Short answer: the JTR Speakers Captivator S2 ranks #9 of 110 subwoofers by sound quality at $3995; the WW Speaker Cabinets X21 - B&C 21DS115-4 ranks #3 at $3995. Close enough in price that the sound-quality gap is the deciding factor.
What the JTR Speakers Captivator S2 offers: Independent CEA-2010 testing records 115.1 dB at 20 Hz and 129.4 dB through 40-80 Hz. The sealed enclosure with 2x 18” (457mm) drivers has the headroom for demanding film bass in a large room. Watch for: The 1016.0H x 533.4W x 457.2D mm cabinet and 99.8 kg mass make this a serious placement and moving commitment. A sealed cabinet still needs careful placement and calibration to avoid room-mode peaks.
What the WW Speaker Cabinets X21 - B&C 21DS115-4 offers: 21-inch driver in a large ported cabinet delivers 131.3dB CEA-2010-A average, the highest output of any passive subwoofer tested. Watch for: Premium $3,995 price, massive 52 kg cabinet, and ported room gain dependency.
Buy the WW Speaker Cabinets X21 - B&C 21DS115-4. It ranks higher for sound quality than the JTR Speakers Captivator S2 at the same price, which settles it without a real tradeoff to make.
Still deciding? The full Subwoofers rankings cover every ranked option.
Specifications Side By Side
| JTR Speakers Captivator S2 | WW Speaker Cabinets X21 - B&C 21DS115-4 | |
|---|---|---|
| Price | $3995 | $3995 Passive |
| Ranked | #9 of 110 in Large Home Subwoofers (Over 75 lbs) | #3 of 110 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | sealed | ported, front |
| Output SPL at 10 Hz | 100.3 dB | - |
| Output SPL at 12.5 Hz | 103.3 dB | 96.2 dB |
| Output SPL at 15 Hz | 108.7 dB | 111.9 dB |
| Output SPL at 20 Hz | 115.1 dB | 121.9 dB |
| Output SPL at 25 Hz | 119.7 dB | 120.8 dB |
| Output SPL at 31.5 Hz | 124.8 dB | 122.5 dB |
| Output SPL at 40 Hz | 129.3 dB | 126.7 dB |
| Output SPL at 50 Hz | 130.3 dB | 129.2 dB |
| Output SPL at 63 Hz | 129.4 dB | 132.9 dB |
| Output SPL at 80 Hz | 128.5 dB | 136.3 dB |
| Output SPL at 100 Hz | 128.1 dB | 139.0 dB |
| Output SPL at 125 Hz | 128.0 dB | 140.1 dB |
| CEA-2010-A Average (40-80Hz) | 129.4 dB | 131.3 dB |
| Dimensions | 40"H x 21"W x 18"D (1016.0 x 533.4 x 457.2 mm) | 24"H x 32"W x 32"D (609.6 x 812.8 x 812.8 mm) |
| Weight | 220 lbs (99.8 kg) | 115.1 lbs (52.2 kg) |
| Warranty | 5/3 | - |
| Country | United States | - |
| Measurement Source | Data-bass | Data-bass |
| Drivers | 2x 18" (457mm) drivers | 21" (533mm) driver |
| Passive | - | Yes |
Related Speaker Comparisons
How WW Speaker Cabinets X21 - B&C 21DS115-4 compares with other leading options:
- Pro Audio Technology LFC-24sm vs WW Speaker Cabinets X21 - B&C 21DS115-4
- JTR Speakers Growler (2015) vs WW Speaker Cabinets X21 - B&C 21DS115-4
- Danley Sound Labs DTS10 vs WW Speaker Cabinets X21 - B&C 21DS115-4
- Monoprice Monolith 16 THX Ultra vs WW Speaker Cabinets X21 - B&C 21DS115-4
- Reaction Audio PV-15X vs WW Speaker Cabinets X21 - B&C 21DS115-4
Prices on this page were last checked September 14, 2026 at 1:47 AM 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
JTR Speakers Captivator S2: $3995 eBay
Pros: Independent CEA-2010 testing records 115.1 dB at 20 Hz and 129.4 dB through 40-80 Hz. The sealed enclosure with 2x 18” (457mm) drivers has the headroom for demanding film bass in a large room.
