In this review, we will be comparing Motion 15i and Q350, two Passive Bookshelf speakers from MartinLogan and KEF. Let's have a brief look at the main features
of MartinLogan 15i and KEF Q350 first before getting into our more
detailed comparison.
What size room are the MartinLogan 15i and KEF Q350 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 KEF Q350 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 Q350 are 2-way speakers.
| Driver |
MartinLogan 15i |
KEF Q350 |
|
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 Q350 features a 1" vented aluminum Dome Tweeter and 1 x 6.5" Aluminum Woofer with a Crossover frequency at 2500Hz.
Frequency Response
Motion 15i has a frequency range of 60-25k Hz whereas Q350 has a frequency range of 63-28k Hz. With a minimum frequency of 60Hz, the Motion 15i can go slightly deeper then the Q350's min frequency of 63Hz.
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 Q350 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 Q350's is rated at 87 dB. This 5 dB difference makes the MartinLogan 15i a more sensitive speaker compared to KEF Q350, 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 Q350 has a max power handling value of 120 watts RMS, 80 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
Motion 15i features Post type posts and Q350 has a Post type posts. None of these speakers feature bi-amping/bi-wiring.
MartinLogan 15i's Custom 5-way tool-less binding posts terminals
KEF Q350's Post terminals
Cabinet Type and Port Position
Both Motion 15i and Q350 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 15i's and KEF Q350'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 KEF Q350 has external dimensions of 358.0 x 210.0 x 306.0mm ( 14.0 x 8.2 x 12.0inch) .
KEF Q350 is clearly the larger of the two speakers. Its body is 37mm wider, 68mm taller and 66mm deeper than MartinLogan 15i.
Below you can see the front view size comparison of MartinLogan 15i and KEF Q350 in scale.
Comparison image of MartinLogan 15i and KEF Q350 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 15i is approximately 415.2cm2 / 64.4inch2 and base area of the KEF Q350 is approximately 642.6cm2 / 99.6inch2. The Motion 15i requires 35% less surface area than the Q350 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 15i and KEF Q350 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 15i weighs 5.40kg / 11.9lbs and the KEF Q350 weighs 7.60kg / 16.7lbs. This makes the Q350 41% heavier than the Motion 15i.
Here is a comparison of how Motion 15i and Q350'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 KEF Q350?
Here are the items that come with the Q350:
2 Bookshelf loudspeakers 2 Foam port plugs 8 Self-adhesive rubber feet Owner's Manual Warranty Registration Card
 Max Input Power |
200 watts
vs
120 watts
|
Handle more power from your amplifier |
 Sensitivity |
92 dB
vs
87 dB
|
Play louder with same amount of amplification power |
 Low Frequency Response |
60 Hz
vs
63 Hz
|
Generates deeper bass |
 Height |
290mm
vs
358mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
415cm2 (173x240mm)
vs
642cm2 (210x306mm)
|
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 |
 High Frequency Response |
28k Hz
vs
25k Hz
|
Generates higher frequency |
 Price per pair* |
750USD
vs
900USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Motion 15i |
KEF Q350 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-200 watts |
10-120 watts |
| Sensitivity |
92 dB |
87 dB |
| Impedance |
5 ohms |
8 ohms |
| Impedance |
n/a |
3.7 ohms |
| Frequency Response |
60-25k Hz |
63-28k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5.25" |
6.5" |
| Woofer Composition |
Aluminum |
Aluminum |
| Woofer Surround Material |
Rubber |
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 |
2500Hz |
| 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") |
358.0mm (14.1") |
| Width |
173.0mm (6.8") |
210.0mm (8.3") |
| Depth |
240.0mm (9.4") |
306.0mm (12") |
| Weight |
5.40kg (11.9lbs) |
7.60kg (16.7lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Lacquer |
MDF/Vinyl-wrapped |
| Available Colors |
Gloss Black, Matt White, Red Walnut |
Black, Walnut, White |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
26-28" |
18-24" |
| 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 |