In this review, we will be comparing Motion B10 and XT20, two Passive Bookshelf speakers from MartinLogan and Polk Audio. Let's have a brief look at the main features
of MartinLogan Motion B10 and Polk XT20 first before getting into our more
detailed comparison.
What size room are the MartinLogan Motion B10 and Polk XT20 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 B10 and Polk XT20 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
Both Motion B10 and XT20 are 2-way speakers.
| Driver |
MartinLogan Motion B10 |
Polk XT20 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1.0 x 1.4-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5.25-inch
|
1 x 6.5-inch
|
Motion B10 features a 1.0 x 1.4" Folded Motion Ribbon Tweeter and 1 x 5.25" Woven Fiberglass Woofer with a Crossover frequency at 2370Hz. On the other hand, the XT20 features a 1" Soft-Dome Tweeter and 1 x 6.5" Bi-laminate paper Woofer .
Frequency Response
Motion B10 has a frequency range of 56-25k Hz whereas XT20 has a frequency range of 38-40k Hz. With a minimum frequency of 38Hz, the XT20 can go significantly deeper on the low side and provide stronger bass compared to the Motion B10's min frequency of 56Hz.
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 B10 is a 5 ohms speaker compared to the XT20 which has a nominal impedance of 8 ohms.
These two speakers also have different sensitivity levels. Motion B10 sensitivity is rated at 92 dB and the XT20's is rated at 87 dB. This 5 dB difference makes the MartinLogan Motion B10 a more sensitive speaker compared to Polk XT20, 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.
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 B10 features 5-Way post type posts and XT20 has a 5-Way post type posts. None of these speakers feature bi-amping/bi-wiring.
MartinLogan Motion B10's Custom 5-way binding posts terminals
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 B10's and Polk XT20's external dimensions. MartinLogan Motion B10 has external dimensions of 318 x 178 x 248mm ( 12-1/2inch x 7inch x 9-3/4inch ) whereas Polk XT20 has external dimensions of 332.0 x 193.0 x 281.0mm ( 13-1/16 x 7-9/16 x 11-1/16inch) .
Polk XT20 is clearly the larger of the two speakers. Its body is 15mm wider, 14mm taller and 33mm deeper than MartinLogan Motion B10.
Below you can see the front view size comparison of MartinLogan Motion B10 and Polk XT20 in scale.
Comparison image of MartinLogan Motion B10 and Polk XT20 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 B10 is approximately 441.4cm2 / 68.4inch2 and base area of the Polk XT20 is approximately 542.3cm2 / 84.1inch2. The Motion B10 requires 19% less surface area than the XT20 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 B10 and Polk XT20 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 B10 weighs 6.60kg / 14.5lbs and the Polk XT20 weighs 5.45kg / 12lbs. This makes the Motion B10 21% heavier than the XT20.
Here is a comparison of how Motion B10 and XT20's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of Polk XT20?
Here are the items that come with the XT20:
2 Bookshelf loudspeakers2 Grilles (attached)8 Self-adhesive rubber feetOwners ManualOnline Product Registration
 Sensitivity |
92 dB
vs
87 dB
|
Play louder with same amount of amplification power |
 Height |
318mm
vs
332mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
441cm2 (178x248mm)
vs
542cm2 (193x281mm)
|
Takes less floor space |
 Nominal Impedance |
8 ohms
vs
5 ohms
|
Less selective with amplifiers |
 Woofer Size |
6.5 inches
vs
5.25 inches
|
Larger woofer |
| Low Frequency Response |
38 Hz
vs
56 Hz
|
Generates deeper bass |
 High Frequency Response |
40k Hz
vs
25k Hz
|
Generates higher frequency |
 Price per pair* |
299USD
vs
1198USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Motion® B10 |
Polk Audio Monitor XT20 |
| Brand |
MartinLogan |
Polk Audio |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-200 watts |
30-200 watts |
| Sensitivity |
92 dB |
87 dB |
| Impedance |
5 ohms |
8 ohms |
| Frequency Response |
56-25k Hz |
38-40k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
6.5" |
| Woofer Composition |
Woven Fiberglass |
Bi-laminate paper |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1.0 x 1.4" |
1" |
| Tweeter Type |
Folded Motion Ribbon |
Soft-Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2370Hz |
n/a |
| Firing Direction |
rear |
n/a |
| Suggested Break-in Period |
Allow 72 hours of break-in |
n/a |
Physical Specs |
|
|
| Height |
318.0mm (12.5") |
332.0mm (13.1") |
| Width |
178.0mm (7") |
193.0mm (7.6") |
| Depth |
248.0mm (9.8") |
281.0mm (11.1") |
| Weight |
6.60kg (14.5lbs) |
5.45kg (12lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
n/a |
MDF, Vinyl |
| Available Colors |
Gloss Black, Walnut, and Satin White |
Black |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-28" |
24-28" |
| 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 |