Short answer: the REL Acoustics T/9x. It ranks #47 of 212 subwoofers by sound quality, rated 3.9/5, at $1,549. The KEF Kube 15 MIE ranks #78, rated 3.8/5, at $1,499.99, $49.01 cheaper, a saving that is not big enough to make up the sound-quality gap.
The case for the REL Acoustics T/9x: Flagship of the Serie T/x line pairing a front-firing 10-inch FibreAlloy driver with a down-firing 10-inch passive radiator powered by a 300W Class A/B amplifier. Watch for: Passive radiator configuration requires careful boundary positioning away from corners to avoid room mode excitation.
Why pick the KEF Kube 15 MIE: Largest member of the Kube MIE series, housing a 15-inch front-firing driver in a sealed cabinet powered by 300W Class-D amplification. The catch: Weighs 60.6 lbs (27.5 kg) with dimensions over 500mm on each side, making it a substantial presence in a room, and requires dedicated placement without easy concealment.
Buy the REL Acoustics T/9x. It is rated higher for sound quality, and saving $49.01 with the KEF Kube 15 MIE does not make up for the sound-quality gap.
About the ratings: neither speaker has been measured yet, so both ratings are estimated from measured siblings and predecessors (likely ranges: REL Acoustics T/9x 3.7 to 4.1; KEF Kube 15 MIE 3.6 to 4.0). Treat this verdict as provisional.
Want more options? Browse the full Subwoofers rankings.
Specifications Side By Side
| REL Acoustics T/9x | KEF Kube 15 MIE | |
|---|---|---|
| Price | $1,549.00 | $1,499.99 |
| Ranked | #47 of 212 in Medium Home Subwoofers (30-75 lbs) Estimated | #78 of 212 in Medium Home Subwoofers (30-75 lbs) Estimated |
| Country | United Kingdom | United Kingdom |
| Warranty | 3 | 5/2 |
| Enclosure | passive radiator | sealed |
| Drivers | 10” (254mm) active FibreAlloy driver, 10” (254mm) down-firing passive radiator | 15” driver |
| Amplifier Power | 300W RMS (Class A/B) | 300W |
| Frequency Response | 27Hz at -6dB (manufacturer specified) | 20Hz - 140Hz (±3dB) (manufacturer specified) |
| Dimensions | 13.4”H x 15.2”W x 15.5”D (340 x 387 x 393 mm) | 20.4”H x 19.7”W x 20.3”D (519 x 500 x 515 mm) |
| Weight | 45.4 lbs (20.6 kg) | 60.6 lbs (27.5 kg) |
| Maximum SPL | - | 116 dB |
| Cabinet Color | - | black |
Related Speaker Comparisons
How REL Acoustics T/9x compares with other leading options:
- Rythmik E15 vs REL Acoustics T/9x
- Arendal 1723 Subwoofer 1S vs REL Acoustics T/9x
- REL Acoustics T/9x vs ELAC Varro RS700
- ELAC Varro RS700 vs KEF Kube 15 MIE
- KEF Kube 15 MIE vs Q Acoustics Q SUB120
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 T/9x: $1,549.00 Estimated Amazon eBay
Same family: the REL Acoustics T/5x (smaller subwoofer, ranked lower, estimated 3.5/5) and the REL Acoustics T/7x (smaller subwoofer, ranked lower, estimated 3.6/5). See every REL T Series generation.
Pros: Flagship of the Serie T/x line pairing a front-firing 10-inch FibreAlloy driver with a down-firing 10-inch passive radiator powered by a 300W Class A/B amplifier. Extends reach down to 27Hz at -6dB with fast musical transient speed.
Cons: Passive radiator configuration requires careful boundary positioning away from corners to avoid room mode excitation. Commands a premium price without onboard DSP or smartphone app calibration.
Full REL Acoustics T/9x review and specifications →
| Released | Apr 2021 (5 years ago) |
|---|---|
| Amplifier Power | 300W RMS (Class A/B) |
| Country | United Kingdom |
| Dimensions | 13.4”H x 15.2”W x 15.5”D (340 x 387 x 393 mm) |
| Drivers | 10” (254mm) active FibreAlloy driver, 10” (254mm) down-firing passive radiator |
| Enclosure | passive radiator |
| Frequency Response | 27Hz at -6dB (manufacturer specified) |
| Warranty | 3 |
| Weight | 45.4 lbs (20.6 kg) |
- Links
- 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 Kube 15 MIE: $1,499.99 Estimated Amazon KEF eBay
Same family: the KEF Kube 8 MIE (smaller subwoofer, estimated 3.6/5), the KEF Kube 10 MIE (smaller subwoofer, estimated 3.7/5) and the KEF Kube 12 MIE (smaller subwoofer, ranked lower, estimated 3.7/5). See every KEF Kube generation.
Pros: Largest member of the Kube MIE series, housing a 15-inch front-firing driver in a sealed cabinet powered by 300W Class-D amplification. Delivers 20Hz to 140Hz (±3dB) extension and 116dB max SPL with Music Integrity Engine DSP processing and multiple room placement presets.
Cons: Weighs 27.5 kg with dimensions over 500mm on each side, making it a substantial presence in a room, and requires dedicated placement without easy concealment.
Full KEF Kube 15 MIE review and specifications →
| Released | Feb 2024 (2 years ago) |
|---|---|
| Amplifier Power | 300W |
| Cabinet Color | black |
| Country | United Kingdom |
| Dimensions | 20.4”H x 19.7”W x 20.3”D (519 x 500 x 515 mm) |
| Drivers | 15” driver |
| Enclosure | sealed |
| Frequency Response | 20Hz - 140Hz (±3dB) (manufacturer specified) |
| Maximum SPL | 116 dB |
| Warranty | 5/2 |
| Weight | 60.6 lbs (27.5 kg) |
- Links
- 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