Short answer: the WW Speaker Cabinets X21 - B&C 21DS115-4. It ranks #3 of 110 subwoofers by sound quality at $3995; the JBL 4645C ranks #24 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 (114.6 lbs) cabinet, and ported room gain dependency.
Buy the WW Speaker Cabinets X21 - B&C 21DS115-4. It ranks higher for sound quality than the JBL 4645C and costs less, which settles it without a real tradeoff to make.
Still deciding? The full Subwoofers rankings cover every ranked option.
Specifications Side By Side
| JBL 4645C | WW Speaker Cabinets X21 - B&C 21DS115-4 | |
|---|---|---|
| Price | $4999 Passive | $3995 Passive |
| Ranked | #24 of 110 in Large Home Subwoofers (Over 75 lbs) | #3 of 110 in Large 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 | 39.7"H x 26.5"W x 17.7"D (1009.6 x 673.1 x 450.8 mm) | 24"H x 32"W x 32"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 | 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 |
Related Speaker Comparisons
More worthwhile head-to-heads for WW Speaker Cabinets X21 - B&C 21DS115-4:
- Pro Audio Technology LFC-24sm vs WW Speaker Cabinets X21 - B&C 21DS115-4
- JTR Speakers Captivator S2 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
Prices on this page were last checked September 22, 2026 at 5:11 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.
As an eBay Partner, we may be compensated if you make a purchase.
The Two Speakers In Full
JBL 4645C: $4999 Passive eBay
Pros: Independent CEA-2010 testing records 98.9 dB at 20 Hz and 127.3 dB through 40-80 Hz. The ported, front enclosure with 18” (457mm) driver is best suited to upper-bass support in a modest room.
Cons: Deep-bass output is limited relative to its midbass result, so it is not the right choice for the lowest movie effects. The 1009.6H x 673.1W x 450.8D mm cabinet and 62.6 kg mass still need deliberate placement and calibration.
Full JBL 4645C review and specifications →
| CEA-2010-A Average (40-80Hz) | 127.3 dB |
|---|---|
| Cabinet Color | black |
| Country | United States |
| Dimensions | 39.7"H x 26.5"W x 17.7"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) |
- 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
- JBL 4645C vs Reaction Audio PV-15X
- JBL 4645C vs Monoprice Monolith 16 THX Ultra
- JBL 4645C vs Chase Home Theater SS18.1
- JBL 4645C vs Danley Sound Labs DTS10
- JBL 4645C vs JTR Speakers Growler (2015)
- JBL 4645C vs JTR Speakers Captivator S2
- JBL 4645C vs Pro Audio Technology LFC-24sm
- JBL 4645C vs HSU Research VTF-15H MK2
- See all 9 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 $3995 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 |
|---|---|
| Country | United States |
| 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 Captivator S2
- 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 Chase Home Theater SS18.1
- WW Speaker Cabinets X21 - B&C 21DS115-4 vs HSU Research VTF-15H MK2
- See all 9 comparisons