Monoprice Monolith M15-S vs Rythmik F18

Last updated: September 17, 2026

Short answer: the Monoprice Monolith M15-S. Both are rated 4.1/5 for sound quality (#72 and #69 of 110 subwoofers), and the Monoprice Monolith M15-S costs $999 against $2344 for the Rythmik F18, and with sound quality even, the cheaper one is the better buy.

Monoprice Monolith M15-S vs Rythmik F18

Buy the Monoprice Monolith M15-S. Both are rated the same for sound quality, and it costs $1345 less than the Rythmik F18.

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

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

Specifications Side By Side

Monoprice Monolith M15-S Rythmik F18
Price$999$1,850
Ranked#72 of 110 in Large Home Subwoofers (Over 75 lbs)#69 of 110 in Large Home Subwoofers (Over 75 lbs)
Enclosuresealedsealed
Output SPL at 15 Hz100.1 dB102.0 dB
Output SPL at 20 Hz105.6 dB106.2 dB
Output SPL at 25 Hz111.2 dB110.9 dB
Output SPL at 31.5 Hz115.2 dB114.3 dB
Output SPL at 40 Hz118.4 dB117.1 dB
Output SPL at 50 Hz119.3 dB119.1 dB
Output SPL at 63 Hz119.6 dB120.5 dB
Output SPL at 80 Hz118.9 dB121.2 dB
Output SPL at 100 Hz119.1 dB121.4 dB
Output SPL at 125 Hz118.9 dB121.4 dB
CEA-2010-A Average (40-80Hz)119.0 dB119.5 dB
Dimensions23.5"H x 16.7"W x 19.7"D (596.9 x 424.2 x 500.4 mm)20.5"H x 20.5"W x 21"D (520.7 x 520.7 x 533.4 mm)
Warranty55/3
CountryUnited StatesUnited States
Measurement SourceManufacturerData-bass
Weight80 lbs (36.3 kg)115.1 lbs (52.2 kg)
Drivers15" (381mm) driver18" (457mm) driver
Output SPL at 10 Hz-93.7 dB
Output SPL at 12.5 Hz-97.4 dB
Cabinet Color-black
Inputs-XLR (2), RCA (line/LFE)
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
Buy the Rythmik F18 at Rythmik Audio ($2,344) →

How Rythmik F18 compares with other leading options:

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.

As an eBay Partner, we may be compensated if you make a purchase.

The Two Speakers In Full

Monoprice Monolith M15-S: $999 eBay

Monoprice Monolith M15-S ranking card

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
CountryUnited States
Dimensions23.5"H x 16.7"W x 19.7"D (596.9 x 424.2 x 500.4 mm)
Drivers15" (381mm) driver
Enclosuresealed
Measurement SourceManufacturer
Output SPL at 15 Hz100.1 dB
Output SPL at 20 Hz105.6 dB
Output SPL at 25 Hz111.2 dB
Output SPL at 31.5 Hz115.2 dB
Output SPL at 40 Hz118.4 dB
Output SPL at 50 Hz119.3 dB
Output SPL at 63 Hz119.6 dB
Output SPL at 80 Hz118.9 dB
Output SPL at 100 Hz119.1 dB
Output SPL at 125 Hz118.9 dB
Warranty5
Weight80 lbs (36.3 kg)
Search eBay for Monoprice Monolith M15-S →

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 →