KEF Blade Meta One

On 8/6/2023 at 11:24 PM, krass said:

I did an extensive demo with the Blade 2 version.

I moved on to Vivid Audio (Kaya) & Wilson (Sabrina) which I much preferred, being more open & in my opinion natural sounding.

I auditioned the Blades one (not meta) but moved on to Vivid G2 and now G2 Series 2.

I did like the Blades very much

On 8/7/2023 at 12:06 AM, Kal Rubinson said:

I auditioned the Blade 2 Metas in my own home and, subsequently, bought them.  And while I prize "more open" and "natural," there can be too much of even such good things. 

Interesting comment Kal, can a piano sound too naturally like a piano ?...or perhaps naturalness in one area can come with trade-offs in other areas?

What was it that grabbed you about the Blade 2 metas that struck you as just the right amount of naturalness and openess beyond which it becomes undesirable ?

2 hours ago, Kal Rubinson said:

Indeed.  It is not that a piano can sound too natural but that a component can alter the sound such that it alters the sound in such a way that some (or even many) believe to be an enhancement of piano recordings.  Such a coloration is likely to not do be as "complementary" to other instruments or voices but, despite that, it many appeal to some listeners.

I will refer you to what I wrote in my review but will add that I do not believe that any coloration is beneficial and prefer transparency.  There's a wide range of pianos (and other instruments) and they should sound different and not homogenized.  The Blade 2s achieve that and the measurements (by JA and, also, in my room) confirm it.  I would not trust my ears without the support of the measurements. 

I agree then, epistemic difficulties aside, there can not be too much naturalness (or openness) if that is one's goal - but as you say some folks prefer a coloration that sounds good to them, describing it as more natural (enhanced). The problem is when creating a color cast , as beautiful as it may be, you must like it everywhere unless you can apply it selectively

2 hours ago, Kal Rubinson said:

I keep falling back on the analogy to rose-colored glasses.

Sonic sunglasses 👓 🕶 😎 

4 hours ago, Kal Rubinson said:

So, I think it is this, rather than directivity per se, that makes setup not difficult but different.

That makes sense to me. I wouldn't have anticipated the Blades (which I have auditioned) to be particularly difficult to setup due to "directivity" issues. or to lend themselves to certain 'sounding rooms'.

I would also expect reverberation (RT60) measured in a smallish room with non-diffuse sound-field to be problematic in this context, being more comfortable talking about early and late reflections and modal resonances wrt setup. That said I am interested in things like decay spectrograms and things that may affect them rather than RT60 per se

3 hours ago, Axiom05 said:

Placement of the woofers within the room is something that has always concerned me with the Blades. In a narrow room, where one side of the speaker could be quite near the side wall, I suspect there could be some issues. Unfortunately, there is no way to know w/o actually trying them in one's own room. I know low frequencies are omnidirectional, but I would imagine that some unpredictable "loading" wrt the side wall could occur. My Studio2's are only around 14" from the side wall which seems a bit close for the side firing woofers and could also result in some lower midrange coloration.

I think it possibly depends on the proximity of the acoustic centres of motion of the bass drivers wrt energizing modal resonances. 14" from sidewall is likely an issue in most rooms irrespective of where the driver faces

59 minutes ago, Kal Rubinson said:

Yeah.  KEF recommends:

A- Rear of speaker to front wall:  225mm (9")!!!

B- Side of speaker to side wall:  1m (36")

W- Distance between speakers:  2-3m (6-10 feet)

D- Centerline distance to MLP:  1-1.2 x W

The most curious item is how small A is but that may be due to the controlled directivity.  I am planning to experiment with that as I now have them about 36" from the front wall.

At 9" the lower freq modal resonances in corners and along the front wall would be exacerbated irrespective of higher frequency directivity, no? Did KEF give any explanation of "A- Rear of speaker to front wall:  225mm (9")!!!" Are they expecting bass reinforcement from room modes?

1 hour ago, Kal Rubinson said:

Floyd Toole told me that he expected problems with "B." Side of speaker to side wall:  1m (36")

Did he give any explanation?

8 hours ago, Arindal said:

I suspect difficulties in combining them with different rooms and getting pretty opposite tonal results can be merely prescribed to the directivity pattern over frequency. It ranges from 0 or even (theoretically) negative directivity index while woofers are still active to something close to omnidirectional in the (lower) midrange due to curved and narrow baffle to steadily decreasing off-axis energy the moment tweeter with waveguide comes into the equation.

Have you got a particular reference to the measured results of the Blades and where this is identified as an issue?

@Kal Rubinson mentioned reasons for careful placement in relation to bass room modes (which makes sense) but didn't echo ( <--poor attempt at pun) your other concerns. Kal did mention in room measurements were done and input from IIRC JA and Toole.

9 hours ago, Kal Rubinson said:

I did not mention JA in this context and my interaction with Floyd on this was casual (although I always appreciate their comments).

