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KEF Reference 4C Review (Center Speaker)

Rate this speaker:

  • 1. Poor (headless panther)

    Votes: 5 1.5%
  • 2. Not terrible (postman panther)

    Votes: 6 1.9%
  • 3. Fine (happy panther)

    Votes: 73 22.5%
  • 4. Great (golfing panther)

    Votes: 240 74.1%

  • Total voters
    324

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
37,893
Likes
161,487
Location
Seattle Area
This is a review and detailed measurements of the KEF Reference 4C Center home theater speaker. It was kindly purchased new by a member and drop shipped to me. 4C costs US $7,500.

KEF REFERENCE 4C Review CSD Waterfall Centre Channel Speaker.jpg


Apology for using stock picture. Speaker weighs 100 pounds and I got interrupted mid-review with our home flooding so still in measurement room. I had finished the measurements though and hence this write up. You can't tell from above picture but this speaker is deep, very deep. The finish is gorgeous but I found a tiny blemish which was disappointing. Back bindings are custom tool metal ones and the best I have seen and felt. No question KEF has targeted high level of execution with this speaker.

A coaxial driver handles midrange and tweeter responsibility. Woofers then bring the bass along (3-way total).

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the center of the tweeter (aligned by eye). Measurement room was at 10 degrees C which may lower bass output a bit. I used a higher resolution scan than normal which turned out to not be necessary as the speaker is very well behaved in higher frequencies. Accuracy is better than 1% as a result in most of the frequency spectrum.

KEF 4C Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

KEF REFERENCE 4C Measurement Frequency Response Centre Channel Speaker.png


While not ruler flan, on-axis response is very good. Even better is directivity index (dashed blue at the bottom) showing that important early reflections are similar to on-axis response which you can see better here:

KEF REFERENCE 4C Measurement Early Window Frequency Response Centre Channel Speaker.png


Bass response is stepped down due to port tuning being low. We can see this in the near-field response:

KEF REFERENCE 4C Measurement Driver near-field Frequency Response Centre Channel Speaker.png


Cabinet/port resonances are kept at bay so don't cause coloration in upper midrange as they usually do in ported speakers.

Predicted in-room response is excellent:
KEF REFERENCE 4C Measurement Predicted in-room Frequency Response Centre Channel Speaker.png


BTW, sensitivity is also excellent at 90 dB although you better have an amplifier that doesn't mind the very low impedance dip of just 2.9 ohm:

KEF REFERENCE 4C Measurement IMpedance and phase Response Centre Channel Speaker.png


The quad bass drivers and capable mid-range translate into incredibly low distortion and power capability:

KEF REFERENCE 4C Measurement THD Distortion Centre Channel Speaker.png

KEF REFERENCE 4C Measurement Relative THD Distortion Centre Channel Speaker.png


The biggest issue with the design of most center speakers is that the doubled up woofer/mid-woofer causes horizontal dispersion to narrow due to timing differential between them. Is that solved here with the coaxial mid-range/mid-woofer? Let's see:


KEF REFERENCE 4C Measurement Horizontal Beam width Response Centre Channel Speaker.png


KEF REFERENCE 4C Measurement Horizontal Directivity Response Centre Channel Speaker.png


Speaker is so wide that there is still good bit of distance between the woofers causing some cancellation. But generally, this is way better than most center speakers we have tested.

The vertical response though shows how good this could be if all the drivers were aligned horizontally:

KEF REFERENCE 4C Measurement Vertical Directivity Response Centre Channel Speaker.png


For fan of timing analysis, here are the rest of the measurements of that type:
KEF REFERENCE 4C Measurement CSD Waterfall Centre Channel Speaker.png

KEF REFERENCE 4C Measurement Impulse Response Centre Channel Speaker.png



KEF REFERENCE 4C Measurement Step Response Centre Channel Speaker.png


Listening Tests
I was in the process of wiring up the speaker to listen to it in the measurement lab when my worried wife ran into the room and said: "downstairs bathroom is flooding!" I rushed out to deal with that and have not had a chance to listen to the 4C yet. I hope to still get a chance to do so and report back.

