Rythmik F18 vs BK Electronics Monolith-DF

Last updated: September 16, 2026

Short answer: the Rythmik F18. It ranks #69 of 110 subwoofers by sound quality at $2344; the BK Electronics Monolith-DF ranks #107 and costs $8995, which makes this an easy call rather than a real tradeoff.

Rythmik F18 vs BK Electronics Monolith-DF

What the Rythmik F18 offers: 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. Watch for: 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.

What the BK Electronics Monolith-DF offers: Independent CEA-2010 testing records 102.0 dB at 20 Hz and 108.4 dB through 40-80 Hz. The ported, bottom enclosure with 12” (305mm) driver with ported design 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 603.8H x 539.8W x 419.9D mm cabinet and 46.8 kg mass still require deliberate placement and calibration.

Buy the Rythmik F18. It ranks higher for sound quality than the BK Electronics Monolith-DF and costs less, so there is no real case for the other one.

If sound quality matters at all to you, skip the BK Electronics Monolith-DF. It ranks near the bottom of the 110 subwoofers, so look higher up the list instead.

Looking for alternatives? See the complete Subwoofers rankings.

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

Specifications Side By Side

Rythmik F18 BK Electronics Monolith-DF
Price$1,850$8995
Ranked#69 of 110 in Large Home Subwoofers (Over 75 lbs)#107 of 110 in Large Home Subwoofers (Over 75 lbs)
Enclosuresealedported, bottom
Output SPL at 10 Hz93.7 dB-
Output SPL at 12.5 Hz97.4 dB-
Output SPL at 15 Hz102.0 dB91.3 dB
Output SPL at 20 Hz106.2 dB102.0 dB
Output SPL at 25 Hz110.9 dB106.4 dB
Output SPL at 31.5 Hz114.3 dB108.3 dB
Output SPL at 40 Hz117.1 dB108.6 dB
Output SPL at 50 Hz119.1 dB108.7 dB
Output SPL at 63 Hz120.5 dB108.6 dB
Output SPL at 80 Hz121.2 dB107.7 dB
Output SPL at 100 Hz121.4 dB-
Output SPL at 125 Hz121.4 dB-
CEA-2010-A Average (40-80Hz)119.5 dB108.4 dB
Dimensions20.5"H x 20.5"W x 21"D (520.7 x 520.7 x 533.4 mm)23.8"H x 21.3"W x 16.5"D (603.8 x 539.8 x 419.9 mm)
Weight115.1 lbs (52.2 kg)103.2 lbs (46.8 kg)
Warranty5/32
Cabinet Colorblackblack, wood
CountryUnited StatesUnited Kingdom
Measurement SourceData-bassIlkka Rissanen
Drivers18" (457mm) driver12" (305mm) driver with ported design
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 16, 2026 at 12:41 AM 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

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 →

CEA-2010-A Average (40-80Hz)119.5 dB
Cabinet Colorblack
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
Measurement SourceData-bass
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
Warranty5/3
Weight115.1 lbs (52.2 kg)
Check current price at Rythmik Audio ($2,344) →Search eBay for Rythmik F18 →

BK Electronics Monolith-DF: $8995 eBay

BK Electronics Monolith-DF ranking card

Pros: Independent CEA-2010 testing records 102.0 dB at 20 Hz and 108.4 dB through 40-80 Hz. The ported, bottom enclosure with 12” (305mm) driver with ported design 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 603.8H x 539.8W x 419.9D mm cabinet and 46.8 kg mass still require deliberate placement and calibration.

Full BK Electronics Monolith-DF review and specifications →

CEA-2010-A Average (40-80Hz)108.4 dB
Cabinet Colorblack, wood
CountryUnited Kingdom
Dimensions23.8"H x 21.3"W x 16.5"D (603.8 x 539.8 x 419.9 mm)
Drivers12" (305mm) driver with ported design
Enclosureported, bottom
Measurement SourceIlkka Rissanen
Output SPL at 15 Hz91.3 dB
Output SPL at 20 Hz102.0 dB
Output SPL at 25 Hz106.4 dB
Output SPL at 31.5 Hz108.3 dB
Output SPL at 40 Hz108.6 dB
Output SPL at 50 Hz108.7 dB
Output SPL at 63 Hz108.6 dB
Output SPL at 80 Hz107.7 dB
Warranty2
Weight103.2 lbs (46.8 kg)
Search eBay for BK Electronics Monolith-DF →