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 #142 (rated 3.3/5) for the SVS SB13-Plus.
The Monoprice Monolith 16 THX Ultra is the better-sounding option. A THX Ultra certified 16 inch ported subwoofer with huge output for far less money than most rivals, now worth finding used. Watch for: Heavy at 172 lbs (78 kg) and ported design can interact with room acoustics.
What the SVS SB13-Plus does well: A sealed 13 inch subwoofer with XLR and RCA inputs in a compact cube cabinet, now discontinued. Watch for: Deep-bass output is more limited than the strong 40-80 Hz result suggests, so it is not the right choice when the lowest movie effects are the priority.
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 sealed 13 inch subwoofer with XLR and RCA inputs in a compact cube cabinet, now discontinued.
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 | SVS SB13-Plus | |
|---|---|---|
| Price | $2,300 Discontinued | $1,399 Discontinued |
| Ranked | #19 of 143 in Large Home Subwoofers (Over 75 lbs) | #142 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 | 92.3 dB |
| Output SPL at 25 Hz | 123.3 dB | 97.2 dB |
| Output SPL at 31.5 Hz | 125.1 dB | 97.2 dB |
| Output SPL at 40 Hz | 126.3 dB | 108.1 dB |
| Output SPL at 50 Hz | 126.5 dB | 108.1 dB |
| Output SPL at 63 Hz | 126.6 dB | 108.1 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 | 108.1 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) | 17”H x 17”W x 18”D (431.8 x 431.8 x 457.2 mm) |
| Weight | 171.5 lbs (77.8 kg) | 95 lbs (43.1 kg) |
| Warranty | 5 | 5 |
| Cabinet Color | black | - |
| Country | United States | United States |
| Measurement Source | Audioholics | Brent Butterworth |
| Drivers | 16” (406mm) driver | 13” (330mm) driver |
| Inputs | XLR, RCA, XLR out | XLR (balanced), 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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