Short answer: the JTR Speakers Captivator 4000ULF for better sound quality, the Monoprice Monolith M15-S for the lower price. The JTR Speakers Captivator 4000ULF ranks #6 of 110 subwoofers, rated 4.5/5, at $5699. The Monoprice Monolith M15-S ranks #72, rated 4.1/5, at $999, $4700 cheaper.
Buy the JTR Speakers Captivator 4000ULF if sound quality matters more than the price. Buy the Monoprice Monolith M15-S if the price matters more than sound quality.
Want more options? Browse the full Subwoofers rankings.
Specifications Side By Side
| JTR Speakers Captivator 4000ULF | Monoprice Monolith M15-S | |
|---|---|---|
| Price | $5,000 | $999 |
| Ranked | #6 of 110 in Large Home Subwoofers (Over 75 lbs) | #72 of 110 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | sealed |
| Output SPL at 10 Hz | 111.0 dB | - |
| Output SPL at 12.5 Hz | 115.3 dB | - |
| Output SPL at 15 Hz | 119.3 dB | 100.1 dB |
| Output SPL at 20 Hz | 122.3 dB | 105.6 dB |
| Output SPL at 25 Hz | 126.1 dB | 111.2 dB |
| Output SPL at 31.5 Hz | 129.3 dB | 115.2 dB |
| Output SPL at 40 Hz | 130.7 dB | 118.4 dB |
| Output SPL at 50 Hz | 131.2 dB | 119.3 dB |
| Output SPL at 63 Hz | 130.9 dB | 119.6 dB |
| Output SPL at 80 Hz | 130.6 dB | 118.9 dB |
| Output SPL at 100 Hz | 130.5 dB | 119.1 dB |
| Output SPL at 125 Hz | 129.5 dB | 118.9 dB |
| CEA-2010-A Average (40-80Hz) | 130.8 dB | 119.0 dB |
| Dimensions | 41"H x 20.5"W x 39.5"D (1041.4 x 520.7 x 1003.3 mm) | 23.5"H x 16.7"W x 19.7"D (596.9 x 424.2 x 500.4 mm) |
| Weight | 265 lbs (120.2 kg) | 80 lbs (36.3 kg) |
| Warranty | 5/3 | 5 |
| Cabinet Color | black, custom | - |
| Country | United States | United States |
| Measurement Source | Data-bass | Manufacturer |
| Drivers | 2x 18" (457mm) driver | 15" (381mm) driver |
| Inputs | XLR, RCA | - |
| 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 | - |
Related Speaker Comparisons
How JTR Speakers Captivator 4000ULF compares with other leading options:
- JTR Speakers Captivator 4000ULF vs JTR Speakers Orbit Shifter PRO
- JTR Speakers Captivator 4000ULF vs JTR Speakers Orbit Shifter LFU
- JTR Speakers Captivator 4000ULF vs Power Sound Audio (PSA) TRIAX
- JTR Speakers Captivator 215PRO vs JTR Speakers Captivator 4000ULF
- JTR Speakers Captivator 4000ULF vs Power Sound Audio (PSA) T18
Prices on this page were last checked September 23, 2026 at 11:24 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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The Two Speakers In Full
JTR Speakers Captivator 4000ULF: $5,000 JTR Speakers eBay
Pros: Independent CEA-2010 testing records 122.3 dB at 20 Hz and 130.8 dB through 40-80 Hz. The ported, front enclosure with 2x 18” (457mm) driver has the headroom for demanding film bass in a large room.
Cons: The 1041.4H x 520.7W x 1003.3D mm cabinet and 120.2 kg mass make this a serious placement and moving commitment. Ported output does not solve room modes, so careful placement and calibration remain essential.
