In this review, we will be comparing Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer and KUBE 8b, two Powered Subwoofer speakers from Aperion 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 Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer 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.Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer and KEF KUBE 8b have a totally different setup: the Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer features 2 x 15-inch drivers whereas the KUBE 8b features 1 x 8-inch drivers.
Frequency Response
Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer has a frequency range of 17-180 Hz whereas KUBE 8b has a frequency range of 34-140 Hz. With a minimum frequency of 17Hz, the Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer 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
Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer
High Frequency
Subwoofer Speakers
Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer
Cabinet Type
The Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer has a Bass Reflex type cabinet. 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. 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 Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer's and KEF KUBE 8b's external dimensions. Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer has external dimensions of 1099.8 x 551.2 x 299.7mm (43.3 x 21.7 x 11.8inch) 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).
KEF KUBE 8b is 255.2mm narrower and 805.8mm shorter than Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer but it is also 39.3mm deeper.
Size, drawn to scale
Both speakers 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 surface and pushed back to the same wall, so the deeper one visibly sticks out further.
Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer needs about 65% more floor or shelf area. KEF KUBE 8b is 39mm deeper, so it stands that much further out from the wall. Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer is 806mm taller.
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 Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer is approximately 1651.9cm2 / 256.0inch2 and base area of the KEF KUBE 8b is approximately 1003.4cm2 / 155.5inch2. The Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer requires 65% 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 Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer weighs 71.53kg / 157.4lbs and the KEF KUBE 8b weighs 11.36kg / 25lbs. This makes the Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer 530% heavier than the KUBE 8b.
Here is a comparison of how Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer and KUBE 8b's weights compare with the average, max and min weights in Powered Subwoofer class.
Weight
All Subwoofer Speakers
Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer
 Woofer Size |
15 inches
vs
8 inches
|
Larger woofer |
| Number of Woofers |
2
vs
1
|
More woofers |
| Low Frequency Response |
17 Hz
vs
34 Hz
|
Generates deeper bass |
 High Frequency Response |
180 Hz
vs
140 Hz
|
Generates higher frequency |
 Height |
294mm
vs
1099mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
1003cm2
vs
1651cm2
|
Takes less floor space |
 Price per pair* |
600USD
vs
4499USD
|
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.
Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer needs about 65% more floor area. KEF KUBE 8b stands 39mm further into the room. Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer is 806mm taller.
| General |
Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer |
KEF KUBE 8b |
| Brand |
Aperion |
KEF |
| Speaker Type |
Powered Subwoofer |
Powered Subwoofer |
| Max Amplifier Output |
1300 watts |
300 watts |
| Impedance |
4 ohms |
n/a |
| Frequency Response |
17-180 Hz |
34-140 Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
1300-watt RMS |
300-watt RMS |
Drivers |
|
|
| Woofer Quantity |
2 |
1 |
| Woofer Size |
15" |
8" |
| Woofer Composition |
|
|
| Tweeter Size |
- |
- |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
40-160 Hz |
40-140 Hz |
| Firing Direction |
n/a |
front |
Physical Specs |
|
|
| Height |
1099.8mm (43.3") |
294.0mm (11.6") |
| Width |
551.2mm (21.7") |
296.0mm (11.7") |
| Depth |
299.7mm (11.8") |
339.0mm (13.3") |
| Weight |
71.53kg (157.4lbs) |
11.36kg (25lbs) |
| Enclosure |
Bass Reflex |
Acoustic Suspension |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
Other |
|
|
| Parts Warranty |
|
2 Years |
| Labor Warranty |
|
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 | Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer goes deeper - 17Hz 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 | Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer has the bigger amplifier - 1300W against 300W RMS, about 6.4dB more on tap. In a large room that is headroom before the DSP starts limiting. |
| Driver area | A | Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer moves more air: 2 x 15" against 8" is 7.03x the cone area, not the 2.65x the diameters suggest. More area means the same output with less excursion, and less distortion with it. |
| Enclosure | depends | Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer 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. |
| Cabinet size | depends | KEF KUBE 8b is about 84% 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. |
| Price | B | KEF KUBE 8b costs less - $600 against $4,499, about 87% less. |
A Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer 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: Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer measures better, KEF KUBE 8b costs about 87% less. In a normal room, placement will make a bigger difference than the gap between these two. Films or music? If this is mainly a home cinema, Aperion Bravus III B215S Dual 15" Slim Cinema Powered Subwoofer 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 $4,499 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.