In this review, we will be comparing Gravis VI 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 VI 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 VI 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.Sonus faber Gravis VI and KEF KUBE 8b have a totally different setup: the Sonus faber Gravis VI features 2 x 12.5-inch drivers whereas the KUBE 8b features 1 x 8-inch drivers.
Frequency Response
Gravis VI 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 Gravis VI 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 Sonus faber Gravis VI 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 Sonus faber Gravis VI's and KEF KUBE 8b's external dimensions. Sonus faber Gravis VI has external dimensions of 616.0 x 448.0 x 585.0mm ( 24-1/4 x 17-5/8 x 23-1/16inch) 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) .
Sonus faber Gravis VI is clearly the larger of the two speakers. Its body is 152mm wider, 322mm taller and 246mm 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 VI is approximately 2620.8cm2 / 406.2inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The Gravis VI requires 161% 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 VI weighs 52.00kg / 114.4lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the Gravis VI 358% heavier than the KUBE 8b.
Here is a comparison of how Gravis VI and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
12.5 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
616mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2
vs
2620cm2
|
Takes less floor space |
| General |
Sonus faber Gravis VI |
KEF KUBE 8b |
| Brand |
Sonus faber |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
1700 watts |
300 watts |
| Frequency Response |
18-120 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
1700-watt RMS |
300-watt RMS |
| Watts Peak (Max) |
2400-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
2 |
1 |
| Woofer Size |
12.5" |
8" |
| Woofer Composition |
Honeycomb sandwich |
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
Continuously adjustable |
40-140 Hz |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
616.0mm (24.3") |
294.0mm (11.6") |
| Width |
448.0mm (17.6") |
296.0mm (11.7") |
| Depth |
585.0mm (23") |
339.0mm (13.3") |
| Weight |
52.00kg (114.4lbs) |
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 |