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KEF R3 Speaker Review

Martigane

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Again, "hard metallic cone" is just a subjective perception people I did describe above came up. One of the measurable factors that describe this is when the dome breaks up near 20kHz or below so it becomes audible.
To me that is not correct. We can' t just look at the breakup to judge if it's not audible when above 20kHz. How about medium and woofer breakups then? Here on the R3 I guess they'd respectively appear at 9kHz / 6kHz.

Stiff cones tend to have 3 issues:

1) Elevated peak of energy due to breakup
2) Stored energy at breakup making CSD look bad
3) Breakup creates peaks in THD, which in turn re-stimulates the breakup and issue 1) and 2) become problematic again even if crossed over took care to attenuate breakup.

The Kef R3' s CSD is not exactly clean, so maybe there are issues related to breakup/stored energy.
Its THD looks suspiciously clean to me, especially considering the 105dB SPL..
I'm not a big fan of having THD shown in %..
I did some listening tests and indeed found 3rd and 5th harmonic (7th being even worse). already objectionable at low levels (from -50dB 3rd is clearly audible) while testing on sines. So just looking at the highest peaks of THD is not a good indication of perceived distortion.


Anyway, here's an example of a metal cone, SEAS M15CH (pretty bad for the sake of the example)
The breakup peak of that woofer is some 15dB (!) above its SPL in usable range:
m15ch-jam_315mm_2v83_0grad.png

And what you see in the THD measurement is that this peak gets replicated in low frequencies:
m15ch-jam_315mm_2v83hd.png

Then in the CSD we can see that it' s ringing like a bell at breakup frequency:
m15ch-jam_waterfall.png
Another example of a metal cone driver behaving pretty well in comparison:
https://hificompass.com/en/speakers/measurements/sbacoustics/sb-acoustics-sb17nbac35-8
cone is bigger, breakup a bit lower, but lightly damped, and THD is much cleaner.


I would take any day 1 positive review/opinion from someone with credentials than 100 bad reviews
To me that's quite the opposite: If I look for reviews online, I'll always see plenty positive reviews. I even see reviewers that do not give any bad review, everything is great for them. How is that meaningful?
To me, only the negative reviews (or at least some cons) might warn you about issues that would be too late to notice once you bought the stuff.
Granted, one should always question reviews and spot BS.


I'm interested in finding out the max SPL for the KEF R3 or R5 or R7 along the frequency response, similar to this Neuman graph. Is there such a thing?
I think they only do that for active speakers. For passive, you'd have to respect both excursion and thermal limits and see how far you could push the speaker. I guess driver specs and cross over transfer function should lead you a good educated guess if you can' t measure. That' s some work..

In my view, the most important part of that curve should be below 200Hz where excursion limitation is most likely to occur, which can typically be obtained from woofer box simulation software too.
 

thewas

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KEF uses mainly 3 technologies to reduce their (bass-)mid drivers cone driver resonances or to bring them to higher frequencies, cone ribs, modal drive (which Technics used already in 1979) and damping between voice coil and cone called neck control:

The front aluminium skin provides the stiffness necessary to provide pistonic radiation and therefore temporal accuracy within the working range of the driver. However, like all stiff materials, the stiffness is not infinite and at some frequency diaphragm breakup sets in and the Q (sharpness) of the resonances is high – the response peaks at resonance can be as much as 20dB above the pistonic response. Such resonances are not readily suppressed by the relatively gradual attenuation of the crossover network and, if left unchecked, will cause colouration. To reduce the intrusion of these higher-frequency resonances, the paper cone is joined to the aluminium skin at a nodal ring, not at the periphery. The nodal ring is an antinode of the lowest resonance and, when driven there, the resonance is not excited.

1600848900144.png


Source: https://us.kef.com/pub/media/documents/rseries/rseries2018-white-paper.pdf

The issue with metal diaphragms is that when they do enter breakup, as they have little internal damping, very large irregularities in the response occur. These can be easily 15dB or more in magnitude. This is large enough to be a problem even if breakup occurs well above the crossover frequency. It is possible to add damping material directly to the cone to control these resonances, however, this is not a good solution as this direct damping application is very heavy and this results in a driver with low sensitivity. KEF use a unique technology called cone neck control to avoid the traditional breakup problems of metal cone drivers. With cone neck control the cone is not rigidly connected to the voice coil of the driver. A resilient high damping link is used to connect the two parts together. This link is carefully designed and fine tuned with the help of computer modelling so that within the band of the driver the force from the voice coil is fully transferred to the cone. Above crossover, however, the resilient link begins to ¡ ex and to damp the cone motion. The effect on the driver response is quite dramatic. The breakup peak from the driver is reduced by around 15dB and the driver response is considerably smoother. The penalty is a small mass increase in the moving parts, albeit much less than using a direct damping approach. Figure 45 shows the modelled frequency response of a midrange driver with and without cone neck control technology. The overall frequency response of the midrange driver is shown in Figure 46. The frequency response is very smooth and well controlled to well above the crossover frequency of approximately 2.5kHz.

1600849048368.png


Source: https://www.shop.us.kef.com/pub/med...rence/REF_White_Paper_preview_path_200514.pdf
 

Martigane

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With cone neck control the cone is not rigidly connected to the voice coil of the driver
Thanks for the info :)
Oh wow I did not know they would implement a mechanical low pass like that. Pretty bad compromise if you ask me, the driver must have a poor Qms and not be very responsive.
That much increase in 2-3k area is odd. Making the paralel with filter, its a low pass filter with very high Q (increase of energy before cutoff, followed by a sharp drop after cutoff.).
Of course more damping means better frequency response, but that damping happens between voice coil and cone, so the cone's own breakup is not damped at all. This is tricky as you think your breakup is solved because measured frequency response is flat (when driving coil), while actually external perturbations are still going to trigger that ringing since the cone itself is not damped.
It would not be the first time I see drivers being stimulated by sources other than its own voice coil.
This could for example come from tweeter radiating energy close to mid, or mid's own distortion creating content landing on that breakup.
Can we buy the mid/tweeter driver separately? I d be interested to attempt a diy design.
 
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ctrl

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Some mention that they are not very subtle, and a bit harsh, and ... hold on... "lifeless". I can understrand that hard metallic cone has a sound signature of its own, but I do not see this reflected in the measurements (assuming cone breakup is already being taken care of by 20dB+ attenuation below main frequency response SPL)
It looks like a well engineered loudspeaker, but I can't shake the idea that we are missing something here.
Again, "hard metallic cone" is just a subjective perception people I did describe above came up. One of the measurable factors that describe this is when the dome breaks up near 20kHz or below so it becomes audible. As you have noticed there are usually Zero backings in those claims and there is nothing in Amir's or other site measurements that showings this.
To me that is not correct. We can' t just look at the breakup to judge if it's not audible when above 20kHz. How about medium and woofer breakups then? Here on the R3 I guess they'd respectively appear at 9kHz / 6kHz.

Whenever it is reported that a loudspeaker is supposed to sound "a bit harsh", distortions are always considered to be evildoers.
Even if distortion measurements do not give any clues.

Warning: Anecdotal story of an old man.
Years ago I tested different tweeters and midrange drivers in a loudspeaker that sounded harsh above a certain sound pressure level. The harsh sound was present at similar axis frequency response independent of the driver and this although HD as well as MD (multi-tone distortion) was always very low.

The frequency range 2-5kHz is especially critical and there the R3 shows a small problem in horizontal and vertical radiation.

With non-coaxial loudspeakers, the crossover frequency to the tweeter is often in the 2-3kHz range. This means that "sound energy" is destroyed vertically in this range by cancellation, which can compensate a little bit for a horizontal widening of the radiation - this is not possible with coaxial loudspeakers.

The R3 now shows a widening in radiation in the range of 2-3kHz both horizontally and vertically, which may cause the sound to become somewhat harsh at higher sound pressure levels - if this widening is not completely compensated by the axis frequency response (the axis frequency response should show a slight dip in this range).

So I would rather see the radiation as a possible problem than the influence of distortions.

Except the R3 would sound harsh even outdoors or in very large rooms with no close boundary surfaces, which would indicate distortions as a cause.

1600859927670.png
 

Martigane

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Yes! You have a point!
We might have gotten used to bad vertical off axis by means of overall low energy in 2-3k range, while the coaxial has, comparatively speaking, too much in that region.

