Short answer: both are discontinued, so this only matters if you are buying used. Used, the Monoprice Monolith 16 THX Ultra is the better pick: it ranks #19 of 143 subwoofers by sound quality (rated 4.4/5), against #30 (rated 4.3/5) for the JTR Speakers Captivator 1400.
What the Monoprice Monolith 16 THX Ultra does well: A THX Ultra certified 16 inch ported subwoofer with huge output for far less money than most rivals, now worth finding used. The tradeoff: Heavy at 172 lbs (78 kg) and ported design can interact with room acoustics.
The case for the JTR Speakers Captivator 1400: A low, wide 18 inch ported subwoofer with strong deep bass for movies, easy to tuck under a screen or riser. The tradeoff: The 508.0H x 762.0W x 571.5D mm cabinet and 142 lbs (64.4 kg) mass make this a serious placement and moving commitment.
Buy the Monoprice Monolith 16 THX Ultra only if you find one used in good condition; both are discontinued, and it is the better rated of the two.
Want more options? Browse the full Subwoofers rankings.
A THX Ultra certified 16 inch ported subwoofer with huge output for far less money than most rivals, now worth finding used.
A low, wide 18 inch ported subwoofer with strong deep bass for movies, easy to tuck under a screen or riser.
Prices on this page were last checked October 29, 2026 at 4:42 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
| Monoprice Monolith 16 THX Ultra | JTR Speakers Captivator 1400 | |
|---|---|---|
| Price | $2,300 Discontinued | $2,495 Discontinued |
| Ranked | #19 of 143 in Large Home Subwoofers (Over 75 lbs) | #30 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | ported, front |
| Output SPL at 15 Hz | 107.3 dB | 111.9 dB |
| Output SPL at 20 Hz | 118.4 dB | 116.1 dB |
| Output SPL at 25 Hz | 123.3 dB | 119.2 dB |
| Output SPL at 31.5 Hz | 125.1 dB | 121.7 dB |
| Output SPL at 40 Hz | 126.3 dB | 124.8 dB |
| Output SPL at 50 Hz | 126.5 dB | 126.4 dB |
| Output SPL at 63 Hz | 126.6 dB | 125.4 dB |
| Output SPL at 80 Hz | 126.8 dB | 124.0 dB |
| Output SPL at 100 Hz | 127.2 dB | 126.0 dB |
| Output SPL at 125 Hz | 127.6 dB | 124.7 dB |
| CEA-2010-A Average (40-80Hz) | 126.5 dB | 125.2 dB |
| Dimensions | 25.6”H x 22”W x 28.1”D (650.2 x 558.8 x 713.7 mm) | 20”H x 30”W x 22.5”D (508.0 x 762.0 x 571.5 mm) |
| Weight | 171.5 lbs (77.8 kg) | 142 lbs (64.4 kg) |
| Warranty | 5 | 5/3 |
| Cabinet Color | black | - |
| Country | United States | United States |
| Measurement Source | Audioholics | Data-bass |
| Drivers | 16” (406mm) driver | 18” (457mm) driver |
| Inputs | XLR, RCA, XLR out | XLR, RCA |
| 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 |
| Output SPL at 12.5 Hz | - | 99.3 dB |
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