In this review, we will be comparing Motion 35XTi and LS50, two Passive Bookshelf speakers from MartinLogan and KEF.
Let's have a brief look at the main features
of MartinLogan 35XTi and KEF LS50 first before getting into our more
detailed comparison.
| Key Specs | MartinLogan 35XTi | KEF LS50 |
|---|
| Brand | MartinLogan
United States · founded 1982 | KEF
United Kingdom · founded 1961 |
|---|
| Design | 2-way | 2-way |
|---|
| Uni-Q driver | — | 11th Generation Uni-Q |
|---|
| Tweeter | 1.25 x 2.4" Folded Motion XT | 1" Vented dome |
|---|
| Woofer | 6.5" Aluminum | 5.25" Magnesium/aluminum alloy |
|---|
| Frequency response | 50-25k Hz | 79-28k Hz |
|---|
| Sensitivity | 92 dB | 85 dB |
|---|
| Impedance | 4 ohms | 8 ohms |
|---|
| Power range | 20-250 watts | 25-100 watts |
|---|
| Weight | 8.40kg / 18.5lbs | 7.20kg / 15.8lbs |
|---|
| Dimensions (H x W x D) | 13.5" x 7.5" x 11.8"
343.0 x 192.0 x 300.0mm | 11.8" x 7.8" x 10.9"
302.0 x 200.0 x 278.0mm |
|---|
What size room are the MartinLogan 35XTi and KEF LS50 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 35XTi |
KEF LS50 |
| Near-field |
Poor |
Average |
| Small Room |
Poor |
Good |
| Mid-size Room |
Good |
Average |
| Large Room |
Good |
Poor |
| Very Large Room |
Average |
Bad |
(* 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 35XTi and LS50 are 2-way speakers.
MartinLogan 35XTiKEF LS50
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 35XTi |
KEF LS50 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1.25 x 2.4-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 6.5-inch
|
1 x 5.25-inch
|
Motion 35XTi features a 1.25 x 2.4" Folded Motion XT Tweeter and 1 x 6.5" Aluminum Woofer with a Crossover frequency at 2200Hz. On the other hand, the LS50 features a 1" Aluminum Vented dome Tweeter and 1 x 5.25" Magnesium/aluminum alloy Woofer with a Crossover frequency at 2200Hz.
Frequency Response
Motion 35XTi has a frequency range of 50-25k Hz whereas LS50 has a frequency range of 79-28k Hz. With a minimum frequency of 50Hz, the Motion 35XTi can go significantly deeper on the low side and provide stronger bass compared to the LS50's min frequency of 79Hz.
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 35XTi is a 4 ohms speaker compared to the LS50 which has a nominal impedance of 8 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 35XTi can provide this impedance level.
These two speakers also have different sensitivity levels. Motion 35XTi sensitivity is rated at 92 dB and the LS50's is rated at 85 dB. This 7 dB difference makes the MartinLogan 35XTi a more sensitive speaker compared to KEF LS50, 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 35XTi can handle a max power of 250 watts RMS, whereas LS50 has a max power handling value of 100 watts RMS, 150 watts less than the Motion 35XTi.
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 35XTi features Custom 5-way bi-wire tool-less binding posts posts which make bi-amping or bi-wiring possible. LS50 has a Post which doesn't feature bi-amping/bi-wiring.
MartinLogan 35XTi's Custom 5-way bi-wire tool-less binding posts terminals allows Bi-amping or bi-wiring
KEF LS50's Post terminals
Cabinet Type and Port Position
Both Motion 35XTi and LS50 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 35XTi's and KEF LS50's external dimensions. MartinLogan 35XTi has external dimensions of 343.0 x 192.0 x 300.0mm (13.5 x 7.5 x 11.8inch) whereas KEF LS50 has external dimensions of 302.0 x 200.0 x 278.0mm (11.8 x 7.8 x 10.9inch).
KEF LS50 is 41mm shorter and 22mm less deeper than MartinLogan 35XTi but it is also 8mm wider.
Below you can see the front view size comparison of MartinLogan 35XTi and KEF LS50 in scale.
Comparison image of MartinLogan 35XTi and KEF LS50 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 35XTi is approximately 576.0cm2 / 89.3inch2 and base area of the KEF LS50 is approximately 556.0cm2 / 86.2inch2. The Motion 35XTi requires 4% more surface area than the LS50 which gives it a small disadvantage on placement in tight spaces.
Here is 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 35XTi and KEF LS50 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 35XTi weighs 8.40kg / 18.5lbs and the KEF LS50 weighs 7.20kg / 15.8lbs. This makes the Motion 35XTi 17% heavier than the LS50.
Here is a comparison of how Motion 35XTi and LS50'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 35XTi?
Here are the items that are included inside the box of Motion 35XTi:
- Bookshelf loudspeaker
- Grille
- 4 Rubber feet
- 2 Jumper-straps (pre-installed)
- Users Manual
- Warranty/Registration Information
What's in the Box of KEF LS50?
Here are the items that come with the LS50:
- 2 Bookshelf loudspeakers
- 2 Foam port plugs
- 8 Self-adhesive rubber feet
- Owner's Manual
- Warranty Registration Card
 Max Input Power |
250 watts
vs
100 watts
|
Handle more power from your amplifier |
 Sensitivity |
92 dB
vs
85 dB
|
Play louder with same amount of amplification power |
 Woofer Size |
6.5 inches
vs
5.25 inches
|
Larger woofer |
|
Low Frequency Response |
50 Hz
vs
79 Hz
|
Generates deeper bass |
 Bi-Amping and Bi-Wiring |
Yes
vs
No
|
Allows bi-amping and bi-wiring connections |
 Nominal Impedance |
8 ohms
vs
4 ohms
|
Less selective with amplifiers |
 High Frequency Response |
28k Hz
vs
25k Hz
|
Generates higher frequency |
 Height |
302mm
vs
343mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
556cm2
vs
576cm2
|
Takes less floor space |
 Price per pair* |
1300USD
vs
1500USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Motion 35XTi |
KEF LS50 |
| Brand |
MartinLogan |
KEF |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-250 watts |
25-100 watts |
| Sensitivity |
92 dB |
85 dB |
| Impedance |
4 ohms |
8 ohms |
| Impedance |
n/a |
3.2 ohms |
| Frequency Response |
50-25k Hz |
79-28k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
6.5" |
5.25" |
| Woofer Composition |
Aluminum |
Magnesium/aluminum alloy |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1.25 x 2.4" |
1" |
| Tweeter Type |
Folded Motion XT |
Vented dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2200Hz |
2200Hz |
| Firing Direction |
rear |
rear |
| Suggested Break-in Period |
Allow 72 hours of break-in at 90 dB |
n/a |
Physical Specs |
|
|
| Height |
343.0mm (13.5") |
302.0mm (11.9") |
| Width |
192.0mm (7.6") |
200.0mm (7.9") |
| Depth |
300.0mm (11.8") |
278.0mm (10.9") |
| Weight |
8.40kg (18.5lbs) |
7.20kg (15.8lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Lacquer |
Polymer/Lacquer |
| Available Colors |
Gloss Black, Matt White, Red Walnut |
Black, High Gloss Piano Black, High Gloss Piano White |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-26" |
18-28" |
| Grille |
Yes |
n/a |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
Yes |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
A generation apart: MartinLogan 35XTi is the newer design, against a 2012 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass | A | MartinLogan 35XTi digs deeper - 50Hz against 79Hz. |
| Amplifier needs | A | MartinLogan 35XTi is more sensitive (92dB vs 85dB), so it goes louder on the same amplifier. |
| Amplifier match | B | KEF LS50 is the easier load at 8 ohms; the other is 4 ohms and wants an amplifier rated for it. |
| Headroom | A | MartinLogan 35XTi takes more power (250W vs 100W) - more in hand in a big room. |
| Size | depends | Similar cabinet size - neither is easier to fit. |
| Expandability | A | MartinLogan 35XTi: bi-amping. MartinLogan 35XTi sits in a wider range (18 models), so a matched surround system is easier later. |
| Price | B | KEF LS50 is cheaper - $1,300 against $1,500, about 13% less. |
A MartinLogan 35XTi B KEF LS50
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 35XTi leads across most of the measured areas for a fairly modest premium, which makes it the easier pick if the budget stretches. KEF LS50 is the one to take if it does not. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 79Hz anyway, which makes the cheaper KEF LS50 much easier to justify. Match it to your room: we rate MartinLogan 35XTi the better fit for a mid-size room, a large room and a very large room, and KEF LS50 for near-field listening and a small room.
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.