Can you finish your anecdotal story? What was the rootcause for that harshness in the end?
I am on the edge of my seat here :)
 

ctrl

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Can you finish your anecdotal story? What was the rootcause for that harshness in the end?
I am on the edge of my seat here
But only if you calm down again, I cannot be responsible for you tearing your hair out in shock :eek::eek:

Responsible for the harsh reproduction of the loudspeaker was...
...
...the horizontal radiation - I know this comes as a complete surprise!

After the widening in the horizontal radiation had been compensated over the axis frequency response, the harsh sound occurring in some parts had also disappeared. A friend of mine then copied the loudspeaker and is very happy with it.

1600863344561.png 1600863318169.png
 

aarons915

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The frequency range 2-5kHz is especially critical and there the R3 shows a small problem in horizontal and vertical radiation.

With non-coaxial loudspeakers, the crossover frequency to the tweeter is often in the 2-3kHz range. This means that "sound energy" is destroyed vertically in this range by cancellation, which can compensate a little bit for a horizontal widening of the radiation - this is not possible with coaxial loudspeakers.

The R3 now shows a widening in radiation in the range of 2-3kHz both horizontally and vertically, which may cause the sound to become somewhat harsh at higher sound pressure levels - if this widening is not completely compensated by the axis frequency response (the axis frequency response should show a slight dip in this range).

I might have mentioned in this thread but definitely the EQ community project thread that the 2700Hz peak off-axis is definitely the cause of any harshness this speaker exhibits but because of the directivity of the R3 you have to EQ the dip to be on-axis. I've tried to EQ the LW flat in that area and the ER to be smooth (which creates a dip in the LW of course) and the smooth ER has always been preferred. As you mentioned, coaxials don't have a cancellation in the vertical plane so I think that makes the ER curve even more critical than a typical line source speaker. As OCD as I am about having a perfectly flat LW, I've experimented a lot and I really can't tell there is a dip in the LW since all of the reflections perceptually fill in the dip, similarly to how reflections fill in the stereo cross-talk dip.
 

tuga

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Whenever it is reported that a loudspeaker is supposed to sound "a bit harsh", distortions are always considered to be evildoers.
Even if distortion measurements do not give any clues.

And partnering electronic equipment can also be the cause of harsh sound.
 

sfdoddsy

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I have undoubtedly mentioned this before, but this thread is a prime example.

This site is supposedly focused on the science of audio reproduction. Hence the name.

In terms of speakers, there is (again supposedly) a broad agreement that the current science involves adherence to the principles espoused by Floyd Toole, Sean Olive and co.

Hence the emphasis on spinoramas.

The R3, as evidenced by its lofty position in the preference ratings, measures superbly based on these criteria.

And yet one unsubstantiated comment has created pages of increasingly granular nonsense.

For a start, the general consensus is not that R3 is disappointing. Rather that it is a superb sounding speaker that matches its superb measurements.

The only glitch in this assessment that I am aware of has been from this site, notably when Amir didn't love it subjectively.

But, again, if we trust the science, who cares what Amir thinks subjectively? He's just recommended a speaker which had a preference score of 1.9.

If such anecdotal evidence trumps objective evidence we are back in Absolute Sound la-la-land.

Until recently I owned R3s. In my room they measured very close to the other measurements quoted here, ie superbly despite the tiny 1K dip. They sounded just as good as they measured. Which is exactly what I would expect.

If they didn't, I would be questioning the science.
 

Snoochers

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To me that is not correct. We can' t just look at the breakup to judge if it's not audible when above 20kHz. How about medium and woofer breakups then? Here on the R3 I guess they'd respectively appear at 9kHz / 6kHz.

Stiff cones tend to have 3 issues:

1) Elevated peak of energy due to breakup
2) Stored energy at breakup making CSD look bad
3) Breakup creates peaks in THD, which in turn re-stimulates the breakup and issue 1) and 2) become problematic again even if crossed over took care to attenuate breakup.

