Short answer: the Rythmik F18. It ranks #85 of 143 subwoofers by sound quality (rated 4.1/5) at $2,344 and is still sold new; the BK Electronics Monolith-DF ranks #141 (rated 3.3/5) and is discontinued, so it is only an option used.
The Rythmik F18 is the better-sounding choice. A massive sealed 18 inch subwoofer with tight, powerful bass and balanced XLR inputs, built for big home theaters. Watch for: The 520.7H x 520.7W x 533.4D mm cabinet and 115.1 lbs (52.2 kg) mass make this a serious placement and moving commitment.
Why pick the BK Electronics Monolith-DF: A down ported 12 inch subwoofer with balanced XLR and RCA inputs at a low price, now discontinued. The catch: 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 Rythmik F18. It is rated higher for sound quality; the BK Electronics Monolith-DF is no longer sold new.
Looking for alternatives? See the complete Subwoofers rankings.
A massive sealed 18 inch subwoofer with tight, powerful bass and balanced XLR inputs, built for big home theaters.
A down ported 12 inch subwoofer with balanced XLR and RCA inputs at a low price, now discontinued.
Prices on this page were last checked October 31, 2026 at 7:11 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
| Rythmik F18 | BK Electronics Monolith-DF | |
|---|---|---|
| Price | $2,344 | £406.95 Discontinued |
| Ranked | #85 of 143 in Large Home Subwoofers (Over 75 lbs) | #141 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | sealed | ported, bottom |
| Output SPL at 10 Hz | 93.7 dB | - |
| Output SPL at 12.5 Hz | 97.4 dB | - |
| Output SPL at 15 Hz | 102.0 dB | 91.3 dB |
| Output SPL at 20 Hz | 106.2 dB | 102.0 dB |
| Output SPL at 25 Hz | 110.9 dB | 106.4 dB |
| Output SPL at 31.5 Hz | 114.3 dB | 108.3 dB |
| Output SPL at 40 Hz | 117.1 dB | 108.6 dB |
| Output SPL at 50 Hz | 119.1 dB | 108.7 dB |
| Output SPL at 63 Hz | 120.5 dB | 108.6 dB |
| Output SPL at 80 Hz | 121.2 dB | 107.7 dB |
| Output SPL at 100 Hz | 121.4 dB | - |
| Output SPL at 125 Hz | 121.4 dB | - |
| CEA-2010-A Average (40-80Hz) | 119.5 dB | 108.4 dB |
| Dimensions | 20.5”H x 20.5”W x 21”D (520.7 x 520.7 x 533.4 mm) | 23.8”H x 21.3”W x 16.5”D (603.8 x 539.8 x 419.9 mm) |
| Weight | 115.1 lbs (52.2 kg) | 103.2 lbs (46.8 kg) |
| Warranty | 5/3 | 2 |
| Cabinet Color | black | black, wood |
| Country | United States | United Kingdom |
| Measurement Source | Data-bass | Ilkka Rissanen |
| Drivers | 18” (457mm) driver | 12” (305mm) driver with ported design |
| Inputs | XLR (2), RCA (line/LFE) | XLR (balanced), RCA (unbalanced) |
| 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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