less dynamic range and higher multitone distortion, reflecting the smaller driver complement. A niche product size-wise - the reviewer couldn’t identify a clear direct competitor in the same size/price/SPL class.
Full Radiant Acoustics Clarity 4.2 review and specifications →
| Amplifier Required | Yes |
|---|---|
| Bass Extension (-10dB) | 35 Hz (measured, Erin's Audio Corner) |
| Bass Extension (-3dB) | 44 Hz (measured, Erin's Audio Corner) |
| Dimensions | 9.5"H x 6.3"W x 9.4"D (241 x 160 x 239 mm) |
| Drivers | (2) 4" (102mm) woofer + AMT tweeter |
| Frequency Response | 40 Hz - 25 kHz |
| Impedance | 4 ohms |
| Recommended Power | 50-200W |
| Sensitivity | 78 dB |
| Tweeter | AMT (Air Motion Transformer) |
| Weight | 28.7 lbs / 13 kg (per pair: 57.3 lbs / 26 kg) |
| Woofer | 4" (102mm) PURIFI USHINDI |
| Woofer Cabinet | passive radiator |
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