The Kef R3' s CSD is not exactly clean, so maybe there are issues related to breakup/stored energy.
Its THD looks suspiciously clean to me, especially considering the 105dB SPL..
I'm not a big fan of having THD shown in %..
I did some listening tests and indeed found 3rd and 5th harmonic (7th being even worse). already objectionable at low levels (from -50dB 3rd is clearly audible) while testing on sines. So just looking at the highest peaks of THD is not a good indication of perceived distortion.


Anyway, here's an example of a metal cone, SEAS M15CH (pretty bad for the sake of the example)
The breakup peak of that woofer is some 15dB (!) above its SPL in usable range:
View attachment 84406
And what you see in the THD measurement is that this peak gets replicated in low frequencies:
View attachment 84407
Then in the CSD we can see that it' s ringing like a bell at breakup frequency:
View attachment 84408Another example of a metal cone driver behaving pretty well in comparison:
https://hificompass.com/en/speakers/measurements/sbacoustics/sb-acoustics-sb17nbac35-8
cone is bigger, breakup a bit lower, but lightly damped, and THD is much cleaner.



To me that's quite the opposite: If I look for reviews online, I'll always see plenty positive reviews. I even see reviewers that do not give any bad review, everything is great for them. How is that meaningful?
To me, only the negative reviews (or at least some cons) might warn you about issues that would be too late to notice once you bought the stuff.
Granted, one should always question reviews and spot BS.



I think they only do that for active speakers. For passive, you'd have to respect both excursion and thermal limits and see how far you could push the speaker. I guess driver specs and cross over transfer function should lead you a good educated guess if you can' t measure. That' s some work..

In my view, the most important part of that curve should be below 200Hz where excursion limitation is most likely to occur, which can typically be obtained from woofer box simulation software too.

Wow thanks man. I guess my issue is I want the R7s for a home theatre and I keep debating whether they'll get loud enough or not in the lower end. WIthout great measurements it is hard to say.
 

Pepperjack

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I have undoubtedly mentioned this before, but this thread is a prime example.

This site is supposedly focused on the science of audio reproduction. Hence the name.

In terms of speakers, there is (again supposedly) a broad agreement that the current science involves adherence to the principles espoused by Floyd Toole, Sean Olive and co.

Hence the emphasis on spinoramas.

The R3, as evidenced by its lofty position in the preference ratings, measures superbly based on these criteria.

And yet one unsubstantiated comment has created pages of increasingly granular nonsense.

For a start, the general consensus is not that R3 is disappointing. Rather that it is a superb sounding speaker that matches its superb measurements.

The only glitch in this assessment that I am aware of has been from this site, notably when Amir didn't love it subjectively.

But, again, if we trust the science, who cares what Amir thinks subjectively? He's just recommended a speaker which had a preference score of 1.9.

If such anecdotal evidence trumps objective evidence we are back in Absolute Sound la-la-land.

Until recently I owned R3s. In my room they measured very close to the other measurements quoted here, ie superbly despite the tiny 1K dip. They sounded just as good as they measured. Which is exactly what I would expect.

If they didn't, I would be questioning the science.

Ironically he gave it a solid recommend at first and then later wrapped back around to explain that he had positioned them incorrectly and really enjoyed the sound thereafter (though I always thought he ought to go back and strike through those previous comments and revise with the updated information.) so assuming it was good before but not his favorite it would presumably have been very good to excellent (subjectively) after the adjustment. Thus, the only real negative feedback has been from some people (like me for a while) who may later have realized they had made an error in evaluation (like me). Though I am happy with my kh310 that is possibly because I decided to be happy with them and quit at that point, so yea, I agree with you for the most part.
 

echopraxia

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And yet one unsubstantiated comment has created pages of increasingly granular nonsense.

For a start, the general consensus is not that R3 is disappointing. Rather that it is a superb sounding speaker that matches its superb measurements.

The only glitch in this assessment that I am aware of has been from this site, notably when Amir didn't love it subjectively.
There are actually quite a few people here and on other forums who express some degree of disappointment in the R3's, not just Amir. For example, when I had R3's, I blind tested them against speakers that presumably measure much worse (Ascend Sierra 2EX), and yet the KEF R3's lost by a pretty notable margin.

But in retrospect, I suspect that much of this can be explained by two things we see in the measurements (1) dispersion width (which depends on individual preference and song choice), and (2) the slight but broad midrange recession.

