In this review, we will be comparing Q650c and R400, two Passive Center Channel speakers from KEF and Polk Audio.
Let's have a brief look at the main features
of KEF Q650c and Polk R400 first before getting into our more
detailed comparison.
| Key Specs | KEF Q650c | Polk R400 |
|---|
| Design | 2-way | 2-way |
|---|
| Uni-Q driver | 11th Generation Uni-Q | — |
|---|
| Tweeter | 1" Dome | 1" Pinnacle Ring Radiator |
|---|
| Woofer | 2 x 6.5" aluminum | 2 x 6.5" Polypropylene Turbine Cone |
|---|
| Frequency response | 64-28k Hz | 48-39K Hz |
|---|
| Sensitivity | 87 dB | 89 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | 15-150 watts | 20-200 watts |
|---|
| Weight | 13.64kg / 30lbs | 14.91kg / 32.8lbs |
|---|
| Dimensions (H x W x D) | 8-5/16" x 24-13/16" x 11-15/16"
212.0 x 631.0 x 304.0mm | 7-13/16" x 24-5/16" x 14-5/8"
199.0 x 618.0 x 372.0mm |
|---|
What size room are the KEF Q650c and Polk R400 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 |
Polk R400 |
| 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.
**This post contains affiliate links, and we will be compensated if you make a purchase after clicking
through our links. As an Amazon Associate I earn from qualifying purchases.
Drivers
Both Q650c and R400 are 2-way speakers.
KEF Q650cPolk R400
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
KEF Q650c |
Polk R400 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
2 x 6.5-inch
|
2 x 6.5-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 R400 features a 1" Pinnacle Ring Radiator Tweeter and 2 x 6.5" Polypropylene Turbine Cone Woofer with a Crossover frequency at 2500Hz.
Frequency Response
Q650c has a frequency range of 64-28k Hz whereas R400 has a frequency range of 48-39K Hz. With a minimum frequency of 48Hz, the R400 can go significantly deeper on the low side and provide stronger bass compared to the Q650c's min frequency of 64Hz.
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
Q650c and R400 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. Q650c sensitivity is rated at 87 dB and the R400's is at 89 dB. This 2 dB difference makes the Polk R400 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. Staying
within that range gives nominal performance; driving the speaker beyond its maximum wattage can damage it.
R400 can handle a max power of 200 watts RMS, whereas Q650c has a max power handling value of 150 watts RMS, 50 watts less than the R400.
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
Q650c features Binding post type posts and R400 has a Binding post type posts. None of these speakers feature bi-amping/bi-wiring.
KEF Q650c's Binding post terminals
Polk R400's Binding post terminals
Polk R400 dual 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 KEF Q650c's and Polk R400'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 Polk R400 has external dimensions of 199.0 x 618.0 x 372.0mm (7-13/16 x 24-5/16 x 14-5/8inch).
Polk R400 is 13mm narrower and 13mm shorter than KEF Q650c but it is also 68mm deeper.
Below you can see the front view size comparison of KEF Q650c and Polk R400 in scale.
Comparison image of KEF Q650c and Polk R400 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 KEF Q650c is approximately 1918.2cm2 / 297.3inch2 and base area of the Polk R400 is approximately 2299.0cm2 / 356.3inch2. The Q650c requires 17% less surface area than the R400 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 KEF Q650c weighs 13.64kg / 30lbs and the Polk R400 weighs 14.91kg / 32.8lbs. This makes the R400 9% heavier than the Q650c.
Here is a comparison of how Q650c and R400's weights compare with the average, max and min weights in Passive Center Channel class.
Weight
All Center Channel Speakers
What's in the Box of KEF Q650c?
Here are the items that are included inside the box of Q650c:
- Center-channel loudspeaker
- 4 Self-adhesive rubber feet
- Owners Manual
- Warranty Information
What's in the Box of Polk R400?
Here are the items that come with the R400:
- Center-channel loudspeaker
- Grille
- Owners Manual
- Online Registration
 Minimum Impedance |
4.2 ohms
vs
4.1 ohms
|
Very low impedance levels puts more pressure on amplifier |
|
Passive Radiator |
one 6.5-inch
vs
None
|
Increases the bass performance |
 Base Surface Area |
1918cm2
vs
2299cm2
|
Takes less floor space |
 Max Input Power |
200 watts
vs
150 watts
|
Handle more power from your amplifier |
 Sensitivity |
89 dB
vs
87 dB
|
Play louder with same amount of amplification power |
 Low Frequency Response |
48 Hz
vs
64 Hz
|
Generates deeper bass |
 High Frequency Response |
39k Hz
vs
28k Hz
|
Generates higher frequency |
 Height |
199mm
vs
212mm
|
Easier to fit in smaller spaces |
 Price per pair* |
649USD
vs
750USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
KEF Q650c |
Polk Audio Reserve R400 |
| Brand |
KEF |
Polk Audio |
| Speaker Type |
Center channel speaker |
Center channel speaker |
| Power Range |
15-150 watts |
20-200 watts |
| Sensitivity |
87 dB |
89 dB |
| Impedance |
8 ohms |
8 ohms |
| Impedance |
4.2 ohms |
4.1 ohms |
| Frequency Response |
64-28k Hz |
48-39K Hz |
Drivers |
|
|
| Woofer Quantity |
2 |
2 |
| Woofer Size |
6.5" |
6.5" |
| Woofer Composition |
aluminum |
Polypropylene Turbine Cone |
| Woofer Surround Material |
Rubber |
Rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Dome |
Pinnacle Ring Radiator |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
2500Hz |
2500Hz |
| Firing Direction |
n/a |
rear |
Physical Specs |
|
|
| Height |
212.0mm (8.3") |
199.0mm (7.8") |
| Width |
631.0mm (24.8") |
618.0mm (24.3") |
| Depth |
304.0mm (12") |
372.0mm (14.6") |
| Weight |
13.64kg (30lbs) |
14.91kg (32.8lbs) |
| Enclosure |
Passive Radiator |
Bass Reflex |
| Available Colors |
Satin White, Satin Black, Walnut |
Black, Walnut |
| Grille |
optional |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
n/a |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
A generation apart: Polk R400 is the newer design, against a 2017 model. Newer is not automatically better, but the older one is more likely to be discounted or near run-out.
| Area | Better | Why |
|---|
| Bass |
B |
Polk R400 digs deeper - 48Hz against 64Hz. |
| Amplifier needs |
B |
Polk R400 is more sensitive (89dB vs 87dB), so it goes louder on the same amplifier. |
| Headroom |
B |
Polk R400 takes more power (200W vs 150W) - more in hand in a big room. |
| Size |
depends |
Similar cabinet size - neither is easier to fit. |
| Cabinet |
depends |
Passive Radiator vs Ported. |
| Expandability |
depends |
Neither adds bi-amping, a sub output or height drivers. Polk R400 sits in a wider range (10 models), so a matched surround system is easier later. |
| Price |
B |
Polk R400 is cheaper - $649 against $750, about 13% less. |
A KEF Q650c
B Polk R400
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?
Polk R400 is the easier recommendation: it leads on most of the measured areas and costs less. Take KEF Q650c if its size, looks or fit in your room suit you better. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 64Hz anyway, so judge these on the other rows instead. If your amplifier is modest, vintage or valve-based, Polk R400 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.