I was really just searching for further comment on the measurement profile of the Blades in relation to supposed difficulties matching them to certain rooms.

the https://www.erinsaudiocorner.com/loudspeakers/kef_blade2_meta/erinsaudiocorner review measurements were offered (not by you) to support this difficulty

The review concluded:

• Exceptional sound quality and objective measurements
• Incredible on-axis linearity and off-axis is top notch not just horizontally but vertically as well

There was no discussion or interpretation regarding directivity or dispersion patterns in relation to any special difficulties.

One thing I learned from JA over the years of reading his measurement and listening reviews was to be very careful interpreting any one speaker measurement to predict how it will sound .This includes polar dispersion plots and in room "balance" or voicing of that speaker. He did talk about difficulty predicting effects of discontinuous or uneven radiation patterns especially at crossover regions where driver size and wavelength size may not be optimal. Even more difficult when considering on axis vs off axis voicing of perceived in-room response.

I am not saying that the frequency balance contained in reflected sound is not important or that speakers will have a perfectly uniform on and off axis dispersion, smoothly increasing directivity with increasing frequency.

So what do you make of the dispersion plots for the Blades when matched to your room and listening experience? Are they well "voiced" to match most rooms or difficult?

OTOH do they measure extremely well and, as with any other well designed speaker, room interactions must be controlled and individually tailored?

4 hours ago, Arindal said:

 

That is absolutely matching my experience. Measurements are very useful to understand how a speaker works and give a good idea if it would be acoustically compatible with a given environment. The moment anyone would be trying to extrapolate how it will actually sound solely based on measurements, this will inevitably fail. In the real world the result is in most cases far from the prediction.

 

 

That is accurate as well if it is about predicting sound characteristics. If you just want to know if a speaker is a match for the given room or which major flaws are to expected in case of a clear incompatibility, the directivity plot is very useful and pretty reliable. That is particularly true to the most common incompatibilities like overly broad dispersion (low directive index) either full range or in some frequency bands (typically lowest octave of a tweeter or a midrange) or continuously increasing directivity index i.e. dispersion pattern narrowing down towards higher frequencies.

 

The latter might work perfectly in some rooms, like those showing signs of overdamping in the bass and lowers mids or overly huge ´open spaces´ with almost no reflective side walls. In smaller rooms like a typical living room with reflective walls on the sides and decreasing RT60 towards higher frequency, you will almost certainly get a lower-midrage-heavy, dull and softened tonality resulting from the indirect sound. There is not much that can be done against it, particularly speaker positioning or DSP equalization cannot provide any solution.

There are some concerns for me here, for example on one hand you say you cannot extrapolate from measurements how it will actually sound and will inevitably fail in the real world, but on the other hand it seems you can extrapolate from measurements how it will actually sound in real rooms in the real world. I am struggling a little with the compatibility of those statements. Sorry, if I have misunderstood.

I do (hopefully) understand a little bit about the reasoning behind dispersion patterns and interaction with room acoustics. That is a matter of science. I am still wary of looking at one measurement, like polar plot of dispersion/radiation and confidently predicting how it will sound in any given room or type of room. I am of course interested if there is an uneven and discontinuous pattern which might make the reflected sound voiced very differently to the direct sound.

Now, what about the speaker deemed to have great on axis as well as off axis response - lets call that (perhaps) a dispersion pattern wide in lower frequencies and smoothly "narrowing down towards higher frequencies.". I am not at all sure that is "best" but prima facie, I would say okay lets run with that, given wavelengths and driver sizes and practical limitations, laws of physics etc

I now have concerns about your conclusions that:

4 hours ago, Arindal said:

The latter might work perfectly in some rooms, like those showing signs of overdamping in the bass and lowers mids or overly huge ´open spaces´ with almost no reflective side walls. In smaller rooms like a typical living room with reflective walls on the sides and decreasing RT60 towards higher frequency, you will almost certainly get a lower-midrage-heavy, dull and softened tonality resulting from the indirect sound. There is not much that can be done against it, particularly speaker positioning or DSP equalization cannot provide any solution.

There are issues talking about RT60's in small spaces. lets move past that for now. Lets leave DSP out for now....

The characteristics of the speaker also aside for now, the room will need acoustic treatment for any speaker you put in it. You can measure the room but you already know (in some cases where the geometry is more predictable) where the room resonant modes are going to be. You know where the higher frequency first reflections will be. You treat accordingly and as much as needed (for me, by listening). You know where diffraction/diffusers might help. You know if you stuff the room full of a thousand pillows, it will suck up high frequencies etc etc. You know that placing the speaker in a corner will likely not be a good position and there will be other more suitable positions to try. same goes for listening position.

So now you take your speaker with a supposedly "great" measured on axis and off axis response which is predictable and you place it into your room. As said, you know where the room will likely need acoustic treatment. That treatment may be different for some speakers. Different but not difficult more or less. If the room is "showing signs of overdamping in the bass and lowers mids", fix the room. If you can't fix the room, and many cannot for obvious reasons, I predict it won't matter what speaker you place in it - you will hear the room to more or less extent. Enter the DSP discussion (but its not my thing)

43 minutes ago, Arindal said:

 

Maybe I have not made myself clear and will try to explain.

