In this review, we will be comparing Gravis VI and Monitor XT12, two Powered Subwoofer speakers from Sonus faber and Polk Audio. 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 Polk Monitor XT12 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 VI and Polk Monitor XT12 have a totally different setup: the Sonus faber Gravis VI features 2 x 12.5-inch drivers whereas the Monitor XT12 features 1 x 12-inch drivers.
Frequency Response
Gravis VI has a frequency range of 18-120 Hz whereas Monitor XT12 has a frequency range of 24-160 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 Monitor XT12's min frequency of 24Hz.
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 VI has a Acoustic Suspension type cabinet. 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. On the other hand the Polk Monitor XT12 have Bass Reflex type enclosure. Bass Reflex type subwoofers (aka Ported, Vented or Reflex Port) have enclosures that uses a port, hole or vent cut into the cabinet. Ported designs are generally more efficient than the Sealed 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 VI's and Polk Monitor XT12'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 Polk Monitor XT12 has external dimensions of 418.0 x 408.0 x 485.0mm (16-7/16inch x 16-1/16inch x 19-1/16inch).
Sonus faber Gravis VI is clearly the larger of the two speakers. Its body is 40mm wider, 198mm taller and 100mm deeper than Polk Monitor XT12.
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 VI needs about 32% more floor or shelf area. Sonus faber Gravis VI is 100mm deeper, so it stands that much further out from the wall. Sonus faber Gravis VI is 198mm 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 VI is approximately 2620.8cm2 / 406.2inch2 and base area of the Polk Monitor XT12 is approximately 1978.8cm2 / 306.7inch2. The Gravis VI requires 32% more surface area than the Monitor XT12 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 Polk Monitor XT12 weighs 17.73kg / 39lbs. This makes the Gravis VI 193% heavier than the Monitor XT12.
Here is a comparison of how Gravis VI and Monitor XT12's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Woofer Size |
12.5 inches
vs
12 inches
|
Larger woofer |
| Number of Woofers |
2
vs
1
|
More woofers |
| Low Frequency Response |
18 Hz
vs
24 Hz
|
Generates deeper bass |
 High Frequency Response |
160 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
418mm
vs
616mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1978cm2
vs
2620cm2
|
Takes less floor space |
 Price per pair* |
399USD
vs
6500USD
|
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 VI needs about 32% more floor area. Sonus faber Gravis VI stands 100mm further into the room. Sonus faber Gravis VI is 198mm taller.
| General |
Sonus faber Gravis VI |
Polk Monitor XT12 |
| Brand |
Sonus faber |
Polk Audio |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
1700 watts |
50 watts |
| Frequency Response |
18-120 Hz |
24-160 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
1700-watt RMS |
50-watt RMS |
| Watts Peak (Max) |
2400-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
2 |
1 |
| Woofer Size |
12.5" |
12" |
| Woofer Composition |
Honeycomb sandwich |
Bi-laminate paper |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
Continuously adjustable |
n/a |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
616.0mm (24.3") |
418.0mm (16.5") |
| Width |
448.0mm (17.6") |
408.0mm (16.1") |
| Depth |
585.0mm (23") |
485.0mm (19.1") |
| Weight |
52.00kg (114.4lbs) |
17.73kg (39lbs) |
| Enclosure |
Acoustic Suspension |
Bass Reflex |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
|
3 Years |
| Labor Warranty |
|
3 Years |
A sealed subwoofer against a ported one. That is the most consequential line on this page: it decides how the bass rolls off, how it behaves in a small room, and how much output you get for the size of the box.
| Area | Better | Why |
|---|
| Bass depth | A | Sonus faber Gravis VI goes deeper - 18Hz against 24Hz. Under 20Hz is felt more than heard - the bottom of a pipe organ and the bottom of a film mix. |
| Amplifier power | A | Sonus faber Gravis VI has the bigger amplifier - 1700W against 50W RMS, about 15.3dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | Sonus faber Gravis VI moves more air: 2 x 12.5" against 12" is 2.17x the cone area, not the 1.47x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Enclosure | depends | Sonus faber Gravis VI is sealed - a sealed box rolls off gently and is usually the easier one to integrate in a small or awkward room; Polk Monitor XT12 is ported - a ported box gives more output low down for its size, at the cost of a steeper roll-off below tuning. Neither is better in the abstract; ported tends to suit films and sealed tends to suit music, and both generalisations have exceptions. |
| Cabinet size | depends | Polk Monitor XT12 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 | Polk Monitor XT12 costs less - $399 against $6,500, about 94% less. |
A Sonus faber Gravis VI B Polk Monitor XT12
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?
The usual trade-off: Sonus faber Gravis VI measures better, Polk Monitor XT12 costs about 94% less. In a normal room, placement will make a bigger difference than the gap between these two. Films or music? If this is mainly a home cinema, Polk Monitor XT12 will hit harder for the money; if it is mainly for music in a normal-sized room, Sonus faber Gravis VI is usually the easier one to make sound right. 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 $399 each, two Polk Monitor XT12 cost about $798 against $6,500 for one of the other, which is worth a thought.
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.