In this review, we will be comparing Motion XT C100 and L400, two Passive Center Channel speakers from MartinLogan and Polk Audio.
Let's have a brief look at the main features
of MartinLogan Motion XT C100 and Polk L400 first before getting into our more
detailed comparison.
| Key Specs | MartinLogan Motion XT C100 | Polk L400 |
|---|
| Design | 2-way | 3-way |
|---|
| Tweeter | 1.25 x 2.4" Folded Motion XT | 1" Pinnacle Ring Radiator |
|---|
| Midrange | — | 4" |
|---|
| Woofer | 2 x 6.5" Aluminum | 2 x 6.5" |
|---|
| Frequency response | 42-25k Hz | 55-38k Hz |
|---|
| Sensitivity | 93 dB | 87.5 dB |
|---|
| Impedance | 5 ohms | 4 ohms |
|---|
| Power range | 20-300 watts | 25-300 watts |
|---|
| Weight | 15.40kg / 33.9lbs | 18.55kg / 40.8lbs |
|---|
| Dimensions (H x W x D) | 8" x 24" x 14-1/2"
203 x 610 x 368mm | 9-5/8" x 26-1/16" x 13-1/2"
245.0 x 662.0 x 343.0mm |
|---|
What size room are the MartinLogan Motion XT C100 and Polk L400 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 Motion XT C100 |
Polk L400 |
| Near-field |
Poor |
Poor |
| Small Room |
Poor |
Poor |
| Mid-size Room |
Good |
Good |
| Large Room |
Good |
Good |
| Very Large Room |
Average |
Average |
(* 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.
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through our links. As an Amazon Associate I earn from qualifying purchases.
Drivers
One of the fundamental differences between these two speakers is that Motion XT C100 is a 2-way design whereas the L400 is a 3-way speaker. 3-way designs utilize a midrange driver in addition to the tweeter and woofer on 2-way designs. Designing a crossover for a 3-way speaker is a complicated process and generally increases the overall cost of the speaker.
MartinLogan Motion XT C100Polk L400
TweeterMidrangeWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
MartinLogan Motion XT C100 |
Polk L400 |
|
Driver Setup
|
2-way
|
3-way
|
|
Tweeter
|
1.25 x 2.4-inch
|
1-inch
|
|
Midrange
|
- |
1 x 4-inch |
|
Woofer
|
2 x 6.5-inch
|
2 x 6.5-inch
|
Motion XT C100 features a 1.25 x 2.4" Folded Motion XT Tweeter and 2 x 6.5" Aluminum Woofer with a Crossover frequency at 1300Hz and 2500Hz. On the other hand, the L400 features a 1" Pinnacle Ring Radiator Tweeter, a 4" Midrange and 2 x 6.5" Woofer.
Frequency Response
Motion XT C100 has a frequency range of 42-25k Hz whereas L400 has a frequency range of 55-38k Hz. With a minimum frequency of 42Hz, the Motion XT C100 can go significantly deeper on the low side and provide stronger bass compared to the L400's min frequency of 55Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Center Channel class in our database.
Low Frequency
Center Channel 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 XT C100 is a 5 ohms speaker compared to the L400 which has a nominal impedance of 4 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 L400 can provide this impedance level.
These two speakers also have different sensitivity levels. Motion XT C100 sensitivity is rated at 93 dB and the L400's is rated at 87.5 dB. This 5 dB difference makes the MartinLogan Motion XT C100 a more sensitive speaker compared to Polk L400, hence will play louder with the same amount of watts.
Sensitivity
Center Channel 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.
Both handle the same maximum of 300 watts RMS, though Motion XT C100 is rated 20-300 watts and L400 25-300 watts.
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.
MartinLogan Motion XT C100
Input Type and Bi-Amping / Bi-Wiring
Motion XT C100 features Custom 5-way bi-wire tool-less binding posts posts which make bi-amping or bi-wiring possible. L400 has a Binding post which doesn't feature bi-amping/bi-wiring.
MartinLogan Motion XT C100's Custom 5-way bi-wire tool-less binding posts terminals allows Bi-amping or bi-wiring
Polk L400's Binding post terminals
Cabinet Type and Port Position
Both Motion XT C100 and L400 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.
Polk L400 Port
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 Motion XT C100's and Polk L400's external dimensions. MartinLogan Motion XT C100 has external dimensions of 203 x 610 x 368mm (8inch x 24inch x 14-1/2inch) whereas Polk L400 has external dimensions of 245.0 x 662.0 x 343.0mm (9-5/8 x 26-1/16 x 13-1/2inch).
