In this review, we will be comparing Motion 15 and LS50, two Passive Bookshelf speakers from MartinLogan and KEF. Let's have a brief look at the main features
of MartinLogan 15 and KEF LS50 first before getting into our more
detailed comparison.
What size room are the MartinLogan 15 and KEF LS50 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 KEF LS50 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 LS50 are 2-way speakers.
| Driver |
MartinLogan 15 |
KEF LS50 |
|
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 LS50 features a 1" Aluminum Vented dome Tweeter and 1 x 5.25" Magnesium/aluminum alloy Woofer with a Crossover frequency at 2200Hz.
Frequency Response
Motion 15 has a frequency range of 60-25k Hz whereas LS50 has a frequency range of 79-28k Hz. With a minimum frequency of 60Hz, the Motion 15 can go significantly deeper on the low side and provide stronger bass compared to the LS50's min frequency of 79Hz.
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 LS50 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 LS50's is rated at 85 dB. This 7 dB difference makes the MartinLogan 15 a more sensitive speaker compared to KEF LS50, 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 LS50 has a max power handling value of 100 watts RMS, 100 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 Post type posts and LS50 has a Post type posts. None of these speakers feature bi-amping/bi-wiring.
KEF LS50's Post terminals
Cabinet Type and Port Position
Both Motion 15 and LS50 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 KEF LS50'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 KEF LS50 has external dimensions of 302.0 x 200.0 x 278.0mm ( 11.8 x 7.8 x 10.9inch) .
KEF LS50 is clearly the larger of the two speakers. Its body is 27mm wider, 12mm taller and 38mm deeper than MartinLogan 15.
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 KEF LS50 is approximately 556.0cm2 / 86.2inch2. The Motion 15 requires 25% less surface area than the LS50 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 MartinLogan 15 weighs 5.40kg / 11.9lbs and the KEF LS50 weighs 7.20kg / 15.8lbs. This makes the LS50 33% heavier than the Motion 15.
Here is a comparison of how Motion 15 and LS50'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 KEF LS50?
Here are the items that come with the LS50:
2 Bookshelf loudspeakers 2 Foam port plugs 8 Self-adhesive rubber feet Owner's Manual Warranty Registration Card
 Max Input Power |
200 watts
vs
100 watts
|
Handle more power from your amplifier |
 Sensitivity |
92 dB
vs
85 dB
|
Play louder with same amount of amplification power |
 Low Frequency Response |
60 Hz
vs
79 Hz
|
Generates deeper bass |
 Height |
290mm
vs
302mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
415cm2 (173x240mm)
vs
556cm2 (200x278mm)
|
Takes less floor space |
 Nominal Impedance |
8 ohms
vs
5 ohms
|
Less selective with amplifiers |
 High Frequency Response |
28k Hz
vs
25k Hz
|
Generates higher frequency |
| General |
MartinLogan Motion 15 |
KEF LS50 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-200 watts |
25-100 watts |
| Sensitivity |
92 dB |
85 dB |
| Impedance |
5 ohms |
8 ohms |
| Impedance |
n/a |
3.2 ohms |
| Frequency Response |
60-25k Hz |
79-28k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
5.25" |
| Woofer Composition |
Aluminum |
Magnesium/aluminum alloy |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1.0 x 1.4" |
1" |
| Tweeter Type |
Folded Motion |
Vented dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2700Hz |
2200Hz |
| 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") |
302.0mm (11.9") |
| Width |
173.0mm (6.8") |
200.0mm (7.9") |
| Depth |
240.0mm (9.4") |
278.0mm (10.9") |
| Weight |
5.40kg (11.9lbs) |
7.20kg (15.8lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
Piano Lacquer |
Polymer/Lacquer |
| Available Colors |
Gloss Black, Matt White, Red Walnut |
Black, High Gloss Piano Black, High Gloss Piano White |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-30" |
18-28" |
| Grille |
Yes |
n/a |
| 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 |