Short answer: the Rythmik F18, if you are buying new. The Monoprice Monolith M15-S measures as well as it (#88 vs #85 of 143 subwoofers, 4.1/5 vs 4.1/5) but is discontinued, so only consider it used; the Rythmik F18 is still sold new at $2,344.
Buy the Rythmik F18 if you want one new; the Monoprice Monolith M15-S is discontinued, so only look for it used.
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
| Monoprice Monolith M15-S | Rythmik F18 | |
|---|---|---|
| Price | $999 Discontinued | $2,344 |
| Ranked | #88 of 143 in Large Home Subwoofers (Over 75 lbs) | #85 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | sealed | sealed |
| Output SPL at 15 Hz | 100.1 dB | 102.0 dB |
| Output SPL at 20 Hz | 105.6 dB | 106.2 dB |
| Output SPL at 25 Hz | 111.2 dB | 110.9 dB |
| Output SPL at 31.5 Hz | 115.2 dB | 114.3 dB |
| Output SPL at 40 Hz | 118.4 dB | 117.1 dB |
| Output SPL at 50 Hz | 119.3 dB | 119.1 dB |
| Output SPL at 63 Hz | 119.6 dB | 120.5 dB |
| Output SPL at 80 Hz | 118.9 dB | 121.2 dB |
| Output SPL at 100 Hz | 119.1 dB | 121.4 dB |
| Output SPL at 125 Hz | 118.9 dB | 121.4 dB |
| CEA-2010-A Average (40-80Hz) | 119.0 dB | 119.5 dB |
| Dimensions | 23.5”H x 16.7”W x 19.7”D (596.9 x 424.2 x 500.4 mm) | 20.5”H x 20.5”W x 21”D (520.7 x 520.7 x 533.4 mm) |
| Warranty | 5 | 5/3 |
| Country | United States | United States |
| Measurement Source | Manufacturer | Data-bass |
| Weight | 80 lbs (36.3 kg) | 115.1 lbs (52.2 kg) |
| Drivers | 15” (381mm) driver | 18” (457mm) driver |
| Output SPL at 10 Hz | - | 93.7 dB |
| Output SPL at 12.5 Hz | - | 97.4 dB |
| Cabinet Color | - | black |
| Inputs | - | XLR (2), RCA (line/LFE) |
| XLR Input | - | Yes |
| RCA Input | - | Yes |
| TRS Input | - | No |
| Optical Input | - | No |
| Coaxial Input | - | No |
| USB Input | - | No |
| HDMI Input | - | No |
| AES Input | - | No |
| Aux Input | - | No |
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