In this review, we will be comparing Grotto 15 and A120P, two Powered Subwoofer speakers from MartinLogan and JBL. Being Powered subwoofers, they both have built-in amplifiers so you don't need an external power amp or an integrated amp to power them. Let's have a brief look at the main features of MartinLogan Grotto 15 and JBL Stage A120P first before getting into our more detailed comparison.
In the following sections, we will get into details in order to better understand how the MartinLogan Grotto 15 and JBL Stage A120P compare and hopefully end up with enough arguments to decide which one of these subwoofers is the better choice for you.
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Drivers
The efficiency of a subwoofer is directly proportional to the total radiating are squared hence the woofer quantity and diameter.Both MartinLogan Grotto 15and JBL Stage A120P have a single woofer setup however the MartinLogan Grotto 15's woofer is 15-inch whereas the JBL Stage A120P features a 12-inch woofer.
Frequency Response
Grotto 15 has a frequency range of 20-120 Hz whereas A120P has a frequency range of 32-150 Hz. With a minimum frequency of 20Hz, the Grotto 15 can go significantly deeper on the low side and provide stronger bass compared to the A120P's min frequency of 32Hz.
Below graphs depict how these two speakers compare with the max, min and average values of the Min and Max Frequencies of other speakers in the Subwoofer class in our database.
Low Frequency
Subwoofer Speakers
High Frequency
Subwoofer Speakers
Cabinet Type
The MartinLogan Grotto 15 has a Acoustic Suspension type cabinet. Acoustic Suspension aka Sealed type subwoofers have enclosures that are sealed hence no ports or holes exists on the cabinet. Sealed designs helps to provide more accurate and tight bass responses compared to ported designs. On the other hand the JBL Stage A120P have Bass reflex type enclosure.
Physical Specs
Size of a speaker can sometimes become an important decision factor due to space constraints or in some cases purely for esthetic reasons. In this section, we are going to compare MartinLogan Grotto 15's and JBL Stage A120P's external dimensions. MartinLogan Grotto 15 has external dimensions of 522.0 x 554.0 x 554.0mm ( 20-9/16 x 21-13/16 x 21-13/16inch) whereas JBL Stage A120P has external dimensions of 415.0 x 393.0 x 475.0mm ( 16-5/16 x 15-7/16 x 18-11/16inch) .
MartinLogan Grotto 15 is clearly the larger of the two speakers. Its body is 161mm wider, 107mm taller and 79mm deeper than JBL Stage A120P.
Base Surface Area Comparison
Base surface area of a loudspeaker may become a determining factor when the space in your room or desk is limited.
The base surface area of the MartinLogan Grotto 15 is approximately 3069.2cm2 / 475.7inch2 and base area of the JBL Stage A120P is approximately 1866.8cm2 / 289.4inch2. The Grotto 15 requires 64% more surface area than the A120P which gives it a small disadvantage on placement in tight spaces.
Weight Comparison The weight of a subwoofer may become an important factor if you need to move and reposition the unit often to find the optimal positioning, also known as 'Subwoofer Crawling'. The MartinLogan Grotto 15 weighs 53.50kg / 117.7lbs and the JBL Stage A120P weighs 18.68kg / 41.1lbs. This makes the Grotto 15 186% heavier than the A120P.
Here is a comparison of how Grotto 15 and A120P's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
15 inches
vs
12 inches
|
Larger woofer |
| Low Frequency Response |
20 Hz
vs
32 Hz
|
Generates deeper bass |
 Passive Radiator |
2 x 15-inch
vs
None
|
Increases the bass performance |
 High Frequency Response |
150k Hz
vs
120k Hz
|
Generates higher frequency |
 Height |
415mm
vs
522mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1866cm2
vs
3069cm2
|
Takes less floor space |
 Price per pair* |
300USD
vs
2800USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Grotto 15 |
JBL Stage A120P |
| Brand |
MartinLogan |
JBL |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
1000 watts |
250 watts |
| Frequency Response |
20-120 Hz |
32-150 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
1000-watt RMS |
250-watt RMS |
| Watts Peak (Max) |
2000-watt RMS |
500-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
15" |
12" |
| Woofer Composition |
Aluminium |
Polycellulose |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
35–120Hz |
n/a |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
522.0mm (20.6") |
415.0mm (16.3") |
| Width |
554.0mm (21.8") |
393.0mm (15.5") |
| Depth |
554.0mm (21.8") |
475.0mm (18.7") |
| Weight |
53.50kg (117.7lbs) |
18.68kg (41.1lbs) |
| Enclosure |
Acoustic Suspension |
Bass reflex |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
|
1 Year |
| Labor Warranty |
|
1 Year |