In this review, we will be comparing LSX II and R-51PM, two Powered Bookshelf speakers from KEF and Klipsch. 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 Klipsch R-51PM first before getting into our more
detailed comparison.
In the following sections, we will get into more detail in order to better understand how the KEF LSX II and Klipsch R-51PM compare and hopefully end up with enough arguments to decide which one of these loudspeakers is the better choice for you.
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Drivers
Both LSX II and R-51PM are 2-way speakers.
Driver |
KEF LSX II |
Klipsch R-51PM |
Driver Setup
|
2-way
|
2-way
|
Tweeter
|
0.75-inch
|
1.0-inch
|
Midrange
|
- |
- |
Woofer
|
1 x 4.5-inch
|
1 x 5.25-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 R-51PM features a 1.0" Aluminum LTS Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1663Hz.
Frequency Response
LSX II has a frequency range of 54-28k Hz whereas R-51PM has a frequency range of 68-21k Hz. With a minimum frequency of 54Hz, the LSX II can go significantly deeper on the low side and provide stronger bass compared to the R-51PM's min frequency of 68Hz.
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 Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
High Frequency
Bookshelf Speakers
None of these speakers achieves full range experience which is commonly agreed as 20Hz-20kHz. In order to achieve lower lows / deeper bass, we recommend you pair these with a subwoofer. Visit our Powered Subwoofers section to find out more about the available options.
Cabinet Type and Port Position
Both LSX II and R-51PM 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.
Physical Specs
Size of a speaker can sometimes become 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 Klipsch R-51PM's external dimensions. KEF LSX II has external dimensions of 240 × 155 × 180 mm ( 9.5 × 6.1 × 7.1 inch) whereas Klipsch R-51PM has external dimensions of 330.2 x 179.4 x 260.3mm ( 13 x 7.0625 x 10.25inch) .
Klipsch R-51PM is clearly the larger of the two speakers. Its body is 24.4mm wider, 90.2mm taller and 80.3mm deeper than KEF LSX II.
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 Klipsch R-51PM is approximately 467.0cm2 / 72.4inch2. The LSX II requires 40% less surface area than the R-51PM 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 Klipsch R-51PM weighs 4.80kg / 10.6lbs. This makes the R-51PM 33% heavier than the LSX II.
Here is a comparison of how LSX II and R-51PM'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 speakersTwo 6.5-feet AC power cords10-feet Cat-6 interconnect speaker cableRemote control2 AAA batteries Quick Start Guide Important Safety Information Warranty Information Maintenance Guide
What's in the Box of Klipsch R-51PM?
Here are the items that come with the R-51PM:
Powered speaker (right)Passive speaker (left)2 Grilles68-inch AC power cordRemote control2
Low Frequency Response |
54 Hz
vs
68 Hz
|
Generates deeper bass |
High Frequency Response |
28k Hz
vs
21k Hz
|
Generates higher frequency |
App-Based Control |
Apple iOS, Android
vs
None
|
Control the speaker via an app |
Height |
240mm
vs
330mm
|
Easier to fit in smaller spaces |
Base Surface Area |
279cm2 (155x180mm)
vs
467cm2 (179x260mm)
|
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 |
5.25 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 |
Phono Input |
Yes
vs
No
|
Connect your turntable directly |
General |
KEF LSX II |
Klipsch Reference R-51PM |
Brand |
KEF |
Klipsch |
Speaker Type |
Powered Stereo Speakers |
Powered Stereo Speakers |
Frequency Response |
54-28k Hz |
68-21k Hz |
Amplifier |
|
|
Watts RMS (Continuous) |
200-watt RMS |
120-watt RMS |
Watts Peak (Max) |
n/a |
240-watt RMS |
Max Bit Depth |
24-bit |
24-bit |
Max Sample Rate |
384 kHz |
96 kHz |
Drivers |
|
|
Woofer Quantity |
1 |
1 |
Woofer Size |
4.5" |
5.25" |
Woofer Composition |
Magnesium/Aluminium alloy |
Copper-spun IMG |
Woofer Surround Material |
Rubber |
n/a |
Tweeter Size |
0.75" |
1.0" |
Tweeter Type |
Hard-Dome |
Tractrix Horn |
Aimable Tweeter |
No |
No |
Midrange Driver |
No |
No |
Crossover Frequency |
n/a |
1663Hz |
Firing Direction |
rear |
rear |
Physical Specs |
|
|
Height |
240.0mm (9.4") |
330.2mm (13") |
Width |
155.0mm (6.1") |
179.4mm (7.1") |
Depth |
180.0mm (7.1") |
260.3mm (10.2") |
Weight |
3.60kg (7.9lbs) |
4.80kg (10.6lbs) |
Enclosure |
Bass Reflex |
Bass Reflex |
Available Colors |
Carbon Black, Mineral White, Cobalt Blue, Lava Red, and Soundwave |
n/a |
Mounting Bracket |
No |
No |
Grille |
n/a |
Yes |
Moisture Resistancy |
No |
No |
Connections |
|
|
Aux Inputs |
3.5mm |
3.5mm, RCA |
USB Port |
USB-C (connects to your computer) |
USB-B |
Phone Input |
No |
Yes |
Subwoofer Output |
Wired |
Wired |
Digital Input |
Optical |
Optical |
HDMI Input |
ARC |
No |
Headphone Jack |
No |
No |
Ethernet Port |
Yes |
No |
Other |
|
|
Parts Warranty |
1 Year |
1 Year |
Labor Warranty |
1 Year |
1 Year |