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KEF Q100 Speaker Review

amirm

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#1
This is a review and detailed measurements of the KEF Q100 bookshelf speaker. It is on kind loan from a member. The Q100 is discontinued but I think it cost US $550.

I always say speaker business is 80% about marketing and KEF has mastered that art:

KEF Q100 Bookshelf Speaker Coaxial Driver Audio Review.jpg

The coaxial driver looks great and caters to audiophile intuition of "point source being good."

Speaker is lighter than I imagined them being.

Here is the back panel:

KEF Q100 Bookshelf Speaker Coaxial Driver Back Panel Bi-wire Audio Review.jpg

I thought those two knobs were level controls which is surprising in a passive speaker. Turns out they are just shunting knobs that short the highs and lows together. Or disconnect them if you want to bi-wire wire/bi-amp them.

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 anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

All measurements are reference to tweeter axis with the grill removed. Frequency resolution is 0.7 Hz (yes, less than 1 Hz) and plots are at 20 points/octave. Spatial 3-D resolution is 1 degree.

Over 700 points around the speaker were measured (from 20 to 20 kHz) which resulted in well under 1% error in identification of the sound field up to 16.5 kHz. After that error climbs to 2% which should not be material. Final database of measurements and data is 1.2 Gigabytes in size.

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

KEF Q100 Bookshelf Speaker Coaxial Driver CEA-2034 Spinorama Audio Measurements.png


We have a broad lift from 700 to 1.5 kHz and another from 5 kHz to beyond 10 kHz. The actual variation is a few dB but because they are so wide, they will hit a lot more notes so colorations will be a lot more audible.

There is a cancellation (notch) at 1.4 kHz which I will address later.

Above graph is also our sensitivity. At mid-frequencies it is 85 dB but drops to 80 dB in bass frequencies. So you need to have good bit of power to drive it loud.

In-room response is more or less what we have on-axis, tilted down:

KEF Q100 Bookshelf Speaker Coaxial Driver CEA-2034 Spinorama Predicted In-Room Response Audio ...png


That's it for most major aspect of the speaker that sets listener preference in controlled testing.

Basic Speaker Measurements
Impedance drops to below 4 ohm in bass frequency so you better have a good amplifier to drive it:

JBL 705P Studio Powered Monitor Impedance and Phase Speaker Review.png


Here is gated room measurement and distortion with floor of -50 dB:

KEF Q100 Bookshelf Speaker Coaxial Driver  SPL and Distortion Audio Measurements.png


Zooming in we get:

KEF Q100 Bookshelf Speaker Coaxial Driver  SPL and Distortion Percentage Audio Measurements.png


Waterfall display shows some of the resonances:
KEF Q100 Bookshelf Speaker Coaxial Driver Waterfall CSD Audio Measurements.png


Advanced Speaker Measurements
One benefit of coaxial drivers is that their vertical dispersion is better than simple 2-way speakers:

KEF Q100 Bookshelf Speaker Coaxial Driver Horizontal Countour Audio Measurements.png


KEF Q100 Bookshelf Speaker Coaxial Driver Vertical Countour Audio Measurements.png


Eye-candy Measurements
Using the power of 1 degree measurement in 3-D space, we can analyze what is going on with the speaker. To wit, let's see what happens at 1.4 kHz that we had a dip:

KEF Q100 Bookshelf Speaker Coaxial Driver Vertical Port Cancellation Audio Measurements.png

The "nref" arrow is the center of the coaxial driver as you would look into it. We see that there is a strong sound source below it which has to be the port. Something coming out of that port is combing with the main driver and causing cancellation in the middle (to some extent). The frequency is 1.4 kHz. If we convert that to wavelength we get nearly 12 inches which happens to be the height of the cabinet. So it looks like it is a longitudinal mode of the internal cabinet coming out the port causing that partial cancellation.

Note that the bandwidth ("ERB") of the notch is too small to be that audible. It is just an interesting thing to analyze nevertheless.

Speaker Listening Tests
I used the KEF Q100 in my main system, playing in mono (provides best discrimination). Experience was not that positive. Hardly any of my tracks sounded good. Bass loading was rather high and boomy. The location causes some of that but seems to be exaggerated here. There was a general lack of evenness response with some notes forward, some not. There was also some distortion which seemed to be constant throughout everything I played. A buzzing type of secondary tones.

