KEF R Series with MAT white paper

[Vacceo]

You're exactly right. Since the low-frequency roll-off of a loudspeaker is minimum phase (at least to a good first order approximation) then the transient response is inextricably linked to the frequency response. If you EQ the closed box to have the same response as the ported (using minimum phase EQ) then they would have the same transient response as one another. You just need to be careful of not exceeding the available displacement, power and port velocity. Also, with a passive loudspeaker the ability to apply EQ is rather limited unfortunately.

I can only imagine the fun of playing with Dirac and an LS active system...

 

[fineMen]

Ported speakers as well will always be inferior in transient response due to the system order, which could be tied to the perception of bass 'timing' but their benefits (bass extension and lower displacement/lower distortion)(at least in passive speakers) tend to outperform this inherent issue.

Of course you set the term "timing" in quotes as to give indication that it shouldn't be taken literally. But further in the sentence you use the term "issue". It think this use of words interferes with peoples' understanding of the matter. Most of all I don't think it makes sense to speak of a transient response in respect to a certain part of the bandwith, as the transient response is logically determined by the whole bandwith.

I suggest that most of the more agile appeal of sealed (closed) enclosures originates in the emphasis, technically and attention wise, on the harmonics. In case they aren't masked by the base tone. It sounds simple but might nevertheless be true (anecdoteally confirmed for my own ears and brain). To my astonishment the KEF drivers are less prone to intermodulation and harmonic distortion. The argument that the enrichment of sound with overtones and other might contribute beneficial to the feel of a tight and articulate bass doesn't hold here.

Anyway, we here had a discussion lately, why the R series uses that peculiar shelf in the lower registers. Of course the group delay is different from a textbook alignment, but I'm quite sure the group delay wasn't the motivation.

 

[Rhubarb]

I bought Q15s when they came out (my first speakers!) and I am still happily listening to them as my main speakers almost thirty years later.

Sounds like my mind will be blown if I ever buy any of the new KEFs! I’ve read a number of the white papers over the years and have always felt gratitude for the human-values-centered approach putting science, an iterative approach, and openness/honesty at the center of your business.

Thank you, KEF people, for all of the truth and beauty you’ve brought to my life.

 

[feitaishi]

The guy who had them used a NAD C700.

thanks

 

[sarumbear]

Hi @sarumbear , that sounds like a serious setup. Both speakers of the CiXXXXREFM-THX type, 5160 and 3160 have just been released with a metamaterial absorber on the tweeter as you point out. The CiXXXXRL-THX speakers (also 5160 and 3160) have been in the market for a while now so don't have MAT, which we have been introducing into our line-up since LS50 Meta. Adding MAT does take some time as we take the opportunity to redesign the Uni-Q and crossovers (in some cases LF drivers too) and do a lot of system modifications.

Thank you. It is indeed a serious system but the in-wall speakers hide all seriousness, which I like. I think I can live with non-Meta on the surrounds and ceilings -- at least for a while

 

[sarumbear]

I wish you enjoy the Ci5160REFM-THX! Cheers

I am enjoying them. Thank you.

 

[sarumbear]

Hi @pjn that's right, on the floorstanding models the LF section is divided into two enclosures. The main reason is that you want the biggest dimension of the enclosure (the height in this case) to be shorter to move the first longitudinal acoustical resonance (standing wave) higher in frequency, since it's being excited by the asymmetrical position of the LF driver(s) along this dimension. So if say, you have a standing wave at around 400 Hz with two enclosures (happening in both), you'd have that standing wave at around 200 Hz with one enclosure. You want to move this frequency higher where the LF output is already attenuated as the crossover to the MF has begun and it will also likely be easier to damp with wadding, plus with two enclosures you'd be able to use twice the wadding on the velocity antinode of the resonance. The brace also adds stiffness to the cabinet walls, which being long, also want to resonate lower in frequency. The positions of the ports are determined so that the leakage of the standing waves is minimal. The upper and lower ports are the same, the enclosure volume is roughly the same, so the tuning of the two enclosures ends up being similar. However, you can certainly play with partially or totally closing up either or both of the ports (with the foam bungs provided) to tailor the response of the speaker in your room if the walls are more rigid and/or closer than usual. I find the lower port tends to have the biggest effect since it's loaded by the ground boundary more than the upper port.

This my fellow members is what knowledge in speaker design is all about

 

[davidbosch]

Kudos on the manufacturer transparency, not often that big names in the audio space even interact with forums.

I do have a tangential question, will the Q series ever get the meta-material and tweeter gap damper?

I ask because I currently use a Q100 driver as part of a DIY 3 way centre channel, and would love to get my hands on some of the newer KEF tech without paying R series prices. There was a french shop called setelec that sold KEF drivers standalone but they seem to have stopped.

Hi @alex-z I am not allowed to talk about anything that is not released unfortunately. But as you can see, we're really trying to incorporate MAT across our line-up.

 

[davidbosch]

Hi Mr.Bosch. I'd like to ask something technical.

In my experience, KEF sound has been quite consistent over the generations. From my old IQ's, to newer LS50 WII, to Blade Meta, the radiation pattern is relatively similar; the differences are in SPL, frequency extension and the clarity of reproduction.

To me, that is a demonstration that similar results can be archived with a multitude of approaches. My question is, all things equal (motor, speaker, waveguide, cabinet...), would you rather use a passive crossover or a DSP?

I was quite surprised to notice how the LS50 meta and the Wireless II sound surprisingly similar.

Hi @Vacceo I think you might not like my answer, for I think that active speakers should be designed differently than passive speakers, particularly the LF section, for many reasons. In the rare case where you take a passive speaker and make it active, such as LS50, then the DSP has many advantages: dynamic bass extension, phase correction, input limiters, much better crossovers, etc. However, these products are more than active speakers, they are all-in-one systems, which is good for people who want excellent performance and a plug-and-play approach but they come with drawbacks that some other might not want, such as not being able to choose or mix your own components (and choose really hi-end amps for example) or having to operate the speaker from a phone, rather than physically turning a knob. If you talk only about crossovers, using DSP is still superior, due to the number and complexity of the filters you can achieve and because there are no more electrical components adding distortion or even vibrating and taking space inside the enclosure. If you're asking what I would personally have: that would probably be an active speaker (designed from the ground up to be used as an active speaker) with separate electronics that I can tinker with and DSP I can access.

 

[Purité Audio]

David so can we expect an active/dsp version of the Blade?
I am extremely impressed with my LS60s.
Superb contribution thank you.
‘Keith

 

[thewas]

Since the low-frequency roll-off of a loudspeaker is minimum phase (at least to a good first order approximation) then the transient response is inextricably linked to the frequency response. If you EQ the closed box to have the same response as the ported (using minimum phase EQ) then they would have the same transient response as one another.

And the nice thing is that this also works the other way around, meaning you can EQ the ported version to the same response as the closed one getting also the same transient response but with the advantage of lower distortions. In my primitive home experiments though I often had the impression/illusion? that closing the port of my subwoofers gave me a cleaner room response despite equalising to the same response, possibly though just placebo or still small differences in response?

 

[davidbosch]

Thanks again, and this is excellent information. So far I have been very happy with the R8 Meta (compared to the Q50a's). I assume when wall-mounted the grilles don't really matter? I have them off (like the looks better).

Maybe you can shed some light on some other conversations that are happening in ASR of the Reference vs R Series? There are a couple of Kef YT videos explaining the different drivers that are used in the Series. I have personally (at home) compared the R11, R900 and Reference 5s and obviously the Ref 5 is night-and-day better. However, it seems like some members insist that a R3 Meta should sound equal to the non-Meta Reference Series. I did try the R3 Meta vs Reference 5s at home (with a 200Hz crossover set to mostly remove the obviously LF benefits of the 4 LF drivers) and I still found the Reference 5 Uni-Q to be clearly superior (obviously the Reference Uni-Q will bring this to yet another level, but unless the stock market explodes that's a purchase for another day/year). Also, the LF in the Reference 5 is fantastic, and comparable but more controntrolled compared to the R900 (2x8" drivers). I've always found the R11s to be lacking a bit of LF (coming from 1990s Reference Fours).

I haven't caught up with all the conversations however I would say that what one listens to is the whole system, and the driver(s) is only part of the story. The enclosure inside and outside, its built and materials, the crossover, the final balance etc. all contribute to the end result. To say the R3 Meta should sound equal to the Ref 1 non-Meta kind of disregards that the Ref 1 non-Meta still has a better LF driver, a better cabinet (and larger), better crossover, etc. The Uni-Q is from 2014, so in that area the R3 Meta wins: low distortion MF motor, better tweeter, tweeter gap damper, metamaterial absorber on the tweeter, smaller MF suspension, flexible decoupling chassis, stiffening ribs on the tangerine rear side, etc. I think this doesn't align with what you experienced listening to R3 meta vs Ref 5 non-Meta, but again, the end result could be more than the Uni-Q.

 

[sarumbear]

If you're asking what I would personally have: that would probably be an active speaker (designed from the ground up to be used as an active speaker) with separate electronics that I can tinker with and DSP I can access.

which KEF doesn’t produce

 

[davidbosch]

David so can we expect an active/dsp version of the Blade?
I am extremely impressed with my LS60s.
Superb contribution thank you.
‘Keith

I can't comment on this but the LS60W has had a good reception and it's in many ways a mini Blade, so let's cross our fingers.

 

[Purité Audio]

which KEF doesn’t produce

But is that down to the marketing department and the current ‘audiophile’ paradigm ( upgrade nonsense) rather than the engineering team.
Keith

 

[davidbosch]

which KEF doesn’t produce

And that's the end of my contributions today.

 

[sarumbear]

And that's the end of my contributions today.

I hope I didn’t offend you? I did put the smiley just in case my comment was seen as negative.

 

[BrokenEnglishGuy]

Personally i dont know why companies still use pasive crossover… these things should be external…

Hope one day these lots of boxes will be more useful, because a external digital crossover is better than the traditional passive crossover and it takes space in the box, why this is a good idea ? Put the electronics inside the box seems like a bad idea to me…
Maybe the speakers could come with the external crossover box.. idk but you can make a speaker very unique and better in the market and still being a pasive speaker vs the traditional inside passive crossover speakers..

 

[davidbosch]

I hope I didn’t offend you? I did put the smiley just in case my comment was seen as negative.

Oh no worries, I was just joking! it's also 5 pm here . I do hope though the market will lead us into making speakers like this that keep expanding the umbrella of active/DSP systems that are proper Hi-Fi and push the boundaries we find in current designs of both passive and active speakers.

 

[sarumbear]

Oh no worries, I was just joking! it's also 5 pm here . I do hope though the market will lead us into making speakers like this that keep expanding the umbrella of active/DSP systems that are proper Hi-Fi and push the boundaries we find in current designs of both passive and active speakers.

Phew!