In retrospect, I wish I had tried EQ'ing them as @aarons915 mentions. For example, as an experiment, I tried EQ'ing my Genelec 8351B's to have a similar midrange recession as we see in the graphs here, and the sound does have that 'subtly boring with mild treble harshness' character I recall from when I had the KEF R3's. So it seems quite reasonable to me that an EQ'ed pair of R3's could sound very close to what their preference score indicates (i.e. very close to Genelec coaxial sound quality).

But at the same time, this criticism is valid, because the reality is most people simply aren't going to EQ their speakers like this.

Personally, I'd love to see a DSP KEF R3 with all these issues tuned to perfection + active crossovers :) But until then, it sounds like owners of them have really good luck with DSP on the input signal on correcting any complaints.
 

tuga

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There are actually quite a few people here and on other forums who express some degree of disappointment in the R3's, not just Amir. For example, when I had R3's, I blind tested them against speakers that presumably measure much worse (Ascend Sierra 2EX), and the KEF R3's lost by a pretty notable margin.

Preference is, well, a matter of taste.

The fact that a speaker performs better than most on the test bench does not mean that many or most people will enjoy how it reproduces music.
 

ElNino

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In my room they measured very close to the other measurements quoted here, ie superbly despite the tiny 1K dip. They sounded just as good as they measured. Which is exactly what I would expect.

If they didn't, I would be questioning the science.

I think the issue with the 1K dip is that it's broad (nearly an octave wide). Based on Olive and Toole's work, broader dips tend to be more audible.

I have a pair of the previous R series (R500), which have a similarly shallow but even broader dip, centered a little higher in frequency, and at least on those, the dip is predictably audible with certain material, especially movie dialogue.
 

ctrl

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For a start, the general consensus is not that R3 is disappointing. Rather that it is a superb sounding speaker that matches its superb measurements.
I don't think anyone has claimed this (in the last comments).
It was said that "Some mention that they are not very subtle, and a bit harsh...". I then went into this, using the measurements as a basis.


If such anecdotal evidence trumps objective evidence we are back in Absolute Sound la-la-land.
Interpretation of measurements is anything but "sound-la-la-land", because this is exactly what measurements are made for. The interpretation I made is actually quite obvious if you look at the in-room responses of the R3 shown by @napilopez in post#866. There is in the mentioned range around 2-3kHz the in-room response a bit too prominent.
Must everyone see it that way? No, but my argumentation is based on measurements from different sources.

1600870686731.png



Take Two:
If such anecdotal evidence trumps objective evidence we are back in Absolute Sound la-la-land.
Okay,... anecdotal evidence is stupid, I got that.
Until recently I owned R3s. In my room they measured very close to the other measurements quoted here, ie superbly despite the tiny 1K dip. They sounded just as good as they measured. Which is exactly what I would expect.
;)
 

Martigane

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Kudos, Ctrl, for being so factual and cool headed.
In you view, this compensation would become more important as the room is under-damped and reverberates a lot of that off axis?
In other words, for a typical (WAF-friendly) room, would you say that 30degrees should primarily be flat (steadily decreasing) rather than the on axis?
Then in a highly damped room, this target should go from ~ 30 to 10C?

I understand that it depends on how you toe-in the speakers, but I am trying to get a relation between room reverberation properties and directivity target. (I am designing my own 3 way with 6"mid+1"tweeter with waveguide and will soon design final cross over).
 

ctrl

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In you view, this compensation would become more important as the room is under-damped and reverberates a lot of that off axis?
yep, I would just phrase it a bit more cautiously and say the other way round, the further away the boundary surfaces are from the loudspeaker, the less weight a non-optimal radiation will have.

If the speaker is 2m or more away from the side wall and there is a large ceiling height, I wouldn't really expect any problems, like harsh sound with a sound radiation like the R3 has - but you only know for sure when you hear it ;)

In other words, for a typical (WAF-friendly) room, would you say that 30degrees should primarily be flat (steadily decreasing) rather than the on axis?
Then in a highly damped room, this target should go from ~ 30 to 10C?

