JTR Speakers Captivator 4000ULF vs Rythmik F18

Short answer: the JTR Speakers Captivator 4000ULF on measured sound quality, the Rythmik F18 on price. The JTR Speakers Captivator 4000ULF ranks #6 of 110 subwoofers, rated 4.5/5, at $5699. The Rythmik F18 ranks #69, rated 4.1/5, at $2344, $3355 cheaper.

Buy the JTR Speakers Captivator 4000ULF if sound quality is the priority over the price, or the Rythmik F18 if the price is the priority over sound quality.

Still deciding? The full Subwoofers rankings cover every ranked option.

Specifications Side By Side

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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
  • JTR Speakers Captivator 4000ULF Website
• 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

Rythmik F18: $1,850 Rythmik Audio eBay

Pros: Independent CEA-2010 testing records 106.2 dB at 20 Hz and 119.5 dB through 40-80 Hz. The sealed enclosure with 18” (457mm) driver has the headroom for demanding film bass in a large room.

Cons: The 520.7H x 520.7W x 533.4D mm cabinet and 52.2 kg mass make this a serious placement and moving commitment. A sealed cabinet still needs careful placement and calibration to avoid room-mode peaks.

Full Rythmik F18 review and specifications →

AES Input	No
Aux Input	No
CEA-2010-A Average (40-80Hz)	119.5 dB
Cabinet Color	black
Coaxial Input	No
Country	United States
Dimensions	20.5"H x 20.5"W x 21"D (520.7 x 520.7 x 533.4 mm)
Drivers	18" (457mm) driver
Enclosure	sealed
HDMI Input	No
Inputs	XLR (2), RCA (line/LFE)
Measurement Source	Data-bass
Optical Input	No
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
Output SPL at 20 Hz	106.2 dB
Output SPL at 25 Hz	110.9 dB
Output SPL at 31.5 Hz	114.3 dB
Output SPL at 40 Hz	117.1 dB
Output SPL at 50 Hz	119.1 dB
Output SPL at 63 Hz	120.5 dB
Output SPL at 80 Hz	121.2 dB
Output SPL at 100 Hz	121.4 dB
Output SPL at 125 Hz	121.4 dB
RCA Input	Yes
TRS Input	No
USB Input	No
Warranty	5/3
Weight	115.1 lbs (52.2 kg)
XLR Input	Yes

• Links
  • Rythmik F18 Website
• Reviews, Comparisons and Sound Samples
  • Independently measured by Data-bass; the published figures above come from this ASR subwoofer measurement thread.
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