Short answer: the Paradigm Signature Sub 2. It ranks #31 of 109 subwoofers by sound quality, rated 4.3/5, at $9,494.56; the RBH Sound Unrivaled 21-SF/R ranks #75, rated 4.1/5, and costs $11,995, so there is little reason to consider the other one.
The case for the Paradigm Signature Sub 2: Independent CEA-2010 testing records 109.4 dB at 20 Hz and 123.7 dB through 40-80 Hz. The catch: The 622.3H x 603.2W x 568.2D mm cabinet and 104.3 kg mass make this a serious placement and moving commitment.
The case for the RBH Sound Unrivaled 21-SF/R: Manufacturer-supplied CEA-2010 data records 112.3 dB at 20 Hz and 118.8 dB through 40-80 Hz, with a passing result down to 10 Hz. Watch for: At around 333 lbs, moving or placing this cabinet is a multi-person job, and the price puts it well outside typical home theater budgets.
Buy the Paradigm Signature Sub 2. It is rated higher for sound quality than the RBH Sound Unrivaled 21-SF/R and costs less, so only choose the other one for a particular feature it does better.
Want more options? Browse the full Subwoofers rankings.
Specifications Side By Side
| Paradigm Signature Sub 2 | RBH Sound Unrivaled 21-SF/R | |
|---|---|---|
| Price | $9,494.56 | $11,995 |
| Ranked | #31 of 109 in Large Home Subwoofers (Over 75 lbs) | #75 of 109 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | sealed | sealed |
| Output SPL at 10 Hz | 97.7 dB | 91.3 dB |
| Output SPL at 12.5 Hz | 101.2 dB | 97.7 dB |
| Output SPL at 15 Hz | 105.6 dB | - |
| Output SPL at 20 Hz | 109.4 dB | 112.3 dB |
| Output SPL at 25 Hz | 112.9 dB | 117.2 dB |
| Output SPL at 31.5 Hz | 116.2 dB | 120.1 dB |
| Output SPL at 40 Hz | 119.9 dB | 119.5 dB |
| Output SPL at 50 Hz | 123.2 dB | 118.7 dB |
| Output SPL at 63 Hz | 125.5 dB | 118.4 dB |
| Output SPL at 80 Hz | 126.0 dB | 118.7 dB |
| Output SPL at 100 Hz | 125.1 dB | 119.2 dB |
| Output SPL at 125 Hz | 123.3 dB | - |
| CEA-2010-A Average (40-80Hz) | 123.7 dB | 118.8 dB |
| Dimensions | 24.5”H x 23.7”W x 22.4”D (622.3 x 603.2 x 568.2 mm) | 27.3”H x 43”W x 21”D (692.2 x 1092.2 x 533.4 mm) |
| Weight | 229.9 lbs (104.3 kg) | 332.9 lbs (151.0 kg) |
| Warranty | 3 | - |
| Cabinet Color | black, wood | - |
| Country | Canada | United States |
| Measurement Source | Audioholics | Manufacturer |
| Drivers | 6x 10” (254mm) driver | 21” carbon fiber driver |
| Inputs | RCA (stereo/mono), LFE, XLR (balanced) | - |
| XLR Input | Yes | - |
| RCA Input | Yes | - |
| TRS Input | No | - |
| Optical Input | No | - |
| Coaxial Input | No | - |
| USB Input | No | - |
| HDMI Input | No | - |
| AES Input | No | - |
| Aux Input | No | - |
| Output SPL at 14 Hz | - | 100.8 dB |
| Output SPL at 16 Hz | - | 105.5 dB |
| Frequency Response | - | 12-80Hz, ±3dB |
| Power Handling | - | 4000W thermal power handling |
Related Speaker Comparisons
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- Monoprice Monolith 16 THX Ultra vs Paradigm Signature Sub 2
- Paradigm Signature Sub 2 vs Reaction Audio PS-15X
- Perlisten Audio D215s vs RBH Sound Unrivaled 21-SF/R
- Harbottle Audio C24 L2 vs RBH Sound Unrivaled 21-SF/R
- RBH Sound Unrivaled 21-SF/R vs Perlisten Audio R212s
Prices on this page were last checked September 29, 2026 at 3:43 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
Paradigm Signature Sub 2: $9,494.56 eBay
Pros: Independent CEA-2010 testing records 109.4 dB at 20 Hz and 123.7 dB through 40-80 Hz. The sealed enclosure with 6x 10” (254mm) driver has the headroom for demanding film bass in a large room.
