In this review, we will be comparing R-121SW and Alpha S8, two Powered Subwoofer speakers from Klipsch and PSB. 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 Klipsch R-121SW and PSB Alpha S8 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 Klipsch R-121SWand PSB Alpha S8 have a single woofer setup however the Klipsch R-121SW's woofer is 12-inch whereas the PSB Alpha S8 features a 8-inch woofer.
Frequency Response
R-121SW has a frequency range of 28-120 Hz whereas Alpha S8 has a frequency range of 35-150 Hz. With a minimum frequency of 28Hz, the R-121SW can go significantly deeper on the low side and provide stronger bass compared to the Alpha S8's min frequency of 35Hz.
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 Klipsch R-121SW and PSB Alpha S8 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.
Klipsch R-121SW Port
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 Klipsch R-121SW's and PSB Alpha S8's external dimensions. Klipsch R-121SW has external dimensions of 423.0 x 407.0 x 532.0mm (16-5/8inch x 16inch x 20-15/16inch) whereas PSB Alpha S8 has external dimensions of 318.0 x 293.0 x 413.0mm (12-1/2 x 11-1/2 x 16-1/4inch).
Klipsch R-121SW is clearly the larger of the two speakers. Its body is 114mm wider, 105mm taller and 119mm deeper than PSB Alpha S8.
Below you can see the front view size comparison of Klipsch R-121SW and PSB Alpha S8 in scale.
Comparison image of Klipsch R-121SW and PSB Alpha S8 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 Klipsch R-121SW is approximately 2165.2cm2 / 335.6inch2 and base area of the PSB Alpha S8 is approximately 1210.1cm2 / 187.6inch2. The R-121SW requires 79% more surface area than the Alpha S8 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 Klipsch R-121SW weighs 16.00kg / 35.2lbs and the PSB Alpha S8 weighs 9.55kg / 21lbs. This makes the R-121SW 68% heavier than the Alpha S8.
Here is a comparison of how R-121SW and Alpha S8's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
What's in the Box of Klipsch R-121SW?
Here are the items that are included inside the box of R-121SW:
- Powered subwoofer
- Grille
- 6.5-feet AC power cord
- User Manual
- Important Safety Instructions
- Warranty Information
What's in the Box of PSB Alpha S8?
Here are the items that come with the Alpha S8:
- Powered subwoofer
- Grille
- 5-feet AC power cord
- 4 Rubber feet
- 4 Spike feet
- 4 Hex-nuts
- Quick Start Guide
- Important Safety Instructions
- Warranty Information
 Woofer Size |
12 inches
vs
8 inches
|
Larger woofer |
| Low Frequency Response |
28 Hz
vs
35 Hz
|
Generates deeper bass |
 High Frequency Response |
150 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
318mm
vs
423mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1210cm2
vs
2165cm2
|
Takes less floor space |
 Price per pair* |
549USD
vs
599USD
|
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.
Klipsch R-121SW needs about 79% more floor area. Klipsch R-121SW stands 119mm further into the room. Klipsch R-121SW is 105mm taller.
| General |
Klipsch Reference R-121SW |
PSB Alpha S8 |
| Brand |
Klipsch |
PSB |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
200 watts |
150 watts |
| Frequency Response |
28-120 Hz |
35-150 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
200-watt RMS |
150-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
12" |
8" |
| Woofer Composition |
Spun-Copper TCP |
Polypropylene |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Firing Direction |
front |
front |
Physical Specs |
|
|
| Height |
423.0mm (16.7") |
318.0mm (12.5") |
| Width |
407.0mm (16") |
293.0mm (11.5") |
| Depth |
532.0mm (20.9") |
413.0mm (16.3") |
| Weight |
16.00kg (35.2lbs) |
9.55kg (21lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
2 Years |
1 Year |
| Labor Warranty |
2 Years |
1 Year |
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 | Klipsch R-121SW goes deeper - 28Hz against 35Hz. A real difference, though most music has little content below 35Hz. |
| Amplifier power | A | Klipsch R-121SW has the bigger amplifier - 200W against 150W RMS, about 1.2dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | Klipsch R-121SW 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. |
| Cabinet size | depends | PSB Alpha S8 is about 58% 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 | Klipsch R-121SW carries 2 years on parts against 1 years. A subwoofer amplifier works harder than anything else in the system, so this is not a throwaway line. |
| Price | B | PSB Alpha S8 costs less - $549 against $599, about 8% less. |
A Klipsch R-121SW B PSB Alpha S8
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 R-121SW leads across most of the measured areas for a modest premium, so it is the easier pick if the budget stretches. PSB Alpha S8 is the one to take if it does not. If placement is the constraint - a corner, behind a sofa, under a desk - PSB Alpha S8 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.