In this review, we will be comparing Grotto 15 and KC62, two Powered Subwoofer speakers from MartinLogan and KEF. 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 KEF KC62 first before getting into our more detailed comparison.
The sections below take each area in turn: driver and amplifier, frequency response, physical size and connectivity.
Drivers
The efficiency of a subwoofer is directly proportional to the total radiating are squared hence the woofer quantity and diameter.MartinLogan Grotto 15 and KEF KC62 have a totally different setup: the MartinLogan Grotto 15 features 1 x 15-inch drivers whereas the KC62 features 2 x 6.5-inch drivers.
Frequency Response
Grotto 15 has a frequency range of 20-120 Hz whereas KC62 has a frequency range of 11-200 Hz. With a minimum frequency of 11Hz, the KC62 can go significantly deeper on the low side and provide stronger bass compared to the Grotto 15's min frequency of 20Hz.
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
Both MartinLogan Grotto 15 and KEF KC62 have Acoustic Suspension type cabinets. 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.
Physical Specs
The size of a speaker can sometimes be 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 KEF KC62'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 KEF KC62 has external dimensions of 245.0 x 258.0 x 281.0mm (9-5/8inch x 10-1/8inch x 11-1/16inch).
MartinLogan Grotto 15 is clearly the larger of the two speakers. Its body is 296mm wider, 277mm taller and 273mm deeper than KEF KC62.
Size, drawn to scale
Both speakers and both views share one scale, so everything here is directly comparable. Hover a box for its dimensions.
One scale for both, standing on the same surface and pushed back to the same wall, so the deeper one visibly sticks out further.
MartinLogan Grotto 15 needs about 323% more floor or shelf area. MartinLogan Grotto 15 is 273mm deeper, so it stands that much further out from the wall. MartinLogan Grotto 15 is 277mm taller.
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 KEF KC62 is approximately 725.0cm2 / 112.4inch2. The Grotto 15 requires 323% more surface area than the KC62 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 KEF KC62 weighs 14.05kg / 30.9lbs. This makes the Grotto 15 281% heavier than the KC62.
Here is a comparison of how Grotto 15 and KC62's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
15 inches
vs
6.5 inches
|
Larger woofer |
 Passive Radiator |
2 x 15-inch
vs
None
|
Increases the bass performance |
| Number of Woofers |
2
vs
1
|
More woofers |
| Low Frequency Response |
11 Hz
vs
20 Hz
|
Generates deeper bass |
 High Frequency Response |
200 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
245mm
vs
522mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
725cm2
vs
3069cm2
|
Takes less floor space |
 Price per pair* |
1500USD
vs
2800USD
|
costs less (*prices may change depending on the seller, location and time) |
Size, drawn to scale
Both subwoofers and both views share one scale, so everything here is directly comparable. Hover a box for its dimensions.
One scale for both, standing on the same floor and pushed back to the same wall, so the bigger one visibly takes more of the room.
MartinLogan Grotto 15 needs about 323% more floor area. MartinLogan Grotto 15 stands 273mm further into the room. MartinLogan Grotto 15 is 277mm taller.
| General |
MartinLogan Grotto 15 |
KEF KC62 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
1000 watts |
1000 watts |
| Frequency Response |
20-120 Hz |
11-200 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
1000-watt RMS |
1000-watt RMS |
| Watts Peak (Max) |
2000-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
1 |
2 |
| Woofer Size |
15" |
6.5" |
| Woofer Composition |
Aluminium |
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
35–120Hz |
n/a |
| Firing Direction |
n/a |
side |
Physical Specs |
|
|
| Height |
522.0mm (20.6") |
245.0mm (9.6") |
| Width |
554.0mm (21.8") |
258.0mm (10.2") |
| Depth |
554.0mm (21.8") |
281.0mm (11.1") |
| Weight |
53.50kg (117.7lbs) |
14.05kg (30.9lbs) |
| Enclosure |
Acoustic Suspension |
Acoustic Suspension |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
|
2 Years |
| Labor Warranty |
|
2 Years |
Two quite different sizes of subwoofer. Room volume decides this more than anything else on the page: a big driver in a small room is wasted, and a small one in a large room is worked to death.
| Area | Better | Why |
|---|
| Bass depth | B | KEF KC62 goes deeper - 11Hz against 20Hz. Under 20Hz is felt more than heard - the bottom of a pipe organ and the bottom of a film mix. |
| Amplifier power | evenly matched | Much the same amplifier (1000W vs 1000W RMS) - under 1dB apart. |
| Driver area | A | MartinLogan Grotto 15 moves more air: 15" against 2 x 6.5" is 2.66x the cone area, not the 1.63x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Enclosure | evenly matched | Both are sealed designs, so they roll off in much the same way. |
| Driver placement | depends | MartinLogan Grotto 15 fires front and KEF KC62 fires side. A down-firing driver is more forgiving of a grille-less look and of a hard floor; a front-firing one is the safer choice on a thick carpet or a suspended timber floor. |
| Cabinet size | depends | KEF KC62 is about 89% smaller by volume. In a subwoofer that is a real trade rather than a preference: box volume is how you get output low down without a bigger amplifier. |
| Price | B | KEF KC62 costs less - $1,500 against $2,800, about 46% less. |
A MartinLogan Grotto 15 B KEF KC62
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both subwoofers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Neither runs away with it - they trade advantages. Let your room size and where the box can actually stand settle it. Two small subwoofers beat one big one in most rooms - a pair evens out the room modes in a way no single box can, whatever its specs. At $1,500 each, two KEF KC62 cost about $3,000 against $2,800 for one of the other, which is worth a thought. If placement is the constraint - a corner, behind a sofa, under a desk - KEF KC62 is the one that will actually go there, and a well-placed small subwoofer beats a badly-placed big one every time.
One thing outweighs everything above: where the subwoofer stands. Room modes can add or remove 10dB or more at a given seat, which is far larger than any difference on this page. Before spending more, try the sub in two or three positions - the crawl test, where you put it in the listening seat and crawl the room to find where the bass sounds best, costs nothing and usually beats an upgrade.