Short answer: the Rythmik FVX15. It ranks #104 of 143 subwoofers by sound quality, rated 4.1/5, at $1,859; the MartinLogan Grotto 12 ranks #111, rated 4.0/5, and costs $1,954.99, so there is little reason to consider the other one.
Why pick the Rythmik FVX15: A 15” Direct Servo subwoofer in the same multi-tuned ported cabinet as the measured Rythmik FV15HP, with one band of parametric EQ and a lower power amplifier. The tradeoff: No independent measurements yet, so its output can’t be compared directly with ranked subwoofers; the rating is estimated from the measured Rythmik FV15HP (122.0dB in the 40 to 80Hz CEA-2010 bands and 111.1dB at 20Hz), which shares its cabinet but has a more powerful amplifier, so it is placed a little below it.
The case for the MartinLogan Grotto 12: A 12” active aluminum woofer with two 12” passive radiators in a braced 1” MDF cabinet, driven by a 2000W peak (1000W continuous) Magnitude amplifier and rated 22 to 120Hz (±3dB). The catch: No independent measurements yet, so its output can’t be compared directly with ranked subwoofers; the rating is estimated from MartinLogan’s measured subs, including the 12” MartinLogan Dynamo 1100X (116.5dB in the 40 to 80Hz CEA-2010 bands); the Grotto 12 adds two passive radiators and far more amplifier power.
Buy the Rythmik FVX15. It is rated higher for sound quality than the MartinLogan Grotto 12 and costs less, which makes it the one to get unless you need something the other one does better.
About the ratings: neither speaker has been measured yet, so both ratings are estimated from measured siblings and predecessors (likely ranges: Rythmik FVX15 3.8 to 4.3; MartinLogan Grotto 12 3.6 to 4.2). Treat this verdict as provisional.
Want more options? Browse the full Subwoofers rankings.
Specifications Side By Side
| Rythmik FVX15 | MartinLogan Grotto 12 | |
|---|---|---|
| Price | $1,859.00 | $1,954.99 |
| Ranked | #104 of 143 in Large Home Subwoofers (Over 75 lbs) Estimated | #111 of 143 in Large Home Subwoofers (Over 75 lbs) Estimated |
| Country | United States | United States |
| Warranty | 5/3 | 3 |
| Enclosure | ported, front (multi-tuned) | passive radiator |
| Drivers | 15” servo-controlled woofer | 12” aluminum woofer, 2 x 12” passive radiators |
| Dimensions | 24.5”H x 18.3”W x 24.3”D (622 x 464 x 616 mm) | 17.8”H x 17.9”W x 17.9”D (452 x 454 x 454 mm) |
| Weight | 119.9 lbs (54.4 kg) | 82.5 lbs (37.4 kg) |
| Amplifier Power | - | 1000W continuous (2000W peak) |
| Frequency Response | - | 22-120Hz ±3dB (manufacturer specified) |
| XLR Input | - | Yes |
| AES Input | - | No |
Related Speaker Comparisons
More worthwhile head-to-heads for Rythmik FVX15:
- SVS PB-3000 R|Evolution vs Rythmik FVX15
- SVS SB-5000 R-Evolution vs Rythmik FVX15
- Rythmik FVX12 vs Rythmik FVX15
- MartinLogan Grotto 15 vs MartinLogan Grotto 12
- Monoprice Monolith 16 THX Ultra vs SVS PB12-Plus
Prices on this page were last checked October 11, 2026 at 4:59 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
Rythmik FVX15: $1,859.00 Estimated Rythmik Audio eBay
Same family: the Rythmik FVX12 (smaller subwoofer, ranked lower, estimated 4.1/5).
Pros: A 15” Direct Servo subwoofer in the same multi-tuned ported cabinet as the measured Rythmik FV15HP, with one band of parametric EQ and a lower power amplifier. Sold direct.
Cons: No independent measurements yet, so its output can’t be compared directly with ranked subwoofers; the rating is estimated from the measured Rythmik FV15HP (122.0dB in the 40 to 80Hz CEA-2010 bands and 111.1dB at 20Hz), which shares its cabinet but has a more powerful amplifier, so it is placed a little below it. It weighs 54kg.
Full Rythmik FVX15 review and specifications →
| Country | United States |
|---|---|
| Dimensions | 24.5”H x 18.3”W x 24.3”D (622 x 464 x 616 mm) |
| Drivers | 15” servo-controlled woofer |
| Enclosure | ported, front (multi-tuned) |
| Warranty | 5/3 |
| Weight | 119.9 lbs (54.4 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- No independent measurement review is linked for this model; it is ranked from hands-on listening and comparison against similarly priced speakers.
- Head-to-Head Comparisons
MartinLogan Grotto 12: $1,954.99 Estimated Audio Advice eBay
Same family: the MartinLogan Grotto 15 (larger subwoofer, ranked higher, estimated 4.2/5).
Pros: A 12” active aluminum woofer with two 12” passive radiators in a braced 1” MDF cabinet, driven by a 2000W peak (1000W continuous) Magnitude amplifier and rated 22 to 120Hz (±3dB). App control and Anthem Room Correction are included.
Cons: No independent measurements yet, so its output can’t be compared directly with ranked subwoofers; the rating is estimated from MartinLogan’s measured subs, including the 12” MartinLogan Dynamo 1100X (116.5dB in the 40 to 80Hz CEA-2010 bands); the Grotto 12 adds two passive radiators and far more amplifier power. It weighs 37.4kg.
Full MartinLogan Grotto 12 review and specifications →
| Released | Oct 2025 (1 year ago) |
|---|---|
| AES Input | No |
| Amplifier Power | 1000W continuous (2000W peak) |
| Country | United States |
| Dimensions | 17.8”H x 17.9”W x 17.9”D (452 x 454 x 454 mm) |
| Drivers | 12” aluminum woofer, 2 x 12” passive radiators |
| Enclosure | passive radiator |
| Frequency Response | 22-120Hz ±3dB (manufacturer specified) |
| Warranty | 3 |
| Weight | 82.5 lbs (37.4 kg) |
| XLR Input | Yes |
- Links
- Reviews, Comparisons and Sound Samples
- No independent measurement review is linked for this model; it is ranked from hands-on listening and comparison against similarly priced speakers.
- Head-to-Head Comparisons