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MartinLogan Grotto 15 Subwoofer Review
MartinLogan Grotto 15 - Front View

Main Features

  • 15" Aluminium Woofer
  • 2 x 15-inch Passive Radiators
  • 1,000 watts RMS Output
  • 20-120 Hz Frequency Response
  • Weight: 117.95 lbs / 53.50kg
  • Dimensions (H x W x D): 20-9/16" x 21-13/16" x 21-13/16"
MSRP: $2,800 (list price)
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MartinLogan Grotto 15 Subwoofer Review
MartinLogan Grotto 15 MartinLogan Grotto 1...
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Grotto 15 is a Sealed type Powered Subwoofer by MartinLogan with a frequency range of 20-120 Hz. It was released in 2021. It features 1 x 15" Aluminium Woofer, and powered by a Class D 1000 watts amplifier. Grotto 15 also employs 2 x 15-inch passive radiators.

A sealed subwoofer with a 15 inch woofer plus 2 passive radiators on a 1000 W RMS (2000 W peak) Class D amplifier, 20 Hz to 120 Hz. Anthem Room Correction is built in. Grotto pairs one driven woofer with two passive radiators in a sealed cabinet, which buys the output of a much larger box without a port.

Grotto 15 is a member of MartinLogan's Grotto series of Powered subwoofers. Below you can see the main specs of these subwoofers as well as review and comparison links.

MartinLogan Grotto Series Subwoofers
Model Frequency Woofer Amp Power Weight
MartinLogan Grotto 12
Compare
22-120k Hz 12" 1000 watts 37.40kg
MartinLogan Grotto 15
20-120k Hz 15" 1000 watts 53.50kg


**This post contains affiliate links, and I will be compensated if you make a purchase after clicking through my links. As an Amazon Associate I earn from qualifying purchases.

Frequency Response

MartinLogan Grotto 15 has a Frequency response range of 20-120 Hz at ±3dB. Thanks to its 1 x 15-inch driver and 1000 watts RMS ( 2000 watts MAX ) amplifier, the Grotto 15 can go as low as 20 Hz which means you can get a Full range (20Hz-20kHz) listening experience when coupled with almost any loudspeaker in the market.

Here we have a comparison of how Grotto 15's Low and High frequency values compare with the average, max and min Low and High frequency values in its class.
Low Frequency
Powered Subwoofers
MartinLogan Grotto 15
Min
Average
Max
High Frequency
Subwoofer Speakers
MartinLogan Grotto 15
Min
Average
Max

Among all subwoofers in our database with a max MSRP price of 3000$, these are the 5 Powered Subwoofer models that can reach deeper bass levels than the MartinLogan Grotto 15's 20Hz:

  • B&W DB4S with Low Frequency of 10 Hz (Compare w/ Grotto 15)
  • GoldenEar SuperSub XXL with Low Frequency of 10 Hz (Compare w/ Grotto 15)
  • KEF KF92 with Low Frequency of 11 Hz (Compare w/ Grotto 15)
  • KEF KC62 with Low Frequency of 11 Hz (Compare w/ Grotto 15)
  • KEF KC92 with Low Frequency of 11 Hz (Compare w/ Grotto 15)

Inputs and Outputs

  • PreampLevel Inputs: Stereo RCA line, LFE, XLR, speaker level
  • SpeakerLevel Inputs: Yes

MartinLogan Grotto 15 External Dimensions and Weight

MartinLogan Grotto 15 has external dimensions of (Height x Width x Depth) 20-9/16 x 21-13/16 x 21-13/16inch (522.0 x 554.0 x 554.0mm ).

Base Surface Area
Base surface area of a loudspeaker may become a determining factor when the space in your room or desk is limited. The base area of MartinLogan Grotto 15 is approximately 3069.2cm2 / 475.7inch2.

Weight

The MartinLogan Grotto 15 weighs 53.50kg / 117.7lbs. Weight of a subwoofer is an important factor when you need to move and reposition the unit often to find the optimal positioning, also known as 'Subwoofer Crawling'. Here is a comparison of how Grotto 15's weight compares with the average, max and min weights in its class.

Weight
All Subwoofer Speakers
MartinLogan Grotto 15
Min
Average
Max
Weight
Subwoofer Speakers under $3000
MartinLogan Grotto 15
Min
Average
Max

Cabinet type and Materials

MartinLogan Grotto 15 has a Acoustic Suspension type cabinet. Acoustic suspension aka Sealed subwoofers are preferred for music oriented systems whereas the Ported subwoofers are generally accepted to be more suitable for home theatre systems.

Does the MartinLogan Grotto 15 come with a Grille?

Grotto 15 comes with grilles. The purpose of the grille is to protect the delicate driver elements from external impacts while still allowing the sound to pass as clearly as possible.

Recommended Accessories

Here is a list of accessories that we think you may need for the MartinLogan Grotto 15.

  • Vibration Isolators: IsoAcoustics isolators are our favorite isolators but you may find more affordable options too.
  • Acoustic Panels and Treatments: Your room is as important as your stereo equipment so acoustic treatments goes a long way in improving the overall performance.

