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KEF Q350 Speaker Review

"evidentiary bar".. "hearsay".. You are either a lawyer or you really like watching series like "The Good Fight". :D
So you claim the defendant is well know for being "handsy " , I'd suggest such a claim, your claim relays solely on malicious gossip and hearsay.
 
I have done this before and the answer was no back then, but this was not with horns, so I must do it again! Good idea!!

I have noticed errors in playback setting that I was not aware of before. Weird things to do with PC settings like routing sound through JRiver without maxing the desktop volume first creates a close echo in the impulse. IIR filters being audiably different to PIR -without controlling phase (can't remember if this was min or linear phase control) It was always there, but I never noticed somthing was clearly wrong until using a horn.

Back before I'd worked out how to add controlled amounts of distortion to a signal, I listened to these files.

FWIW, I think it is possible there would be an audible difference between 0.1% and 0.4%, depending on the type of distortion and the IMD, but I don't think it would likely be the difference between music sounding "real" and not real...
 
FWIW, I think it is possible there would be an audible difference between 0.1% and 0.4%, depending on the type of distortion and the IMD, but I don't think it would likely be the difference between music sounding "real" and not real...

It may be the difference with voices when only a few (or none) instruments are playing.
 
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It may be the difference with voices when onyl a few (or none) instruments are playing.

It may be, sure, but given that the two speakers have extremely different radiation patterns and no doubt somewhat different frequency responses, I'd place that degree of distortion quite low on the list of likely candidates.
 
It may be, sure, but given that the two speakers have extremely different radiation patterns and no doubt somewhat different frequency responses, I'd place that degree of distortion quite low on the list of likely candidates.

I fully agree.
 
Harman found out that while the Kef Referece scored higher than Revel, the Revel was still prefered by listeners. When they investigated this further, they came to the conclusion that is was because the Kef had a fairly high amount of audible intermodulation distortion.

I see others have corrected that it wasn't the Reference but if you read further in that AVS thread you'll see I go back and forth a bit with the Revel guys and find out it's actually a Q300 that was being compared to the Revel M16. They claim to compare to speakers at or up to double the price point of their speakers but considering the Q300 came out at $650, it does seem to be cherry picked. I've also very rarely heard of IMD distortion being a problem even in the 2-ways, playing a single speaker full range and loud is about the only way to hear it.
 
Even as a KEF owner, somehow I can't warm up to the Q350. Perhaps it's because the Elac DBR-62's are so good for the price, or in my mind the Revel M16's represent a better value even if one has to pay the full $900 in the US. In Europe the KEF's cost less, so over there they may look at it differently.
 
Harman found out that while the Kef Referece scored higher than Revel, the Revel was still prefered by listeners. When they investigated this further, they came to the conclusion that is was because the Kef had a fairly high amount of audible intermodulation distortion.


KEF also seems to be aware of that. Below is a white paper from KEF REFERENCE 5.

"
The Reference Uni-Q is designed to cover the frequency range from 350Hz upwards. This allows the Uni-Q array to cover the entire critical upper six octaves of the audio band whilst at the same time not requiring excessive excursion of the midrange cone. This is very important as with the tweeter and midrange driver in such close proximity there is the potential for interaction to occur if the midrange movement was not kept to an insignificant level. This 350Hz cut off also allows the midrange driver size to be chosen based on optimal dispersion matching with the tweeter, rather than based on the bass output requirements.
"


I think KEF is a speaker company with a fairly high level of technology, and I agree with them. If there is a separate woofer unit like the R300 and REFERENCE 5, we don't need to worry about IMD. But, on the contrary, for a model that isn't, we should keep in mind the potential possibilities.
 
The KEF Reference series is also in the hard for me to love category. It just looks like one gets nearly all of the concept and technology in the R series for about a quarter of the price. Of course there are differences, but they could fall into the "everything matters" category. Just look at how well the R3 measures and ask what does the reference do for an encore?
 
KEF also seems to be aware of that. Below is a white paper from KEF REFERENCE 5.

"
The Reference Uni-Q is designed to cover the frequency range from 350Hz upwards. This allows the Uni-Q array to cover the entire critical upper six octaves of the audio band whilst at the same time not requiring excessive excursion of the midrange cone. This is very important as with the tweeter and midrange driver in such close proximity there is the potential for interaction to occur if the midrange movement was not kept to an insignificant level. This 350Hz cut off also allows the midrange driver size to be chosen based on optimal dispersion matching with the tweeter, rather than based on the bass output requirements.
"


I think KEF is a speaker company with a fairly high level of technology, and I agree with them. If there is a separate woofer unit like the R300 and REFERENCE 5, we don't need to worry about IMD. But, on the contrary, for a model that isn't, we should keep in mind the potential possibilities.


Around 2012 I did some testing of the Q100 drive unit which illustrates the HF IM distortion they are discussing here.

https://erinsaudiocorner.com/driveunits/kef-q100-drive-unit/

(toward bottom)
 
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Someone posted a link to a review of the R11 that contained IMD measurements at 2 volume settings, but I cannot find it now.
 
