In this review, we will be comparing Motion XT B100 and R3, two Passive Bookshelf speakers from MartinLogan and KEF. Let's have a brief look at the main features
of MartinLogan Motion XT B100 and KEF R3 first before getting into our more
detailed comparison.
What size room are the MartinLogan Motion XT B100 and KEF R3 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 Motion XT B100 and KEF R3 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 Motion XT B100 is a 2-way design whereas the R3 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 |
MartinLogan Motion XT B100 |
KEF R3 |
|
Driver Setup
|
2-way
|
3-way
|
|
Tweeter
|
1.25 x 2.4-inch
|
1-inch
|
|
Midrange
|
- |
1 x 5-inch |
|
Woofer
|
1 x 6.5-inch
|
1 x 6.5-inch
|
Motion XT B100 features a 1.25 x 2.4" Folded Motion XT Tweeter and 1 x 6.5" Kevlar Woofer with a Crossover frequency at 2600Hz. On the other hand, the R3 features a 1" aluminum Dome Tweeter , a 5" Midrange and 1 x 6.5" Hybrid aluminum Woofer with a Crossover frequency at 400Hz and 2900Hz.
Frequency Response
Motion XT B100 has a frequency range of 45-25k Hz whereas R3 has a frequency range of 52-28k Hz. With a minimum frequency of 45Hz, the Motion XT B100 can go significantly deeper on the low side and provide stronger bass compared to the R3's min frequency of 52Hz.
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
MartinLogan Motion XT B100
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 XT B100 is a 4 ohms speaker compared to the R3 which has a nominal impedance of 8 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 Motion XT B100 can provide this impedance level.
These two speakers also have different sensitivity levels. Motion XT B100 sensitivity is rated at 93 dB and the R3's is rated at 87 dB. This 6 dB difference makes the MartinLogan Motion XT B100 a more sensitive speaker compared to KEF R3, 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 XT B100 can handle a max power of 250 watts RMS from the amp the whereas R3 has a max power handling value of 180 watts RMS, 70 watts less than the Motion XT B100.
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
Both Motion XT B100 and R3 features dual binding post speaker terminals for bi-amping or bi-wiring.
MartinLogan Motion XT B100's Custom 5-way bi-wire tool-less binding posts terminals allows Bi-amping or bi-wiring
Cabinet Type and Port Position
Both Motion XT B100 and R3 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.
KEF R3 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 MartinLogan Motion XT B100's and KEF R3's external dimensions. MartinLogan Motion XT B100 has external dimensions of 368 x 203 x 318mm ( 14-1/2-inch x 8inch x 12-1/2inch ) whereas KEF R3 has external dimensions of 423.0 x 199.0 x 337.0mm ( 16-5/8 x 7-13/16 x 13-1/4inch) .
MartinLogan Motion XT B100 is 55mm shorter and 19mm less deeper than KEF R3 but it is also 4mm wider.
Below you can see the front view size comparison of MartinLogan Motion XT B100 and KEF R3 in scale.
Comparison image of MartinLogan Motion XT B100 and KEF R3 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 MartinLogan Motion XT B100 is approximately 645.5cm2 / 100.1inch2 and base area of the KEF R3 is approximately 670.6cm2 / 103.9inch2. The Motion XT B100 requires 4% less surface area than the R3 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 MartinLogan Motion XT B100 and KEF R3 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 MartinLogan Motion XT B100 weighs 9.30kg / 20.5lbs and the KEF R3 weighs 13.55kg / 29.8lbs. This makes the R3 46% heavier than the Motion XT B100.
Here is a comparison of how Motion XT B100 and R3's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
MartinLogan Motion XT B100
What's in the Box of KEF R3?
Here are the items that come with the R3:
2 Bookshelf loudspeakers2 Grilles2 Foam port plugs8 Self-adhesive rubber feetUser ManualWarranty Information
 Max Input Power |
250 watts
vs
180 watts
|
Handle more power from your amplifier |
 Sensitivity |
93 dB
vs
87 dB
|
Play louder with same amount of amplification power |
 Low Frequency Response |
45 Hz
vs
52 Hz
|
Generates deeper bass |
 Height |
368mm
vs
423mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
645cm2 (203x318mm)
vs
670cm2 (199x337mm)
|
Takes less floor space |
 Price per pair* |
1598USD
vs
2200USD
|
costs less (*prices may change depending on the seller, location and time) |
 Driver Setup |
3-way
vs
2-way
|
Have a dedicated mid-range driver |
 Nominal Impedance |
8 ohms
vs
4 ohms
|
Less selective with amplifiers |
 High Frequency Response |
28k Hz
vs
25k Hz
|
Generates higher frequency |
| General |
MartinLogan Motion® XT B100 |
KEF R3 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-250 watts |
15-180 watts |
| Sensitivity |
93 dB |
87 dB |
| Impedance |
4 ohms |
8 ohms |
| Impedance |
n/a |
3.2 ohms |
| Frequency Response |
45-25k Hz |
52-28k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
6.5" |
6.5" |
| Woofer Composition |
Kevlar |
Hybrid aluminum |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1.25 x 2.4" |
1" |
| Tweeter Type |
Folded Motion XT |
Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
5" |
| Crossover Frequency |
2600Hz |
400Hz and 2900Hz |
| Firing Direction |
rear |
rear |
| Suggested Break-in Period |
Allow 72 hours of break-in |
n/a |
Physical Specs |
|
|
| Height |
368.0mm (14.5") |
423.0mm (16.7") |
| Width |
203.0mm (8") |
199.0mm (7.8") |
| Depth |
318.0mm (12.5") |
337.0mm (13.3") |
| Weight |
9.30kg (20.5lbs) |
13.55kg (29.8lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Wood veneer |
MDF/Lacquer |
| Available Colors |
Gloss Black, Walnut, and Satin White |
Black Gloss, White Gloss, Walnut |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-28" |
n/a |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
Yes |
Yes |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |