Short answer: the SVS SB13-Plus on measured sound quality, the Monoprice THX 121456 on price. The SVS SB13-Plus ranks #95 of 97 subwoofers at $1399. The Monoprice THX 121456 ranks #96 at $899, $500 cheaper.
What the Monoprice THX 121456 offers: Independent CEA-2010 testing records 94.6 dB at 20 Hz and 108.0 dB through 40-80 Hz. The subwoofer enclosure with 12” (305mm) driver delivers substantial upper-bass output for movie effects and music. 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. The 0.0H x 0.0W x 0.0D mm cabinet and 44.7 kg mass still require deliberate placement and calibration.
What the SVS SB13-Plus offers: Independent CEA-2010 testing records 92.3 dB at 20 Hz and 108.1 dB (avg of 3/4 bands) through 40-80 Hz. The sealed enclosure with 13” (330mm) driver delivers substantial upper-bass output for movie effects and music. 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. The 431.8H x 431.8W x 457.2D mm cabinet and 43.1 kg mass still require deliberate placement and calibration.
Buy the Monoprice THX 121456 if the price is the priority over sound quality, or the SVS SB13-Plus if sound quality is the priority over the price.
Skip both if sound quality is the priority. There are better options higher up the 97 subwoofers.
Specifications Side By Side
| Monoprice THX 121456 | SVS SB13-Plus | |
|---|---|---|
| Price | $899 | $1399 |
| Ranked | #96 of 97 in Large Powered Home Subwoofers (Over 75 lbs) | #95 of 97 in Large Powered Home Subwoofers (Over 75 lbs) |
| Output SPL at 15 Hz | 92.0 dB | - |
| Output SPL at 20 Hz | 94.6 dB | 92.3 dB |
| Output SPL at 25 Hz | 100.1 dB | 97.2 dB |
| Output SPL at 31.5 Hz | 103.2 dB | 97.2 dB |
| Output SPL at 40 Hz | 104.7 dB | 108.1 dB |
| Output SPL at 50 Hz | 107.3 dB | 108.1 dB |
| Output SPL at 63 Hz | 109.3 dB | 108.1 dB |
| Output SPL at 80 Hz | 110.5 dB | - |
| CEA-2010-A Average (40-80Hz) | 108.0 dB | 108.1 dB (avg of 3/4 bands) |
| Dimensions | 0"H x 0"W x 0"D (0.0 x 0.0 x 0.0 mm) | 17"H x 17"W x 18"D (431.8 x 431.8 x 457.2 mm) |
| Country | United States | United States |
| Measurement Source | Brent Butterworth | Brent Butterworth |
| Weight | 98.5 lbs / 44.7 kg | 95 lbs / 43.1 kg |
| Drivers | 12" (305mm) driver | 13" (330mm) driver |
| Enclosure | - | sealed |
| Warranty | - | 5 |
Related Speaker Comparisons
More useful head-to-heads from the same speaker class:
- BK Electronics Monolith-DF vs Genelec HTS4B
- Genelec HTS4B vs Magico Audio ASUB
- Magico Audio ASUB vs Genelec 7070A
- SVS SB13-Plus vs BK Electronics Monolith-DF
- Genelec 7070A vs Velodyne Acoustics DD-15
Prices on this page were last checked September 8, 2026 at 6:02 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.
As an eBay Partner, we may be compensated if you make a purchase.
The Two Speakers In Full
Monoprice THX 121456: $899 eBay
Pros: Independent CEA-2010 testing records 94.6 dB at 20 Hz and 108.0 dB through 40-80 Hz. The subwoofer enclosure with 12” (305mm) driver delivers substantial upper-bass output for movie effects and music.
Cons: 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. The 0.0H x 0.0W x 0.0D mm cabinet and 44.7 kg mass still require deliberate placement and calibration.
Notes: Product # 121456
Full Monoprice THX 121456 review and specifications →
| CEA-2010-A Average (40-80Hz) | 108.0 dB |
|---|---|
| Country | United States |
| Dimensions | 0"H x 0"W x 0"D (0.0 x 0.0 x 0.0 mm) |
| Drivers | 12" (305mm) driver |
| Measurement Source | Brent Butterworth |
| Output SPL at 15 Hz | 92.0 dB |
| Output SPL at 20 Hz | 94.6 dB |
| Output SPL at 25 Hz | 100.1 dB |
| Output SPL at 31.5 Hz | 103.2 dB |
| Output SPL at 40 Hz | 104.7 dB |
| Output SPL at 50 Hz | 107.3 dB |
| Output SPL at 63 Hz | 109.3 dB |
| Output SPL at 80 Hz | 110.5 dB |
| Weight | 98.5 lbs / 44.7 kg |
- Reviews, Comparisons and Sound Samples
SVS SB13-Plus: $1399 eBay
Pros: Independent CEA-2010 testing records 92.3 dB at 20 Hz and 108.1 dB (avg of 3/4 bands) through 40-80 Hz. The sealed enclosure with 13” (330mm) driver delivers substantial upper-bass output for movie effects and music.
Cons: 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. The 431.8H x 431.8W x 457.2D mm cabinet and 43.1 kg mass still require deliberate placement and calibration.
Full SVS SB13-Plus review and specifications →
| CEA-2010-A Average (40-80Hz) | 108.1 dB (avg of 3/4 bands) |
|---|---|
| Country | United States |
| Dimensions | 17"H x 17"W x 18"D (431.8 x 431.8 x 457.2 mm) |
| Drivers | 13" (330mm) driver |
| Enclosure | sealed |
| Measurement Source | Brent Butterworth |
| Output SPL at 20 Hz | 92.3 dB |
| Output SPL at 25 Hz | 97.2 dB |
| Output SPL at 31.5 Hz | 97.2 dB |
| Output SPL at 40 Hz | 108.1 dB |
| Output SPL at 50 Hz | 108.1 dB |
| Output SPL at 63 Hz | 108.1 dB |
| Warranty | 5 |
| Weight | 95 lbs / 43.1 kg |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons