In this review, we will be comparing LSX II and M20 HD, two Powered Bookshelf speakers from KEF and Q Acoustics. Being Powered speakers, 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 LSX II and Q Acoustics M20 HD first before getting into our more
detailed comparison.
| Key Specs | KEF LSX II | Q Acoustics M20 HD |
|---|
| Brand | KEF
United Kingdom · founded 1961 | Q Acoustics
United Kingdom · founded 2006 |
|---|
| Design | 2-way | 2-way |
|---|
| Built-in amplifier | 200-watt RMS | 128-watt RMS |
|---|
| Uni-Q driver | 11th Generation Uni-Q | — |
|---|
| Tweeter | 0.75" Hard-Dome | 0.875" Dome |
|---|
| Woofer | 4.5" Magnesium/Aluminium alloy | 5" |
|---|
| Frequency response | 54-28k Hz | 55-22k Hz |
|---|
| Max depth / sample rate | 24-bit / 384 kHz | 24-bit / 192 kHz |
|---|
| Bluetooth | Built-in 4.2 | Built-in 5.0 |
|---|
| App control | Yes | — |
|---|
| Weight | 3.60kg / 7.9lbs | 5.10kg / 11.2lbs |
|---|
| Dimensions (H x W x D) | 9.5" x 6.1" x 7.1"
240 × 155 × 180 mm | 10-15/16" x 6-11/16" x 12-3/16"
278.0 x 170.0 x 310.0mm |
|---|
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
Drivers
Both LSX II and M20 HD are 2-way speakers.
KEF LSX IIQ Acoustics M20 HD
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
KEF LSX II |
Q Acoustics M20 HD |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
0.75-inch
|
0.875-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 4.5-inch
|
1 x 5-inch
|
LSX II features a 0.75" Aluminum Hard-Dome Tweeter and 1 x 4.5" Magnesium/Aluminium alloy Woofer. On the other hand, the M20 HD features a 0.875" Dome Tweeter and 1 x 5" Woofer.
Frequency Response
LSX II has a frequency range of 54-28k Hz whereas M20 HD has a frequency range of 55-22k Hz. With a minimum frequency of 54Hz, the LSX II can go slightly deeper then the M20 HD's min frequency of 55Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
Neither pair reaches down to 20Hz, the usual definition of full-range, which is normal for speakers of this size. If you want the bottom octave for movies or bass-heavy music, add a subwoofer to whichever you choose. Visit our Powered Subwoofers section to find out more about the available options.
Cabinet Type and Port Position
Both LSX II and M20 HD have rear firing ports. Rear ported speakers generally need more room between the backside of the speaker and the wall compared to sealed and front/bottom ported speakers. Placing the speakers too close to the walls may cause the bass to sound boomy.
If you are limited in space and can't get the speakers away from the backwall, check our Speakers with Front Firing Ports page.
KEF LSX II Port
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 LSX II's and Q Acoustics M20 HD's external dimensions. KEF LSX II has external dimensions of 240 × 155 × 180 mm (9.5 × 6.1 × 7.1 inch) whereas Q Acoustics M20 HD has external dimensions of 278.0 x 170.0 x 310.0mm (10-15/16 x 6-11/16 x 12-3/16inch).
Q Acoustics M20 HD is clearly the larger of the two speakers. Its body is 15mm wider, 38mm taller and 130mm deeper than KEF LSX II.
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.
Q Acoustics M20 HD needs about 89% more floor or shelf area. Q Acoustics M20 HD is 130mm deeper, so it stands that much further out from the wall. Q Acoustics M20 HD is 38mm 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 KEF LSX II is approximately 279.0cm2 / 43.2inch2 and base area of the Q Acoustics M20 HD is approximately 527.0cm2 / 81.7inch2. The LSX II requires 47% less surface area than the M20 HD which gives it a small advantage on placement in tight spaces.
Weight Comparison The weight of a loudspeaker can become an important factor if you need to move and reposition the unit often. Weight of a speaker can also "sometimes" be an indicator of the rigidity of the enclosure and the quality of the internal components used. The KEF LSX II weighs 3.60kg / 7.9lbs and the Q Acoustics M20 HD weighs 5.10kg / 11.2lbs. This makes the M20 HD 42% heavier than the LSX II.
Here is a comparison of how LSX II and M20 HD's weights compare with the average, max and min weights in Powered Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of KEF LSX II?
