In this review, we will be comparing Gravis II and KUBE 8b, 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 II 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 Sonus faber Gravis II 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.Both Sonus faber Gravis IIand KEF KUBE 8b have a single woofer setup however the Sonus faber Gravis II's woofer is 10-inch whereas the KEF KUBE 8b features a 8-inch woofer.
Frequency Response
Gravis II has a frequency range of 25-120 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 25Hz, the Gravis II 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
The Sonus faber Gravis II has a Passive Radiator type cabinet. Passive Radiator type subwoofers sports a non-powered cone that moves in response to the main woofer to move air out in order to generate stronger bass in a smaller body compared to ported or sealed designs. On the other hand the KEF KUBE 8b have Acoustic Suspension type enclosure. 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 Sonus faber Gravis II's and KEF KUBE 8b's external dimensions. Sonus faber Gravis II has external dimensions of 407.0 x 358.0 x 435.0mm ( 16inch x 14-1/16inch x 17-1/8inch ) 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) .
Sonus faber Gravis II is clearly the larger of the two speakers. Its body is 62mm wider, 113mm taller and 96mm 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 Sonus faber Gravis II is approximately 1557.3cm2 / 241.4inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The Gravis II requires 55% 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 Sonus faber Gravis II weighs 21.50kg / 47.3lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the Gravis II 89% heavier than the KUBE 8b.
Here is a comparison of how Gravis II and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
What's in the Box of Sonus faber Gravis II?
Here are the items that are included inside the box of Gravis II:
Powered subwooferGrille6-feet AC power cord33-feet Speakon cableOwners ManualEnvironmental Information
What's in the Box of KEF KUBE 8b?
Here are the items that come with the KUBE 8b:
Powered subwoofer6.5-feet AC power cordSpeaker-level input blockUser ManualImportant Safety InformationWarranty Information
 Woofer Size |
10 inches
vs
8 inches
|
Larger woofer |
| Low Frequency Response |
25 Hz
vs
34 Hz
|
Generates deeper bass |
 Passive Radiator |
2 x 10-inch
vs
None
|
Increases the bass performance |
 Driver Setup |
1-way
vs
-way
|
Have a dedicated mid-range driver |
 High Frequency Response |
140k Hz
vs
120k Hz
|
Generates higher frequency |
 Height |
294mm
vs
407mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2 (296x339mm)
vs
1557cm2 (358x435mm)
|
Takes less floor space |
 Price per pair* |
600USD
vs
1499USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Sonus faber Gravis II |
KEF KUBE 8b |
| Brand |
Sonus Faber |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
350 watts |
300 watts |
| Frequency Response |
25-120 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
350-watt RMS |
300-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
10" |
8" |
| Woofer Composition |
Treated Paper |
Not given |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
40-140 Hz |
| Firing Direction |
front |
front |
Physical Specs |
|
|
| Height |
407.0mm (16") |
294.0mm (11.6") |
| Width |
358.0mm (14.1") |
296.0mm (11.7") |
| Depth |
435.0mm (17.1") |
339.0mm (13.3") |
| Weight |
21.50kg (47.3lbs) |
11.36kg (25lbs) |
| Enclosure |
Passive Radiator |
Acoustic Suspension |
| Available Colors |
Piano Black,Matte White |
n/a |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
2 Yr/3 Yr registered |
2 Years |
| Labor Warranty |
2 Yr/3 Yr registered |
2 Years |