In this review, we will be comparing KUBE 8b and Sub Air, two Powered Subwoofer speakers from KEF and Focal. 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 KEF KUBE 8b and Focal Sub Air 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.KEF KUBE 8band Focal Sub Air have the same driver set up: Both subwoofers have 1 x 8" drivers.
Frequency Response
KUBE 8b has a frequency range of 34-140 Hz whereas Sub Air has a frequency range of 40-200 Hz. With a minimum frequency of 34Hz, the KUBE 8b can go significantly deeper on the low side and provide stronger bass compared to the Sub Air's min frequency of 40Hz.
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 KEF KUBE 8b has a Acoustic Suspension type cabinet. 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. On the other hand the Focal Sub Air have Bass Reflex type enclosure. 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.
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 KEF KUBE 8b's and Focal Sub Air's external dimensions. 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) whereas Focal Sub Air has external dimensions of 410.0 x 362.0 x 162.0mm (16-1/8 x 14-1/4 x 6-3/8inch).
KEF KUBE 8b is 66mm narrower and 116mm shorter than Focal Sub Air but it is also 177mm deeper.
Below you can see the front view size comparison of KEF KUBE 8b and Focal Sub Air in scale.
Comparison image of KEF KUBE 8b and Focal Sub Air 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 KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2 and base area of the Focal Sub Air is approximately 586.4cm2 / 90.9inch2. The KUBE 8b requires 71% more surface area than the Sub Air 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 KEF KUBE 8b weighs 11.36kg / 25lbs and the Focal Sub Air weighs 7.73kg / 17lbs. This makes the KUBE 8b 47% heavier than the Sub Air.
Here is a comparison of how KUBE 8b and Sub Air's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
What's in the Box of KEF KUBE 8b?
Here are the items that are included inside the box of KUBE 8b:
- Powered subwoofer
- 6.5-feet AC power cord
- Speaker-level input block
- User Manual
- Important Safety Information
- Warranty Information
What's in the Box of Focal Sub Air?
Here are the items that come with the Sub Air:
- Wireless powered subwoofer
- Wireless transmitter
- AC power adapter (attached 6-feet DC cord)
- AC power plug insert (2-prong)
- 8-feet AC power cord
- 4 Rubber feet
- 2 Brackets
- Four M4 x 10mm machine screws
- Four M4 x 17mm machine screws
- 4 Wood-screws
- 4 Wall-anchors
- User Manual
 Low Frequency Response |
34 Hz
vs
40 Hz
|
Generates deeper bass |
 Height |
294mm
vs
410mm
|
Easier to fit in smaller spaces |
 Price per pair* |
600USD
vs
1299USD
|
costs less (*prices may change depending on the seller, location and time) |
 High Frequency Response |
200 Hz
vs
140 Hz
|
Generates higher frequency |
 Base Surface Area |
586cm2
vs
1003cm2
|
Takes less floor space |
 Wireless Operation |
Yes
vs
No
|
Connect your subwoofer to your system wireless |
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 71% more floor area. KEF KUBE 8b stands 177mm further into the room. Focal Sub Air is 116mm taller.
| General |
KEF KUBE 8b |
Focal Sub Air |
| Brand |
KEF |
Focal |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
300 watts |
110 watts |
| Frequency Response |
34-140 Hz |
40-200 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
300-watt RMS |
110-watt RMS |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
8" |
8" |
| Woofer Composition |
|
Cellulose Pulp |
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
40-140 Hz |
n/a |
| Firing Direction |
front |
front |
Physical Specs |
|
|
| Height |
294.0mm (11.6") |
410.0mm (16.1") |
| Width |
296.0mm (11.7") |
362.0mm (14.3") |
| Depth |
339.0mm (13.3") |
162.0mm (6.4") |
| Weight |
11.36kg (25lbs) |
7.73kg (17lbs) |
| Enclosure |
Acoustic Suspension |
Bass Reflex |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
2 Years |
3 Years |
| Labor Warranty |
2 Years |
3 Years |
A sealed subwoofer against a ported 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 | KEF KUBE 8b goes deeper - 34Hz against 40Hz. A real difference, though most music has little content below 40Hz. |
| Amplifier power | A | KEF KUBE 8b has the bigger amplifier - 300W against 110W RMS, about 4.4dB 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 | 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; Focal Sub Air is ported - a ported box gives more output low down for its size, at the cost of a steeper roll-off below tuning. Neither is better in the abstract; ported tends to suit films and sealed tends to suit music, and both generalisations have exceptions. |
| Wireless option | depends | Only Focal Sub Air offers a wireless link. It decides where the sub can go if you cannot run a cable, and is worth nothing if you can. |
| Cabinet size | depends | Focal Sub Air is about 18% 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 | Focal Sub Air 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 | KEF KUBE 8b costs less - $600 against $1,299, about 54% less. |
A KEF KUBE 8b B Focal Sub Air
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. Films or music? If this is mainly a home cinema, Focal Sub Air 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. 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 $1,299 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.