I understand that it depends on how you toe-in the speakers, but I am trying to get a relation between room reverberation properties and directivity target.
When tuning the loudspeakers I pay special attention to the "interaction" of on-axis FR and the 60° frequency response (the 60° FR should be as uniform as possible and should not show any peak in the 2-4kHz range). This is now a very rough generalization, but in a typical position in a typical listening room, the 60° FR represents the first lateral reflection:
1600887283388.png

Since the loudspeaker is usually not aimed at the tip of the nose but rather at the shoulder, the 75° in the figure become the aforementioned 60°.
But this is just my personal philosophy when it comes to speaker tuning.
 

Martigane

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I would just phrase it a bit more cautiously and say the other way round, the further away / more absorbant the boundary surfaces are from the loudspeaker, the less weight a non-optimal radiation will have.
Indeed that is more accurate, I dared to make a small modification in bold. Then it's up to the designer to compromise OFF Vs ON axis.

I guess an upscaled version of the Kef R3 would perform better in terms of directivity thanks to the earlier beaming of a bigger medium.
Or maybe a higher mid/tweeter crossover point would help too.

When tuning the loudspeakers I pay special attention to the "interaction" of on-axis FR and the 60° frequency response (the 60° FR should be as uniform as possible and should not show any peak in the 2-4kHz range).
Thanks for the tip!

[OFF TOPIC:
I'll keep this in mind for my design. Hopefully choosing the right cross over frequency together with the use of a deep waveguide should help achieve great results.
I expect same or better directivity than Buchardt S400 (using SB17NBAC), especially around 2.4k mostly thanks to less beaming on my mid (MR16P-8).
1600928071791.png

/OFF TOPIC]
 
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tecnogadget

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Thanks for the info :)
Oh wow I did not know they would implement a mechanical low pass like that. Pretty bad compromise if you ask me, the driver must have a poor Qms and not be very responsive.
That much increase in 2-3k area is odd. Making the paralel with filter, its a low pass filter with very high Q (increase of energy before cutoff, followed by a sharp drop after cutoff.).
Of course more damping means better frequency response, but that damping happens between voice coil and cone, so the cone's own breakup is not damped at all. This is tricky as you think your breakup is solved because measured frequency response is flat (when driving coil), while actually external perturbations are still going to trigger that ringing since the cone itself is not damped.
It would not be the first time I see drivers being stimulated by sources other than its own voice coil.
This could for example come from tweeter radiating energy close to mid, or mid's own distortion creating content landing on that breakup.
Can we buy the mid/tweeter driver separately? I d be interested to attempt a diy design.

Along with the “lossy interface between voice coil and midrange cone” (aka Neck Control) there is another trick used by KEF to suppress midrange driver break up and improve pistonic behavior: those ribs stamped on the cone itself improves structural strength.

"The stiffness is increased by the radial embossing in the cone profile, but nevertheless it is prone to high-Q breakup in the frequency range covered by the tweeter.” (that’s the reason neck control is also needed to suppress any possible out of band break up) All of this stuff is overly explained in the Blade Concept Whitepaper for whoever is interested.

One could say if we compare KEF Engineers work with the common audio company competitor and several DIY kits...this guys have made their homework and know their stuff.

By the way, the graph uploaded by @thewas_ corrsponds to The Reference line, this one is from 2018 R series UniQ:
E51C246F-B8DF-4444-8780-6FFBFFD83A85.jpeg

Just remember this is a 1300£/1600€/2000$ speaker (price could be much lower with discounts and Black Friday). I think what you get was simply inconceivable a few years ago at this pricepoint. Lets move on
 

Martigane

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One could say if we compare KEF Engineers work with the common audio company competitor and several DIY kits...this guys have made their homework and know their stuff.
No doubt about that. I never said R3 was a bad speaker. On the contrary, I almost bought them after doing my research, and that's saying something..

It measures great and I wanted to see if more detailed/specific measurements were needed to reveal reported issues. Turns out that the answer might have already been in there with the off axis responses, surprising since they looked near perfect in Amir's measurements.

We are discussing the science behind audio transducers on ... a forum about audio science. To me that's what makes ASR special place where we see great contributors. My excuses if you find this Out of Topic or annoying.

*prays the gods of science to remain in ignorance.
 
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