In this review, we will be comparing Monitor XT12 and Dynamo 400, two Powered Subwoofer speakers from Polk Audio and MartinLogan. 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 Polk Monitor XT12 and MartinLogan 400 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 Polk Monitor XT12and MartinLogan 400 have a single woofer setup however the Polk Monitor XT12's woofer is 12-inch whereas the MartinLogan 400 features a 8-inch woofer.
Frequency Response
Monitor XT12 has a frequency range of 24-160 Hz whereas Dynamo 400 has a frequency range of 30-200 Hz. With a minimum frequency of 24Hz, the Monitor XT12 can go significantly deeper on the low side and provide stronger bass compared to the Dynamo 400's min frequency of 30Hz.
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 Polk Monitor XT12 has a Bass Reflex type cabinet. 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. On the other hand the MartinLogan 400 have Bass reflex type enclosure.
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 Polk Monitor XT12's and MartinLogan 400's external dimensions. 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) whereas MartinLogan 400 has external dimensions of 385.0 x 339.0 x 388.0mm (15-1/8 x 13-5/16 x 15-1/4inch).
Polk Monitor XT12 is clearly the larger of the two speakers. Its body is 69mm wider, 33mm taller and 97mm deeper than MartinLogan 400.
Below you can see the front view size comparison of Polk Monitor XT12 and MartinLogan 400 in scale.
Comparison image of Polk Monitor XT12 and MartinLogan 400 Size and External Dimensions
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 Polk Monitor XT12 is approximately 1978.8cm2 / 306.7inch2 and base area of the MartinLogan 400 is approximately 1315.3cm2 / 203.9inch2. The Monitor XT12 requires 50% more surface area than the Dynamo 400 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 Polk Monitor XT12 weighs 17.73kg / 39lbs and the MartinLogan 400 weighs 12.95kg / 28.5lbs. This makes the Monitor XT12 37% heavier than the Dynamo 400.
Here is a comparison of how Monitor XT12 and Dynamo 400's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
What's in the Box of Polk Monitor XT12?
Here are the items that are included inside the box of Monitor XT12:
- Black powered subwoofer
- 6.5-feet AC power cord
- Grille
- Owners Manual
- Online registration card
What's in the Box of MartinLogan 400?
Here are the items that come with the Dynamo 400:
- Powered subwoofer
- 6.5-feet AC power cord
- User-feets Manual
 Woofer Size |
12 inches
vs
8 inches
|
Larger woofer |
| Low Frequency Response |
24 Hz
vs
30 Hz
|
Generates deeper bass |
 Price per pair* |
399USD
vs
500USD
|
costs less (*prices may change depending on the seller, location and time) |
 High Frequency Response |
200 Hz
vs
160 Hz
|
Generates higher frequency |
 Height |
385mm
vs
418mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1315cm2
vs
1978cm2
|
Takes less floor space |
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.
Polk Monitor XT12 needs about 50% more floor area. Polk Monitor XT12 stands 97mm further into the room. Polk Monitor XT12 is 33mm taller.
| General |
Polk Monitor XT12 |
MartinLogan Dynamo 400 |
| Brand |
Polk Audio |
MartinLogan |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
50 watts |
75 watts |
| Frequency Response |
24-160 Hz |
30-200 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
50-watt RMS |
75-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
12" |
8" |
| Woofer Composition |
Bi-laminate paper |
Polypropylene |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Firing Direction |
front |
bottom |
Physical Specs |
|
|
| Height |
418.0mm (16.5") |
385.0mm (15.2") |
| Width |
408.0mm (16.1") |
339.0mm (13.3") |
| Depth |
485.0mm (19.1") |
388.0mm (15.3") |
| Weight |
17.73kg (39lbs) |
12.95kg (28.5lbs) |
| Enclosure |
Bass Reflex |
Bass reflex |
| Available Colors |
n/a |
Satin Black |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
3 Years |
3 Yrs w/ Registration |
| Labor Warranty |
3 Years |
3 Yrs w/ Registration |
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 | A | Polk Monitor XT12 goes deeper - 24Hz against 30Hz. That gap covers the lowest notes of a five-string bass and a concert bass drum. |
| Amplifier power | B | MartinLogan 400 has the bigger amplifier - 75W against 50W RMS, about 1.8dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | Polk Monitor XT12 moves more air: 12" against 8" is 2.25x the cone area, not the 1.5x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Enclosure | evenly matched | Both are ported designs, so they roll off in much the same way. |
| Driver placement | depends | Polk Monitor XT12 fires front and MartinLogan 400 fires down. A down-firing driver is more forgiving of a grille-less look and of a hard floor; a front-firing one is the safer choice on a thick carpet or a suspended timber floor. |
| Cabinet size | depends | MartinLogan 400 is about 39% 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 | A | Polk Monitor XT12 costs less - $399 against $500, about 20% less. |
A Polk Monitor XT12 B MartinLogan 400
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?
Polk Monitor XT12 has the edge on paper, though not by much. The "depends" rows are more likely to decide this than the score is. If placement is the constraint - a corner, behind a sofa, under a desk - MartinLogan 400 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.