Conclusions
The fit and finish, design and capabilities of the 4C clearly show that this is a very serious engineering effort by KEF to produce a highly capable center speaker. Physics of sound wavelengths still attack it a bit causing slight narrowing of directivity but otherwise, it is very hard to find fault with this speaker.

I am going to recommend the KEF 4C based on objective data and subjective look and feel of the unit. I expect it to be a super capable center speaker and a great one for 2-channel listening if you use it vertically.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Attachments

  • KEF Reference 4C Frequency Response ASR.zip
    61.6 KB · Views: 60

enricoclaudio

Senior Member
Manufacturer
Joined
Jan 7, 2021
Messages
464
Likes
708
WOW…Price aside, looks like we got a very excellent rival for the Revel C426Be. Thanks @amirm for another great review!!
 

JD_Spoon

Member
Joined
Oct 20, 2021
Messages
26
Likes
120
Location
DFW, TX area
Hi, I'm the donor of this particular speaker, thanks to @amirm for doing all the heavy lifting, figuratively and literally. :) Regarding the speaker's cost, it's the same price for the Reference 4c trio as it would be for a Revel PerformaBe F328Be and C426Be trio, and significantly less if you can take advantage of the promotional deal KEF USA has had going on for a couple of months now. Not even going to pretend it's an inexpensive acquisition even at that level, but if you have the means, they're still out there as of this writing.
 

wavesharp

Member
Joined
Mar 5, 2021
Messages
15
Likes
37
Hi, I'm the donor of this particular speaker, thanks to @amirm for doing all the heavy lifting, figuratively and literally. :) Regarding the speaker's cost, it's the same price for the Reference 4c trio as it would be for a Revel PerformaBe F328Be and C426Be trio, and significantly less if you can take advantage of the promotional deal KEF USA has had going on for a couple of months now. Not even going to pretend it's an inexpensive acquisition even at that level, but if you have the means, they're still out there as of this writing.
I have also one KEF Reference 4C. Now I believe I selected one nice center speaker
 

respice finem

Major Contributor
Joined
Feb 1, 2021
Messages
1,272
Likes
2,232
You're unstoppable :cool: thanks.

Very heavy and even more expensive, but a fine big center speaker, if you need one.
For a smaller room, you might IMHO be better off with a compact coax from KEF, like
for 10% of the price.
 

alex-z

Senior Member
Joined
Feb 19, 2021
Messages
473
Likes
797
Location
Canada
Honey I shrunk the distortion...

Less than .5% THD from 150-4500Hz even at 96dB. I would call this the perfect centre channel if they moved the port tuning up maybe 10Hz.
 

FeddyLost

Senior Member
Joined
May 24, 2020
Messages
495
Likes
352
It would be interesting to dampen enclosure better and check CSD and subjective impressions again.
With such low distortion from drivers, only non-suppressed resonances might affect SQ.
 

Maiky76

Senior Member
Joined
May 28, 2020
Messages
340
Likes
2,588
Location
French, leaving in China
This is a review and detailed measurements of the KEF Reference 4C Center home theater speaker. It was kindly purchased new by a member and drop shipped to me. 4C costs US $7,500.

View attachment 179847

Apology for using stock picture. Speaker weighs 100 pounds and I got interrupted mid-review with our home flooding so still in measurement room. I had finished the measurements though and hence this write up. You can't tell from above picture but this speaker is deep, very deep. The finish is gorgeous but I found a tiny blemish which was disappointing. Back bindings are custom tool metal ones and the best I have seen and felt. No question KEF has targeted high level of execution with this speaker.

A coaxial driver handles midrange and tweeter responsibility. Woofers then bring the bass along (3-way total).

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the center of the tweeter (aligned by eye). Measurement room was at 10 degrees C which may lower bass output a bit. I used a higher resolution scan than normal which turned out to not be necessary as the speaker is very well behaved in higher frequencies. Accuracy is better than 1% as a result in most of the frequency spectrum.