I believe a port plug comes with the speaker. For testing, I just stuck my hand in the port. That nicely lowered the bass boominess and seemed to reduce the distortion I was hearing. This was in near-field listening because obviously I could not reach with my hand 10 feet. :)

Conclusions
I think the famous reputation Q100 has more to do with its great looks than sound. Measurements are not horrible but they lack the evenness that we need to see in on-axis measurements.

Overall, I can't recommend the KEF Q100. Look forward to testing their current production models.

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

Hate going to the local grocery store on Tuesdays. Why? Because they have a 10% discount for "seniors" and they always ask me if I am old enough to qualify. Makes me depressed that I must have lost by great and young looks! Anyway, I always walk away depressed. Please make me feel better by donating money using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

AudioJester

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#3
Is what you heard with bass loading, something that can be predicted from the measurements?

There is a lot of hype around Kef, thanks for measuring.
 
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amirm

amirm

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Thread Starter #4
Is what you heard with bass loading, something that can be predicted from the measurements?
No, you would need room measurements to know.
 

napilopez

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#5
Thanks Amir!

Measurements look good to me for the price, imo better than the LS50.

KEF seems to generally design their speakers with off-axis listening in mind, and perhaps even as the priority, based on my inquiries.

The listening window seems to tame that treble shelf a fair bit so I'm going to guess these are flattest around 20 degrees off axis as I've usually seen with KEF, which is approximately using no toe in the average listening room. A bit of excess energy around 1K but the broad trends shouldn't be too hard to EQ out!

EDIT: Audible distortion is concerning though.
 

JohnYang1997

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#6
I don't know why, it just sounds honky to me. Hs7 also has a hump in there but doesn't sound remotely as lean.
 
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amirm

amirm

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Thread Starter #7
By the way, I made a new absorber for the microphone cage/fixture which seems to have been quite effective in getting rid of comb filtering above 10 kHz.
 

MZKM

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#8
Would like to see what differences exists with the current Q150, they switched to rear-ported.

Your comment about hearing distortion seems odd given the distortion measurement being very good.

Preference Rating
SCORE: 5.0
SCORE w/ subwoofer: 7.3
 
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napilopez

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#9
Just checked the spin data and indeed, around 20 degrees off-axis seems best, which is a pretty common "point them straight forward" angle. I also found this to be the case with the R3 and LS50W - well, 15 degrees, since I was using 15-degree increments back then - so at this point, I'm pretty sure that's just how KEF designs speakers.:)

As always, data scaled to 25dB per decade, as defined by CTA-2034A even though Harman doesn't even use it =]

Q100.jpg


If you don't toe them in and reduce some of that excess 1K energy, you have a much more linear speaker.

P.S. REW now lets you use dashed lines, so I'm a very happy camper.

EDIT: @MZKM if you get the chance, would you mind computing the score with 20 degrees as the on-axis? The ER/PIR would technically also change slightly but that's likely a much smaller difference.
 
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digicidal

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#12
Has @maty seen this haha he’s gonna go bonkers
You mean as opposed to "normal" @maty or relative to the general population? ;) (I predict 3 font colors at a minimum)
 

thewas

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#13
EDIT: Audible distortion is concerning though.
Is it? It is rather less audible than on the much newer and more expensive JBL 705P, atlhough it was measured on a higher SPL.
1583908822747.png 1583908840777.png
(please note the different y-axis scaling)

Also its on-axis and predicted in room responses are imho not so much worse (just have that highs boost) than on that modern active DSP monitor, which is quite impressive considering it is a long discontinued (released 10 years ago), was the cheapest hifi speaker of KEF, just a passive loudspeaker and a much more difficult to engineer coaxial (with inherent advantages in the vertical directivity)

1583909028950.png 1583909075984.png
1583909109652.png 1583909049012.png
1583909371385.png 1583909389654.png

and thus got even a higher Harman based preference rating of 5.0 vs 4.7

Only the Harman product got a happy panther though... ;):rolleyes:
 
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digicidal

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#14
Would like to see what differences exists with the current Q150, they switched to rear-ported.

Your comment about hearing distortion seems odd given the distortion measurement being very good.

