Short answer: both are discontinued, so this only matters if you are buying used. Used, the JBL 4645C is the better pick: it ranks #25 of 143 subwoofers by sound quality (rated 4.4/5), against #140 (rated 3.4/5) for the BK Electronics Extreme. If you want one new, the JTR Speakers Orbit Shifter PRO ranks #1 at $4,499.
The JBL 4645C is the better-sounding choice. A pro cinema 18 inch ported subwoofer with very strong upper bass punch, suited to adding impact in a modest room. Watch for: Deep-bass output is limited relative to its midbass result, so it is not the right choice for the lowest movie effects.
Why pick the BK Electronics Extreme: A big 15 inch subwoofer with a powerful amplifier and continuous phase control for flexible setup, now discontinued. Watch for: It weighs 200.6 lbs (91 kg), which takes two or more people to move and needs a strong floor.
Buy the JBL 4645C only if you find one used in good condition; both are discontinued, and it is the better rated of the two. For a new speaker, start with the JTR Speakers Orbit Shifter PRO instead.
Looking for alternatives? See the complete Subwoofers rankings.
Prices on this page were last checked November 14, 2026 at 6:17 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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Specifications Side By Side
| JBL 4645C | BK Electronics Extreme | |
|---|---|---|
| Price | $4,999 Passive, Discontinued | $5,995 Discontinued |
| Ranked | #25 of 143 in Large Home Subwoofers (Over 75 lbs) | #140 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | - |
| Passive | Yes | - |
| Output SPL at 20 Hz | 98.9 dB | 100.7 dB |
| Output SPL at 25 Hz | 114.0 dB | 106.6 dB |
| Output SPL at 31.5 Hz | 118.7 dB | 110.7 dB |
| Output SPL at 40 Hz | 122.0 dB | 111.4 dB |
| Output SPL at 50 Hz | 123.7 dB | 111.1 dB |
| Output SPL at 63 Hz | 129.7 dB | 110.5 dB |
| Output SPL at 80 Hz | 133.9 dB | 109.0 dB |
| Output SPL at 100 Hz | 135.1 dB | - |
| Output SPL at 125 Hz | 135.8 dB | - |
| CEA-2010-A Average (40-80Hz) | 127.3 dB | 110.5 dB |
| Dimensions | 39.7”H x 26.5”W x 17.7”D (1009.6 x 673.1 x 450.8 mm) | - |
| Weight | 138 lbs (62.6 kg) | 200.6 lbs (91 kg) |
| Warranty | 5/3/2 | - |
| Cabinet Color | black | - |
| Country | United States | United Kingdom |
| Measurement Source | Data-bass | Ilkka Rissanen |
| Drivers | 18” (457mm) driver | 15” (381mm) driver |
| Output SPL at 15 Hz | - | 92.8 dB |
| Amplifier Power | - | 1000W RMS |
Where the Ratings Come From
- JBL 4645C: manufacturer specifications and listening comparisons; no independent measurement has been published yet.
- BK Electronics Extreme: manufacturer specifications and listening comparisons; no independent measurement has been published yet.
This comparison is generated from the ratings, specifications and measurements on each product’s own page, and it updates when that data changes. How we rank explains how each rating is decided.
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