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new KEF KC62 dual 6.5" subwoofer

prmfeddema

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Update: from Kef USA There is a fix for that known issue that affects some customers and they are being dealt with as needed. New subs will have the fix but, obviously, units which were already in transit or sitting on shelves won't have it. If when you get yours you find you have the issue, then let us know and it'll be fixed for free. So yes, that would mean returning it to us as it's not a customer fix. If your dealer is an authorized repair center then they should have the ability to fix it as well.
 

kokoon

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I found out that going full-range signal into the sub, I'm getting far fewer issues with either the sub not coming from the standby quickly enough, or going into standby at lower volumes. So - still as hot signal as possible without clipping (this then means lower volume on the sub, around 9 o'clock), and LPF on the sub.
 

nothingman

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It’s good that there’s a workaround, but I assume we all agree that there shouldn’t be any such thing as a workaround on a $1500 subwoofer.
 

Tokyo_John

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Can anyone explain how the electronics, crossover, and pass through works in the KC62?

I originally thought the crossover was purely analogue, since all of the inputs and outputs are analogue this seems to make sense. But in this thread I’m seeing references to it having an internal ADC, a DSP, and then this would seem to imply a DAC as well to feed the pass through signal back as analogue. And it also has 2x500W power amps on board. If true, then this would seem to be a fairly electronics-heavy subwoofer in terms of cost for its components. But it seems strange to think that using the KC62 pass through in my system would result in the loudspeaker signal going through 2 DACs (the one upstream from the sub, and the one inside the sub generating the pass through signal) and an ADC in between…this is a lot of processing in the signal chain, how good is the signal coming out of the KC62 after all of that?
 

nothingman

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DSP in subs isn’t unusual. I wouldn’t worry about the ADC to DAC. At those frequencies your ear isn’t going to come close to knowing the difference, and KEF have implemented considerable DSP-based distortion control to help this tiny sub produce a cleaner sound and to prevent any sort of clipping.
 

Tokyo_John

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DSP in subs isn’t unusual. I wouldn’t worry about the ADC to DAC. At those frequencies your ear isn’t going to come close to knowing the difference, and KEF have implemented considerable DSP-based distortion control to help this tiny sub produce a cleaner sound and to prevent any sort of clipping.

I'm not worried about what comes out of the sub, I'm worried about the garbled pass through signal that eventually makes its way to my main loudspeakers after such a convoluted path. If this is how the KC62 works, then I will probably not buy one since I would not use the passthrough in this way and I would be paying a premium for a bunch of electronics that I would never use.
 

nothingman

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Sorry, you’re right, I didn’t address your main concern. Y’know, now that I think of it more closely, the high pass filter uses dip switches and isn’t accessible from the app. Could indicate it’s in the analog domain, unlike the rest? Just conjecture. I’d email KEF if I were you for a definitive answer.
 

YSC

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I'm not worried about what comes out of the sub, I'm worried about the garbled pass through signal that eventually makes its way to my main loudspeakers after such a convoluted path. If this is how the KC62 works, then I will probably not buy one since I would not use the passthrough in this way and I would be paying a premium for a bunch of electronics that I would never use.
I believe what they will do and alter are <cross over bandwidth, the signal and cross over might be dealt with by the dsp as it makes switching crossover point and make bass linear much easier for this purpose
 

FrantzM

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what



yes - actual measurements are missing - something i am desparately waiting for. Note that i like the svs features and looks better than Kef’s, but in the end the deciding factor is how they will match my LS50w2’s... ie sound quality in combination with the la50s

Hi!

