In this review, we will be comparing Thetis 340 and Monitor XT12, two Powered Subwoofer speakers from Triangle 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 Triangle Thetis 340 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.Both Triangle Thetis 340and Polk Monitor XT12 have a single woofer setup however the Triangle Thetis 340's woofer is 10-inch whereas the Polk Monitor XT12 features a 12-inch woofer.
Frequency Response
Thetis 340 has a frequency range of 25-120 Hz whereas Monitor XT12 has a frequency range of 24-160 Hz. With a minimum frequency of 24Hz, the Monitor XT12 can go slightly deeper then the Thetis 340's min frequency of 25Hz.
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 Triangle Thetis 340 and Polk Monitor XT12 have Bass Reflex type cabinets. 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 Triangle Thetis 340's and Polk Monitor XT12's external dimensions. Triangle Thetis 340 has external dimensions of 380.0 x 340.0 x 340.0mm (14-15/16 x 13-3/8 x 13-3/8inch) 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).
Polk Monitor XT12 is clearly the larger of the two speakers. Its body is 68mm wider, 38mm taller and 145mm deeper than Triangle Thetis 340.
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.
Polk Monitor XT12 needs about 71% more floor or shelf area. Polk Monitor XT12 is 145mm deeper, so it stands that much further out from the wall. Polk Monitor XT12 is 38mm 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 Triangle Thetis 340 is approximately 1156.0cm2 / 179.2inch2 and base area of the Polk Monitor XT12 is approximately 1978.8cm2 / 306.7inch2. The Thetis 340 requires 42% less surface area than the Monitor XT12 which gives it a small advantage 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 Triangle Thetis 340 weighs 16.10kg / 35.4lbs and the Polk Monitor XT12 weighs 17.73kg / 39lbs. This makes the Monitor XT12 10% heavier than the Thetis 340.
Here is a comparison of how Thetis 340 and Monitor XT12's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Height |
380mm
vs
418mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1156cm2
vs
1978cm2
|
Takes less floor space |
 Woofer Size |
12 inches
vs
10 inches
|
Larger woofer |
| Low Frequency Response |
24 Hz
vs
25 Hz
|
Generates deeper bass |
 High Frequency Response |
160 Hz
vs
120 Hz
|
Generates higher frequency |
 Price per pair* |
399USD
vs
825USD
|
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.
Polk Monitor XT12 needs about 71% more floor area. Polk Monitor XT12 stands 145mm further into the room. Polk Monitor XT12 is 38mm taller.
| General |
Triangle Thetis 340 |
Polk Monitor XT12 |
| Brand |
Triangle |
Polk Audio |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
250 watts |
50 watts |
| Frequency Response |
25-120 Hz |
24-160 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
250-watt RMS |
50-watt RMS |
| Watts Peak (Max) |
400-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
10" |
12" |
| Woofer Composition |
Paper composite |
Bi-laminate paper |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
380.0mm (15") |
418.0mm (16.5") |
| Width |
340.0mm (13.4") |
408.0mm (16.1") |
| Depth |
340.0mm (13.4") |
485.0mm (19.1") |
| Weight |
16.10kg (35.4lbs) |
17.73kg (39lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
5 Years |
3 Years |
| Labor Warranty |
5 Years |
3 Years |
Different price classes - Triangle Thetis 340 costs roughly 2.1x what Polk Monitor XT12 does. Before paying it, read the note below about two smaller subwoofers.
| Area | Better | Why |
|---|
| Bass depth | evenly matched | Effectively the same reach (25Hz vs 24Hz). |
| Amplifier power | A | Triangle Thetis 340 has the bigger amplifier - 250W against 50W RMS, about 7dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | B | 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 | evenly matched | Both are ported designs, so they roll off in much the same way. |
| Driver placement | depends | Triangle Thetis 340 fires down and Polk Monitor XT12 fires front. 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 | Triangle Thetis 340 is about 47% 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 | Triangle Thetis 340 carries 5 years on parts against 3 years. A subwoofer amplifier works harder than anything else in the system, so this is not a throwaway line. |
| Price | B | Polk Monitor XT12 costs less - $399 against $825, about 52% less. |
A Triangle Thetis 340 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?
Triangle Thetis 340 is ahead, but on only 1 of the measured areas, and it costs about 107% more. Polk Monitor XT12 is the sensible buy unless your room is large enough to need the extra. 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 $825 for one of the other, which is worth a thought. If placement is the constraint - a corner, behind a sofa, under a desk - Triangle Thetis 340 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.