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new KEF KC62 dual 6.5" subwoofer

BrokenEnglishGuy

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The surround from KC62 its very special and apparently allow to deliver very high excursion

They should update their bass driver in all of the speaker from Kef
 

trl

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I see some in-room measurements here: https://www.avforums.com/threads/kef-kc62-subwoofer-owners-thread.2349760/#post-29034154. Looks pretty impressive to me, definitely above my expectations for a sub with 6.5" drivers inside. It might be better than a single SVS SB-3000 Micro. however, looking forward for a measurement done in an anechoic room (or outside the room).

Twin_KC62_measurements.png
 

Supalite SV

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I picked up a white KC62 to pair with an NAD M33, but sadly had to return it after seven days. There are a number of issues I experienced:
  • The KC62 won’t wake from sleep using the M33’s sub-out unless I increase the volumes to high levels. This is partially due to the M33’s low voltage output (max 1.1V) and the KC62’s wake threshold being too high (even their own KEF products struggle to wake the sub).
  • There was a hum or ruffling sound from the subwoofer that would come and go. Changing the ground lift switch would sometimes fix the issue, only for it to reappear again randomly.
  • When using the M33’s pre-outs, there was an ENORMOUS pop from the subwoofer when it would come out of sleep. This would be a full excursion movement of the woofer cones. The first time it happened, I’m certain it shortened my life by a few years. I posted a video of it on the KEF owner’s forum on Facebook if you’d like to see the incredible excursion of the little woofers.
The KC62 is a marvel of mechanical engineering, but it feels like a beta product. I’ll definitely be looking at the V2 version of this subwoofer, when all the kinks are worked out.
To FIX SUB OUT - You need to configure DIRAC with Sub1 enabled in the app.
Everything will work after that.
Best Martin.
 

sarumbear

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sarumbear

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50mm Xmax is almost beyond the realm of possibility for anything but something meant for a Cinema. Highly doubt that’s the case.
I agree, I simply wanted to show that 11Hz from such a small subwoofer is beyond the limits of physics. Even at 30Hz you need the same excursion to reach the 115dBSPL level people are aiming for.
 

fcracer

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To FIX SUB OUT - You need to configure DIRAC with Sub1 enabled in the app.
Everything will work after that.
Best Martin.
The software cannot fix the low output voltage of the sub out (1.1V) on the M33 which is a poor match to the RC62 which requires ~2V to function normally. You can play loud bass heavy music to wake the RC62, but after 20 mins of lower volume listening, it’ll turn itself off again.

Using Dirac, it’s possible to set it up so that Dirac will add 10db gain to the sub output (calibrate with the sub -10db from flat), which will help with the wake issue, but then you’ll still face the hum issue, and in my unit’s case, the turn on pop.

I love the design and thinking behind the RC62, it just needs another go at the firmware and software. NAD also needs to rethink the gain on their sub out for the M33.
 

carewser

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My paradigm sub goes down to 22 hz and it's the deepest bass i've ever heard and little wonder since I cant hear much if anything lower so even if the KC62 could go down to 11hz, what's the point? You wouldn't hear it anyway
 

Chrispy

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My paradigm sub goes down to 22 hz and it's the deepest bass i've ever heard and little wonder since I cant hear much if anything lower so even if the KC62 could go down to 11hz, what's the point? You wouldn't hear it anyway
Feeling it is fun....
 

KMO

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I don't know how much I can trust REW+Umik-1 at these frequencies, but I've measured a maximum of 99dB at MLP from my KF92 at 11Hz. (That's the KC62's 9" big brother with similar DSP). Mind you, that's its peak low-end response, just at the point it rolls off sharply- most I've had at 20Hz is 94dB.

You are in a room, not an infinite open space. The 11Hz waves (so large they can barely be called waves) are being constrained and hence amplified. We're not trying to get 100dB anechoic response here.

And being logarithmic, Xmax drops off sharply with the decibels. Using the calculator again, if Xmax=50mm at 90dB anechoic, then 80dB anechoic needs a more reasonable 15mm.

Given the fancy P-flex surround shenanigans going on, I could believe they can move 15mm. Seen no definite measurements or specs on Xmax though. Not much video evidence. Here you can see someone testing feeding it 12Hz, 20Hz and a sweep, but don't know how hard they pushed the level (link to relevant part):


And the KF92 doing some subsonics (link to relevant part):


Basically, you do get perceptible output down there - you'll sense the infrasonics are happening - but it's not going to shake the building.

Another way of looking at it: Assuming the KC62's Xmax is as good as the KF92's (which doesn't have P-flex), then by driver calculation, the KC62 should be 5-6dB lower than the KF92 (which agree's with KEF's declared 5dB difference) which means it should manage 93-94dB @11Hz in my room.

And the graph at 8:26 of the Small Change video shows 103dB from 2 KF92s at 11Hz. I think that implies a single KC62 would do 90dB in that space (same Xmax, half the drivers and smaller).

But again, how much can you trust any normal measurement mic here? Do they calibrate that low?
 