We all are yearning for measurements. In their absence, I am skeptical of Kef claims concerning this KC62.
3 or 4 years ago, I fully committed to the objectivist, measurements-based audiophile philosophy, I tried The Bucket Subwoofers. A crude contraption of a small 8' driver in a 5-gallons bucket... Easy to assemble. I made 4 of those and tried them with the miniDSP 2x4. As subwoofers they worked... to a point. I came to realize that once you add low frequency transducers to an audio system and taking some care thus time to integrate these, the results will be pleasurable.; most often objectively better than the main speakers by themselves. This, for any speakers, regardless of the intrinsic low frequency capabilities of the main speakers.. They could actually be more capable than the subs. The presence of subs and the integration provide better results objectively and subjectively all things being equal (integration is key). I actually measured (posted these here in ASR) lows down to 20 Hz with no doubt copious amount of THD (I didn't know then how to measure that :( ). They rattled, buzzed and shuffled when asked to provide high SPL but they filled the lows.
And that is what any low frequency transducer brings to any system. By that I mean any additional low frequency apparatus. I have no doubt the Kef can reproduce some lows... I would think above 45 Hz in a medium room , it may generate some decent SPL perhaps around 100 dB at the LP and added to that reproduced by the mains will help. I am deeply skeptical of the value and performance of the Kef KC62. I don't think it is worth the asking price. It is brilliant marketing and audiophiles will like it. I believe however the laws of physics are against it. For my personal needs... 3 small inexpensive small subs + miniDSP would address more competently the issues of stealth and performance, for the same budget. YMMV

Peace
 

nothingman

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I hesitate to even engage here, but 1) your experience is seemingly entirely based off your time with homemade, self-professed “redneck” bucket subs, which c’mon, 2) whatever the KC62 marketing, there are genuine innovations in motor design, cabinet (alloy), DSP, and surrounds — none of this stuff is off the shelf, 3) advertising a sub’s +/-3db frequency response without any mention of the SPL is perfectly common, everyone is getting hung up on the 11hz thing like they’ve never seen specs communicated like this before, 4) if your advice is that people should really look at three small subwoofers instead of the KC62, then clearly you don’t understand who this product is targeted at, and 5) we have Joe N Tell’s in-room measurements of the KC62 and SVS 3000 Micro and it’s clear they both have their appeal, and it shows that KEF has accomplished something (not everything!) considering the size. “Considering the size” has always been the operative words.

Making the comparison to the SVS, if you want SPL in the 105db range, but you’re ok with that starting around 35hz and higher, then go for the Micro. If you want the maximum frequency response range, i.e. the famed 11hz figure, but you’re ok to that being limited to 90db at the lowest lows, the KEF delivers that in a way that the Micro simply can’t and in a way the skeptics said was simply impossible. The KC62 provides up to 18db more there than the 3000 Micro. Lastly, the equalizing factor, if you’re going to room-correct with typical curve at 20hz anyway, then neither sub is getting you more than 95db, so they’re functionally the same with different strengths (the KC62 isn’t dropping like a rock lower than 20hz, and the SVS has more headroom from 25-65hz).

And speaking of marketing fluff, SVS says the 3000 Micro is -3db down at 23hz, but Joe N Tell shows it’s down more like -10db. I don’t personally care, they all have their compromises. It’s up to us to make educated choices.
 

FrantzM

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I hesitate to even engage here, but 1) your experience is seemingly entirely based off your time with homemade, self-professed “redneck” bucket subs, which c’mon, 2) whatever the KC62 marketing, there are genuine innovations in motor design, cabinet (alloy), DSP, and surrounds — none of this stuff is off the shelf, 3) advertising a sub’s +/-3db frequency response without any mention of the SPL is perfectly common, everyone is getting hung up on the 11hz thing like they’ve never seen specs communicated like this before, 4) if your advice is that people should really look at three small subwoofers instead of the KC62, then clearly you don’t understand who this product is targeted at, and 5) we have Joe N Tell’s in-room measurements of the KC62 and SVS 3000 Micro and it’s clear they both have their appeal, and it shows that KEF has accomplished something (not everything!) considering the size. “Considering the size” has always been the operative words.

Making the comparison to the SVS, if you want SPL in the 105db range, but you’re ok with that starting around 35hz and higher, then go for the Micro. If you want the maximum frequency response range, i.e. the famed 11hz figure, but you’re ok to that being limited to 90db at the lowest lows, the KEF delivers that in a way that the Micro simply can’t and in a way the skeptics said was simply impossible. The KC62 provides up to 18db more there than the 3000 Micro. Lastly, the equalizing factor, if you’re going to room-correct with typical curve at 20hz anyway, then neither sub is getting you more than 95db, so they’re functionally the same with different strengths (the KC62 isn’t dropping like a rock lower than 20hz, and the SVS has more headroom from 25-65hz).

