Short answer: the WW Speaker Cabinets X21 - B&C 21DS115-4. It ranks #1 of 7 subwoofers at $3995; the JBL 4645C ranks #5 and costs $4999, so there is not much of a tradeoff to weigh.
On the WW Speaker Cabinets X21 - B&C 21DS115-4 side: 21-inch driver in a large ported cabinet delivers 131.3dB CEA-2010-A average, the highest output of any passive subwoofer tested. Set against that: Premium $3,995 price, massive 52 kg cabinet, and ported room gain dependency.
Buy the JBL 4645C if the price matters more than the ranking. Buy the WW Speaker Cabinets X21 - B&C 21DS115-4 if the ranking matters more than the price.
Specifications Side By Side
| JBL 4645C | WW Speaker Cabinets X21 - B&C 21DS115-4 | |
|---|---|---|
| Price | $4999 | $3995 |
| Ranked | #5 of 7 in Large Passive Home Subwoofers (Over 75 lbs) | #1 of 7 in Large Passive Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | ported, front |
| Passive | Yes | Yes |
| Output SPL at 20 Hz | 98.9 dB | 121.9 dB |
| Output SPL at 25 Hz | 114.0 dB | 120.8 dB |
| Output SPL at 31.5 Hz | 118.7 dB | 122.5 dB |
| Output SPL at 40 Hz | 122.0 dB | 126.7 dB |
| Output SPL at 50 Hz | 123.7 dB | 129.2 dB |
| Output SPL at 63 Hz | 129.7 dB | 132.9 dB |
| Output SPL at 80 Hz | 133.9 dB | 136.3 dB |
| Output SPL at 100 Hz | 135.1 dB | 139.0 dB |
| Output SPL at 125 Hz | 135.8 dB | 140.1 dB |
| CEA-2010-A Average (40-80Hz) | 127.3 dB | 131.3 dB |
| Dimensions | 39.75"H x 26.5"W x 17.75"D (1009.6 x 673.1 x 450.8 mm) | 24.0"H x 32.0"W x 32.0"D (609.6 x 812.8 x 812.8 mm) |
| Weight | 138 lbs / 62.6 kg | 115.1 lbs / 52.2 kg |
| Warranty | 5/3/2 | - |
| Cabinet Color | black | - |
| Country | United States | - |
| Measurement Source | Data-bass | Data-bass |
| Drivers | 18" (457mm) driver | 21" (533mm) driver |
| Output SPL at 12.5 Hz | - | 96.2 dB |
| Output SPL at 15 Hz | - | 111.9 dB |
The Two Speakers In Full
JBL 4645C: $4999
| CEA-2010-A Average (40-80Hz) | 127.3 dB |
|---|---|
| Cabinet Color | black |
| Country | United States |
| Dimensions | 39.75"H x 26.5"W x 17.75"D (1009.6 x 673.1 x 450.8 mm) |
| Drivers | 18" (457mm) driver |
| Enclosure | ported, front |
| Measurement Source | Data-bass |
| Output SPL at 20 Hz | 98.9 dB |
| Output SPL at 25 Hz | 114.0 dB |
| Output SPL at 31.5 Hz | 118.7 dB |
| Output SPL at 40 Hz | 122.0 dB |
| Output SPL at 50 Hz | 123.7 dB |
| Output SPL at 63 Hz | 129.7 dB |
| Output SPL at 80 Hz | 133.9 dB |
| Output SPL at 100 Hz | 135.1 dB |
| Output SPL at 125 Hz | 135.8 dB |
| Passive | Yes |
| Warranty | 5/3/2 |
| Weight | 138 lbs / 62.6 kg |
- Head-to-Head Comparisons
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WW Speaker Cabinets X21 - B&C 21DS115-4: $3995
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.
| CEA-2010-A Average (40-80Hz) | 131.3 dB |
|---|---|
| Dimensions | 24.0"H x 32.0"W x 32.0"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 |
- Head-to-Head Comparisons
- Links
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Product prices and availability were last checked August 9, 2026 at 6:57 AM UTC 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.