In this review, we will be comparing BalancedForce 210 and KUBE 8b, two Powered Subwoofer speakers from MartinLogan 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 MartinLogan BalancedForce 210 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.MartinLogan BalancedForce 210 and KEF KUBE 8b have a totally different setup: the MartinLogan BalancedForce 210 features 2 x 10-inch drivers whereas the KUBE 8b features 1 x 8-inch drivers.
Frequency Response
BalancedForce 210 has a frequency range of 20-120 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 20Hz, the BalancedForce 210 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
MartinLogan BalancedForce 210
High Frequency
Subwoofer Speakers
MartinLogan BalancedForce 210
Cabinet Type
Both MartinLogan BalancedForce 210 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 MartinLogan BalancedForce 210's and KEF KUBE 8b's external dimensions. MartinLogan BalancedForce 210 has external dimensions of 485.0 x 486.0 x 543.0mm (19-1/16inch x 19-1/8inch x 21-3/8inch) 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).
MartinLogan BalancedForce 210 is clearly the larger of the two speakers. Its body is 190mm wider, 191mm taller and 204mm deeper than KEF KUBE 8b.
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 MartinLogan BalancedForce 210 is approximately 2639.0cm2 / 409.0inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The BalancedForce 210 requires 163% 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 MartinLogan BalancedForce 210 weighs 43.64kg / 96lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the BalancedForce 210 284% heavier than the KUBE 8b.
Here is a comparison of how BalancedForce 210 and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
MartinLogan BalancedForce 210
What's in the Box of MartinLogan BalancedForce 210?
Here are the items that are included inside the box of BalancedForce 210:
- Powered subwoofer
- Top-glass cover
- 2 Grilles
- 8-feet AC power cord
- 4 Spike feet
- 4 Collars
- USB thumbdrive
- User-feets Manual
- Online Registration Card
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 |
| Number of Woofers |
2
vs
1
|
More woofers |
| Low Frequency Response |
20 Hz
vs
34 Hz
|
Generates deeper bass |
 High Frequency Response |
140 Hz
vs
120 Hz
|
Generates higher frequency |
 Height |
294mm
vs
485mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2
vs
2639cm2
|
Takes less floor space |
 Price per pair* |
600USD
vs
3499USD
|
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.
MartinLogan BalancedForce 210 needs about 163% more floor area. MartinLogan BalancedForce 210 stands 204mm further into the room. MartinLogan BalancedForce 210 is 191mm taller.
| General |
MartinLogan BalancedForce 210 |
KEF KUBE 8b |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
850 watts |
300 watts |
| Frequency Response |
20-120 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
850-watt RMS |
300-watt RMS |
| Watts Peak (Max) |
1700-watt RMS |
n/a |
Drivers |
|
|
| Woofer Quantity |
2 |
1 |
| Woofer Size |
10" |
8" |
| Woofer Composition |
Aluminum |
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
40-140 Hz |
| Firing Direction |
front |
front |
Physical Specs |
|
|
| Height |
485.0mm (19.1") |
294.0mm (11.6") |
| Width |
486.0mm (19.1") |
296.0mm (11.7") |
| Depth |
543.0mm (21.4") |
339.0mm (13.3") |
| Weight |
43.64kg (96lbs) |
11.36kg (25lbs) |
| Enclosure |
Acoustic Suspension |
Acoustic Suspension |
| Available Colors |
Gloss Black, Black Ash |
n/a |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
3 Years w/ Registration |
2 Years |
| Labor Warranty |
3 Years w/ Registration |
2 Years |
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 | MartinLogan BalancedForce 210 goes deeper - 20Hz against 34Hz. Under 20Hz is felt more than heard - the bottom of a pipe organ and the bottom of a film mix. |
| Amplifier power | A | MartinLogan BalancedForce 210 has the bigger amplifier - 850W against 300W RMS, about 4.5dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | MartinLogan BalancedForce 210 moves more air: 2 x 10" against 8" is 3.13x the cone area, not the 1.77x 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 | MartinLogan BalancedForce 210 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. |
| Driver placement | depends | MartinLogan BalancedForce 210 fires side and KEF KUBE 8b 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 | KEF KUBE 8b is about 77% 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 | MartinLogan BalancedForce 210 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 | B | KEF KUBE 8b costs less - $600 against $3,499, about 83% less. |
A MartinLogan BalancedForce 210 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?
The usual trade-off: MartinLogan BalancedForce 210 measures better, KEF KUBE 8b costs about 83% less. In a normal room, placement will make a bigger difference than the gap between these two. Check your amplifier first: if it has no subwoofer or preamp output, MartinLogan BalancedForce 210 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 $3,499 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.