And speaking of marketing fluff, SVS says the 3000 Micro is -3db down at 23hz, but Joe N Tell shows it’s down more like -10db. I don’t personally care, they all have their compromises. It’s up to us to make educated choices.

Hi

Don't worry, Engage. This is a discussion forum and we will and must debate. It ad
My post may not have been clear enough but my experience with subs is a bit more extended. My experience as an audiophile is much longer too. I've been in it for the past 5 decades... I have had my share of subwoofers. I am currently using dirt cheap Dayton Audio Sub 1500, I have 3 of these but use 2 at the moment. SVS or Rythmik are in the works.
I fail to see what are the "innovations" in this subwoofer. Cabinets? What is so innovative about the cabinet? Motor? Well it is a adual opposed with a shared voice coil. I am waiting to learn what such an arrangement brings to the table or in this case to the bass.
In the absoute a tweeter is able to reproduce 20 Hz, it could even be measurable, perhaps -100 dB down ... That thing will not reproduce 11 Hz at 40 dB SPL in-room, in which case only elephants or whales will hear or feel it. Not Humans.

We have to ask manufacturers to be true in their specifications. Some do ( Genelec is one of those, Neuman ) once in a while Kef is true but ...
The market to which this is addressed. Let's not go there else we will rationalize the existence of >$5,000 USB and Ethernet cables. There is a market for these, a vibrant, enthusiastic market. I do understand the market for which it is intended but in the name of objective performance which is what this forum is about... It doesn't matter to me what it’s targeted market is. A gear performs or doesn't…
While the SVS micro may fall like a rock at 20 Hz where most music doesn't reach.The SVS Micro is 10 dB louder from 30 Hz to 200 Hz, where it does matter. The response of the SVS is also flat, the KC62 is not if we are to base ourselves on the Joentell measurements. If anyone wans to reach 20 Hz in room at substantial levels and choose a 6.5 woofers .... I have a quantum-tuned speaker cable I am selling for less than $10k.

They will sell a few. The performance is not what I would pay $1500 for. Size be damned 2 SVS micro are a better solution
 
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kyle_neuron

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Different type, had to re-read it myself.

“To reduce total harmonic distortion (THD), KEF has included its Smart Distortion Control Technology in the KC62. Many subwoofers use an electromechanical sensor to monitor the driver’s position relative to the waveform of the input signal. When non-linear discrepancies occur, which is common at high excursion, the driver’s motion is limited to reduce distortion. By contrast, Uni-Core’s low voice-coil inductance allows the KC62 to use an analog current sensor to directly and instantaneously measure the current in the voice coil, which is much more accurate than an electromechanical sensor, thereby reducing THD up to 75 percent.”

This is essentially their own version of what Klippel proposes as part of the KCS system. With an accurate model of the loudspeaker, including nonlinear behaviours, plus measurements during development you can combine a current sensor and some reasonable DSP grunt to enable dynamic mirror filters that ‘fix’ behaviours at certain drive levels that would otherwise be undesirable.

There’s a whole bunch of papers from Klippel on the concept, many of which are free on their website. Worth a read. I wouldn’t be surprised if this concept was a key part of the design aiming for such a low cut off in a small box. I’d also be unsurprised if the filters changed once you drove the system hard, raising the cut off to keep things reasonably linear and in distorted.

A small sub is also likely to be used in a small room, so that 80 dB (assume linear?) figure is going to be raised by quite a bit once corner loaded in a modal environment.
 

nothingman

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Fair enougn, I’ll take you up on the offer in the spirit of discussion. I’m no KC62 fanboy. I have one on order, but I’m also going to demo the 3000 Micro in my room to see if that suits me better.

