Short answer: both are discontinued, so this only matters if you are buying used. Used, the Power Sound Audio (PSA) T18 is the better pick: it ranks #8 of 143 subwoofers by sound quality (rated 4.5/5), against #19 (rated 4.4/5) for the Monoprice Monolith 16 THX Ultra. If you want one new, the JTR Speakers Orbit Shifter PRO ranks #1 at $4,499.
Why pick the Monoprice Monolith 16 THX Ultra: A THX Ultra certified 16 inch ported subwoofer with huge output for far less money than most rivals, now worth finding used. The catch: Heavy at 172 lbs (78 kg) and ported design can interact with room acoustics.
The case for the Power Sound Audio (PSA) T18: A sealed 18 inch subwoofer with deep, powerful bass for large home theaters and balanced inputs for pro style setups. The catch: The 596.9H x 787.4W x 698.5D mm cabinet and 170 lbs (77.1 kg) mass make this a serious placement and moving commitment.
Buy the Power Sound Audio (PSA) T18 only if you find one used in good condition; both are discontinued, and it is the better rated of the two. For a new speaker, start with the JTR Speakers Orbit Shifter PRO instead.
Looking for alternatives? See the complete 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 sealed 18 inch subwoofer with deep, powerful bass for large home theaters and balanced inputs for pro style setups.
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 | Power Sound Audio (PSA) T18 | |
|---|---|---|
| Price | $2,300 Discontinued | $4,995 Discontinued |
| Ranked | #19 of 143 in Large Home Subwoofers (Over 75 lbs) | #8 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | sealed |
| Output SPL at 15 Hz | 107.3 dB | - |
| Output SPL at 20 Hz | 118.4 dB | 115.7 dB |
| Output SPL at 25 Hz | 123.3 dB | 115.7 dB |
| Output SPL at 31.5 Hz | 125.1 dB | 115.7 dB |
| Output SPL at 40 Hz | 126.3 dB | 129.7 dB |
| Output SPL at 50 Hz | 126.5 dB | 129.7 dB |
| Output SPL at 63 Hz | 126.6 dB | 129.7 dB |
| Output SPL at 80 Hz | 126.8 dB | - |
| Output SPL at 100 Hz | 127.2 dB | - |
| Output SPL at 125 Hz | 127.6 dB | - |
| CEA-2010-A Average (40-80Hz) | 126.5 dB | 129.7 dB (avg of 3/4 bands) |
| Dimensions | 25.6”H x 22”W x 28.1”D (650.2 x 558.8 x 713.7 mm) | 23.5”H x 31”W x 27.5”D (596.9 x 787.4 x 698.5 mm) |
| Weight | 171.5 lbs (77.8 kg) | 170 lbs (77.1 kg) |
| Warranty | 5 | 5 |
| Cabinet Color | black | - |
| Country | United States | United States |
| Measurement Source | Audioholics | Manufacturer |
| Drivers | 16” (406mm) driver | 18” (457mm) driver |
| Inputs | XLR, RCA, XLR out | XLR (balanced, with loop output), 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 |
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