In this review, we will be comparing Radius 390 and SPL-120, two Powered Subwoofer speakers from Monitor Audio and Klipsch. 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 Monitor Audio Radius 390 and Klipsch SPL-120 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 Monitor Audio Radius 390and Klipsch SPL-120 have a single woofer setup however the Monitor Audio Radius 390's woofer is 10-inch whereas the Klipsch SPL-120 features a 12-inch woofer.
Frequency Response
Radius 390 has a frequency range of 30-120 Hz whereas SPL-120 has a frequency range of 24-125 Hz. With a minimum frequency of 24Hz, the SPL-120 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 Monitor Audio Radius 390 has a Passive Radiator type cabinet. 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. On the other hand the Klipsch SPL-120 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 Monitor Audio Radius 390's and Klipsch SPL-120's external dimensions. 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) whereas Klipsch SPL-120 has external dimensions of 450.0 x 375.0 x 540.0mm (17-11/16 x 14-3/4 x 21-1/4inch).
Klipsch SPL-120 is clearly the larger of the two speakers. Its body is 44mm wider, 102mm taller and 155mm deeper than Monitor Audio Radius 390.
Below you can see the front view size comparison of Monitor Audio Radius 390 and Klipsch SPL-120 in scale.
Comparison image of Monitor Audio Radius 390 and Klipsch SPL-120 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 Monitor Audio Radius 390 is approximately 1274.4cm2 / 197.5inch2 and base area of the Klipsch SPL-120 is approximately 2025.0cm2 / 313.9inch2. The Radius 390 requires 37% less surface area than the SPL-120 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 Monitor Audio Radius 390 weighs 13.77kg / 30.3lbs and the Klipsch SPL-120 weighs 20.45kg / 45lbs. This makes the SPL-120 49% heavier than the Radius 390.
Here is a comparison of how Radius 390 and SPL-120's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
What's in the Box of Monitor Audio Radius 390?
Here are the items that are included inside the box of Radius 390:
- Powered sub
- 6-feet AC power cord
- 10.75-feet Mono minijack cable
- Owners Manual
- Important Safety Instructions
What's in the Box of Klipsch SPL-120?
Here are the items that come with the SPL-120:
- Powered sub
- Grille
- 6.5-feet AC power cord
- User Manual
- Important Safety Instructions
- Warranty Information
 Height |
348mm
vs
450mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1274cm2
vs
2025cm2
|
Takes less floor space |
 Woofer Size |
12 inches
vs
10 inches
|
Larger woofer |
| Low Frequency Response |
24 Hz
vs
30 Hz
|
Generates deeper bass |
 High Frequency Response |
125 Hz
vs
120 Hz
|
Generates higher frequency |
 Price per pair* |
499USD
vs
1150USD
|
costs less (*prices may change depending on the seller, location and time) |
 Wireless Operation |
Optional
vs
No
|
Connect your subwoofer to your system wireless |
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.
Klipsch SPL-120 needs about 59% more floor area. Klipsch SPL-120 stands 155mm further into the room. Klipsch SPL-120 is 102mm taller.
| General |
Monitor Audio Radius 390 |
Klipsch SPL-120 |
| Brand |
Monitor Audio |
Klipsch |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
220 watts |
300 watts |
| Frequency Response |
30-120 Hz |
24-125 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
220-watt RMS |
300-watt RMS |
| Watts Peak (Max) |
n/a |
600-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
10" |
12" |
| Woofer Composition |
C-CAM |
Cerametallic |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Firing Direction |
side |
front |
Physical Specs |
|
|
| Height |
348.0mm (13.7") |
450.0mm (17.7") |
| Width |
331.0mm (13") |
375.0mm (14.8") |
| Depth |
385.0mm (15.2") |
540.0mm (21.3") |
| Weight |
13.77kg (30.3lbs) |
20.45kg (45lbs) |
| Enclosure |
Passive Radiator |
Bass Reflex |
| Grille |
n/a |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
2 Years |
2 Years |
| Labor Warranty |
2 Years |
2 Years |
A passive radiator 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 | B | Klipsch SPL-120 goes deeper - 24Hz against 30Hz. That gap covers the lowest notes of a five-string bass and a concert bass drum. |
| Amplifier power | B | Klipsch SPL-120 has the bigger amplifier - 300W against 220W RMS, about 1.3dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | B | Klipsch SPL-120 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 | Monitor Audio Radius 390 is passive radiator - a passive radiator behaves like a port without the pipe noise, and suits a slim cabinet; Klipsch SPL-120 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. |
| Wireless option | depends | Only Klipsch SPL-120 offers a wireless link (as a paid option). It decides where the sub can go if you cannot run a cable, and is worth nothing if you can. |
| Driver placement | depends | Monitor Audio Radius 390 fires side and Klipsch SPL-120 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 | Monitor Audio Radius 390 is about 51% 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 | Klipsch SPL-120 costs less - $499 against $1,150, about 57% less. |
A Monitor Audio Radius 390 B Klipsch SPL-120
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?
Klipsch SPL-120 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. 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 $499 each, two Klipsch SPL-120 cost about $998 against $1,150 for one of the other, which is worth a thought. If placement is the constraint - a corner, behind a sofa, under a desk - Monitor Audio Radius 390 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.