I fail to see what are the "innovations" in this subwoofer. Cabinets? What is so innovative about the cabinet? Motor? Well it is a adual opposed with a shared voice coil. I am waiting to learn what such an arrangement brings to the table or in this case to the bass.

You know many subs with extruded aluminum cabinets that are an integral part of the heat dispersion design? Shared voice coils are indeed another innovation, never been done before. @kyle_neuron just mentioned the DSP, there is all sorts of distortion correction goin on. The surrounds are also a new design. All of those things are innovative, like them or not.

In the absoute a tweeter is able to reproduce 20 Hz, it could even be measurable, perhaps -100 dB down ... That thing will not reproduce 11 Hz at 40 dB SPL in-room, in which case only elephants or whales will hear or feel it. Not Humans.

Right except @joentell measurements show 90db at 12hz. Whether that’s loud enough, or whether there’s any information that low even on movie soundtracks is another debate, but it’s still pretty incredible given the sub’s size.

We have to ask manufacturers to be true in their specifications. Some do ( Genelec is one of those, Neuman ) once in a while Kef is true but ...

Good luck! That is two companies out of how many? The +/- 3db frequency response spec for speakers and subs has always required interpretation by consumers. Always.

There is a market for these, a vibrant, enthusiastic market. I do understand the market for which it is intended but in the name of objective performance which is what this forum is about... It doesn't matter to me what it’s targeted market is. A gear performs or doesn't…

We agree there is a market, but your ending is where I think you have things wrong. Everything is a matter of compromise, especially when including budget, aesthetics (especially important for sub), and user-friendliness in the equation. The KC62 performs objectively, but not on the criteria you feel is most important.

Everyone has their own use case. If you only listen at up to 85-90db (which is most people!) and you have a small room and you want maximize performance in relation to size and aesthetics, the KC62 is a great option that simply didn’t exist like this before. KEF knows there are people willing to pay a premium for the right balance for them! That’s why they’re backordered everywhere.

While the SVS micro may fall like a rock at 20 Hz where most music doesn't reach.The SVS Micro is 10 dB louder from 30 Hz to 200 Hz, where it does matter. The response of the SVS is also flat, the KC62 is not if we are to base ourselves on the Joentell measurements. If anyone wans to reach 20 Hz in room at substantial levels and choose a 6.5 woofers .... I have a quantum-tuned speaker cable I am selling for less than $10k.

I totally get what you’re saying about 30+hz performance of the 3000 Micro and the flat profile. It’s a legitimate argument, and exactly the one I made and why I am trying the 3000 Micro myself. However, at 20hz, the two subs are exactly equal. Whether 90-95db in-room is enough for people, that’s for them to decide. Call it a waste of money all you want, but there are so many worse (and commonly accepted) ways for someone to spend $1500 in their system than with a KC62 to pair with the stand-mounts.

Size be damned 2 SVS micro are a better solution

Another example of not really getting it. “Size be damned” isn’t an option for a lot of people. Audiophiles, at least the purists online, just don’t get that people can’t place their speakers 5 feet from any wall, sit at the ideal 1/3rd or 2/3rd mark in their room, and scatter subs all around. Just not an option!
 

bwng29

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How do you guys think the Kc62 can stack up against a Rel S/3 that was introduced a few years ago? The S/3 is obviously bigger and probably has better driver material but has none of the tech and R&R the Kef has in the last few years
 

Tokyo_John

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I sent an inquiry to KEF about the pass through on the KC62 and after checking they got back to me as follows:

The cycle is A/D converter → MUSIC Integrity Engine (DSP) → D/A converter.

A follow-up question I have is what effect this will have on sound quality passed through to the mains, when the KC62 is used as an active DSP-driven crossover? If one listens to digital music, the paths will look like (the parts handled by the KC62 in bold italics):

Source stream -> DAC -> ADC -> DSP -> High pass stream + Low pass stream
Low pass stream -> Sub DAC -> Sub Power Amp -> Subwoofers
High pass stream -> Mains DAC -> Mains Pre -> Mains Power Amp -> Mains

If KEF could manage all of this while producing negligible THD+N in what ends up being passed through to the mains, then this would be quite an amazing feat, and helps to justify the cost of the KC62.

