Short answer: both are discontinued, so this only matters if you are buying used. Used, the JTR Speakers Growler (2015) is the better pick: it ranks #13 of 143 subwoofers by sound quality (rated 4.5/5), against #25 (rated 4.4/5) for the JBL 4645C. If you want one new, the JTR Speakers Orbit Shifter PRO ranks #1 at $4,499.

Buy the JTR Speakers Growler (2015) 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.
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Specifications Side By Side
| JBL 4645C | JTR Speakers Growler (2015) | |
|---|---|---|
| Price | $4,999 Passive, Discontinued | $2,995 Passive, Discontinued |
| Ranked | #25 of 143 in Large Home Subwoofers (Over 75 lbs) | #13 of 143 in Large Home Subwoofers (Over 75 lbs) |
| Enclosure | ported, front | ported, front |
| Passive | Yes | Yes |
| Output SPL at 20 Hz | 98.9 dB | 92.8 dB |
| Output SPL at 25 Hz | 114.0 dB | 97.2 dB |
| Output SPL at 31.5 Hz | 118.7 dB | 106.6 dB |
| Output SPL at 40 Hz | 122.0 dB | 122.7 dB |
| Output SPL at 50 Hz | 123.7 dB | 130.0 dB |
| Output SPL at 63 Hz | 129.7 dB | 133.6 dB |
| Output SPL at 80 Hz | 133.9 dB | 134.4 dB |
| Output SPL at 100 Hz | 135.1 dB | 135.5 dB |
| Output SPL at 125 Hz | 135.8 dB | 136.0 dB |
| CEA-2010-A Average (40-80Hz) | 127.3 dB | 130.2 dB |
| Dimensions | 39.7”H x 26.5”W x 17.7”D (1009.6 x 673.1 x 450.8 mm) | 22.5”H x 30”W x 20”D (571.5 x 762.0 x 508.0 mm) |
| Weight | 138 lbs (62.6 kg) | 100.1 lbs (45.4 kg) |
| Warranty | 5/3/2 | 5 years |
| Cabinet Color | black | - |
| Country | United States | United States |
| Measurement Source | Data-bass | Data-bass |
| Drivers | 18” (457mm) driver | 12” (305mm) driver |
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