In this review, we will be comparing Motion 15 and Q350, two Passive Bookshelf speakers from MartinLogan and KEF.
Let's have a brief look at the main features
of MartinLogan 15 and KEF Q350 first before getting into our more
detailed comparison.
| Key Specs | MartinLogan 15 | KEF Q350 |
|---|
| Brand | MartinLogan
United States · founded 1982 | KEF
United Kingdom · founded 1961 |
|---|
| Design | 2-way | 2-way |
|---|
| Uni-Q driver | — | 11th Generation Uni-Q |
|---|
| Tweeter | 1.0 x 1.4" Folded Motion | 1" Dome |
|---|
| Woofer | 5.25" Aluminum | 6.5" Aluminum |
|---|
| Frequency response | 60-25k Hz | 63-28k Hz |
|---|
| Sensitivity | 92 dB | 87 dB |
|---|
| Impedance | 5 ohms | 8 ohms |
|---|
| Power range | 20-200 watts | 10-120 watts |
|---|
| Weight | 5.40kg / 11.9lbs | 7.60kg / 16.7lbs |
|---|
| Dimensions (H x W x D) | 11.4" x 6.8" x 9.4"
290.0 x 173.0 x 240.0mm | 14.0" x 8.2" x 12.0"
358.0 x 210.0 x 306.0mm |
|---|
What size room are the MartinLogan 15 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:
| Listening Environment* |
MartinLogan 15 |
KEF Q350 |
| Near-field |
Poor |
Poor |
| Small Room |
Average |
Average |
| Mid-size Room |
Good |
Good |
| Large Room |
Average |
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.)
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
Drivers
Both Motion 15 and Q350 are 2-way speakers.
MartinLogan 15KEF Q350
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
MartinLogan 15 |
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 15 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 15 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 15 can go slightly deeper then the Q350's min frequency of 63Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
Neither pair reaches down to 20Hz, the usual definition of full-range, which is normal for speakers of this size. If you want the bottom octave for movies or bass-heavy music, add a subwoofer to whichever you choose. Visit our Powered Subwoofers section to find out more about the available options.
Impedance and Sensitivity
Motion 15 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 15 sensitivity is rated at 92 dB and the Q350's is rated at 87 dB. This 5 dB difference makes the MartinLogan 15 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. Staying
within that range gives nominal performance; driving the speaker beyond its maximum wattage can damage it.
Motion 15 can handle a max power of 200 watts RMS, whereas Q350 has a max power handling value of 120 watts RMS, 80 watts less than the Motion 15.
Note that higher power handling does not make a speaker louder: that depends mainly on
sensitivity and impedance. The calculator below shows how loud each of these actually plays
on a real amplifier.
Which plays louder on your amplifier?
Starting with a popular amplifier - change it to the one you own, or any you are
considering, and watch both numbers move.
Input Type and Bi-Amping / Bi-Wiring
Motion 15 features Post type posts and Q350 has a Post type posts. None of these speakers feature bi-amping/bi-wiring.
KEF Q350's Post terminals
Cabinet Type and Port Position
Both Motion 15 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
The size of a speaker can sometimes be 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 15's and KEF Q350's external dimensions. MartinLogan 15 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 15.
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 15 is approximately 415.2cm2 / 64.4inch2 and base area of the KEF Q350 is approximately 642.6cm2 / 99.6inch2. The Motion 15 requires 35% less surface area than the Q350 which gives it a small advantage on placement in tight spaces.
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 15 weighs 5.40kg / 11.9lbs and the KEF Q350 weighs 7.60kg / 16.7lbs. This makes the Q350 41% heavier than the Motion 15.
Here is a comparison of how Motion 15 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 15?
Here are the items that are included inside the box of Motion 15:
- 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
vs
642cm2
|
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
800USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Motion 15 |
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 |
Piano Lacquer |
MDF/Vinyl-wrapped |
| Available Colors |
Gloss Black, Matt White, Red Walnut |
Black, Walnut, White |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-30" |
18-24" |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
No |
No |
Other |
|
|
| Parts Warranty |
5 Yrs w/ Registration |
5 Years |
| Labor Warranty |
5 Yrs w/ Registration |
5 Years |
No single best speaker here - they are built to different priorities, and the right one depends on your room, your amplifier and what you listen to.
| Area | Better | Why |
|---|
| Bass | A | MartinLogan 15 digs deeper - 60Hz against 63Hz. A subwoofer would even that out. |
| Amplifier needs | A | MartinLogan 15 is more sensitive (92dB vs 87dB), so it goes louder on the same amplifier. |
| Amplifier match | B | KEF Q350 is the easier load at 8 ohms. |
| Headroom | A | MartinLogan 15 takes more power (200W vs 120W) - more in hand in a big room. |
| Size | depends | MartinLogan 15 is easier to place; KEF Q350 is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | depends | Neither adds bi-amping, a sub output or height drivers. MartinLogan 15 sits in a wider range (18 models), so a matched surround system is easier later. |
| Price | evenly matched | Much the same money ($800 vs $750 a pair). |
A MartinLogan 15 B KEF Q350
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
MartinLogan 15 has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. In a large or open-plan room, KEF Q350 has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, MartinLogan 15 is the easier speaker to get right. If your amplifier is modest, vintage or valve-based, MartinLogan 15 is the safer partner - the other will want more current or more watts to sound its best.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.