In this review, we will be comparing Monitor XT12 and Radius 390, two Powered Subwoofer speakers from Polk Audio and Monitor 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 Polk Monitor XT12 and Monitor Audio Radius 390 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 Monitor Audio Radius 390 have a single woofer setup however the Polk Monitor XT12's woofer is 12-inch whereas the Monitor Audio Radius 390 features a 10-inch woofer.
Frequency Response
Monitor XT12 has a frequency range of 24-160 Hz whereas Radius 390 has a frequency range of 30-120 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 Radius 390'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 Monitor Audio Radius 390 have Passive Radiator type enclosure. 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.
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 Monitor Audio Radius 390'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 Monitor Audio Radius 390 has external dimensions of 348.0 x 331.0 x 385.0mm (13-11/16 x 13 x 15-1/8inch).
Polk Monitor XT12 is clearly the larger of the two speakers. Its body is 77mm wider, 70mm taller and 100mm deeper than Monitor Audio Radius 390.
Below you can see the front view size comparison of Polk Monitor XT12 and Monitor Audio Radius 390 in scale.
Comparison image of Polk Monitor XT12 and Monitor Audio Radius 390 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 Monitor Audio Radius 390 is approximately 1274.4cm2 / 197.5inch2. The Monitor XT12 requires 55% more surface area than the Radius 390 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 Monitor Audio Radius 390 weighs 13.77kg / 30.3lbs. This makes the Monitor XT12 29% heavier than the Radius 390.
Here is a comparison of how Monitor XT12 and Radius 390'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 Monitor Audio Radius 390?
Here are the items that come with the Radius 390:
- Powered sub
- 6-feet AC power cord
- 10.75-feet Mono minijack cable
- Owners Manual
- Important Safety Instructions
 Woofer Size |
12 inches
vs
10 inches
|
Larger woofer |
| Low Frequency Response |
24 Hz
vs
30 Hz
|
Generates deeper bass |
 High Frequency Response |
160 Hz
vs
120 Hz
|
Generates higher frequency |
 Price per pair* |
399USD
vs
1150USD
|
costs less (*prices may change depending on the seller, location and time) |
 Height |
348mm
vs
418mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1274cm2
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 55% more floor area. Polk Monitor XT12 stands 100mm further into the room. Polk Monitor XT12 is 70mm taller.
| General |
Polk Monitor XT12 |
Monitor Audio Radius 390 |
| Brand |
Polk Audio |
Monitor Audio |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
50 watts |
220 watts |
| Frequency Response |
24-160 Hz |
30-120 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
50-watt RMS |
220-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
12" |
10" |
| Woofer Composition |
Bi-laminate paper |
C-CAM |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Firing Direction |
front |
side |
Physical Specs |
|
|
| Height |
418.0mm (16.5") |
348.0mm (13.7") |
| Width |
408.0mm (16.1") |
331.0mm (13") |
| Depth |
485.0mm (19.1") |
385.0mm (15.2") |
| Weight |
17.73kg (39lbs) |
13.77kg (30.3lbs) |
| Enclosure |
Bass Reflex |
Passive Radiator |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
3 Years |
2 Years |
| Labor Warranty |
3 Years |
2 Years |
A ported subwoofer against a passive radiator 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 | 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 | Monitor Audio Radius 390 has the bigger amplifier - 220W against 50W RMS, about 6.4dB 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 10" is 1.44x the cone area, not the 1.2x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Enclosure | depends | 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; Monitor Audio Radius 390 is passive radiator - a passive radiator behaves like a port without the pipe noise, and suits a slim cabinet. Neither is better in the abstract; ported tends to suit films and sealed tends to suit music, and both generalisations have exceptions. |
| Speaker-level inputs | A | Polk Monitor XT12 takes a speaker-level connection as well as line level. That is what lets it work with an integrated amplifier or a vintage receiver that has no subwoofer output at all. |
| Driver placement | depends | Polk Monitor XT12 fires front and Monitor Audio Radius 390 fires side. 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 | Monitor Audio Radius 390 is about 46% 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. |
| Warranty | A | Polk Monitor XT12 carries 3 years on parts against 2 years. A subwoofer amplifier works harder than anything else in the system, so this is not a throwaway line. |
| Price | A | Polk Monitor XT12 costs less - $399 against $1,150, about 65% less. |
A Polk Monitor XT12 B Monitor Audio Radius 390
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 is the easier recommendation: it leads on most of the measured areas and costs less. Take Monitor Audio Radius 390 if one of the "depends" rows describes your room. Check your amplifier first: if it has no subwoofer or preamp output, Polk Monitor XT12 is the only one of these two you can connect at all. 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 $1,150 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.