MartinLogan Motion XT C100 is 52mm narrower and 42mm shorter than Polk L400 but it is also 25mm deeper.
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 Motion XT C100 is approximately 2244.8cm2 / 347.9inch2 and base area of the Polk L400 is approximately 2270.7cm2 / 352.0inch2. The Motion XT C100 requires 1% less surface area than the L400 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 Motion XT C100 weighs 15.40kg / 33.9lbs and the Polk L400 weighs 18.55kg / 40.8lbs. This makes the L400 20% heavier than the Motion XT C100.
Here is a comparison of how Motion XT C100 and L400's weights compare with the average, max and min weights in Passive Center Channel class.
Weight
All Center Channel Speakers
MartinLogan Motion XT C100
What's in the Box of Polk L400?
Here are the items that come with the L400:
- Center-channel loudspeaker
- Grille
- 2 Jumper-wires
- Cleaning cloth
- Owners Manual
- Online Registration
 Sensitivity |
93 dB
vs
88 dB
|
Play louder with same amount of amplification power |
 Nominal Impedance |
5 ohms
vs
4 ohms
|
Less selective with amplifiers |
 Low Frequency Response |
42 Hz
vs
55 Hz
|
Generates deeper bass |
 Height |
203mm
vs
245mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
2244cm2
vs
2270cm2
|
Takes less floor space |
 Driver Setup |
3-way
vs
2-way
|
Have a dedicated mid-range driver |
 High Frequency Response |
38k Hz
vs
25k Hz
|
Generates higher frequency |
 Price per pair* |
1799USD
vs
2998USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
MartinLogan Motion® XT C100 |
Polk Audio Legend L400 |
| Brand |
MartinLogan |
Polk Audio |
| Speaker Type |
Center channel speaker |
Center channel speaker |
| Power Range |
20-300 watts |
25-300 watts |
| Sensitivity |
93 dB |
87.5 dB |
| Impedance |
5 ohms |
4 ohms |
| Frequency Response |
42-25k Hz |
55-38k Hz |
Drivers |
|
|
| Woofer Quantity |
2 |
2 |
| Woofer Size |
6.5" |
6.5" |
| Woofer Composition |
Aluminum |
|
| Woofer Surround Material |
Rubber |
n/a |
| Tweeter Size |
1.25 x 2.4" |
1" |
| Tweeter Type |
Folded Motion XT |
Pinnacle Ring Radiator |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
4" |
| Crossover Frequency |
1300Hz and 2500Hz |
n/a |
| Firing Direction |
rear |
rear |
| Suggested Break-in Period |
Allow 72 hours of break-in |
n/a |
Physical Specs |
|
|
| Height |
203.0mm (8") |
245.0mm (9.6") |
| Width |
610.0mm (24") |
662.0mm (26.1") |
| Depth |
368.0mm (14.5") |
343.0mm (13.5") |
| Weight |
15.40kg (33.9lbs) |
18.55kg (40.8lbs) |
| Enclosure |
Bass Reflex |
Bass Reflex |
| Finish |
MDF/Wood veneer |
n/a |
| Available Colors |
Gloss Black, Walnut, and Satin White |
Black, Walnut |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
Yes |
n/a |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
These sit in different price classes - MartinLogan Motion XT C100 costs roughly 1.7x what Polk L400 does. Expect it to lead on paper; the question is whether the gap is audible enough in your room to be worth it.
| Area | Better | Why |
|---|
| Bass |
A |
MartinLogan Motion XT C100 digs deeper - 42Hz against 55Hz. |
| Amplifier needs |
A |
MartinLogan Motion XT C100 is more sensitive (93dB vs 88dB), so it goes louder on the same amplifier. |
| Amplifier match |
A |
MartinLogan Motion XT C100 is the easier load at 5 ohms; the other is 4 ohms and wants an amplifier rated for it. |
| Headroom |
evenly matched |
Similar power handling (300W vs 300W). |
| Size |
depends |
Similar cabinet size - neither is easier to fit. |
| Expandability |
A |
MartinLogan Motion XT C100: bi-amping. |
| Price |
B |
Polk L400 is cheaper - $1,799 against $2,998, about 40% less; arguably a different class. |
A MartinLogan Motion XT C100
B Polk L400
depends neither is better in the abstract - it turns on your room, placement 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?
The usual trade-off: MartinLogan Motion XT C100 measures better, Polk L400 costs about 40% less. Whether that gap is worth the money is the call only you can make - and in a normal room it is often smaller than the numbers suggest. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 55Hz anyway, which makes the cheaper Polk L400 much easier to justify. If your amplifier is modest, vintage or valve-based, MartinLogan Motion XT C100 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.