In this review, we will be comparing Gravis III and KF92, two Powered Subwoofer speakers from Sonus faber 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 Sonus faber Gravis III 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.Sonus faber Gravis III and KEF KF92 have a totally different setup: the Sonus faber Gravis III features 1 x 10-inch drivers whereas the KF92 features 2 x 9-inch drivers.
Frequency Response
Gravis III has a frequency range of 25-120 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 Gravis III's min frequency of 25Hz.
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 Sonus faber Gravis III 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 Sonus faber Gravis III's and KEF KF92's external dimensions. Sonus faber Gravis III has external dimensions of 415.0 x 400.0 x 495.0mm (16-5/16 x 15-3/4 x 19-1/2inch) whereas KEF KF92 has external dimensions of 353.0 x 331.0 x 362.0mm (13-7/8 x 13 x 14-1/4inch).
Sonus faber Gravis III is clearly the larger of the two speakers. Its body is 69mm wider, 62mm taller and 133mm 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.
Sonus faber Gravis III needs about 65% more floor or shelf area. Sonus faber Gravis III is 133mm deeper, so it stands that much further out from the wall. Sonus faber Gravis III is 62mm 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 Sonus faber Gravis III is approximately 1980.0cm2 / 306.9inch2 and base area of the KEF KF92 is approximately 1198.2cm2 / 185.7inch2. The Gravis III requires 65% 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 Sonus faber Gravis III weighs 26.70kg / 58.7lbs and the KEF KF92 weighs 20.05kg / 44.1lbs. This makes the Gravis III 33% heavier than the KF92.
Here is a comparison of how Gravis III and KF92's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
10 inches
vs
9 inches
|
Larger woofer |
| Number of Woofers |
2
vs
1
|
More woofers |
| Low Frequency Response |
11 Hz
vs
25 Hz
|
Generates deeper bass |
 High Frequency Response |
200 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
353mm
vs
415mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1198cm2
vs
1980cm2
|
Takes less floor space |
 Price per pair* |
2000USD
vs
2700USD
|
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.
Sonus faber Gravis III needs about 65% more floor area. Sonus faber Gravis III stands 133mm further into the room. Sonus faber Gravis III is 62mm taller.
| General |
Sonus faber Gravis III |
KEF KF92 |
| Brand |
Sonus faber |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
600 watts |
1000 watts |
| Frequency Response |
25-120 Hz |
11-200 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
600-watt RMS |
1000-watt RMS |
| Watts Peak (Max) |
900-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
1 |
2 |
| Woofer Size |
10" |
9" |
| Woofer Composition |
Honeycomb sandwich |
Hybrid aluminum |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
Continuously adjustable |
n/a |
Physical Specs |
|
|
| Height |
415.0mm (16.3") |
353.0mm (13.9") |
| Width |
400.0mm (15.7") |
331.0mm (13") |
| Depth |
495.0mm (19.5") |
362.0mm (14.3") |
| Weight |
26.70kg (58.7lbs) |
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 25Hz. Under 20Hz is felt more than heard - the bottom of a pipe organ and the bottom of a film mix. |
| Amplifier power | B | KEF KF92 has the bigger amplifier - 1000W against 600W RMS, about 2.2dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | B | KEF KF92 moves more air: 2 x 9" against 10" is 1.62x the cone area, not the 1.27x 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 49% 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 $2,700, about 26% less. |
A Sonus faber Gravis III 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?
KEF KF92 is the easier recommendation: it leads on most of the measured areas and costs less. Take Sonus faber Gravis III if one of the "depends" rows describes your room. 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.