Excellent post @napilopez, thank you.

It's informative to see the differences in ER and HR curves between these non-coaxial speakers and to see illustrated how this may translate into better (ie smoother horizontal off-axis) performance than the spinorama seems to suggest.

Having said that, I'd like to make one point that I see as fundamental to the discussion we're having:

Although in each of the examples you've illustrated, the HR and HRDI curves are much straighter/smoother than the ER and ERDI curves, in all cases, they follow essentially the same line of best fit (which is what Olive used to calculate the target slopes).

This is easily illustrated by the Q Acoustics, for example (but holds for multi-way direct radiators in general):

View attachment 64730

What does this tell us IMHO? That, although the ER/ERDI curves can not tell us how smooth the HR/HRDI curves of conventional direct-radiating loudspeakers will be, they can tell us what its slope will be.

This of course makes sense even in the absence of measurements: Although direct-radiating (non-coaxial) designs will tend to exhibit vertical off-axis cancellation at the XO points, they will nevertheless tend to exhibit similar directivity along both (all) axes throughout the rest of the spectrum.

Given this, we can only conclude that, in respect of direct-radiating multi-way speakers, although there may be little correlation in terms of smoothness between ER/ERDI and HR/HRDI, there tends to be a very close correlation in terms of slope.

In turn, from this it can be extrapolated that, in respect of such speakers (and ofc in respect of coaxials too), Olive's target slopes are adequately descriptive in terms of HR/HRDI.*

*Again, of course, within the aforementioned (rather significant) limitations of the studies.

Hmm, would you say that about the 8C though? And i'm not sure it's totally applicable to speakers with asymmetrical tweeters, say the very wide horizontal and quite narrow vertical dispersion of ribbon tweeters. Would take more experimenting =]. Still, for the most part, I agree.

Personally though, I don't pay much mind to the ER/PIR slope since evidence does suggest it is variable with directivity, unless it is tilted more downward or upward than I'd expect based on directivity. But pretty much the only way this happens is if the on-axis is titled too.

Kef has more downward tilting ER slopes than Harman, so why doesn't it sound better? Harman claim they speaker must beat all competitive spekers on the market before going into production, so their speakers must have beaten KEF's in their internal blind tests.

Well, nowhere does the Harman research say more tilt is better. In fact, it's not even necessary for a speaker to tilt in its ER thoughout the entire frequency range. Here's a quote from Dr. Toole:

"Cone/dome loudspeakers tend to show a gently rising directivity index (DI) with frequency, and well designed horn loudspeakers (like the M2) exhibit quite constant DI over their operating frequency range. There is no evidence that either is advantageous - both are highly rated by listeners. "

As the DI curves are simply the difference between the listening window and the ER/SP curves, this quote also says a downward tilt isn't necessary throughout the entire frequency range.

The important bit seems to be smooth changes so the precedence effect is maintained.
 
Hmm, would you say that about the 8C though? And i'm not sure it's totally applicable to speakers with asymmetrical tweeters, say the very wide horizontal and quite narrow vertical dispersion of ribbon tweeters. Would take more experimenting =]. Still, for the most part, I agree.

Personally though, I don't pay much mind to the ER/PIR slope since evidence does suggest it is variable with directivity, unless it is tilted more downward or upward than I'd expect based on directivity. But pretty much the only way this happens is if the on-axis is titled too.



Well, nowhere does the Harman research say more tilt is better. In fact, it's not even necessary for a speaker to tilt in its ER thoughout the entire frequency range. Here's a quote from Dr. Toole:

"Cone/dome loudspeakers tend to show a gently rising directivity index (DI) with frequency, and well designed horn loudspeakers (like the M2) exhibit quite constant DI over their operating frequency range. There is no evidence that either is advantageous - both are highly rated by listeners. "

As the DI curves are simply the difference between the listening window and the ER/SP curves, this quote also says a downward tilt isn't necessary throughout the entire frequency range.

The important bit seems to be smooth changes so the precedence effect is maintained.

Wouldn't wider horizontal directivity imply lower slope of horizontal ERDI?
 
Hmm, would you say that about the 8C though? And i'm not sure it's totally applicable to speakers with asymmetrical tweeters, say the very wide horizontal and quite narrow vertical dispersion of ribbon tweeters. Would take more experimenting =]. Still, for the most part, I agree.

You're right about ribbons. This is not the first time I've completely forgotten they are a thing ;)

Re: the 8C, I presume it uses a non-axisymmetric waveguide. All of what I said applies only to speakers whose drivers radiate essentially axisymmetrically, eg cones and domes basically.

Personally though, I don't pay much mind to the ER/PIR slope since evidence does suggest it is variable with directivity, unless it is tilted more downward or upward than I'd expect based on directivity. But pretty much the only way this happens is if the on-axis is titled too.

I pay quite some attention to these actually.

