In this review, we will be comparing M20 HD and R-51PM, two Powered Bookshelf speakers from Q Acoustics 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 Q Acoustics M20 HD 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 Q Acoustics M20 HD 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 M20 HD and R-51PM are 2-way speakers.
| Driver |
Q Acoustics M20 HD |
Klipsch R-51PM |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
0.875-inch
|
1.0-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5-inch
|
1 x 5.25-inch
|
M20 HD features a 0.875" Dome Tweeter and 1 x 5" 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
M20 HD has a frequency range of 55-22k Hz whereas R-51PM has a frequency range of 68-21k Hz. With a minimum frequency of 55Hz, the M20 HD 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 M20 HD 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 Q Acoustics M20 HD's and Klipsch R-51PM's external dimensions. 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) whereas Klipsch R-51PM has external dimensions of 330.2 x 179.4 x 260.3mm ( 13 x 7.0625 x 10.25inch) .
Q Acoustics M20 HD is 9.4mm narrower and 52.2mm shorter than Klipsch R-51PM but it is also 49.7mm deeper.
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 Q Acoustics M20 HD is approximately 527.0cm2 / 81.7inch2 and base area of the Klipsch R-51PM is approximately 467.0cm2 / 72.4inch2. The M20 HD requires 13% more surface area than the R-51PM which gives it a small disadvantage 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 Q Acoustics M20 HD weighs 5.10kg / 11.2lbs and the Klipsch R-51PM weighs 4.80kg / 10.6lbs. This makes the M20 HD 6% heavier than the R-51PM.
Here is a comparison of how M20 HD 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 Q Acoustics M20 HD?
Here are the items that are included inside the box of 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
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 |
55 Hz
vs
68 Hz
|
Generates deeper bass |
 High Frequency Response |
22k Hz
vs
21k Hz
|
Generates higher frequency |
 Height |
278mm
vs
330mm
|
Easier to fit in smaller spaces |
 USB Port |
USB-B
vs
No
|
USB port adds flexibility |
| Woofer Size |
5.25 inches
vs
5 inches
|
Larger woofer |
 Base Surface Area |
467cm2 (179x260mm)
vs
527cm2 (170x310mm)
|
Takes less floor space |
| USB Port |
USB-B
vs
No
|
USB port adds flexibility |
 Phono Input |
Yes
vs
No
|
Connect your turntable directly |
| General |
Q Acoustics M20 HD Wireless Music System |
Klipsch Reference R-51PM |
| Brand |
Q Acoustics |
Klipsch |
| Speaker Type |
Powered stereo speakers |
Powered Stereo Speakers |
| Frequency Response |
55-22k Hz |
68-21k Hz |
Amplifier |
|
|
| Watts RMS (Continuous) |
128-watt RMS |
120-watt RMS |
| Watts Peak (Max) |
n/a |
240-watt RMS |
| Max Bit Depth |
24-bit |
24-bit |
| Max Sample Rate |
192 kHz |
96 kHz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5" |
5.25" |
| Woofer Composition |
|
Copper-spun IMG |
| Tweeter Size |
0.875" |
1.0" |
| Tweeter Type |
Dome |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
1663Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
278.0mm (10.9") |
330.2mm (13") |
| Width |
170.0mm (6.7") |
179.4mm (7.1") |
| Depth |
310.0mm (12.2") |
260.3mm (10.2") |
| Weight |
5.10kg (11.2lbs) |
4.80kg (10.6lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Available Colors |
Black, White, Walnut |
n/a |
| Mounting Bracket |
No |
No |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Aux Inputs |
3.5mm, Stereo RCA |
3.5mm, RCA |
| USB Port |
USB-B |
USB-B |
| Phone Input |
No |
Yes |
| Subwoofer Output |
mono-RCA |
Wired |
| Digital Input |
Optical |
Optical |
| HDMI Input |
No |
No |
| Headphone Jack |
No |
No |
| Ethernet Port |
No |
No |
Other |
|
|
| Parts Warranty |
2 Years |
1 Year |
| Labor Warranty |
2 Years |
1 Year |