In this review, we will be comparing two different type of speakers by MartinLogan. MartinLogan Motion 20i is a Floor-standing speaker whereas the Motion 15i is a Bookshelf speaker.
Let's have a brief look at the main features
of MartinLogan 20i and MartinLogan 15i first before getting into our more
detailed comparison.
MartinLogan 20i Key Specs
- 2-way Design
- 1.0 x 1.4" Folded Motion Tweeter
- 2 x 5.5" Aluminum Woofer
- 46-25k Hz Frequency Response
- 90 dB Sensitivity
- Impedance: 4ohms
- Power Range:20-200watts
- Weight:15.00kg
- Dimensions (H x W x D): 905.0" x 6-7/8" x 12-1/16"( 905.0 x 175.0 x 307.0mm )
MartinLogan 15i Key Specs
- 2-way Design
- 1.0 x 1.4" Folded Motion Tweeter
- 5.25" Aluminum Woofer
- 60-25k Hz Frequency Response
- 92 dB Sensitivity
- Impedance: 5ohms
- Power Range:20-200watts
- Weight:5.40kg
- Dimensions (H x W x D): 290.0" x 6.8" x 9.4"( 290.0 x 173.0 x 240.0mm )
Motion 20i and Motion 15i are members of MartinLogan's Motion series of speakers. Below you can find the loudspeakers from this series.
MartinLogan Motion Series History
What size room are the MartinLogan 20i and MartinLogan 15i 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* |
MartinLogan 20i |
MartinLogan 15i |
| Near-field |
Bad |
Poor |
| Small Room |
Poor |
Average |
| Mid-size Room |
Good |
Good |
| Large Room |
Good |
Average |
| Very Large Room |
Poor |
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 MartinLogan 20i and MartinLogan 15i 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 20i and Motion 15i are 2-way speakers.
| Driver |
MartinLogan 20i |
MartinLogan 15i |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1.0 x 1.4-inch
|
1.0 x 1.4-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
2 x 5.5-inch
|
1 x 5.25-inch
|
Motion 20i features a 1.0 x 1.4" Folded Motion Tweeter and 2 x 5.5" Aluminum Woofer with a Crossover frequency at 500Hz and 2600Hz. On the other hand, the Motion 15i features a 1.0 x 1.4" Folded Motion Tweeter and 1 x 5.25" Aluminum Woofer with a Crossover frequency at 2700Hz.
Frequency Response
Motion 20i has a frequency range of 46-25k Hz whereas Motion 15i has a frequency range of 60-25k Hz. With a minimum frequency of 46Hz, the Motion 20i can go significantly deeper on the low side and provide stronger bass compared to the Motion 15i's min frequency of 60Hz.
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 Floor-standing class in our database.
Low Frequency
Floor-standing Speakers
High Frequency
Floor-standing 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 20i is a 4 ohms speaker compared to the Motion 15i which has a nominal impedance of 5 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 20i can provide this impedance level.
These two speakers also have different sensitivity levels. Motion 20i sensitivity is rated at 90 dB and the Motion 15i's is rated at 92 dB. This 2 dB difference makes the MartinLogan 15i a more sensitive speaker compared to MartinLogan 20i, hence will play louder with the same amount of watts.
Sensitivity
Floor-standing 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 20i and Motion 15i has the same power range of 20-200 watts.
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 20i features Custom 5-way bi-wire tool-less binding posts posts which make bi-amping or bi-wiring possible. Motion 15i has a Custom 5-way tool-less binding posts which doesn't feature bi-amping/bi-wiring.
MartinLogan 20i's Custom 5-way bi-wire tool-less binding posts terminals allows Bi-amping or bi-wiring
MartinLogan 15i's Custom 5-way tool-less binding posts terminals
Cabinet Type and Port Position
Both Motion 20i and Motion 15i 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 20i's and MartinLogan 15i's external dimensions. MartinLogan 20i has external dimensions of 905.0 x 175.0 x 307.0mm ( 35-5/8 x 6-7/8 x 12-1/16inch) whereas MartinLogan 15i has external dimensions of 290.0 x 173.0 x 240.0mm ( 11.4 x 6.8 x 9.4inch) .
MartinLogan 20i is clearly the larger of the two speakers. Its body is 2mm wider, 615mm taller and 67mm deeper than MartinLogan 15i.
Below you can see the front view size comparison of MartinLogan 20i and MartinLogan 15i in scale.
Comparison image of MartinLogan 20i and MartinLogan 15i 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 20i is approximately 537.3cm2 / 83.3inch2 and base area of the MartinLogan 15i is approximately 415.2cm2 / 64.4inch2. The Motion 20i requires 29% more surface area than the Motion 15i which gives it a small disadvantage on placement in tight spaces.
What's in the Box of MartinLogan 20i?
Here are the items that are included inside the box of Motion 20i:
Floorstanding loudspeaker2 Grilles4 Rubber feet (pre-installed)4 Spike feet (w/ nuts attached)Users ManualWarranty/Registration Information
What's in the Box of MartinLogan 15i?
Here are the items that come with the Motion 15i:
Bookshelf loudspeaker Grille 4 Rubber feet Users Manual Warranty/Registration Information
Woofer Size 
Bi-Amping and Bi-Wiring 
Sensitivity 
Nominal Impedance 
Height 
Base Surface Area 
Price per pair*