In this review, we will be comparing R-51M and Uni-Fi BS U5 Slim, two Passive Bookshelf speakers from Klipsch and ELAC.
Let's have a brief look at the main features
of Klipsch R-51M and ELAC Uni-Fi BS U5 Slim 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 )
ELAC Uni-Fi BS U5 Slim Key Specs
- 3-way Design
- 1" soft dome Tweeter
- 4" Midrange
- 5.25" Aluminum Woofer
- 4" Midrange
- 46-25k Hz Frequency Response
- 85 dB Sensitivity
- Impedance: 4ohms
- Power Range:40-140watts
- Weight:7.50kg
- Dimensions (H x W x D): 340.0" x 7-1/16" x 12-7/8"( 340.0 x 180.0 x 328.0mm )
What size room are the Klipsch R-51M and ELAC Uni-Fi BS U5 Slim 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 |
ELAC Uni-Fi BS U5 Slim |
| Near-field |
Average |
Poor |
| Small Room |
Good |
Average |
| Mid-size Room |
Average |
Good |
| Large Room |
Poor |
Average |
| Very Large Room |
Bad |
Poor |
(* 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 ELAC Uni-Fi BS U5 Slim 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
One of the fundamental differences between these two speakers is that R-51M is a 2-way design whereas the Uni-Fi BS U5 Slim is a 3-way speaker. 3-way designs utilize a midrange driver in addition to the tweeter and woofer on 2-way designs. Designing a crossover for a 3-way speaker is a complicated process and generally increases the overall cost of the speaker.
| Driver |
Klipsch R-51M |
ELAC Uni-Fi BS U5 Slim |
|
Driver Setup
|
2-way
|
3-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
1 x 4-inch |
|
Woofer
|
1 x 5.25-inch
|
1 x 5.25-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 Uni-Fi BS U5 Slim features a 1" soft dome Tweeter , a 4" Midrange and 1 x 5.25" Aluminum Woofer .
Frequency Response
R-51M has a frequency range of 62-21k Hz whereas Uni-Fi BS U5 Slim has a frequency range of 46-25k Hz. With a minimum frequency of 46Hz, the Uni-Fi BS U5 Slim 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 is a 8 ohms speaker compared to the Uni-Fi BS U5 Slim which has a nominal impedance of 4 ohms. Lower impedance speakers, especially the ones that are rated at 4 ohms may put more pressure on the amplifier unit especially when played at high volume levels, so make sure the amp you pair with the Uni-Fi BS U5 Slim can provide this impedance level.
These two speakers also have different sensitivity levels. R-51M sensitivity is rated at 93 dB and the Uni-Fi BS U5 Slim's is rated at 85 dB. This 8 dB difference makes the Klipsch R-51M a more sensitive speaker compared to ELAC Uni-Fi BS U5 Slim, hence will play louder with the same amount of watts.
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 140 watts RMS from the amp the whereas R-51M has a max power handling value of 85 watts RMS , 55 watts less than the Uni-Fi BS U5 Slim.
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 Post type posts and Uni-Fi BS U5 Slim has a Post type posts. None of these speakers feature bi-amping/bi-wiring.
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
ELAC Uni-Fi BS U5 Slim's Post terminals
Cabinet Type and Port Position
Both R-51M and Uni-Fi BS U5 Slim 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 Klipsch R-51M's and ELAC Uni-Fi BS U5 Slim'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 ELAC Uni-Fi BS U5 Slim has external dimensions of 340.0 x 180.0 x 328.0mm ( 13-3/8 x 7-1/16 x 12-7/8inch) .
ELAC Uni-Fi BS U5 Slim is clearly the larger of the two speakers. Its body is 2mm wider, 2mm taller and 113mm deeper than Klipsch R-51M.
Below you can see the front view size comparison of Klipsch R-51M and ELAC Uni-Fi BS U5 Slim in scale.
Comparison image of Klipsch R-51M and ELAC Uni-Fi BS U5 Slim 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 ELAC Uni-Fi BS U5 Slim is approximately 590.4cm2 / 91.5inch2. The R-51M requires 35% less surface area than the Uni-Fi BS U5 Slim which gives it a small advantage 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 ELAC Uni-Fi BS U5 Slim on a Media Console