KEF 4C Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

View attachment 179848

While not ruler flan, on-axis response is very good. Even better is directivity index (dashed blue at the bottom) showing that important early reflections are similar to on-axis response which you can see better here:

View attachment 179849

Bass response is stepped down due to port tuning being low. We can see this in the near-field response:

View attachment 179850

Cabinet/port resonances are kept at bay so don't cause coloration in upper midrange as they usually do in ported speakers.

Predicted in-room response is excellent:
View attachment 179851

BTW, sensitivity is also excellent at 90 dB although you better have an amplifier that doesn't mind the very low impedance dip of just 2.9 ohm:

View attachment 179852

The quad bass drivers and capable mid-range translate into incredibly low distortion and power capability:

View attachment 179853
View attachment 179854

The biggest issue with the design of most center speakers is that the doubled up woofer/mid-woofer causes horizontal dispersion to narrow due to timing differential between them. Is that solved here with the coaxial mid-range/mid-woofer? Let's see:


View attachment 179855

View attachment 179856

Speaker is so wide that there is still good bit of distance between the woofers causing some cancellation. But generally, this is way better than most center speakers we have tested.

The vertical response though shows how good this could be if all the drivers were aligned horizontally:

View attachment 179857

For fan of timing analysis, here are the rest of the measurements of that type:
View attachment 179860
View attachment 179861


View attachment 179862

Listening Tests
I was in the process of wiring up the speaker to listen to it in the measurement lab when my worried wife ran into the room and said: "downstairs bathroom is flooding!" I rushed out to deal with that and have not had a chance to listen to the 4C yet. I hope to still get a chance to do so and report back.

Conclusions
The fit and finish, design and capabilities of the 4C clearly show that this is a very serious engineering effort by KEF to produce a highly capable center speaker. Physics of sound wavelengths still attack it a bit causing slight narrowing of directivity but otherwise, it is very hard to find fault with this speaker.

I am going to recommend the KEF 4C based on objective data and subjective look and feel of the unit. I expect it to be a super capable center speaker and a great one for 2-channel listening if you use it vertically.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Hi,


Score No EQ: 5.9/ 7.3

Not sure if it is relevant...
Score With EQ: 6.7/ 8.1

No EQ Spinorama
KEF R4C No EQ Spinorama.png


EQ Spinorama

KEF R4C Score EQ Spinorama.png

Radar

KEF R4C Radar.png
 

Attachments

  • KEF R4C Vertical 3D Directivity data.png
    KEF R4C Vertical 3D Directivity data.png
    430.9 KB · Views: 45
  • KEF R4C Horizontal 3D Directivity data.png
    KEF R4C Horizontal 3D Directivity data.png
    433.9 KB · Views: 40
  • KEF R4C Normalized Directivity data.png
    KEF R4C Normalized Directivity data.png
    339 KB · Views: 42
  • KEF R4C Raw Directivity data.png
    KEF R4C Raw Directivity data.png
    531.4 KB · Views: 45
  • KEF R4C Reflexion data.png
    KEF R4C Reflexion data.png
    140.8 KB · Views: 34
  • KEF R4C LW data.png
    KEF R4C LW data.png
    163.6 KB · Views: 37
  • KEF R4C 2D surface Directivity Contour Only Data.png
    KEF R4C 2D surface Directivity Contour Only Data.png
    232.9 KB · Views: 34
  • KEF R4C 2D surface Directivity Contour Data.png
    KEF R4C 2D surface Directivity Contour Data.png
    315.2 KB · Views: 42
  • KEF R4C 3D surface Vertical Directivity Data.png
    KEF R4C 3D surface Vertical Directivity Data.png
    462.1 KB · Views: 45
  • KEF R4C LW better data.png
    KEF R4C LW better data.png
    199.6 KB · Views: 49
  • KEF R4C APO EQ Score 96000Hz.txt
    337 bytes · Views: 13
  • KEF R4C 3D surface Horizontal Directivity Data.png
    KEF R4C 3D surface Horizontal Directivity Data.png
    455.1 KB · Views: 48
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