In this review, we will be comparing Dynamo 400 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 400 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 400and KEF KUBE 8b have the same driver set up: Both subwoofers have 1 x 8" drivers.
Frequency Response
Dynamo 400 has a frequency range of 30-200 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 30Hz, the Dynamo 400 can go slightly deeper then 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
The MartinLogan 400 has a Bass reflex type cabinet. On the other hand the KEF KUBE 8b have Acoustic Suspension type enclosure. 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 400's and KEF KUBE 8b's external dimensions. MartinLogan 400 has external dimensions of 385.0 x 339.0 x 388.0mm (15-1/8 x 13-5/16 x 15-1/4inch) 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 400 is clearly the larger of the two speakers. Its body is 43mm wider, 91mm taller and 49mm deeper than KEF KUBE 8b.
Below you can see the front view size comparison of MartinLogan 400 and KEF KUBE 8b in scale.
Comparison image of MartinLogan 400 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 MartinLogan 400 is approximately 1315.3cm2 / 203.9inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The Dynamo 400 requires 31% 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 400 weighs 12.95kg / 28.5lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the Dynamo 400 14% heavier than the KUBE 8b.
Here is a comparison of how Dynamo 400 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 MartinLogan 400?
Here are the items that are included inside the box of Dynamo 400:
- Powered subwoofer
- 6.5-feet AC power cord
- User-feets Manual
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
 Low Frequency Response |
30 Hz
vs
34 Hz
|
Generates deeper bass |
 High Frequency Response |
200 Hz
vs
140 Hz
|
Generates higher frequency |
 Price per pair* |
500USD
vs
600USD
|
costs less (*prices may change depending on the seller, location and time) |
 Height |
294mm
vs
385mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2
vs
1315cm2
|
Takes less floor space |
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 400 needs about 31% more floor area. MartinLogan 400 stands 49mm further into the room. MartinLogan 400 is 91mm taller.
| General |
MartinLogan Dynamo 400 |
KEF KUBE 8b |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
75 watts |
300 watts |
| Frequency Response |
30-200 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
75-watt RMS |
300-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
8" |
8" |
| Woofer Composition |
Polypropylene |
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
40-140 Hz |
| Firing Direction |
bottom |
front |
Physical Specs |
|
|
| Height |
385.0mm (15.2") |
294.0mm (11.6") |
| Width |
339.0mm (13.3") |
296.0mm (11.7") |
| Depth |
388.0mm (15.3") |
339.0mm (13.3") |
| Weight |
12.95kg (28.5lbs) |
11.36kg (25lbs) |
| Enclosure |
Bass reflex |
Acoustic Suspension |
| Available Colors |
Satin Black |
n/a |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
3 Yrs w/ Registration |
2 Years |
| Labor Warranty |
3 Yrs w/ Registration |
2 Years |
A ported subwoofer against a sealed 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 | A | MartinLogan 400 goes deeper - 30Hz against 34Hz. A real difference, though most music has little content below 34Hz. |
| Amplifier power | B | KEF KUBE 8b has the bigger amplifier - 300W against 75W RMS, about 6dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | evenly matched | Near-identical radiating area (8" against 8"). |
| Enclosure | depends | MartinLogan 400 is ported - a ported box gives more output low down for its size, at the cost of a steeper roll-off below tuning; KEF KUBE 8b is sealed - a sealed box rolls off gently and is usually the easier one to integrate in a small or awkward room. Neither is better in the abstract; ported tends to suit films and sealed tends to suit music, and both generalisations have exceptions. |
| Speaker-level inputs | A | MartinLogan 400 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 400 fires down 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 42% 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 400 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 | A | MartinLogan 400 costs less - $500 against $600, about 17% less. |
A MartinLogan 400 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?
MartinLogan 400 is the easier recommendation: it leads on most of the measured areas and costs less. Take KEF KUBE 8b if one of the "depends" rows describes your room. Films or music? If this is mainly a home cinema, MartinLogan 400 will hit harder for the money; if it is mainly for music in a normal-sized room, KEF KUBE 8b is usually the easier one to make sound right. Check your amplifier first: if it has no subwoofer or preamp output, MartinLogan 400 is the only one of these two you can connect at all.
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.