REL Acoustics S/550 vs KEF Reference 8b

Short answer: the REL Acoustics S/550. It ranks #155 of 212 subwoofers by sound quality, rated 3.5/5, at $3,299; the KEF Reference 8b ranks #157, rated 3.4/5, and costs $8,999.99, which makes this an easy call rather than a real tradeoff.

What the REL Acoustics S/550 does well: The smallest model in REL’s 2025 Serie S, replacing the S/510: a 10” CarbonAlloy active driver and a 12” down-firing passive radiator driven by a 550W Linear Class D amplifier, reaching 19Hz (-6dB). The tradeoff: No independent measurements yet, so its output can’t be compared directly with ranked subwoofers; the rating is estimated from the measured REL Acoustics R-528 (112.8dB in three of the four 40 to 80Hz CEA-2010 bands) and its sibling REL Acoustics S/850.

Why pick the KEF Reference 8b: Flagship Reference series subwoofer featuring dual opposing 9-inch drivers in a force-cancelling sealed enclosure, eliminating mechanical cabinet vibration. The tradeoff: Flagship $8,999.99 price tag is aimed strictly at reference luxury installations, and the 77.2 lbs (35 kg) piano-gloss cabinet requires delicate handling.

Buy the REL Acoustics S/550. It is rated higher for sound quality than the KEF Reference 8b and costs less, so it is the default pick unless a specific strength of the other one matters more to you.

About the ratings: neither speaker has been measured yet, so both ratings are estimated from measured siblings and predecessors (likely ranges: REL Acoustics S/550 3.1 to 3.7; KEF Reference 8b 3.2 to 3.6). Treat this verdict as provisional.

Still deciding? The full Subwoofers rankings cover every ranked option.

Specifications Side By Side

Related Speaker Comparisons

How REL Acoustics S/550 compares with other leading options:

• Sigberg Audio INKOGNITO 12 vs REL Acoustics S/550
• REL Acoustics S/850 vs REL Acoustics S/550
• REL Acoustics S/550 vs Genelec 7360A
• REL Acoustics S/850 vs KEF Reference 8b
• Bowers & Wilkins DB2D vs KEF Reference 8b

Prices on this page were last checked October 11, 2026 at 4:59 PM 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

REL Acoustics S/550: $3,299.00 Estimated Audio Advice eBay

Same family: the REL Acoustics S/850 (larger subwoofer, ranked higher, estimated 3.7/5), the REL Acoustics Carbon Special Black Label (larger subwoofer, estimated 3.9/5) and the REL Acoustics 212 Black Label (larger subwoofer, estimated 4.2/5). See every REL S and Reference Series generation.

Pros: The smallest model in REL’s 2025 Serie S, replacing the S/510: a 10” CarbonAlloy active driver and a 12” down-firing passive radiator driven by a 550W Linear Class D amplifier, reaching 19Hz (-6dB). It includes REL’s high-level speaker connection for integrating with stereo amplifiers.

Cons: No independent measurements yet, so its output can’t be compared directly with ranked subwoofers; the rating is estimated from the measured REL Acoustics R-528 (112.8dB in three of the four 40 to 80Hz CEA-2010 bands) and its sibling REL Acoustics S/850. It is placed below the larger REL Acoustics S/850, and at 31.7kg it is heavy for a 10” sub.

Full REL Acoustics S/550 review and specifications →

Released	Oct 2025 (1 year ago)
Amplifier Power	550W Linear Class D
Country	United Kingdom
Dimensions	16.1”H x 15.7”W x 18.3”D (410 x 400 x 464 mm)
Drivers	10” CarbonAlloy driver, 12” down-firing passive radiator
Enclosure	passive radiator
Frequency Response	19Hz -6dB (manufacturer specified)
Warranty	3
Weight	69.9 lbs (31.7 kg)

• Reviews, Comparisons and Sound Samples
  • No independent measurement review is linked for this model; it is ranked from hands-on listening and comparison against similarly priced speakers.
• Head-to-Head Comparisons
  • REL Acoustics S/550 vs Genelec 7360A
  • REL Acoustics S/550 vs REL Acoustics S/850
  • REL Acoustics S/550 vs Sigberg Audio INKOGNITO 12

KEF Reference 8b: $8,999.99 Estimated KEF eBay

Pros: Flagship Reference series subwoofer featuring dual opposing 9-inch drivers in a force-cancelling sealed enclosure, eliminating mechanical cabinet vibration. Driven by twin 500W Class-D amplifiers (1,000W total) with extensive DSP boundary compensation and balanced XLR plus RCA inputs, extending clean bass down to 24Hz (±3dB).

Cons: Flagship $8,999.99 price tag is aimed strictly at reference luxury installations, and the 35 kg piano-gloss cabinet requires delicate handling.

Full KEF Reference 8b review and specifications →

Amplifier Power	1000W
Cabinet Color	Piano Black High Gloss
Country	United Kingdom
Dimensions	15.7”H x 14.4”W x 16.9”D (398 x 365 x 429 mm)
Drivers	dual 9” drivers
Enclosure	sealed
Frequency Response	24Hz - 140Hz (±3dB) (manufacturer specified)
Maximum SPL	110 dB
Warranty	5/2
Weight	77.2 lbs (35.0 kg)
XLR Input	Yes

• Links
  • Official KEF Reference 8b Website
• Reviews, Comparisons and Sound Samples
  • No independent measurement review is linked for this model; it is ranked from hands-on listening and comparison against similarly priced speakers.
• Head-to-Head Comparisons
  • KEF Reference 8b vs REL Acoustics S/850
  • KEF Reference 8b vs Bowers & Wilkins DB2D