In this review, we will be comparing Depth 215 and KUBE 8b, 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 Depth 215 and KEF KUBE 8b 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 Depth 215 and KEF KUBE 8b 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.MartinLogan Depth 215 and KEF KUBE 8b have a totally different setup: the MartinLogan Depth 215 features 2 x 15-inch drivers whereas the KUBE 8b features 1 x 8-inch drivers.
Frequency Response
Depth 215 has a frequency range of 18-120 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 18Hz, the Depth 215 can go significantly deeper on the low side and provide stronger bass compared to the KUBE 8b's min frequency of 34Hz.
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 Depth 215 and KEF KUBE 8b 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
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 Depth 215's and KEF KUBE 8b's external dimensions. MartinLogan Depth 215 has external dimensions of 572.0 x 580.0 x 595.0mm ( 22-1/2 x 22-13/16 x 23-7/16inch) whereas KEF KUBE 8b has external dimensions of 294.0 x 296.0 x 339.0mm ( 11-9/16 x 11-5/8 x 13-5/16inch) .
MartinLogan Depth 215 is clearly the larger of the two speakers. Its body is 284mm wider, 278mm taller and 256mm deeper than KEF KUBE 8b.
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 Depth 215 is approximately 3451.0cm2 / 534.9inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The Depth 215 requires 244% more surface area than the KUBE 8b 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 Depth 215 weighs 78.50kg / 172.7lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the Depth 215 591% heavier than the KUBE 8b.
Here is a comparison of how Depth 215 and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
15 inches
vs
8 inches
|
Larger woofer |
| Number of Woofers |
2
vs
1
|
More woofers |
| Low Frequency Response |
18 Hz
vs
34 Hz
|
Generates deeper bass |
 High Frequency Response |
140k Hz
vs
120k Hz
|
Generates higher frequency |
 Height |
294mm
vs
572mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2
vs
3451cm2
|
Takes less floor space |
 Price per pair* |
600USD
vs
7000USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Depth 215 |
KEF KUBE 8b |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
2200 watts |
300 watts |
| Frequency Response |
18-120 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
2200-watt RMS |
300-watt RMS |
| Watts Peak (Max) |
4400-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
2 |
1 |
| Woofer Size |
15" |
8" |
| 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 |
572.0mm (22.5") |
294.0mm (11.6") |
| Width |
580.0mm (22.8") |
296.0mm (11.7") |
| Depth |
595.0mm (23.4") |
339.0mm (13.3") |
| Weight |
78.50kg (172.7lbs) |
11.36kg (25lbs) |
| Enclosure |
Acoustic Suspension |
Acoustic Suspension |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
|
2 Years |
| Labor Warranty |
|
2 Years |