Short answer: the Sony SS-CS5 M2. It ranks #32 of 63 bookshelf speakers by sound quality at $278; the KEF Q100 ranks #45 and costs $550, so there is not much of a tradeoff to weigh.
On the Sony SS-CS5 M2 side: Added internal bracing (corners, sides, front baffle) plus an updated crossover meaningfully reduce the resonance issues that plagued the original SS-CS5, giving a smoother, more neutral character overall. Set against that: Mild sibilance in the 3-5kHz range stands out on S and T sounds in vocals.
The case for the KEF Q100: 5.25” Uni-Q coaxial driver keeps the tweeter and woofer point-source aligned for consistent imaging. 86dB sensitivity is reasonably easy to drive. The tradeoff: 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.
Buy the Sony SS-CS5 M2. It ranks higher for sound quality than the KEF Q100 and costs less, so there is no real case for the other one.
Specifications Side By Side
| Sony SS-CS5 M2 | KEF Q100 | |
|---|---|---|
| Price | $278.00 | $550 Discontinued |
| Ranked | #32 of 63 in Medium Size Bookshelf Speakers | #45 of 63 in Medium Size Bookshelf Speakers |
| Bass Extension (-10dB) | 54Hz (measured, Erin’s Audio Corner) | 65Hz (measured, Audio Science Review) |
| Bass Extension (-3dB) | 80Hz (measured, Erin’s Audio Corner) | 85Hz (measured, Audio Science Review) |
| Dimensions | 13.2"H x 7"W x 8.7"D (335 x 178 x 220 mm) | 11.8"H x 7.1"W x 10.7"D (300 x 180 x 272 mm) |
| Impedance | 6 ohms | 8 ohms nominal |
| Sensitivity | 82.5dB | 85dB (2.83V/1m, measured, Audio Science Review) |
| Supertweeter | 0.75 in | - |
| Drivers | 5.12" woofer, 0.98 in tweeter | 5.25" Uni-Q aluminum coaxial driver, 1" aluminum dome tweeter |
| Weight | 9.5 lbs / 4.3 kg each | 13 lbs / 5.9 kg each |
| Woofer Cabinet | ported, rear | ported, rear |
| Discontinued | - | Yes |
| Frequency Response | - | 49Hz - 40kHz (+/-3dB) (Manufacturer specified) |
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The Two Speakers In Full
Sony SS-CS5 M2: $278.00 Amazon
Pros: Added internal bracing (corners, sides, front baffle) plus an updated crossover meaningfully reduce the resonance issues that plagued the original SS-CS5, giving a smoother, more neutral character overall. A modest mid-range dip (about 1-2dB) is present but tolerable, and the reviewer would rather have this dip than a peak in that region. Slightly deeper bass than the previous version, measuring about 2dB more output around 60Hz. Distortion drops noticeably when crossed to a subwoofer around 80-120Hz, meaningfully improving midrange clarity and detail versus running full-range. Easy to drive on a standard AVR - no need for a dedicated high-power amplifier. More modern, understated waveguide look compared to the previous version’s glossy trim.
Cons: Mild sibilance in the 3-5kHz range stands out on S and T sounds in vocals. Some forwardness in the midrange noticeable on certain vocal recordings. Soundstage and sense of envelopment are comparatively flat and two-dimensional, especially next to reference-quality speakers with strong 3D imaging. Marketed as a “three-way” design mainly due to an added super-tweeter that the reviewer considers largely superfluous - it engages only at very high frequencies and adds complexity without a clearly audible benefit, when that cost might have been better spent on the main crossover. Output-limited: realistic ceiling is around the mid-90s dB SPL at a few meters, with comfortable listening closer to 75-85dB at 3-4 meters before distortion and compression become audible. Bass noticeably compresses/shelves below about 120Hz as volume increases, softening kick-drum impact at higher output. Smaller drivers and a lighter motor structure than rivals like the Polk XT20, which the reviewer generally prefers for its better directivity and higher SPL capability. Still needs a subwoofer for any real bass extension.
Full Sony SS-CS5 M2 review and specifications →
| Bass Extension (-10dB) | 54Hz (measured, Erin's Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 80Hz (measured, Erin's Audio Corner) |
| Dimensions | 13.2"H x 7"W x 8.7"D (335 x 178 x 220 mm) |
| Drivers | 5.12" woofer, 0.98 in tweeter |
| Impedance | 6 ohms |
| Sensitivity | 82.5dB |
| Supertweeter | 0.75 in |
| Weight | 9.5 lbs / 4.3 kg each |
| Woofer Cabinet | ported, rear |
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KEF Q100: $550 Discontinued
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 |
As an eBay Partner, we may be compensated if you make a purchase.
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons