Should the blade metas be considered cardioid?

[badtimeticket]

Check out the horizontal directivity of the blades (first) vs the Palmer Orbit 11. The Blades actually look somewhat cardioid! With a similar hole that the ASCILAB C8C have

It seems like this bit hasn’t been discussed much. Is this contributing to the Blades sound?

Here’s a bit from the whitepaper

“
As a result, the MF driver polarity has been inverted and the filter transfer functions have been designed to priori�se smoothness in all direc�ons and reduce any troughs and peaks previously appearing in the speaker’s off-axis response around the crossover region. ”

It seems like with passive design, you can get to semi cardioid around the crossover, but this is probably more doable in the blade because of its output capabilities, and is maybe less viable in a cheaper speaker.

 

[badtimeticket]

Same can be said about Genelec 8361, but it’s less clear to me how they achieve it there

 

[ShadowFiend]

No, it does not, definition of cardioid is that the sound radiate to the backside should have very low SPL compare to front sound. If you see your graph then you will see that on the back side of Blade has huge area where SPL is just -3 dB - -6dB compare to front side, while Palmer Orbit 11 has -12dB - -15dB on this area. And the -3dB to -6dB SPL on Blade is exist until 2kHz

Ascilab C8C also has area with -3dB to -6dB on backside radiation but has much more narrower band, from 400-800Hz and in my eyes, their advertising about cardioid is already too liberal.

 

[Keith_W]

Let's compare the Blade Metas with some cardioid speakers.

@SigbergAudio Manta (measurements by Sigberg).

Kii Three (by Erin)

KEF Blade 2 Meta (by Erin)

Note that all 3 contour plots have the same heat map and same horizontal scale (100Hz - 20kHz) so they are directly comparable. The Sigberg Audio is an outlier since it is designed to be used with subwoofers, which is why the bass output is so low. I think you can easily see the cardioid effect down to 100Hz for the first two speakers. The KEF Blades transition to omnidirectional pretty suddenly at about 250Hz, which is probably where the side mounted woofers are crossed over.

 

[thewas]

The KEF Blade woofers due to their side rear placement and baffle shape truly contribute that it controls its directivity down to 200 Hz which is lower compared to classical placement (crossover frequency is 450 Hz)

 

[kimmosto]

No! Blade concept is one of the worst because directivity index collapses to negative soon below lower XO frequency. DI of side woofer band is slightly negative, and mid-range with e.g. 2nd order acoustic high-pass slope cannot support unidirectional directivity much lower than XO point. Most of the other concepts including conventional boxes with front drivers have smoother DI. Blade's and LS60's weaknesses such as vagueness/looseness of lower midrange and placement requirements, have also been revealed in listening comparisons.

Especially flush-mounted in-wall and full range cardioids/dipoles can priovide radically more linear and higher directivity at LF than Blade concept.

 

[Defi]

Blade's and LS60's weaknesses such as vagueness/looseness of lower midrange and placement requirements, have also been revealed in listening comparisons.

Any examples?

 

[Keith_W]

No! Blade concept is one of the worst because directivity index collapses to negative soon below lower XO frequency.

Thank you for pointing that out. I have to confess I haven't given it much thought until you mentioned it, so I spent some time mulling over your point. Erin didn't say anything about that negative DI in his review, at least not that I recall.

A negative DI means that a speaker is radiating less sound on-axis than the spherical average. I suppose this will mean that the speaker will be extraordinarily sensitive to placement up to 200Hz otherwise it would sound a bit weird. Do you have any other comments about how a speaker like that should sound?

 

[Bjorn]

No! Blade concept is one of the worst because directivity index collapses to negative soon below lower XO frequency. DI of side woofer band is slightly negative, and mid-range with e.g. 2nd order acoustic high-pass slope cannot support unidirectional directivity much lower than XO point. Most of the other concepts including conventional boxes with front drivers have smoother DI. Blade's and LS60's weaknesses such as vagueness/looseness of lower midrange and placement requirements, have also been revealed in listening comparisons.
View attachment 549315
Especially flush-mounted in-wall and full range cardioids/dipoles can priovide radically more linear and higher directivity at LF than Blade concept.

That's a pretty strong statement.

First of all, KEF Blade is overall smoother compared to the two others. Is get's gradually narrower but there's not abrupt change. The cardioid speakers has a less smooth response and various more in directivity. A cardioid directivity should be 120° but we can see it's actually to 180° at certain frequencies and closer to 175° below 1000 Hz.

Secondly, the negative DI with KEF Blade is in a frequency area where the room has transitioned to room modes and this will dominate over any directivity. That being said, I agree that it's not ideal to have the transition so high in frequency and close to the Schroder frequency.

Vertically, the KEF Blade is clearly better vs the Kii Three. Combined with less cabinet diffraction and the fact that it acts better as point source, I'm not surprised this is the best speaker Erin has tested (or was when he tested it).

But yeah, there are room for improvements and neither of these speakers avoid that much of room reflections. Cardioids are IMO overated in that regard. You go with a horn speaker if you realy want to minimize room reflections. A speaker that various from 120° to almost 190° should actually be considered to have wide dispersion. With a horn speaker you can achieve something like 80-100° over a wide area and narrower vertically. But clearly with a bigger footprint in the room! No free lunch as we know.

