In this review, we will be comparing TZero MKIII and KUBE 8b, two Powered Subwoofer speakers from REL 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 REL TZero MKIII 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 REL TZero MKIIIand KEF KUBE 8b have a single woofer setup however the REL TZero MKIII's woofer is 6.5-inch whereas the KEF KUBE 8b features a 8-inch woofer.
Frequency Response
TZero MKIII has a frequency range of 37-120 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 34Hz, the KUBE 8b can go slightly deeper then the TZero MKIII's min frequency of 37Hz.
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
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 REL TZero MKIII's and KEF KUBE 8b's external dimensions. REL TZero MKIII has external dimensions of 242.9 x 217.5 x 295.3mm () 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).
KEF KUBE 8b is clearly the larger of the two speakers. Its body is 78.5mm wider, 51.1mm taller and 43.7mm deeper than REL TZero MKIII.
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 REL TZero MKIII is approximately 642.3cm2 / 99.6inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The TZero MKIII requires 36% less surface area than the KUBE 8b 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 REL TZero MKIII weighs 6.80kg / 15lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the KUBE 8b 67% heavier than the TZero MKIII.
Here is a comparison of how TZero MKIII and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
 Height |
242mm
vs
294mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
642cm2
vs
1003cm2
|
Takes less floor space |
 Price per pair* |
599USD
vs
600USD
|
costs less (*prices may change depending on the seller, location and time) |
 Woofer Size |
8 inches
vs
6.5 inches
|
Larger woofer |
| Low Frequency Response |
34 Hz
vs
37 Hz
|
Generates deeper bass |
 High Frequency Response |
140 Hz
vs
120 Hz
|
Generates higher frequency |
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.
KEF KUBE 8b needs about 56% more floor area. KEF KUBE 8b stands 44mm further into the room. KEF KUBE 8b is 51mm taller.
| General |
REL TZero MKIII |
KEF KUBE 8b |
| Brand |
REL |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Frequency Response |
37-120 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
100-watt RMS |
300-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
6.5" |
8" |
| Woofer Composition |
|
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
40-140 Hz |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
242.9mm (9.6") |
294.0mm (11.6") |
| Width |
217.5mm (8.6") |
296.0mm (11.7") |
| Depth |
295.3mm (11.6") |
339.0mm (13.3") |
| Weight |
6.80kg (15lbs) |
11.36kg (25lbs) |
| Enclosure |
|
Acoustic Suspension |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
3 Years |
2 Years |
| Labor Warranty |
3 Years |
2 Years |
No single best subwoofer here. Your room, where the box can physically go, and whether this is mainly for films or mainly for music will settle it long before the specs do.
| Area | Better | Why |
|---|
| Bass depth | B | KEF KUBE 8b goes deeper - 34Hz against 37Hz. A real difference, though most music has little content below 37Hz. |
| Amplifier power | B | KEF KUBE 8b has the bigger amplifier - 300W against 100W RMS, about 4.8dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | B | KEF KUBE 8b moves more air: 8" against 6.5" is 1.51x the cone area, not the 1.23x 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. |
| Cabinet size | depends | REL TZero MKIII 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 | REL TZero MKIII 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 | evenly matched | Priced within a few per cent of each other. |
A REL TZero MKIII 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?
KEF KUBE 8b has the edge on paper, though not by much. The "depends" rows are more likely to decide this than the score is. If placement is the constraint - a corner, behind a sofa, under a desk - REL TZero MKIII 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.