Here are the items that are included inside the box of LSX II:
- 2 Wireless powered speakers
- Two 6.5-feet AC power cords
- 10-feet Cat-6 interconnect speaker cable
- Remote control
- 2 AAA batteries
- Quick Start Guide
- Important Safety Information
- Warranty Information
- Maintenance Guide
What's in the Box of Q Acoustics M20 HD?
Here are the items that come with the M20 HD:
- Powered speaker
- Passive speaker
- 6-feet AC power cord
- Remote control
- 2 AAA batteries
- 13-feet Speaker wire
- 59-inch Optical digital cable
- 2 Foam port plugs
- Owners Manual
 Low Frequency Response |
54 Hz
vs
55 Hz
|
Generates deeper bass |
 High Frequency Response |
28k Hz
vs
22k Hz
|
Generates higher frequency |
 App-Based Control |
Apple iOS, Android
vs
None
|
Control the speaker via an app |
 Height |
240mm
vs
278mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
279cm2
vs
527cm2
|
Takes less floor space |
 Ethernet Connection |
Yes
vs
No
|
High quality streaming over Ethernet |
 USB Port |
USB-C (connects to your computer)
vs
No
|
USB port adds flexibility |
 HDMI Input |
ARC
vs
No
|
Connect HDMI sources directly |
|
Woofer Size |
5 inches
vs
4.5 inches
|
Larger woofer |
 Price per pair* |
599USD
vs
1299USD
|
costs less (*prices may change depending on the seller, location and time) |
 RCA Connection |
Yes
vs
No
|
Connection via RCA input |
| General |
KEF LSX II |
Q Acoustics M20 HD Wireless Music System |
| Brand |
KEF |
Q Acoustics |
| Speaker Type |
Powered Stereo Speakers |
Powered stereo speakers |
| Frequency Response |
54-28k Hz |
55-22k Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
200-watt RMS |
128-watt RMS |
| Max Bit Depth |
24-bit |
24-bit |
| Max Sample Rate |
384 kHz |
192 kHz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
4.5" |
5" |
| Woofer Composition |
Magnesium/Aluminium alloy |
|
| Woofer Surround Material |
Rubber |
n/a |
| Tweeter Size |
0.75" |
0.875" |
| Tweeter Type |
Hard-Dome |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
240.0mm (9.4") |
278.0mm (10.9") |
| Width |
155.0mm (6.1") |
170.0mm (6.7") |
| Depth |
180.0mm (7.1") |
310.0mm (12.2") |
| Weight |
3.60kg (7.9lbs) |
5.10kg (11.2lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Available Colors |
Carbon Black, Mineral White, Cobalt Blue, Lava Red, and Soundwave |
Black, White, Walnut |
| Mounting Bracket |
No |
No |
| Grille |
n/a |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Aux Inputs |
3.5mm |
3.5mm, Stereo RCA |
| USB Port |
USB-C (connects to your computer) |
USB-B |
| Phone Input |
No |
No |
| Subwoofer Output |
Wired |
mono-RCA |
| Digital Input |
Optical |
Optical |
| HDMI Input |
ARC |
No |
| Headphone Jack |
No |
No |
| Ethernet Port |
Yes |
No |
Other |
|
|
| Parts Warranty |
1 Year |
2 Years |
| Labor Warranty |
1 Year |
2 Years |
These sit in different price classes - KEF LSX II costs roughly 2.2x what Q Acoustics M20 HD does. Expect it to lead on paper; the question is whether the gap is audible enough in your room to be worth it.
| Area | Better | Why |
|---|
| Bass | evenly matched | Much the same reach (54Hz vs 55Hz). |
| Built-in power | A | KEF LSX II has the bigger amplifier (200W vs 128W RMS). |
| Connections | A | KEF LSX II adds Wi-Fi and HDMI. |
| Size | depends | KEF LSX II is easier to place; Q Acoustics M20 HD is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | KEF LSX II: a sub output; Q Acoustics M20 HD: a sub output. |
| Price | B | Q Acoustics M20 HD is cheaper - $599 against $1,299, about 54% less; arguably a different class. |
A KEF LSX II B Q Acoustics M20 HD
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 speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
The usual trade-off: KEF LSX II measures better, Q Acoustics M20 HD costs about about 117% more% less. Whether that gap is worth the money is the call only you can make - and in a normal room it is often smaller than the numbers suggest. In a large or open-plan room, Q Acoustics M20 HD has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, KEF LSX II is the easier speaker to get right. Think about the whole system, not just the speakers: the roughly $700 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.