In this review, we will be comparing Depth 215 and KF92, 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 KF92 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 Depth 215and KEF KF92 have a double woofer setup however the MartinLogan Depth 215's woofer is 15-inch whereas the KEF KF92 features a 9-inch woofer.
Frequency Response
Depth 215 has a frequency range of 18-120 Hz whereas KF92 has a frequency range of 11-200 Hz. With a minimum frequency of 11Hz, the KF92 can go significantly deeper on the low side and provide stronger bass compared to the Depth 215's min frequency of 18Hz.
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 KF92 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 Depth 215's and KEF KF92'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 KF92 has external dimensions of 353.0 x 331.0 x 362.0mm (13-7/8 x 13 x 14-1/4inch).
MartinLogan Depth 215 is clearly the larger of the two speakers. Its body is 249mm wider, 219mm taller and 233mm deeper than KEF KF92.
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 Depth 215 needs about 188% more floor or shelf area. MartinLogan Depth 215 is 233mm deeper, so it stands that much further out from the wall. MartinLogan Depth 215 is 219mm 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 Depth 215 is approximately 3451.0cm2 / 534.9inch2 and base area of the KEF KF92 is approximately 1198.2cm2 / 185.7inch2. The Depth 215 requires 188% more surface area than the KF92 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 KF92 weighs 20.05kg / 44.1lbs. This makes the Depth 215 292% heavier than the KF92.
Here is a comparison of how Depth 215 and KF92's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
15 inches
vs
9 inches
|
Larger woofer |
| Low Frequency Response |
11 Hz
vs
18 Hz
|
Generates deeper bass |
 High Frequency Response |
200 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
353mm
vs
572mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1198cm2
vs
3451cm2
|
Takes less floor space |
 Price per pair* |
2000USD
vs
7000USD
|
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 Depth 215 needs about 188% more floor area. MartinLogan Depth 215 stands 233mm further into the room. MartinLogan Depth 215 is 219mm taller.
| General |
MartinLogan Depth 215 |
KEF KF92 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
2200 watts |
1000 watts |
| Frequency Response |
18-120 Hz |
11-200 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
2200-watt RMS |
1000-watt RMS |
| Watts Peak (Max) |
4400-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
2 |
2 |
| Woofer Size |
15" |
9" |
| Woofer Composition |
Aluminium |
Hybrid aluminum |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
35–120Hz |
n/a |
Physical Specs |
|
|
| Height |
572.0mm (22.5") |
353.0mm (13.9") |
| Width |
580.0mm (22.8") |
331.0mm (13") |
| Depth |
595.0mm (23.4") |
362.0mm (14.3") |
| Weight |
78.50kg (172.7lbs) |
20.05kg (44.1lbs) |
| 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 KF92 goes deeper - 11Hz against 18Hz. Under 20Hz is felt more than heard - the bottom of a pipe organ and the bottom of a film mix. |
| Amplifier power | A | MartinLogan Depth 215 has the bigger amplifier - 2200W against 1000W RMS, about 3.4dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | MartinLogan Depth 215 moves more air: 2 x 15" against 2 x 9" is 2.78x the cone area, not the 1.67x 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. |
| Cabinet size | depends | KEF KF92 is about 79% 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 KF92 costs less - $2,000 against $7,000, about 71% less. |
A MartinLogan Depth 215 B KEF KF92
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?
MartinLogan Depth 215 is ahead, but on only 1 of the measured areas, and it costs about 3.5x the price. KEF KF92 is the sensible buy unless your room is large enough to need the extra. 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 $2,000 each, two KEF KF92 cost about $4,000 against $7,000 for one of the other, which is worth a thought. If placement is the constraint - a corner, behind a sofa, under a desk - KEF KF92 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.