In this review, we will be comparing Grotto 15 and KUBE 10b, 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 KUBE 10b 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.Both MartinLogan Grotto 15and KEF KUBE 10b have a single woofer setup however the MartinLogan Grotto 15's woofer is 15-inch whereas the KEF KUBE 10b features a 10-inch woofer.
Frequency Response
Grotto 15 has a frequency range of 20-120 Hz whereas KUBE 10b has a frequency range of 24-140 Hz. With a minimum frequency of 20Hz, the Grotto 15 can go slightly deeper then the KUBE 10b's min frequency of 24Hz.
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 KUBE 10b 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 KUBE 10b'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 KUBE 10b has external dimensions of 372.0 x 356.0 x 397.0mm (14-5/8 x 14 x 15-5/8inch).
MartinLogan Grotto 15 is clearly the larger of the two speakers. Its body is 198mm wider, 150mm taller and 157mm deeper than KEF KUBE 10b.
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 117% more floor or shelf area. MartinLogan Grotto 15 is 157mm deeper, so it stands that much further out from the wall. MartinLogan Grotto 15 is 150mm 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 KUBE 10b is approximately 1413.3cm2 / 219.1inch2. The Grotto 15 requires 117% more surface area than the KUBE 10b 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 KUBE 10b weighs 17.50kg / 38.5lbs. This makes the Grotto 15 206% heavier than the KUBE 10b.
Here is a comparison of how Grotto 15 and KUBE 10b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
15 inches
vs
10 inches
|
Larger woofer |
| Low Frequency Response |
20 Hz
vs
24 Hz
|
Generates deeper bass |
 Passive Radiator |
2 x 15-inch
vs
None
|
Increases the bass performance |
 High Frequency Response |
140 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
372mm
vs
522mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1413cm2
vs
3069cm2
|
Takes less floor space |
 Price per pair* |
750USD
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 117% more floor area. MartinLogan Grotto 15 stands 157mm further into the room. MartinLogan Grotto 15 is 150mm taller.
| General |
MartinLogan Grotto 15 |
KEF KUBE 10b |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
1000 watts |
300 watts |
| Frequency Response |
20-120 Hz |
24-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
1000-watt RMS |
300-watt RMS |
| Watts Peak (Max) |
2000-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
15" |
10" |
| Woofer Composition |
Aluminium |
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
35–120Hz |
40-140 Hz |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
522.0mm (20.6") |
372.0mm (14.6") |
| Width |
554.0mm (21.8") |
356.0mm (14") |
| Depth |
554.0mm (21.8") |
397.0mm (15.6") |
| Weight |
53.50kg (117.7lbs) |
17.50kg (38.5lbs) |
| 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 | A | MartinLogan Grotto 15 goes deeper - 20Hz against 24Hz. Under 20Hz is felt more than heard - the bottom of a pipe organ and the bottom of a film mix. |
| Amplifier power | A | MartinLogan Grotto 15 has the bigger amplifier - 1000W against 300W RMS, about 5.2dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | MartinLogan Grotto 15 moves more air: 15" against 10" is 2.25x the cone area, not the 1.5x 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. |
| Speaker-level inputs | A | MartinLogan Grotto 15 takes a speaker-level connection as well as line level. That is what lets it work with an integrated amplifier or a vintage receiver that has no subwoofer output at all. |
| Cabinet size | depends | KEF KUBE 10b is about 67% 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 KUBE 10b costs less - $750 against $2,800, about 73% less. |
A MartinLogan Grotto 15 B KEF KUBE 10b
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?
The usual trade-off: MartinLogan Grotto 15 measures better, KEF KUBE 10b costs about 73% less. In a normal room, placement will make a bigger difference than the gap between these two. Check your amplifier first: if it has no subwoofer or preamp output, MartinLogan Grotto 15 is the only one of these two you can connect at all. 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 $750 each, two KEF KUBE 10b cost about $1,500 against $2,800 for one of the other, which is worth a thought.
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.