 

[kimmosto]

KEF Blade is overall smoother compared to the two others

My point was to show excessive drop in DI at lower mid-range. Not to compare overall smoothness of DI to partially cardioid concepts. Those are not very good in DI linearity, and they must rely on EQ at LF.

Secondly, the negative DI with KEF Blade is in a frequency area where the room has transitioned to room modes and this will dominate over any directivity.

Transition, dominance and speaker concepts cannot be generalized. Listening spaces are individuals, popular open concept living spaces could have multiple openings and leaks, and more serious hifi man caves could have excellent acoustics.

Cardioids are IMO overated in that regard. You go with a horn speaker if you realy want to minimize room reflections.

Full range cardioids with large radiating area and main wavefront to front have never needed room EQ in any room IME. Anyway, there is no such directivity which could beat very bad acoustics with too long EDT. Adequate room treatment is the most effective approch giving possibility to avoid concepts and products with some compromises such as horns and resistance enclosures.

Vertically, the KEF Blade is clearly better

Vertical plane alone has surprisingly low significance. Overall DI and power spectrum dominate over vertical lobing (which is quite random depending on exit angle and frequency). The best sounding speakers have not been coaxials IME - assuming there is no need to support listening both sitting in the spot and standing.

 

[kimmosto]

Do you have any other comments about how a speaker like that should sound?

Generally very low...negative DI at low mid decreases ratio from direct to reflected. Relatively more reflected contains more delayed, wavefront is more broken and sound weaker; less kick and force and rhythmic entertainment.

Side woofers also produce some excess group delay in passive speaker. Side location alone produces delay close to audibility threshold. Delay of XO increases that. Timing and phase matching to support unidirectional directivity is possible to compensate with DSP, but more reflected content in total still reduces micro-dynamics. That can be frequency dependent i.e. unbalanced.
Much lower XO point could enable on-phase reflection and half space radiation using front wall, but eliminating excess delay almost forces to use DSP XO.

Anyway, all this could be insignificant for some of us. That's okay, but I don't respect that kind of designs.

 

[Defi]

Insignificant or not I feel like I have learned something. I had tossed Blades in my "Maybe one day dream speaker" category but as time goes on that category is getting crowded. I have not really heard any objective criticisms of them until now.

 

[kimmosto]

Any examples?

I'm aware of one listening event where Blade 2 Meta was compared to Taipuu Kero L. At least four listeners; Kef owner/user, Kef retailer, Taipuu's "Bob the Builder", and the rest were independent. As far as I know, Blades were driven by McIntosh integrated. Of course also this comparison was sensitive to local environment and setup so Kef could have better chances in some other place and setup.

I have not really heard any objective criticisms of them until now.

Sorry to say that available objective information is quite limited and interpretations of the results are subjective opinions of some individuals. Reviews by Erin's Audio corner are generally better and more inclusive than ASR's, but no one can provide single truth which would override owner's local conditions, setup possibilities, preferences and content of record rack.

 

[Purité Audio]

They weren’t as good as one of your own designs?
Keith

 

[kimmosto]

They weren’t as good as one of your own designs?

That's what I heard afterwards, and listening impressions were also reported to Kef forum and local hifi forum. Designer does not really matter here because Kero L is conventional and slim "decoration product" with quite high spouse acceptance factor, and easy manufacturing was weighted over acoustic perfection. The result tells more about Blade's concept; small point source and diffraction are weighted over directivity index slope, wavefront in a room, woofers' elevation and timing/micro-dynamics.

 

[a4eaudio]

I have not really heard any objective criticisms of them until now.

But what is an OBJECTIVE criticism? The reason the Blades are regarded so highly typically is based on objective Spinorama type measurements. They really do measure that well, so there is not too much that can be criticized from an objective perspective. Thus, the comments on DI by kimmo being quite interesting.

But I recently spoke to two people and casually used the Blades as an example of a Reference speaker, and they both had heard them and disliked them quite a bit. But of course, that is just sighted, subjective opinion.

 

[kimmosto]

They really do measure that well, so there is not too much that can be criticized from an objective perspective.

Spinorama is magnitude responses only in an anechoic. That has not much to do with inclusive objectivity. It's just sad that spinorama has so much weight in reviews and discussion.

 

[SigbergAudio]

But what is an OBJECTIVE criticism? The reason the Blades are regarded so highly typically is based on objective Spinorama type measurements. They really do measure that well, so there is not too much that can be criticized from an objective perspective. Thus, the comments on DI by kimmo being quite interesting.

But I recently spoke to two people and casually used the Blades as an example of a Reference speaker, and they both had heard them and disliked them quite a bit. But of course, that is just sighted, subjective opinion.

I've heard them twice and liked them quite a bit. But that's also sighted, subjective opinion of course.

 

[NTK]

But I recently spoke to two people and casually used the Blades as an example of a Reference speaker, and they both had heard them and disliked them quite a bit. But of course, that is just sighted, subjective opinion.

Kal Rubinson likes them enough to pay his own money to have 3 Blade 2 Meta's (plus a pair of LS60's for surrounds) in his place. Now what? Whose opinions should we take more seriously?

 

[Blueprint]

I don’t understand the suggestion that KEF has weighted dispersion over micro-dynamics. These speakers have vanishingly low distortion, particularly in the key frequency range where micro-dynamics are heard. They are linear at the highest of sound pressure levels. I’ve never heard them, so I don’t have an opinion, but I find it incredibly unlikely that they lack presentation of dynamics in any way.