Firstly, because for most speakers which use direct radiating cones/domes, the horizontal directivity can be inferred from the ER slope.

Secondly, because the tonal character of the speaker can be hinted at in the PIR. For example, one type of speaker I tend to like has a flat on-axis response and a downward-tilted PIR. IME such a speaker tends to sound both clear and accurate, yet also warm, the trade-off being that it won't project the kind of large soundstage a wider-directivity design will. It's not the only kind of speaker I like by a long margin, but it is the kind of speaker I would recommend to someone who says they like "warm" sound (as opposed to a speaker with a downward-tilted on-axis response, which IMO is likely to sound dull rather than warm).
 
Someone posted a link to a review of the R11 that contained IMD measurements at 2 volume settings, but I cannot find it now.

Just to be clear, the IM distortion discussed in relation to the woofer movement relative to the tweeter output is different than the IMD often discussed. TBH, I don't know if "IM Distortion" is the best way to classify the "moving waveguide induced HF distortion"; I have seen some call it doppler distortion... both could be plausible.

But, again, just making sure we understand the waveguide (mid/woofer) related FR HF non-linearity is different than the standard IMD nomenclature.
 
... likely to be Harman owners or at least used to Harman sound.

Why do you assume this to be the case? Everything I've read about Harman blind tests suggests that:

1) They regularly bring people from outside Harman to perform blind tests
2) Employees can't pick out their own speakers during blind tests much of the time.

Not saying that the tests can't be construed to favor their own speakers in some way, but those reasons aren't it.

Particularly if they were assessed in mono, and as @Bjorn mentioned not in ideal conditions in regard to postioning.

It's far too convenient to believe that a Spinorama is enough to characterise the performance of a loudspeaker.

And the same can be said to blind A-B testing a single speaker; adequately positioning two or three stereo pairs of speakers for blind A-B testing would have been a logistical nightmare, so T&O took the easy way out and half-heartedly supported this with some favourable research.

It's in Toole's book and has been mentioned several times in several threads, but Harman does not only perform tests in mono. I do not know why people keep assuming this. Yes, the preference studies were done in mono because decades of NRC/Harman reseach has suggested it is the most effective/quickest/highest confidence way to evaluate flaws in a speaker and that the rankings are carried over to stereo, but this never implies they only do tests in mono.

Here's a quote from Toole's book I mentioned earlier in the thread about Harmans multichannel listening lab where blind tests are performed (figure 3.13):

"The programmable mover can compare up to four single loudspeakers at one time, up to four stereo pairs, or up to three L, C, R combinations. The single loudspeakers can be compared at L, C, or R locations at varied distances from the side walls. The distance from the front wall is also a controlled variable. "

It seems ridiculous that Harman would have built this expensive stereo and three-channel capable mover and never use it because it's "a logistical nightmare." :)Likewise, they do not only test speakers at a single position.

We should not conflate the specific procedure for the preference studies with how they do evaluations in their other market research.

Edit: Note I am do not mean to suggest that Harman's research is infallible or that one should take it as a given that every new Harman speaker is better than its competitors because of their process. It's just the use of mono listening often comes up as a criticism, but just because it's something they do doesn't mean they don't test stereo too. That's all.
 
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Could this be due to directivity? My compression driver horns are also way more revealing than my cone and dome speakers. I kind of assumed that was due to the narrower dispersion, but perhaps distortion also plays a role.

This is why I did it in a open field. Directivity 'shouldn't' matter as there is nothing to reflect off of except the floor, which has much lower importance and is even possibly a good thing due to psycho-acoustics.
 
Just to be clear, the IM distortion discussed in relation to the woofer movement relative to the tweeter output is different than the IMD often discussed. TBH, I don't know if "IM Distortion" is the best way to classify the "moving waveguide induced HF distortion"; I have seen some call it doppler distortion... both could be plausible.

But, again, just making sure we understand the waveguide (mid/woofer) related FR HF non-linearity is different than the standard IMD nomenclature.


I think you might be on my page on this, but I just don't see how once a mid cone is moving reasonable amounts of air at +-6mm or more, how the variable 'step' in its use as a waveguide for the tweeter doesn't screw up everything in a multi tone test.

I am biased as I am yet to hear a coax that I would say sounds very good. I have heard the whole KEF line up, and the big reference model for many hours. Its a Nope from me. Just wish I knew why the measure very well by all accounts. Something is just wrong in the mid range.
 
I think you might be on my page on this, but I just don't see how once a mid cone is moving reasonable amounts of air at +-6mm or more, how the variable 'step' in its use as a waveguide for the tweeter doesn't screw up everything in a multi tone test.

I am biased as I am yet to hear a coax that I would say sounds very good. I have heard the whole KEF line up, and the big reference model for many hours. Its a Nope from me. Just wish I knew why the measure very well by all accounts. Something is just wrong in the mid range.

Ironically, the subjective comments I've most frequently here associated with KEF (other than spatial qualities) is how good their midrange is :). Maybe that's just me though.
 
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