In this review, we will be comparing SubSeries 250 and KUBE 8b, two Powered Subwoofer speakers from PSB and KEF. 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 PSB SubSeries 250 and KEF KUBE 8b 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 PSB SubSeries 250and KEF KUBE 8b have a single woofer setup however the PSB SubSeries 250's woofer is 10-inch whereas the KEF KUBE 8b features a 8-inch woofer.
Frequency Response
SubSeries 250 has a frequency range of 25-150 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 25Hz, the SubSeries 250 can go significantly deeper on the low side and provide stronger bass compared to the KUBE 8b's min frequency of 34Hz.
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 PSB SubSeries 250 and KEF KUBE 8b have Acoustic Suspension type cabinets. Acoustic Suspension aka Sealed type subwoofers have enclosures that are sealed hence no ports or holes exists on the cabinet. Sealed designs helps to provide more accurate and tight bass responses compared to ported 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 PSB SubSeries 250's and KEF KUBE 8b's external dimensions. PSB SubSeries 250 has external dimensions of 362.0 x 348.0 x 397.0mm (14-1/4 x 13-11/16 x 15-5/8inch) whereas KEF KUBE 8b has external dimensions of 294.0 x 296.0 x 339.0mm (11-9/16 x 11-5/8 x 13-5/16inch).
PSB SubSeries 250 is clearly the larger of the two speakers. Its body is 52mm wider, 68mm taller and 58mm deeper than KEF KUBE 8b.
Below you can see the front view size comparison of PSB SubSeries 250 and KEF KUBE 8b in scale.
Comparison image of PSB SubSeries 250 and KEF KUBE 8b 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 PSB SubSeries 250 is approximately 1381.6cm2 / 214.1inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The SubSeries 250 requires 38% more surface area than the KUBE 8b 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 PSB SubSeries 250 weighs 19.09kg / 42lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the SubSeries 250 68% heavier than the KUBE 8b.
Here is a comparison of how SubSeries 250 and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
What's in the Box of PSB SubSeries 250?
Here are the items that are included inside the box of SubSeries 250:
- Powered subwoofer
- Grille
- 6-feet AC power cord
- Quick Start Guide
- Important Safety Instructions
- Warranty Information
What's in the Box of KEF KUBE 8b?
Here are the items that come with the KUBE 8b:
- Powered subwoofer
- 6.5-feet AC power cord
- Speaker-level input block
- User Manual
- Important Safety Information
- Warranty Information
 Woofer Size |
10 inches
vs
8 inches
|
Larger woofer |
| Low Frequency Response |
25 Hz
vs
34 Hz
|
Generates deeper bass |
 High Frequency Response |
150 Hz
vs
140 Hz
|
Generates higher frequency |
 Wireless Operation |
Optional
vs
No
|
Connect your subwoofer to your system wireless |
 Height |
294mm
vs
362mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2
vs
1381cm2
|
Takes less floor space |
 Price per pair* |
600USD
vs
999USD
|
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.
PSB SubSeries 250 needs about 38% more floor area. PSB SubSeries 250 stands 58mm further into the room. PSB SubSeries 250 is 68mm taller.
| General |
PSB SubSeries 250 |
KEF KUBE 8b |
| Brand |
PSB |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
200 watts |
300 watts |
| Frequency Response |
25-150 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
200-watt RMS |
300-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
10" |
8" |
| Woofer Composition |
Polypropylene |
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
50-150 Hz and 80 Hz |
40-140 Hz |
| Firing Direction |
front |
front |
Physical Specs |
|
|
| Height |
362.0mm (14.3") |
294.0mm (11.6") |
| Width |
348.0mm (13.7") |
296.0mm (11.7") |
| Depth |
397.0mm (15.6") |
339.0mm (13.3") |
| Weight |
19.09kg (42lbs) |
11.36kg (25lbs) |
| Enclosure |
Acoustic Suspension |
Acoustic Suspension |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
1 Year |
2 Years |
| Labor Warranty |
1 Year |
2 Years |
Different price classes - PSB SubSeries 250 costs roughly 1.7x what KEF KUBE 8b does. Before paying it, read the note below about two smaller subwoofers.
| Area | Better | Why |
|---|
| Bass depth | A | PSB SubSeries 250 goes deeper - 25Hz against 34Hz. That gap covers the lowest notes of a five-string bass and a concert bass drum. |
| Amplifier power | B | KEF KUBE 8b has the bigger amplifier - 300W against 200W RMS, about 1.8dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | PSB SubSeries 250 moves more air: 10" against 8" is 1.56x the cone area, not the 1.25x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Enclosure | evenly matched | Both are sealed designs, so they roll off in much the same way. |
| Speaker-level inputs | A | PSB SubSeries 250 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. |
| Wireless option | depends | Only PSB SubSeries 250 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. |
| Cabinet size | depends | KEF KUBE 8b is about 41% 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 | B | KEF KUBE 8b 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 | KEF KUBE 8b costs less - $600 against $999, about 40% less. |
A PSB SubSeries 250 B KEF KUBE 8b
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?
PSB SubSeries 250 is ahead, but on only 1 of the measured areas, and it costs about 67% more. KEF KUBE 8b is the sensible buy unless your room is large enough to need the extra. Check your amplifier first: if it has no subwoofer or preamp output, PSB SubSeries 250 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 $600 each, two KEF KUBE 8b cost about $1,200 against $999 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.