Cons: The 622.3H x 603.2W x 568.2D mm cabinet and 104.3 kg mass make this a serious placement and moving commitment. A sealed cabinet still needs careful placement and calibration to avoid room-mode peaks.
Full Paradigm Signature Sub 2 review and specifications →
| AES Input | No |
|---|---|
| Aux Input | No |
| CEA-2010-A Average (40-80Hz) | 123.7 dB |
| Cabinet Color | black, wood |
| Coaxial Input | No |
| Country | Canada |
| Dimensions | 24.5”H x 23.7”W x 22.4”D (622.3 x 603.2 x 568.2 mm) |
| Drivers | 6x 10” (254mm) driver |
| Enclosure | sealed |
| HDMI Input | No |
| Inputs | RCA (stereo/mono), LFE, XLR (balanced) |
| Measurement Source | Audioholics |
| Optical Input | No |
| Output SPL at 10 Hz | 97.7 dB |
| Output SPL at 12.5 Hz | 101.2 dB |
| Output SPL at 15 Hz | 105.6 dB |
| Output SPL at 20 Hz | 109.4 dB |
| Output SPL at 25 Hz | 112.9 dB |
| Output SPL at 31.5 Hz | 116.2 dB |
| Output SPL at 40 Hz | 119.9 dB |
| Output SPL at 50 Hz | 123.2 dB |
| Output SPL at 63 Hz | 125.5 dB |
| Output SPL at 80 Hz | 126.0 dB |
| Output SPL at 100 Hz | 125.1 dB |
| Output SPL at 125 Hz | 123.3 dB |
| RCA Input | Yes |
| TRS Input | No |
| USB Input | No |
| Warranty | 3 |
| Weight | 229.9 lbs (104.3 kg) |
| XLR Input | Yes |
- Links
- Reviews, Comparisons and Sound Samples
- Independently measured by Audioholics; the published figures above come from this ASR subwoofer measurement thread.
- Head-to-Head Comparisons
RBH Sound Unrivaled 21-SF/R: $11,995 eBay
Pros: Manufacturer-supplied CEA-2010 data records 112.3 dB at 20 Hz and 118.8 dB through 40-80 Hz, with a passing result down to 10 Hz. The 21” carbon fiber driver and 4,000W thermal power handling gave this sub the first Extreme Bassaholic room rating on record.
Cons: At around 333 lbs, moving or placing this cabinet is a multi-person job, and the price puts it well outside typical home theater budgets.
Full RBH Sound Unrivaled 21-SF/R review and specifications →
| CEA-2010-A Average (40-80Hz) | 118.8 dB |
|---|---|
| Country | United States |
| Dimensions | 27.3”H x 43”W x 21”D (692.2 x 1092.2 x 533.4 mm) |
| Drivers | 21” carbon fiber driver |
| Enclosure | sealed |
| Frequency Response | 12-80Hz, ±3dB |
| Measurement Source | Manufacturer |
| Output SPL at 10 Hz | 91.3 dB |
| Output SPL at 12.5 Hz | 97.7 dB |
| Output SPL at 14 Hz | 100.8 dB |
| Output SPL at 16 Hz | 105.5 dB |
| Output SPL at 20 Hz | 112.3 dB |
| Output SPL at 25 Hz | 117.2 dB |
| Output SPL at 31.5 Hz | 120.1 dB |
| Output SPL at 40 Hz | 119.5 dB |
| Output SPL at 50 Hz | 118.7 dB |
| Output SPL at 63 Hz | 118.4 dB |
| Output SPL at 80 Hz | 118.7 dB |
| Output SPL at 100 Hz | 119.2 dB |
| Power Handling | 4000W thermal power handling |
| Weight | 332.9 lbs (151.0 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- These figures are manufacturer-specified rather than independently measured.
- Head-to-Head Comparisons