Preference Rating
SCORE: 5.0
SCORE w/ subwoofer: 7.2
Oh very interesting. So better than their higher-binned model? (LS50 was 4.48/6.61) - at the very least that indicates by that metric that the "value" estimation is quite valid, presuming you liked the LS50's sound. I'm one that didn't, so not for me - but I'm in the minority on that it seems.
 

napilopez

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#16
Is it? It is rather less audible than on the much newer and more expensive JBL 705P, atlhough it was measured on a higher SPL.
View attachment 53779 View attachment 53780
(please note the different y-axis scaling)

Also its on-axis and predicted in room responses are imho not so much worse (just have that highs boos) than on that modern active DSP monitor, which is quite impressive considering it is a long discontinued (released 10 years ago), was the cheapest hifi speaker of KEF, just a passive loudspeaker and coaxial (with inherent advantages in the vertical directivity)

View attachment 53781 View attachment 53783
View attachment 53784 View attachment 53782
View attachment 53785 View attachment 53786

Of course the Harman product got a happy panther though... ;):rolleyes:
I was referring to Amir's comments from the listening tests :)"There was also some distortion which seemed to be constant throughout everything I played. A buzzing type of secondary tones. "

Which surprised me because I don't see anything egregious in the distortion measurements as you point out.

EDIT: Agree that it's an impressive result for an old speaker. Notably, the preference score is higher than the LS50 on both counts. Though pretty close overall and we know the hazards of placing too weight on the rankings for speakers grouped closely together, it suggests the speakers were in the same ballpark despite some significant price differences.
 
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McFly

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#17
I do suspect the slightest bit of panther bias in some cases. But people please, the panther is amirs personal choice. Of course it is subject to a bit of bias. Whether he thinks it or not.

Ignore the tiny figurine, read the measurements yourself and draw your own conclusions. Reply accordingly. I think for the price, the kef hasn’t done too bad.
 

thewas

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Oh very interesting. So better than their higher-binned model? (LS50 was 4.48/6.61) - at the very least that indicates by that metric that the "value" estimation is quite valid, presuming you liked the LS50's sound. I'm one that didn't, so not for me - but I'm in the minority on that it seems
I own the LS50 since it was released and without EQ I would prefer the Q100, but with EQ its a better loudspeaker (better driver, distortion and more acoustically optimised and dead housing)
 

thewas

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#19
I do suspect the slightest bit of panther bias in some cases. But people please, the panther is amirs personal choice. Of course it is subject to a bit of bias. Whether he thinks it or not.

Ignore the tiny figurine, read the measurements yourself and draw your own conclusions. Reply accordingly. I think for the price, the kef hasn’t done too bad.
Of course I ignore it, but we shouldn't forget that many visitors to this website just come for quick buying decisions, read "science" in the title, see alot of measurements and then just decide on panthers. ;)
 

stevenswall

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#20
"The coaxial driver looks great and caters to audiophile intuition of "point source being good."" Is this intuition incorrect?

"One of the benefits of a coaxial driver is..."

What are some of the inherent performance disadvantages? (IE: Not price, having to design it right, etc.)

A few potential disadvantages I've heard of:

1. Genelec Emails: On massive models, a coaxial driver cannot handle the SPLs their main monitors can. Have not found evidence to the contrary, as I don't see a coaxial model that can go to 120dB or more.

2. Kii & Buchardt Emails: Coaxials present the tweeter with an ever changing waveguide. Evidence against found on page three: https://assets.ctfassets.net/4zjnzn...3bb717fe31e/genelec_8260a_technical_paper.pdf

3. Forums: Coaxials have a small gap that causes diffraction. Evidence to the contrary in the same document above.

4. Can't remember, but I swear an email with Dutch & Dutch or someone else from a forum a year ago brought up another "disadvantage" that has been resolved for a decade or more. Maybe it was not being time aligned? (The Elac Navis, and KEF LS50, and all other speakers by both brands don't seem to have this issue... People sometimes think of coaxial car stereo drivers I think that might have wonky dispersion.)

Potential Advantages:

1. Easier to not have crossover cancellation. (Off topic PM: why no active crossovers at -999dB per tenth of an octave?)
2. Better vertical dispersion, similar to horizontal.
3. Point source instead of a voice sounding like it's coming from a six inch or foot wide mouth.
4. More compact, shorter speaker designs are possible. 3-way the size of a 2-way.

These measurements are appreciated, this was one of the earliest speakers I looked at buying when I decided to do the DIY HiVi 3.1. Haven't heard this, but would have guessed it sounded better... But that's marketing!
 

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