And…if anyone does manage to do some measurements, I hope that this aspect will be a key target for measurements.
 

nothingman

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I don’t feel like anyone who is a SINAD addict is running their mains signal in and out of a subwoofer. I bet the KC62 does no real damage to the sound, but if you’re OCD about this stuff then figure out a way to manage your bass separately, e.g. DDRC-24.
 

o2so

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Update: from Kef USA There is a fix for that known issue that affects some customers and they are being dealt with as needed. New subs will have the fix but, obviously, units which were already in transit or sitting on shelves won't have it. If when you get yours you find you have the issue, then let us know and it'll be fixed for free. So yes, that would mean returning it to us as it's not a customer fix. If your dealer is an authorized repair center then they should have the ability to fix it as well.
I just bought a kc62 and it does not seem to have any issues of unnecessary standby. I was told by KEF that all serial numbers after SKC6203007N13N2G have had the hardware fix, but they said that only some of the earlier SN have the issue.
I am using the KC62 in a desk set up with KEF lsx and, after applying auto EQ via REW, the integration is seamless and the sound very satisfying, even at quite loud levels (although I am 70cm away from the speakers and 80 from the sub, but in a large room). I keep the sub on a small stand along the wall and get flat response down to 25-30 Hz (after EQ).
The LSX's have some occasional issues with Roon losing control of them every now and then, but otherwise this system sound just as good as my Dynaudio Focus XD 60 + Dirac.
 

DrStuhl

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I've finally got my KC62 and I'm very pleased with its performance - and my main speakers sound way better with HPF (probably because I've got a smaller amp)!

But I've got constantly loud white noise on those main speakers (KEF LS50 - not meta), when using the LINE OUTPUT. I do hear that noise even 3m away - which is not tolerable. Can anyone confirm that?

Even if no Line Input is connected and only "KC62 -> NAD C326 AMP (Main In) -> LS50 is connected, it's producing that noise.
I've got no idea if I should send it back to the reseller or to KEF to see if they fix it. Couldn't find anyone with this problem so far (even though it's probably a rare setup?). The KC62 must be the one to blame here, because there is no noise without it in AMP or speakers.

Tried different RCA-Cables, power cable and sockets - no difference. Any idea on that?
 

Hayabusa

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I've finally got my KC62 and I'm very pleased with its performance - and my main speakers sound way better with HPF (probably because I've got a smaller amp)!

But I've got constantly loud white noise on those main speakers (KEF LS50 - not meta), when using the LINE OUTPUT. I do hear that noise even 3m away - which is not tolerable. Can anyone confirm that?

Even if no Line Input is connected and only "KC62 -> NAD C326 AMP (Main In) -> LS50 is connected, it's producing that noise.
I've got no idea if I should send it back to the reseller or to KEF to see if they fix it. Couldn't find anyone with this problem so far (even though it's probably a rare setup?). The KC62 must be the one to blame here, because there is no noise without it in AMP or speakers.

Tried different RCA-Cables, power cable and sockets - no difference. Any idea on that?

1:change polarity of the power plug of the KC62
2: connect K62 and NAD preferably to same power socket.
 

NTK

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I've finally got my KC62 and I'm very pleased with its performance - and my main speakers sound way better with HPF (probably because I've got a smaller amp)!

But I've got constantly loud white noise on those main speakers (KEF LS50 - not meta), when using the LINE OUTPUT. I do hear that noise even 3m away - which is not tolerable. Can anyone confirm that?

Even if no Line Input is connected and only "KC62 -> NAD C326 AMP (Main In) -> LS50 is connected, it's producing that noise.
I've got no idea if I should send it back to the reseller or to KEF to see if they fix it. Couldn't find anyone with this problem so far (even though it's probably a rare setup?). The KC62 must be the one to blame here, because there is no noise without it in AMP or speakers.

Tried different RCA-Cables, power cable and sockets - no difference. Any idea on that?
Have you tried ground lift?

KC62.PNG
 
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