Monoprice Monolith 16 THX Ultra vs Rythmik F18

Last updated: September 17, 2026

Short answer: the Monoprice Monolith 16 THX Ultra. It ranks #18 of 110 subwoofers by sound quality, rated 4.4/5, at $2300; the Rythmik F18 ranks #69, rated 4.1/5, and costs $2344, so there is not much of a tradeoff to weigh.

Monoprice Monolith 16 THX Ultra vs Rythmik F18

On the Monoprice Monolith 16 THX Ultra side: 16-inch ported driver and THX Ultra certification deliver 126.5dB CEA-2010-A average at a fraction of the price of the subwoofers ranked. Set against that: Heavy at 78 kg (172 lbs) and ported design can interact with room acoustics.

Buy the Monoprice Monolith 16 THX Ultra. It is rated higher for sound quality than the Rythmik F18 and costs less, so there is no real case for the other one.

Looking for alternatives? See the complete Subwoofers rankings.

Buy the Rythmik F18 at Rythmik Audio ($2,344) →

Specifications Side By Side

Monoprice Monolith 16 THX Ultra Rythmik F18
Price$2,300$1,850
Ranked#18 of 110 in Large Home Subwoofers (Over 75 lbs)#69 of 110 in Large Home Subwoofers (Over 75 lbs)
Enclosureported, frontsealed
Output SPL at 15 Hz107.3 dB102.0 dB
Output SPL at 20 Hz118.4 dB106.2 dB
Output SPL at 25 Hz123.3 dB110.9 dB
Output SPL at 31.5 Hz125.1 dB114.3 dB
Output SPL at 40 Hz126.3 dB117.1 dB
Output SPL at 50 Hz126.5 dB119.1 dB
Output SPL at 63 Hz126.6 dB120.5 dB
Output SPL at 80 Hz126.8 dB121.2 dB
Output SPL at 100 Hz127.2 dB121.4 dB
Output SPL at 125 Hz127.6 dB121.4 dB
CEA-2010-A Average (40-80Hz)126.5 dB119.5 dB
Dimensions25.6"H x 22"W x 28.1"D (650.2 x 558.8 x 713.7 mm)20.5"H x 20.5"W x 21"D (520.7 x 520.7 x 533.4 mm)
Weight171.5 lbs (77.8 kg)115.1 lbs (52.2 kg)
Warranty55/3
Cabinet Colorblackblack
CountryUnited StatesUnited States
Measurement SourceAudioholicsData-bass
Drivers16" (406mm) driver18" (457mm) driver
InputsXLR, RCA, XLR outXLR (2), RCA (line/LFE)
XLR InputYesYes
RCA InputYesYes
TRS InputNoNo
Optical InputNoNo
Coaxial InputNoNo
USB InputNoNo
HDMI InputNoNo
AES InputNoNo
Aux InputNoNo
Output SPL at 10 Hz-93.7 dB
Output SPL at 12.5 Hz-97.4 dB
Buy the Rythmik F18 at Rythmik Audio ($2,344) →

More top alternatives to Monoprice Monolith 16 THX Ultra:

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

Monoprice Monolith 16 THX Ultra: $2,300 eBay

Monoprice Monolith 16 THX Ultra ranking card

Pros: 16-inch ported driver and THX Ultra certification deliver 126.5dB CEA-2010-A average at a fraction of the price of the subwoofers ranked above it.

Cons: Heavy at 78 kg and ported design can interact with room acoustics.

Notes: Product # 42031

Full Monoprice Monolith 16 THX Ultra review and specifications →

AES InputNo
Aux InputNo
CEA-2010-A Average (40-80Hz)126.5 dB
Cabinet Colorblack
Coaxial InputNo
CountryUnited States
Dimensions25.6"H x 22"W x 28.1"D (650.2 x 558.8 x 713.7 mm)
Drivers16" (406mm) driver
Enclosureported, front
HDMI InputNo
InputsXLR, RCA, XLR out
Measurement SourceAudioholics
Optical InputNo
Output SPL at 15 Hz107.3 dB
Output SPL at 20 Hz118.4 dB
Output SPL at 25 Hz123.3 dB
Output SPL at 31.5 Hz125.1 dB
Output SPL at 40 Hz126.3 dB
Output SPL at 50 Hz126.5 dB
Output SPL at 63 Hz126.6 dB
Output SPL at 80 Hz126.8 dB
Output SPL at 100 Hz127.2 dB
Output SPL at 125 Hz127.6 dB
RCA InputYes
TRS InputNo
USB InputNo
Warranty5
Weight171.5 lbs (77.8 kg)
XLR InputYes
Search eBay for Monoprice Monolith 16 THX Ultra →

Rythmik F18: $1,850 Rythmik Audio eBay

Rythmik F18 ranking card

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 InputNo
Aux InputNo
CEA-2010-A Average (40-80Hz)119.5 dB
Cabinet Colorblack
Coaxial InputNo
CountryUnited States
Dimensions20.5"H x 20.5"W x 21"D (520.7 x 520.7 x 533.4 mm)
Drivers18" (457mm) driver
Enclosuresealed
HDMI InputNo
InputsXLR (2), RCA (line/LFE)
Measurement SourceData-bass
Optical InputNo
Output SPL at 10 Hz93.7 dB
Output SPL at 12.5 Hz97.4 dB
Output SPL at 15 Hz102.0 dB
Output SPL at 20 Hz106.2 dB
Output SPL at 25 Hz110.9 dB
Output SPL at 31.5 Hz114.3 dB
Output SPL at 40 Hz117.1 dB
Output SPL at 50 Hz119.1 dB
Output SPL at 63 Hz120.5 dB
Output SPL at 80 Hz121.2 dB
Output SPL at 100 Hz121.4 dB
Output SPL at 125 Hz121.4 dB
RCA InputYes
TRS InputNo
USB InputNo
Warranty5/3
Weight115.1 lbs (52.2 kg)
XLR InputYes
Check current price at Rythmik Audio ($2,344) →Search eBay for Rythmik F18 →