Cons: The 1016.0H x 533.4W x 457.2D mm cabinet and 99.8 kg mass make this a serious placement and moving commitment. A sealed cabinet still needs careful placement and calibration to avoid room-mode peaks.
Notes: Replaced by “RS2”
Full JTR Speakers Captivator S2 review and specifications →
| CEA-2010-A Average (40-80Hz) | 129.4 dB |
|---|---|
| Country | United States |
| Dimensions | 40"H x 21"W x 18"D (1016.0 x 533.4 x 457.2 mm) |
| Drivers | 2x 18" (457mm) drivers |
| Enclosure | sealed |
| Measurement Source | Data-bass |
| Output SPL at 10 Hz | 100.3 dB |
| Output SPL at 12.5 Hz | 103.3 dB |
| Output SPL at 15 Hz | 108.7 dB |
| Output SPL at 20 Hz | 115.1 dB |
| Output SPL at 25 Hz | 119.7 dB |
| Output SPL at 31.5 Hz | 124.8 dB |
| Output SPL at 40 Hz | 129.3 dB |
| Output SPL at 50 Hz | 130.3 dB |
| Output SPL at 63 Hz | 129.4 dB |
| Output SPL at 80 Hz | 128.5 dB |
| Output SPL at 100 Hz | 128.1 dB |
| Output SPL at 125 Hz | 128.0 dB |
| Warranty | 5/3 |
| Weight | 220 lbs (99.8 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Independently measured by Data-bass; the published figures above come from this ASR subwoofer measurement thread.
- Head-to-Head Comparisons
- JTR Speakers Captivator S2 vs Power Sound Audio (PSA) T18
- JTR Speakers Captivator S2 vs Power Sound Audio (PSA) V3600I
- JTR Speakers Captivator S2 vs Funk Audio Ultra 24.0
- JTR Speakers Captivator S2 vs JTR Speakers Captivator 215PRO
- JTR Speakers Captivator S2 vs JTR Speakers Captivator 4000ULF
- JTR Speakers Captivator S2 vs Power Sound Audio (PSA) TRIAX
- JTR Speakers Captivator S2 vs JTR Speakers Growler (2015)
- JTR Speakers Captivator S2 vs Pro Audio Technology LFC-24sm
- See all 23 comparisons
WW Speaker Cabinets X21 - B&C 21DS115-4: $3995 Passive eBay
Pros: 21-inch driver in a large ported cabinet delivers 131.3dB CEA-2010-A average, the highest output of any passive subwoofer tested.
Cons: Premium $3,995 price, massive 52 kg cabinet, and ported room gain dependency.
Full WW Speaker Cabinets X21 - B&C 21DS115-4 review and specifications →
| CEA-2010-A Average (40-80Hz) | 131.3 dB |
|---|---|
| Dimensions | 24"H x 32"W x 32"D (609.6 x 812.8 x 812.8 mm) |
| Drivers | 21" (533mm) driver |
| Enclosure | ported, front |
| Measurement Source | Data-bass |
| Output SPL at 12.5 Hz | 96.2 dB |
| Output SPL at 15 Hz | 111.9 dB |
| Output SPL at 20 Hz | 121.9 dB |
| Output SPL at 25 Hz | 120.8 dB |
| Output SPL at 31.5 Hz | 122.5 dB |
| Output SPL at 40 Hz | 126.7 dB |
| Output SPL at 50 Hz | 129.2 dB |
| Output SPL at 63 Hz | 132.9 dB |
| Output SPL at 80 Hz | 136.3 dB |
| Output SPL at 100 Hz | 139.0 dB |
| Output SPL at 125 Hz | 140.1 dB |
| Passive | Yes |
| Weight | 115.1 lbs (52.2 kg) |
- Reviews, Comparisons and Sound Samples
- Independently measured by Data-bass; the published figures above come from this ASR subwoofer measurement thread.
- Head-to-Head Comparisons
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs Pro Audio Technology LFC-24sm
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs JTR Speakers Growler (2015)
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs Danley Sound Labs DTS10
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs Monoprice Monolith 16 THX Ultra
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs Reaction Audio PV-15X
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs JBL 4645C
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs Chase Home Theater SS18.1
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs HSU Research VTF-3 MK5 HP