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At Last... The KC62

S-Man

Kinkless Tetrode Admirer
I have mentioned my "ZRB" (Zero Resonance Bass) bass extenders on here a few times over the years. In general my claims of <10Hz roll-off from 3 X 6.5" drive units per side have been met with derision.

Well, deride no more. The technology (invented by a jolly clever friend of mine) has finally been commercialised:

https://uk.kef.com/products/kc62-subwoofer

I have heard one of these. It does the start-stop thing like very very few speakers/subs can.

I'm yet to hear the LS50 Meta, but if it's as good as it's supposed to be then a pair of these with a pair of KC62s could be a stunning speaker system.
 
That looks very impressive! So what is this new technology of which you speak? It surely has to be more than "just" a woofer set with shared magnet assembly? or 1000W driving it!:eek:
 
Yes it's more than the shared magnet. My "ZRB"s use off the shelf drivers and analogue processing. The KC62 uses (obviously) a custom driver/s and DSP to do the clever stuff.
The benefit of DSP is that KEF can include crossovers and displacement versus SPL tradeoffs. I am not at liberty to say how it's done, all I can say is that unlike a lot of competing systems it inherently corrects the non-linearities of the drivers including those that change significantly with temperature.

IMO KEF has not highlighted the main benefit of the system - low group delay. They prefer to promote low distortion and small size. (Mind you, they are a lot cleverer than me!).
 
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Yes it's more than the shared magnet. My "ZRB"s use off the shelf drivers and analogue processing. The KC62 uses (obviously) a custom driver/s and DSP to do the clever stuff.
The benefit of DSP is that KEF can include crossovers and displacement versus SPL tradeoffs. I am not at liberty to say how it's done, all I can say is that unlike a lot of competing systems it inherently corrects the non-linearities of the drivers including those that change significantly with temperature.

IMO KEF has not highlighted the main benefit of the system - low group delay. They prefer to promote low distortion and small size. (Mind you, there are a lot cleverer than me!).

Pre-distortion was my first guess....
 
Like the Klippel system?:
https://audioxpress.com/article/kli...gy-for-nonlinear-compensation-of-loudspeakers

I am told that this method has some flaws. However I wouldn't even attempt to explain what they are.

I'd never heard of such a thing! It was just an educated guess as to one possibility.... combining it with current drive and some form of motional feedback would be other things that could form the new technique... or it could of course be something so fiendishly clever that Black Adder would have to make up a new metaphor for it! I absolutely respect that it is proprietary:)

Your mate isn't called Graham Holliman by any chance? :D
 
Smart thinking Jez!

I hadn't heard of Graham Holliman until I just googled him.

I think there a quite a few competing schemes to achieve the same objective. I am aware that KEF evaluated some of the others and chose the one they thought was the best.
 
Reminds me of the Devialet Phantoms. I hope these aren't quite as landfill bound like the Devialets (hermetically sealed, non-serviceable without breaking).
 
Reminds me of the Devialet Phantoms. I hope these aren't quite as landfill bound like the Devialets (hermetically sealed, non-serviceable without breaking).

The Phantoms sound quite poor in the bass. The KC62 sounds very good, with the potential to be superb.
 
Wow, how exciting, finally something like the ZRB available to us all. But would we not need two for it to be anything like as coherent as the ZRB?

Regarding the crossover, does that work in a similar way to the ZRB? I'm remembering it was around 110Hz; please correct if I'm wrong. I know it was similar to the Gradient subwoofers made for ESL63s.
 
Wow, how exciting, finally something like the ZRB available to us all. But would we not need two for it to be anything like as coherent as the ZRB?

Based on my my previous experience of trying to integrate an older conventional KEF sub with my main speakers I would have said "yes". However one KC62 with a pair of JR149s was sounding pretty damn good during the brief listening opportunity I had, so I may need to rethink that.
Apparently with the JRs running full range and the KF doing sub-bass, the results were not that good. However, when using the KC's built-in crossover (it monos the bass and has variable high pass frequency to the stereo main speakers) it is much better - that's how I heard it.
IIUC there is a wireless box to properly integrate one or two KCs with LS50W Metas.

Regarding the crossover, does that work in a similar way to the ZRB? I'm remembering it was around 110Hz; please correct if I'm wrong. I know it was similar to the Gradient subwoofers made for ESL63s.

As above, the KC can do the stereo high pass and the frequency is selectable. I don't know if it can take the acoustic rolloff of the main speakers into account (like my analogue crossover does). It's hard to imagine that the KEF guys would miss that trick with the LS50Ws though.
I don't think the 1 KC + 2 JRs sounds quite as natural as 2 ZRBs + 2 JRs. The KC sounded just a touch more obvious than the ZRBs, but nowhere near as obvious as any other sub I've heard! However an extra KC and a lot more time spent integrating them might close, or even reverse the gap.
Of course there may be differences in sound between the DSP crossover and my analogue crossover.
 
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Great, sounds very promising. Further questions arise.

1) Does this kind of approach really only make sense when you are using small monitors like LS50s or JR149s, or would the KF62 work well with medium sized speakers to supplement and augment the bass?

2) the answer to 1 is yes, would a lower crossover point work just as well? I'm asking this without really knowing the range of the crossover point on the KF62, which goes back to the question on my previous post. The ZRB seemed to me to have a cleverly chosen crossover point (as did the Gradient dipoles) at a little above 100Hz. So is the KF62 meant to take over the lower bass entirely, and relieve the pressure on the main driver? If so, it would allow a driver like that on the LS50 focus on what it does best. But that might not make so much sense with an 8 or 10 inch mid/bass driver.
 
As Jez mentions, quite a remarkable achievement that could/should make some waves if it’s all it appears to be. I look forward to hearing it/them at some point.
 


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