Official Product Page

Official manufacturer's product page for the MartinLogan Grotto 15 speaker can be found below:
Official Product Page for MartinLogan Grotto 15

MartinLogan Grotto 15 Detailed Specifications

General
BrandMartinLogan
Full Model NameMartinLogan Grotto 15
TypePowered Subwoofer
Release Date2021
Frequency Response20-120 Hz
Enclosure TypeSealed
EnclosureAcoustic Suspension
Firing DirectionFront
Amplifier & Driver
Power (RMS)1000 watts
Power (Peak)2000 watts
Amplifier TypeClass D
Woofer15-inch Aluminium
Passive Radiator2 x 15-inch

Controls & Connections
Phase ControlYes
Line-level InputsStereo RCA line, LFE, XLR, speaker level
Speaker-level InputsYes
Physical
Dimensions (HxWxD)20-9/16" x 21-13/16" x 21-13/16" (522.0 x 554.0 x 554.0mm)
Weight53.50kg ( 117.95 lbs)
GrilleYes
MartinLogan Grotto 15 Alternatives in Powered Subwoofer Speakers
Model Frequency Woofer Amp Power Dimensions
Polk Monitor XT12
Compare
24-160k Hz 12" 50 watts 16-7/16inch x 16-1/16inch x 19-1/16inch "
SVS SB-1000 Pro
Compare
20-270k Hz 12" 325 watts 13-1/2inch x 13inch x 15-13/16inch "
B&W DB4S
Compare
10-350k Hz 10" 1000 watts 14-3/4 x 14-1/4 x 17-1/16inch"
Klipsch R-121SW
Compare
28-120k Hz 12" 200 watts 16-5/8inch x 16inch x 20-15/16inch "
Klipsch R-101SW
Compare
30-160k Hz 10" 150 watts 14-9/16inch x 14-1/16inch x 20-13/16inch "
Klipsch RP-1200SW
Compare
17-138k Hz 12" 400 watts 18-15/16inch x 17inch x 25-15/16inch "
KEF KC62
Compare
11-200k Hz 6.5" 1000 watts 9-5/8inch x 10-1/8inch x 11-1/16inch "
Klipsch R-100SW
Compare
32-120k Hz 10" 150 watts 14-5/8 x 12-9/16 x 18-1/16inch"
Wharfedale SW-15
Compare
30-120k Hz 15" 400 watts 22-7/16inch x 19-3/8inch x 24-3/16inch "
Klipsch SPL-100
Compare
27-125k Hz 10" 200 watts 16-7/16 x 14-1/16 x 18-13/16inch"
B&W ASW610
Compare
27-140k Hz 10" 200 watts 12-5/8 x 12-1/4 x 15-1/2inch"
KEF KUBE 8b
Compare
34-140k Hz 8" 300 watts 11-9/16 x 11-5/8 x 13-5/16inch"
KEF KUBE 10b
Compare
24-140k Hz 10" 300 watts 14-5/8 x 14 x 15-5/8inch"
B&W ASW608
Compare
32-140k Hz 8" 200 watts 10-11/16 x 10-1/4 x 13-3/4inch"
JBL Stage A120P
Compare
32-150k Hz 12" 250 watts 16-5/16 x 15-7/16 x 18-11/16inch"
Klipsch SPL-120
Compare
24-125k Hz 12" 300 watts 17-11/16 x 14-3/4 x 21-1/4inch"
Frequently Asked Questions about MartinLogan Grotto 15

How low can the MartinLogan Grotto 15 go?

The MartinLogan Grotto 15 has a frequency response of 20-120 Hz. Reaching down to 20Hz, it covers the full range of audible low bass.

How much power does the MartinLogan Grotto 15 have?

The MartinLogan Grotto 15 has a built-in 1000-watt RMS (2000-watt peak) Class D amplifier.

Is the MartinLogan Grotto 15 sealed or ported?

The MartinLogan Grotto 15 uses a Sealed enclosure. Sealed subwoofers trade a little output for tighter, more accurate bass and a smaller cabinet, which many listeners prefer for music.

What driver does the MartinLogan Grotto 15 use?

The MartinLogan Grotto 15 has a 15-inch Aluminium driver. It is paired with 2 x 15-inch passive radiators to reinforce the low end.

Does the MartinLogan Grotto 15 have app control or room correction?

Yes. The MartinLogan Grotto 15 offers phase control, letting you dial the sub into your room and blend it with your speakers.

How do you connect the MartinLogan Grotto 15?

The MartinLogan Grotto 15 connects via line-level Stereo RCA line, LFE, XLR, speaker level and speaker-level Yes inputs.

How big and heavy is the MartinLogan Grotto 15?

The MartinLogan Grotto 15 weighs 53.50kg / 117.7lbs and measures 20-9/16" x 21-13/16" x 21-13/16" (HxWxD).

How much does the MartinLogan Grotto 15 cost?

The MartinLogan Grotto 15 has a manufacturer's list price (MSRP) of $2,800.

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