In this review, we will be comparing Motion 15i and RTi A3, two Passive Bookshelf speakers from MartinLogan and Polk Audio. Let's have a brief look at the main features
of MartinLogan 15i and Polk RTi A3 first before getting into our more
detailed comparison.
What size room are the MartinLogan 15i and Polk RTi A3 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 15i and Polk RTi A3 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 15i and RTi A3 are 2-way speakers.
Driver |
MartinLogan 15i |
Polk RTi A3 |
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 15i 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 RTi A3 features a 1" silk polymer composite Dome Tweeter and 1 x 6.5" Polymer composite Woofer with a Crossover frequency at 2800Hz.
Frequency Response
Motion 15i has a frequency range of 60-25k Hz whereas RTi A3 has a frequency range of 50-26k Hz. With a minimum frequency of 50Hz, the RTi A3 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 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 15i is a 5 ohms speaker compared to the RTi A3 which has a nominal impedance of 8 ohms.
These two speakers also have different sensitivity levels. Motion 15i sensitivity is rated at 92 dB and the RTi A3's is rated at 89 dB. This 3 dB difference makes the MartinLogan 15i a more sensitive speaker compared to Polk RTi A3, 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 15i can handle a max power of 200 watts RMS from the amp the whereas RTi A3 has a max power handling value of 150 watts RMS, 50 watts less than the Motion 15i.
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
RTi A3 features Pair of Dual 5-way Binding Posts - Gold-Plated 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.
Cabinet Type and Port Position
Motion 15i has a rear firing port whereas RTi A3 has a back and front firing ports.
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 15i's and Polk RTi A3's external dimensions. MartinLogan 15i has external dimensions of 290.0 x 173.0 x 240.0mm ( 11.4 x 6.8 x 9.4inch) whereas Polk RTi A3 has external dimensions of 374.7 x 214.4 x 355.6mm ( 14.7 x 8.4 x 14.0inch) .
Polk RTi A3 is clearly the larger of the two speakers. Its body is 41.4mm wider, 84.7mm taller and 115.6mm deeper than MartinLogan 15i.
Below you can see the front view size comparison of MartinLogan 15i and Polk RTi A3 in scale.
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 15i is approximately 415.2cm2 / 64.4inch2 and base area of the Polk RTi A3 is approximately 762.4cm2 / 118.2inch2. The Motion 15i requires 46% less surface area than the RTi A3 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:
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 15i weighs 5.40kg / 11.9lbs and the Polk RTi A3 weighs 7.26kg / 16lbs. This makes the RTi A3 34% heavier than the Motion 15i.
Here is a comparison of how Motion 15i and RTi A3'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 15i?
Here are the items that are included inside the box of Motion 15i:
Bookshelf loudspeaker Grille 4 Rubber feet Users Manual Warranty/Registration Information
What's in the Box of Polk RTi A3?
Here are the items that come with the RTi A3:
2 Cherry bookshelf speakers 2 Self-tapping screws 8 Self-adhesive rubber feet Owner's Manual Template Online registration sheet Polk Audio product brochure
Max Input Power |
200 watts
vs
150 watts
|
Handle more power from your amplifier |
Sensitivity |
92 dB
vs
89 dB
|
Play louder with same amount of amplification power |
Height |
290mm
vs
374mm
|
Easier to fit in smaller spaces |
Base Surface Area |
415cm2 (173x240mm)
vs
762cm2 (214x355mm)
|
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 |
50 Hz
vs
60 Hz
|
Generates deeper bass |
High Frequency Response |
26k Hz
vs
25k Hz
|
Generates higher frequency |
Bi-Amping and Bi-Wiring |
Yes
vs
No
|
Allows bi-amping and bi-wiring connections |
Mounting Bracket |
Yes
vs
No
|
Allows mounting on walls |
Price per pair* |
465USD
vs
900USD
|
costs less (*prices may change depending on the seller, location and time) |
General |
MartinLogan Motion 15i |
Polk Audio RTi A3 |
Brand |
MartinLogan |
Polk Audio |
Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
Power Range |
20-200 watts |
20-150 watts |
Sensitivity |
92 dB |
89 dB |
Impedance |
5 ohms |
8 ohms |
Frequency Response |
60-25k Hz |
50-26k Hz |
Drivers |
|
|
Woofer Quantity |
1 |
1 |
Woofer Size |
5.25" |
6.5" |
Woofer Composition |
Aluminum |
Polymer composite |
Woofer Surround Material |
Rubber |
Butyl rubber |
Tweeter Size |
1.0 x 1.4" |
1" |
Tweeter Type |
Folded Motion |
Dome |
Aimable Tweeter |
No |
No |
Midrange Driver |
No |
No |
Crossover Frequency |
2700Hz |
2800Hz |
Firing Direction |
rear |
back and front |
Suggested Break-in Period |
Allow 72 hours of break-in at 90 dB |
n/a |
Physical Specs |
|
|
Height |
290.0mm (11.4") |
374.7mm (14.8") |
Width |
173.0mm (6.8") |
214.4mm (8.4") |
Depth |
240.0mm (9.4") |
355.6mm (14") |
Weight |
5.40kg (11.9lbs) |
7.26kg (16lbs) |
Enclosure |
Bass Reflex |
Bass Reflex |
Finish |
MDF/Lacquer |
Real wood veneer |
Available Colors |
Gloss Black, Matt White, Red Walnut |
Black, Cherry |
Mounting Bracket |
No |
Keyhole |
Recommended Stand Height |
26-28" |
24-31" |
Grille |
Yes |
n/a |
Moisture Resistancy |
No |
No |
Connections |
|
|
Biamp Inputs |
No |
Yes |
Other |
|
|
Parts Warranty |
5 Years |
5 Years |
Labor Warranty |
5 Years |
5 Years |