Full JTR Speakers Captivator 4000ULF review and specifications →
| AES Input | No |
|---|---|
| Aux Input | No |
| CEA-2010-A Average (40-80Hz) | 130.8 dB |
| Cabinet Color | black, custom |
| Coaxial Input | No |
| Country | United States |
| Dimensions | 41"H x 20.5"W x 39.5"D (1041.4 x 520.7 x 1003.3 mm) |
| Drivers | 2x 18" (457mm) driver |
| Enclosure | ported, front |
| HDMI Input | No |
| Inputs | XLR, RCA |
| Measurement Source | Data-bass |
| Optical Input | No |
| Output SPL at 10 Hz | 111.0 dB |
| Output SPL at 12.5 Hz | 115.3 dB |
| Output SPL at 15 Hz | 119.3 dB |
| Output SPL at 20 Hz | 122.3 dB |
| Output SPL at 25 Hz | 126.1 dB |
| Output SPL at 31.5 Hz | 129.3 dB |
| Output SPL at 40 Hz | 130.7 dB |
| Output SPL at 50 Hz | 131.2 dB |
| Output SPL at 63 Hz | 130.9 dB |
| Output SPL at 80 Hz | 130.6 dB |
| Output SPL at 100 Hz | 130.5 dB |
| Output SPL at 125 Hz | 129.5 dB |
| RCA Input | Yes |
| TRS Input | No |
| USB Input | No |
| Warranty | 5/3 |
| Weight | 265 lbs (120.2 kg) |
| XLR Input | Yes |
- Links
- Reviews, Comparisons and Sound Samples
- Independently measured by Data-bass; the published figures above come from this ASR subwoofer measurement thread.
- Head-to-Head Comparisons
- JTR Speakers Captivator 4000ULF vs JTR Speakers Captivator 215PRO
- JTR Speakers Captivator 4000ULF vs Power Sound Audio (PSA) TRIAX
- JTR Speakers Captivator 4000ULF vs Power Sound Audio (PSA) T18
- JTR Speakers Captivator 4000ULF vs JTR Speakers Captivator S2
- JTR Speakers Captivator 4000ULF vs JTR Speakers Orbit Shifter LFU
- JTR Speakers Captivator 4000ULF vs JTR Speakers Orbit Shifter PRO
- JTR Speakers Captivator 4000ULF vs Monoprice Monolith 16 THX Ultra
- JTR Speakers Captivator 4000ULF vs Reaction Audio PV-15X
- See all 15 comparisons
Monoprice Monolith M15-S: $999 eBay
Pros: Published CEA-2010 specifications list 105.6 dB at 20 Hz and 119.0 dB through 40-80 Hz. The sealed enclosure with 15” (381mm) driver has the headroom for demanding film bass in a large room.
Cons: The 596.9H x 424.2W x 500.4D mm cabinet and 36.3 kg mass make this a serious placement and moving commitment. A sealed cabinet still needs careful placement and calibration to avoid room-mode peaks.
Notes: Product # 35141
Full Monoprice Monolith M15-S review and specifications →
| CEA-2010-A Average (40-80Hz) | 119.0 dB |
|---|---|
| Country | United States |
| Dimensions | 23.5"H x 16.7"W x 19.7"D (596.9 x 424.2 x 500.4 mm) |
| Drivers | 15" (381mm) driver |
| Enclosure | sealed |
| Measurement Source | Manufacturer |
| Output SPL at 15 Hz | 100.1 dB |
| Output SPL at 20 Hz | 105.6 dB |
| Output SPL at 25 Hz | 111.2 dB |
| Output SPL at 31.5 Hz | 115.2 dB |
| Output SPL at 40 Hz | 118.4 dB |
| Output SPL at 50 Hz | 119.3 dB |
| Output SPL at 63 Hz | 119.6 dB |
| Output SPL at 80 Hz | 118.9 dB |
| Output SPL at 100 Hz | 119.1 dB |
| Output SPL at 125 Hz | 118.9 dB |
| Warranty | 5 |
| Weight | 80 lbs (36.3 kg) |
- Reviews, Comparisons and Sound Samples
- These figures are manufacturer-specified rather than independently measured.
- Head-to-Head Comparisons
- Monoprice Monolith M15-S vs Rythmik F18
- Monoprice Monolith M15-S vs Monoprice Monolith M-15 V2
- Monoprice Monolith M15-S vs SVS PB-4000
- Monoprice Monolith M15-S vs HSU Research VTF-3 MK5 HP
- Monoprice Monolith M15-S vs HSU Research VTF-15H MK2
- Monoprice Monolith M15-S vs Rythmik FV15HP
- Monoprice Monolith M15-S vs Monoprice Monolith M-215
- Monoprice Monolith M15-S vs Reaction Audio PV-15X
- See all 15 comparisons