In this review, we will be comparing Motion 15 and R-51M, two Passive Bookshelf speakers from MartinLogan and Klipsch. Let's have a brief look at the main features
of MartinLogan 15 and Klipsch R-51M first before getting into our more
detailed comparison.
What size room are the MartinLogan 15 and Klipsch R-51M 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:
In the following sections, we will get into more detail in order to better understand how the MartinLogan 15 and Klipsch R-51M 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 Motion 15 and R-51M are 2-way speakers.
| Driver |
MartinLogan 15 |
Klipsch R-51M |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1.0 x 1.4-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 5.25-inch
|
Motion 15 features a 1.0 x 1.4" Folded Motion Tweeter and 1 x 5.25" Aluminum Woofer with a Crossover frequency at 2700Hz. On the other hand, the R-51M features a 1" Tractrix Horn Tweeter and 1 x 5.25" Copper-spun IMG Woofer with a Crossover frequency at 1660Hz.
Frequency Response
Motion 15 has a frequency range of 60-25k Hz whereas R-51M has a frequency range of 62-21k Hz. With a minimum frequency of 60Hz, the Motion 15 can go slightly deeper then 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
Motion 15 is a 5 ohms speaker compared to the R-51M which has a nominal impedance of 8 ohms.
These two speakers also have different sensitivity levels. Motion 15 sensitivity is rated at 92 dB and the R-51M's is rated at 93 dB. This 1 dB difference makes the Klipsch R-51M a more sensitive speaker compared to MartinLogan 15, 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.
Motion 15 can handle a max power of 200 watts RMS from the amp the whereas R-51M has a max power handling value of 85 watts RMS, 115 watts less than the Motion 15.
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
Motion 15 features Single Gold Plated Binding Posts - 5-way type posts and R-51M has a Single Gold Plated Binding Posts - 5-way type posts. None of these speakers feature bi-amping/bi-wiring.
Klipsch R-51M's Single Gold Plated Binding Posts - 5-way terminals
Cabinet Type and Port Position
Both Motion 15 and R-51M 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 MartinLogan 15's and Klipsch R-51M's external dimensions. MartinLogan 15 has external dimensions of 290.0 x 173.0 x 240.0mm ( 11.4 x 6.8 x 9.4inch) whereas Klipsch R-51M has external dimensions of 338.0 x 178.0 x 215.0mm ( 13.3 x 7.0 x 8.4inch) .
MartinLogan 15 is 5mm narrower and 48mm shorter than Klipsch R-51M but it is also 25mm 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 MartinLogan 15 is approximately 415.2cm2 / 64.4inch2 and base area of the Klipsch R-51M is approximately 382.7cm2 / 59.3inch2. The Motion 15 requires 8% more surface area than the R-51M 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 MartinLogan 15 weighs 5.40kg / 11.9lbs and the Klipsch R-51M weighs 5.00kg / 11lbs. This makes the Motion 15 8% heavier than the R-51M.
Here is a comparison of how Motion 15 and R-51M's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of MartinLogan 15?
Here are the items that are included inside the box of Motion 15:
Bookshelf loudspeaker Grille 4 Rubber feet Users Manual Warranty/Registration Information
What's in the Box of Klipsch R-51M?
Here are the items that come with the R-51M:
2 Bookshelf loudspeakers 2 Grilles (installed) 8 Self-adhesive rubber feet Quick Setup Guide Important Safety Instructions Warranty Information
 Max Input Power |
200 watts
vs
85 watts
|
Handle more power from your amplifier |
 Low Frequency Response |
60 Hz
vs
62 Hz
|
Generates deeper bass |
 High Frequency Response |
25k Hz
vs
21k Hz
|
Generates higher frequency |
 Height |
290mm
vs
338mm
|
Easier to fit in smaller spaces |
 Sensitivity |
93 dB
vs
92 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
8 ohms
vs
5 ohms
|
Less selective with amplifiers |
 Base Surface Area |
382cm2 (178x215mm)
vs
415cm2 (173x240mm)
|
Takes less floor space |
| General |
MartinLogan Motion 15 |
Klipsch Reference R-51M |
| Brand |
MartinLogan |
Klipsch |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-200 watts |
Up to 85 watts |
| Sensitivity |
92 dB |
93 dB |
| Impedance |
5 ohms |
8 ohms |
| Frequency Response |
60-25k Hz |
62-21k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
5.25" |
| Woofer Composition |
Aluminum |
Copper-spun IMG |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1.0 x 1.4" |
1" |
| Tweeter Type |
Folded Motion |
Tractrix Horn |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2700Hz |
1660Hz |
| Firing Direction |
rear |
rear |
| Suggested Break-in Period |
Allow 72 hours of break-in at 90 dB |
n/a |
Physical Specs |
|
|
| Height |
290.0mm (11.4") |
338.0mm (13.3") |
| Width |
173.0mm (6.8") |
178.0mm (7") |
| Depth |
240.0mm (9.4") |
215.0mm (8.5") |
| Weight |
5.40kg (11.9lbs) |
5.00kg (11lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
Piano Lacquer |
MDF/Wood-grain vinyl |
| Available Colors |
Gloss Black, Matt White, Red Walnut |
Black |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-30" |
24-28" |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
No |
Other |
|
|
| Parts Warranty |
5 Yrs w/ Registration |
5 Years |
| Labor Warranty |
5 Yrs w/ Registration |
5 Years |