In this review, we will be comparing Q650c and Motion 8i, two Passive Center Channel speakers from KEF and MartinLogan.
Let's have a brief look at the main features
of KEF Q650c and MartinLogan 8i first before getting into our more
detailed comparison.
KEF Q650c Key Specs
- 2-way Design
- 11th Generation Uni-Q Driver
- 1" Dome Tweeter
- 2 x 6.5" aluminum Woofer
- 64-28k Hz Frequency Response
- 87 dB Sensitivity
- Impedance: 8ohms
- Power Range:15-150watts
- Weight:13.64kg
- Dimensions (H x W x D): 212.0" x 24-13/16" x 11-15/16"( 212.0 x 631.0 x 304.0mm )
MartinLogan 8i Key Specs
- 2-way Design
- 1.0 x 1.4" Folded Motion Tweeter
- 2 x 4" poly cone woofers with rigid dust caps Woofer
- 70-23k Hz Frequency Response
- 89 dB Sensitivity
- Impedance: 4ohms
- Power Range:20-180watts
- Weight:3.86kg
- Dimensions (H x W x D): 142.0" x 22-1/8" x 5-1/4"( 142.0 x 562.0 x 134.0mm )
What size room are the KEF Q650c and MartinLogan 8i 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* |
KEF Q650c |
MartinLogan 8i |
| 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.)
In the following sections, we will get into more detail in order to better understand how the KEF Q650c and MartinLogan 8i 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 Q650c and Motion 8i are 2-way speakers.
| Driver |
KEF Q650c |
MartinLogan 8i |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1.0 x 1.4-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
2 x 6.5-inch
|
2 x 4-inch
|
Q650c features a 1" vented aluminum Dome Tweeter and 2 x 6.5" aluminum Woofer with a Crossover frequency at 2500Hz. On the other hand, the Motion 8i features a 1.0 x 1.4" Folded Motion Tweeter and 2 x 4" poly cone woofers with rigid dust caps Woofer .
Frequency Response
Q650c has a frequency range of 64-28k Hz whereas Motion 8i has a frequency range of 70-23k Hz. With a minimum frequency of 64Hz, the Q650c can go significantly deeper on the low side and provide stronger bass compared to the Motion 8i's min frequency of 70Hz.
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 Center Channel class in our database.
Low Frequency
Center Channel Speakers
High Frequency
Center Channel 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
Q650c is a 8 ohms speaker compared to the Motion 8i 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 Motion 8i can provide this impedance level.
These two speakers also have different sensitivity levels. Q650c sensitivity is rated at 87 dB and the Motion 8i's is rated at 89 dB. This 2 dB difference makes the MartinLogan 8i a more sensitive speaker compared to KEF Q650c, 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. 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.
Q650c can handle a max power of 180 watts RMS from the amp the whereas Q650c has a max power handling value of 150 watts RMS , 30 watts less than the Motion 8i.
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
Q650c features Spring post type posts and Motion 8i has a Spring post type posts. None of these speakers feature bi-amping/bi-wiring.
KEF Q650c's Binding post terminals
MartinLogan 8i's Spring post terminals
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 KEF Q650c's and MartinLogan 8i's external dimensions. KEF Q650c has external dimensions of 212.0 x 631.0 x 304.0mm ( 8-5/16 x 24-13/16 x 11-15/16inch) whereas MartinLogan 8i has external dimensions of 142.0 x 562.0 x 134.0mm ( 5-9/16 x 22-1/8 x 5-1/4inch) .
KEF Q650c is clearly the larger of the two speakers. Its body is 69mm wider, 70mm taller and 170mm deeper than MartinLogan 8i.
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 KEF Q650c is approximately 1918.2cm2 / 297.3inch2 and base area of the MartinLogan 8i is approximately 753.1cm2 / 116.7inch2. The Q650c requires 155% more surface area than the Motion 8i which gives it a small disadvantage on placement in tight spaces.