 

The attempt to predict solely based on measurements whether a speaker will sound neutral, dull, bright, present, bass-heavy or alike, requiring equalization or not, how loud it will go, how will be its staging, localization and other factors, is impossible according to my experience. I might want to add that there is a certain correlation when it comes to the question how low the bass will reach to the lower cutoff frequency but this will also not allow a prediction what will happen with the bass in the room and how it will be perceived.

 

On the other hand measurements like the directivity plot allow a pretty good estimation whether a combination of a loudspeaker, room and desired loudspeaker placement will lead to acoustical mismatches which cannot be equalized later or not. This is particularly the case with expected dominating indirect sound at a given listener´s position or tonally imbalanced indirect sound (which we are discussing here as the KEF Blade is a textbook example of a speaker showing continously increasing directivity index towards higher frequencies). 

 

Please note that the latter is not a precise prediction how it will sound. It is just a strong hint that certain mismatches will most probably occur, which is particularly useful for making an informed choice as the resulting acoustical problems in most of cases cannot be cured by equalization, reasonable amount of room treatment and speaker placement within a reasonable range (true nearfield placement is an exception here as well as building a matching room from the scratch). 

 

 

I know that this concept of continuously increasing directivity index is pretty popular and in some applications (like nearfield listening, midrange-overdamped rooms, open spaces with no reflective side or back walls in proximity or alike), it is proven to work without major flaws. 

 

That said, we should not forget that in many cases it will not work but lead to the dull tonality described by another poster. 

 

 

Not necessarily. Depends on the speaker, the room and how things will be placed.

 

 

Unfortunately such models are only reliable in rectangularly-shaped rooms with all 6 sides solid concrete/stone/brickwall behavior, no overly huge windows. That is not the norm anymore, as light and resonant walls are pretty popular nowadays, or always have been like in the US or Canada.

 

 

That would not be necessary as overdamping in bass and (lower) midrange is on purpose, like in a studio room, and the aforementioned increasing directivity index of the speaker will acoustically cure this "problem". 

 

In untreated living rooms this behavior is basically non-existent. In most cases you find a rather high amount of bass and lower midrange energy while having more or less well-damped treble which contributes to the described problem of a ´dull-sounding´ speaker due to its increasing DI towards higher frequencies. Please note that these two problems add up so I call it an incurable incompatibility.

 

 

This is absolutely not matching my experience. If you have an untreated room with usual acoustical problems, a speaker with low or very uneven directivity index over frequency will most likely highlight all the problems making listening to music on a certain level or reproduction quality impossible. The longer the distance between listener and speakers, the more. Nearfield listening might help in these cases.

 

If you, on the other hand, take a speaker which was designed as a higher DI and/or constant DI model for such rooms, you can avoid most of the problems originating from reflections as the directivity pattern is to a certain extent simply ´fading out the room´ or making a majority of the reflective walls ´acoustically invisible´ to the sound originating from the speaker, if that makes sense. Which dispersion pattern is best and how much room treatment job might be left to do in order to achieve perfection, is a matter of listening distance and how the room actually behaves in terms of early reflections.

 

Most of loudspeakers getting this constant directivity requirement right are limiting it to the midrange and treble. Some specialized models exist, though, with offer a directional bass as well, mostly dipoles and cardioids. There are also speakers which, in contrary, tend to emphasize bass resonances and most likely cause booming but you would not find any hint in the measurements.

 

I might want to add that sound reinforcement systems particularly in acoustically problematic environments work like this for a long time already. And there is also a long history of dedicated hi-fi speakers relying on a narrow directivity pattern such as electrostatic panel speaker, line arrays, broadband-horns, dipoles and many others. In the past these have been very popular but far from flawless but since we have DSP technology in active speakers it is astonishing what can be achieved.

 

 

I do not think this would be the right place to start such a discussion as the phenomena related to the particular series of KEF speakers are not those which you are capable of countering with digital equalization. You cannot equalize a frequency-dependant mismatch between direct and indirect sound and that is in my understanding the main reason why reports on the Blade´s sound characteristics are widely incompatible with each other.

May I ask do you have any references/articles/sources that deal with the specific issues you have raised that speakers matching the blades directivity plots are dull sounding in typical living rooms? I note you referenced erinsaudiocorner but that guy raved about the measurements, "Incredible on-axis linearity and off-axis is top notch not just horizontally but vertically as well" and he also raved about the sound quality. Kal also raved about the speakers in Stereophile and JA also gave high praise for the measurements for directivity, "The contour lines in this graph are commendably even up to 80° off-axis". A quick google search hit on ASR and even they seem impressed with the (reported) measurements and rave about the sound (possibly because the measurements are so good?).

3 hours ago, Arindal said:

You hardly see it in JA´s polar plot as this one is covering only a 90deg window. Look at what is happening at 100deg

IIRC JA makes the point that beyond 90 deg the (his) measurement method is inherently unreliable for off axis FR, which is why he doesn't offer it. Perhaps something to do with the acoustic center of the driver not matching the center of mass...I would have to search for it....

Regarding treble roll off, if it does exist in the far off axis response in the upper treble region, in this region mostly the direct sound on axis response dominates room curves anyway, at least as measured by Toole. The tweeter is directional and treble indirect imperfections off axis maximally and easily absorbed.