In this review, we will be comparing R-51M and RP-400M, two Passive Bookshelf speakers by Klipsch
Let's have a brief look at the main features
of Klipsch R-51M and Klipsch RP-400M first before getting into our more
detailed comparison.
Klipsch R-51M Key Specs
- 2-way Design
- 1" Tractrix Horn Tweeter
- 5.25" Copper-spun IMG Woofer
- 62-21k Hz Frequency Response
- 93 dB Sensitivity
- Impedance: 8ohms
- Power Range:Up to 85watts
- Weight:5.00kg
- Dimensions (H x W x D): 338.0" x 7.0" x 8.4"( 338.0 x 178.0 x 215.0mm )
Klipsch RP-400M Key Specs
- 2-way Design
- 1" Tractrix Horn Tweeter
- 4" Cerametallic Woofer
- 52-25k Hz Frequency Response
- 93 dB Sensitivity
- Impedance: 8ohms
- Power Range:up to 50watts
- Weight:4.10kg
- Dimensions (H x W x D): 298.0" x 5.6" x 7.5"( 298.0 x 144.0 x 191.0mm )
What size room are the Klipsch R-51M and Klipsch RP-400M speakers good for?
The size of the room in which you are planning to use these loudspeakers is an important decision
factor. Here we have compared their suitability to various sizes of environments considering their size
and max power parameters:
| Listening Environment* |
Klipsch R-51M |
Klipsch RP-400M |
| Near-field |
Average |
Good |
| Small Room |
Good |
Good |
| Mid-size Room |
Average |
Average |
| Large Room |
Poor |
Poor |
| Very Large Room |
Bad |
No way |
(* Approximate Room sizes: Small < 100sq. ft / 9 m2,
Mid-size: 100-220 sq. ft / 9-20 m2, Large 220-400 sq. ft / 20-36 m2, Very Large: >
400 sq. ft / 36 m2.
Average Floor Height: 9" / 2.7m. Typical room sizes differ from country to country, and the actual
listening experience changes depending on floor height, room shape, surface materials, listening
position, speaker locations, etc.)
In the following sections, we will get into more detail in order to better understand how the Klipsch R-51M and Klipsch RP-400M compare and hopefully end up with enough arguments to decide which one of these loudspeakers is the better choice for you.
**This post contains affiliate links, and I will be compensated if you make a purchase after clicking
through my links. As an Amazon Associate I earn from qualifying purchases.
Drivers
Both R-51M and RP-400M are 2-way speakers.
| Driver |
Klipsch R-51M |
Klipsch RP-400M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 4-inch
|
R-51M features a 1" Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1660Hz. On the other hand, the RP-400M features a 1" Tractrix Horn Tweeter and 1 x 4" Cerametallic Woofer with a Crossover frequency at 1500Hz.
Frequency Response
R-51M has a frequency range of 62-21k Hz whereas RP-400M has a frequency range of 52-25k Hz. With a minimum frequency of 52Hz, the RP-400M can go significantly deeper on the low side and provide stronger bass compared to the R-51M's min frequency of 62Hz.
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.
Impedance and Sensitivity
R-51M and RP-400M have the same Impedance of 8 ohms and their sensitivity is also same at 93 dB.
Sensitivity
Bookshelf Speakers
Power Range
Power
range is the range of input power in watts RMS that a loudspeaker is designed to handle. While using
an amplifier within this range ensures the nominal performance , inputting a power that is higher than the
max wattage can result in a damaged speaker.
R-51M can handle a max power of 85 watts RMS from the amp the whereas RP-400M has a max power handling value of 50 watts RMS, 35 watts less than the R-51M.
Keep in mind that a higher max power handling value doesn't necessarily make that a louder speaker
compared to a lower max handling speaker. Loudness or the sound level is also impacted by parameters
such as Impedance, sensitivity and system efficiencies.
Input Type and Bi-Amping / Bi-Wiring
R-51M features Single binding posts type posts and RP-400M has a Single binding posts type posts. None of these speakers feature bi-amping/bi-wiring.
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Klipsch RP-400M's Single binding posts terminals
Cabinet Type and Port Position
Both R-51M and RP-400M 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.
Klipsch RP-400M Tractrix horn-shaped Port
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 Klipsch R-51M's and Klipsch RP-400M's external dimensions. Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm ( 13.3 x 7.0 x 8.4inch) whereas Klipsch RP-400M has external dimensions of 298.0 x 144.0 x 191.0mm ( 11.7 x 5.6 x 7.5inch) .
Klipsch R-51M is clearly the larger of the two speakers. Its body is 34mm wider, 40mm taller and 24mm deeper than Klipsch RP-400M.
Below you can see the front view size comparison of Klipsch R-51M and Klipsch RP-400M in scale.
Comparison image of Klipsch R-51M and Klipsch RP-400M 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 Klipsch R-51M is approximately 382.7cm2 / 59.3inch2 and base area of the Klipsch RP-400M is approximately 275.0cm2 / 42.6inch2. The R-51M requires 39% more surface area than the RP-400M which gives it a small disadvantage on placement in tight spaces.
Here is an another comparison that shows both speakers on a BDI Octave Media Cabinet, next to a standard size amplifier and turntable in scale:
Size Comparison image of Klipsch R-51M and Klipsch RP-400M on a Media Console
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 Klipsch R-51M weighs 5.00kg / 11lbs and the Klipsch RP-400M weighs 4.10kg / 9lbs. This makes the R-51M 22% heavier than the RP-400M.
Here is a comparison of how R-51M and RP-400M's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of Klipsch R-51M?
Here are the items that are included inside the box of R-51M:
2 Bookshelf loudspeakers 2 Grilles (installed) 8 Self-adhesive rubber feet Quick Setup Guide Important Safety Instructions Warranty Information
What's in the Box of Klipsch RP-400M?
Here are the items that come with the RP-400M:
2 Bookshelf loudspeakers 2 Grilles (installed) 8 Self-adhesive rubber feet User Manual Important Safety Instructions Warranty Information
 Max Input Power |
85 watts
vs
50 watts
|
Handle more power from your amplifier |
 Woofer Size |
5.25 inches
vs
4 inches
|
Larger woofer |
 Price per pair* |
359USD
vs
399USD
|
costs less (*prices may change depending on the seller, location and time) |
|
Low Frequency Response |
52 Hz
vs
62 Hz
|
Generates deeper bass |
 High Frequency Response |
25k Hz
vs
21k Hz
|
Generates higher frequency |
 Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
 Height |
298mm
vs
338mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
275cm2
vs
382cm2
|
Takes less floor space |
| General |
Klipsch Reference R-51M |
Klipsch Reference Premiere RP-400M |
| Brand |
Klipsch |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
Up to 85 watts |
up to 50 watts |
| Sensitivity |
93 dB |
93 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
62-21k Hz |
52-25k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
4" |
| Woofer Composition |
Copper-spun IMG |
Cerametallic |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Tractrix Horn |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
1660Hz |
1500Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
338.0mm (13.3") |
298.0mm (11.7") |
| Width |
178.0mm (7") |
144.0mm (5.7") |
| Depth |
215.0mm (8.5") |
191.0mm (7.5") |
| Weight |
5.00kg (11lbs) |
4.10kg (9lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Wood-grain vinyl |
MDF/Wood-grain vinyl |
| Available Colors |
Black |
Ebony, Walnut, Piano Black |
| Mounting Bracket |
No |
Keyhole |
| Recommended Stand Height |
24-28" |
28-30" |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |