MartinLogan Grotto 15 Subwoofer
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Grotto 15 Subwoofer
Grotto 15 continues the legacy of the original Grotto: serious, clean bass from a cabinet that blends discreetly into the room. It uses MartinLogan's largest and most powerful Hybrid Woofer System to date, pairing an active 15-inch aluminium-cone woofer with dual 15-inch passive radiators, driven by a 2,000W peak (1,000W RMS) Magnitude MT-2kW amplifier and a 64-bit Vojtko DSP engine. XLR, RCA, speaker-level and built-in wireless connections, app control and ARC Genesis room correction support make it as flexible as it is powerful.
Bold Performance, Subtle Styling
Three full-face grilles keep Grotto 15 visually understated, but its commanding output becomes obvious the moment the first bass note lands. Ideal if you want authoritative low end without a subwoofer dominating the décor.
15" Hybrid Woofer System
Developed with Klippel analysis for high output and low distortion, the active 15-inch woofer works with two matched 15-inch passive radiators. This gives the deep extension of a ported design with the tighter, more compact character of a sealed one. All cones are aluminium for fast response, high output and reliability, mounted in rigid cast-aluminium baskets with large motor structures.
Magnitude MT-2kW Amplifier
MartinLogan's proprietary Class-D Magnitude amplifier delivers up to 2,000W peak (1,000W RMS) of low-distortion power, with ample reserves for concussive impact and effortless musicality on even the most demanding content.
Vojtko DSP and ARC Genesis
The 500MHz, 64-bit Vojtko DSP engine controls performance in real time and enables Anthem Room Correction (ARC Genesis). Room calibration takes only minutes using the optional ARC Calibration Kit (sold separately).
Solid Construction and Anti-Vibration Feet
The sealed 1-inch MDF cabinet has reinforced woofer baffles and dual centre braces for a stable platform and cleaner bass. Integrated anti-vibration feet reduce floor and wall vibration (carpet spikes included).
Connectivity and Control
XLR LFE, RCA stereo and LFE, speaker-level inputs and an RCA sub output. A wireless receiver is built in and a wireless transmitter is included. Adjust volume, crossover, phase and listening modes from your seat with the MartinLogan Subwoofer Control app.
Specifications
Specifications are subject to change without notice.
| Frequency Response | 20–120 Hz ±3 dB (anechoic, via LFE input) |
| Low Frequency Transducer | Triple 15" Hybrid Woofer System: 1× high-excursion aluminium cone in a cast-aluminium basket, plus 2× aluminium cone passive radiators |
| Amplifier | MartinLogan Magnitude MT-2kW: 2,000W peak (1,000W continuous) |
| Digital Signal Processing | Ultra high-resolution 500MHz Vojtko DSP engine with 64-bit processing |
| Cabinet | Sealed 1" MDF cabinet with dual centre braces and reinforced woofer baffles |
| Inputs | Line level: Left, Right and LFE (RCA) XLR: LFE Speaker level: Left and Right (requires banana plugs) |
| Output | RCA Sub Out (combines and repeats all incoming signals) |
| Wireless | Integrated wireless receiver, wireless transmitter included |
| Controls (Backplate) | Level: LED backlit knob Tone Sweep: start/pause with status light Power Mode: On, 12V Trigger, Auto Wireless pairing button |
| Controls (via Bluetooth app) | Level: −40 to +12dB Low-Pass Filter: 35–120Hz (1Hz steps); Bypass, Third or Fourth order Phase: 0–180° (1° steps); Polarity: Normal, Inverted Listening Modes: Movie, Music, Night 20–30Hz Level: ±10dB ARC Genesis: On/Off Tone Sweep (120–20Hz) |
| Power Draw | Max: 1000W Standby (wireless disabled): 0.5W Standby (wireless enabled): <2W (transmitter and subwoofer combined) |
| Feet | Integrated anti-vibration feet (carpet spikes included) |
| Dimensions (H × W × D) | 52.2 × 55.4 × 55.4 cm (20.5" × 21.8" × 21.8") |
| Weight | 53.5 kg (118 lbs) |
| Finish | Gloss Black |
| Sold As | Each |
Caring for your Speakers and Amplifiers
To Keep your equipment safe these are some best practices to note. Please be advised that this is only to reduce the risk of misuse and is not an exhaustive list.
Speakers
- Speaker terminals are marked red and black, ensure your amplifier to the speakers are wired on the same colours
- Ensure no loose speaker wire from the red touches a loose wire from the black as this will lead to a short circuit and damage either the speaker, the amplifier or both.
- Not all speakers are designed to play at max volume, kindly consider the pairing of your amplifier and speakers
- Speaker cabinets cannot be replaced please handle with care.
AV & Stereo Amplifiers
- If your amplifier has HDMI ports, ensure all devices are off before plugging in the HDMI cable
- Turn off the amplifier before swoping out or adding speaker cable
- Amplifiers generate heat, place them in a well ventilated space. if possible avoid having anything on top of the unit.
- adding a surge protector can assist with power dips which are likely to damage your devices. Isotek and Furman are industry standard.
- Dusty environments can sometimes lead to accumulation of dust in the electronic components that might affect heat regulation
Shipping & Returns
- Free shipping on orders over R500 within the country.
- Standard delivery within 2–5 business days. Delays will be communicated. This might vary slightly depending on your location.
- Return items in original condition for a full refund. (unopened state)
- Returns that are open/unboxed will be subject to a handling fee. Refunds will only be processed after testing the unit.