Short answer: the JTR Speakers Captivator 4000ULF on measured sound quality, the Rythmik F18 on price. The JTR Speakers Captivator 4000ULF ranks #6 of 143 subwoofers, rated 4.5/5, at $5,699. The Rythmik F18 ranks #85, rated 4.1/5, at $2,344, $3,355 cheaper.
Buy the JTR Speakers Captivator 4000ULF if sound quality is the priority over the price, or the Rythmik F18 if the price is the priority over sound quality.
Still deciding? The full Subwoofers rankings cover every ranked option.
Prices on this page were last checked November 7, 2026 at 7:34 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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Specifications Side By Side
| JTR Speakers Captivator 4000ULF | Rythmik F18 | |
|---|---|---|
| Price | $5,699 each | $2,344 |
| Ranked | #6 of 143 in Large Home Subwoofers (Over 75 lbs) | #85 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | sealed |
| Output SPL at 10 Hz | 111.0 dB | 93.7 dB |
| Output SPL at 12.5 Hz | 115.3 dB | 97.4 dB |
| Output SPL at 15 Hz | 119.3 dB | 102.0 dB |
| Output SPL at 20 Hz | 122.3 dB | 106.2 dB |
| Output SPL at 25 Hz | 126.1 dB | 110.9 dB |
| Output SPL at 31.5 Hz | 129.3 dB | 114.3 dB |
| Output SPL at 40 Hz | 130.7 dB | 117.1 dB |
| Output SPL at 50 Hz | 131.2 dB | 119.1 dB |
| Output SPL at 63 Hz | 130.9 dB | 120.5 dB |
| Output SPL at 80 Hz | 130.6 dB | 121.2 dB |
| Output SPL at 100 Hz | 130.5 dB | 121.4 dB |
| Output SPL at 125 Hz | 129.5 dB | 121.4 dB |
| CEA-2010-A Average (40-80Hz) | 130.8 dB | 119.5 dB |
| Dimensions | 41”H x 20.5”W x 39.5”D (1041.4 x 520.7 x 1003.3 mm) | 20.5”H x 20.5”W x 21”D (520.7 x 520.7 x 533.4 mm) |
| Weight | 265 lbs (120.2 kg) | 115.1 lbs (52.2 kg) |
| Warranty | 5/3 | 5/3 |
| Cabinet Color | black, custom | black |
| Country | United States | United States |
| Measurement Source | Data-bass | Data-bass |
| Drivers | 2x 18” (457mm) driver | 18” (457mm) driver |
| Inputs | XLR, RCA | XLR (2), RCA (line/LFE) |
| XLR Input | Yes | Yes |
| RCA Input | Yes | Yes |
| TRS Input | No | No |
| Optical Input | No | No |
| Coaxial Input | No | No |
| USB Input | No | No |
| HDMI Input | No | No |
| AES Input | No | No |
| Aux Input | No | No |
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