Short answer: the Rythmik FV15HP, if you are buying new. The Monoprice Monolith 13 THX Ultra measures as well as it (#63 vs #55 of 143 subwoofers, 4.2/5 vs 4.2/5) but is discontinued, so only consider it used; the Rythmik FV15HP is still sold new at $2,127.
The case for the Rythmik FV15HP: A 15 inch ported subwoofer with output matching pricier rivals, plus balanced and RCA inputs for flexible setups. Watch for: Premium price ($2127), ported design room gain dependency, and mid-to-large 114.6 lbs (52 kg) footprint.
The case for the Monoprice Monolith 13 THX Ultra: A THX Ultra certified 13 inch ported subwoofer with deep, strong bass for large rooms at a good price used. The tradeoff: The 604.5H x 515.6W x 739.1D mm cabinet and 153.2 lbs (69.5 kg) mass make this a serious placement and moving commitment.
Buy the Rythmik FV15HP if you want one new; the Monoprice Monolith 13 THX Ultra is discontinued, so only look for it used.
Looking for alternatives? See the complete Subwoofers rankings.
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
| Rythmik FV15HP | Monoprice Monolith 13 THX Ultra | |
|---|---|---|
| Price | $2,127 | $1,700 Discontinued |
| Ranked | #55 of 143 in Large Home Subwoofers (Over 75 lbs) | #63 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | ported, front |
| Output SPL at 12.5 Hz | 92.8 dB | 94.0 dB |
| Output SPL at 15 Hz | 105.1 dB | 109.1 dB |
| Output SPL at 20 Hz | 111.1 dB | 115.0 dB |
| Output SPL at 25 Hz | 116.1 dB | 118.0 dB |
| Output SPL at 31.5 Hz | 120.0 dB | 119.5 dB |
| Output SPL at 40 Hz | 122.5 dB | 120.3 dB |
| Output SPL at 50 Hz | 122.1 dB | 120.7 dB |
| Output SPL at 63 Hz | 121.8 dB | 121.4 dB |
| Output SPL at 80 Hz | 121.4 dB | 122.1 dB |
| Output SPL at 100 Hz | 121.2 dB | 122.7 dB |
| Output SPL at 125 Hz | 121.1 dB | 123.8 dB |
| CEA-2010-A Average (40-80Hz) | 122.0 dB | 121.1 dB |
| Dimensions | 24.5”H x 18.2”W x 24.2”D (622.3 x 463.5 x 615.9 mm) | 23.8”H x 20.3”W x 29.1”D (604.5 x 515.6 x 739.1 mm) |
| Weight | 115.1 lbs (52.2 kg) | 153.2 lbs (69.5 kg) |
| Warranty | 5/3 | 5 |
| Cabinet Color | black, white | black |
| Country | United States | United States |
| Measurement Source | Audioholics | Audioholics |
| Drivers | 15” (381mm) driver | 13” (330mm) driver |
| Inputs | XLR (2), RCA (line/LFE) | XLR (stereo balanced), RCA (stereo/mono) |
| 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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