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thewas

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According to this calculator at 11Hz you can get around 90dBSPL @ 1m if the woofer Xmax is 50mm, which is pretty large.
In free space, that calculator does not take into consideration the room gain which is usually quite high at those frequencies https://www.audiosciencereview.com/forum/index.php?threads/analytical-analysis-room-gain.23211/

This is shown also in the white paper of the sub:

Frequency Response
Through these new technologies, KC62 exhibits an exceptionally wide and deep frequency response, especially for a subwoofer that is barely larger than a football. Figure 13 shows the frequency response at 1 metre, at several listening levels. Also included are additional dotted lines, showing the in-room frequency response. This takes into account the low frequency enhancement in a typical room.


1640080976774.png




So for outside parties such subwoofers are usually not enough. ;)
 
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Willem

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This KC62 is obviously a great sub for people with small appartments. The physical size is small enough to be unobtrusive, they look beautiful, and at small appartment levels the extension is flat and deep enough. The same kind of logic applies to the KF92, only for medium sized rooms. I guess if you don't mind a big box, the Arendal 2S is probably the best bet for many. It really is horses for courses, although I would not mind to see a direct comparison between the Kef KF92 and the Arendal 2S: at roughly the same price how much ultra bass are you giving up for a much smaller size?
 

Tokyo_John

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Feeling it is fun....
One of the things I really like about the KC62 is the opposed drivers, the only thing moving is the air, no vibrations transmitted through the floors/furniture due to unbalanced vibration of the drivers/cabinet. It makes for a very clean audio experience, maybe not what everyone is looking for, but for me this is what I want out of my system (also no rattle/vibration sounds). It is also good for me since I have mine underneath my NAS, and I don't want to vibrate my disk drives overly much.

That doesn't mean I don't like feeling of bodily bass as a tactile experience. I did once stand on the side of runway, nearly underneath a F-15 as it accelerated vertically upward into the sky, I'll never forget how it played my lungs like a drum. Nothing can compare with that. But maybe that satisfied me...no desire to try and repeat that same experience in my own home, with my children's ear drums in the line of fire.
 

Willem

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My B&W PV1d is in the same style, with two opposed (8 inch) drivers in a small package and some smart dynamic dsp to rein in extension at higher spl. It sounds very clean and tight. It more or less fits in between the KC62 and the KF92, both in price and in size.
 

stren

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One of the things I really like about the KC62 is the opposed drivers, the only thing moving is the air, no vibrations transmitted through the floors/furniture due to unbalanced vibration of the drivers/cabinet. It makes for a very clean audio experience, maybe not what everyone is looking for, but for me this is what I want out of my system (also no rattle/vibration sounds). It is also good for me since I have mine underneath my NAS, and I don't want to vibrate my disk drives overly much.

That doesn't mean I don't like feeling of bodily bass as a tactile experience. I did once stand on the side of runway, nearly underneath a F-15 as it accelerated vertically upward into the sky, I'll never forget how it played my lungs like a drum. Nothing can compare with that. But maybe that satisfied me...no desire to try and repeat that same experience in my own home, with my children's ear drums in the line of fire.

Not worried about big magnets next to your NAS disks?
 

Supalite SV

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The software cannot fix the low output voltage of the sub out (1.1V) on the M33 which is a poor match to the RC62 which requires ~2V to function normally. You can play loud bass heavy music to wake the RC62, but after 20 mins of lower volume listening, it’ll turn itself off again.

Using Dirac, it’s possible to set it up so that Dirac will add 10db gain to the sub output (calibrate with the sub -10db from flat), which will help with the wake issue, but then you’ll still face the hum issue, and in my unit’s case, the turn on pop.

I love the design and thinking behind the RC62, it just needs another go at the firmware and software. NAD also needs to rethink the gain on their sub out for the M33.
Did you try it of just guessing? Had same problem but fixed using Dirac. 1.1V output is a gimmick.
 

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FeddyLost

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I would not mind to see a direct comparison between the Kef KF92 and the Arendal 2S: at roughly the same price how much ultra bass are you giving up for a much smaller size?
If we compare 43 liters with 100 liters, why not to take Arendal 2V and finish the mockery?
 

Chrispy

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One of the things I really like about the KC62 is the opposed drivers, the only thing moving is the air, no vibrations transmitted through the floors/furniture due to unbalanced vibration of the drivers/cabinet. It makes for a very clean audio experience, maybe not what everyone is looking for, but for me this is what I want out of my system (also no rattle/vibration sounds). It is also good for me since I have mine underneath my NAS, and I don't want to vibrate my disk drives overly much.

That doesn't mean I don't like feeling of bodily bass as a tactile experience. I did once stand on the side of runway, nearly underneath a F-15 as it accelerated vertically upward into the sky, I'll never forget how it played my lungs like a drum. Nothing can compare with that. But maybe that satisfied me...no desire to try and repeat that same experience in my own home, with my children's ear drums in the line of fire.

Well a better/more capable sub would be better at producing the tactile experience, even with dual-opposed drivers. I have a dual-opposed 15" sub I use as a stand for my tv, pretty inert cabinet for sure but is a bit more capable at 11hz than that little Kef.
 

fcracer

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Did you try it of just guessing? Had same problem but fixed using Dirac. 1.1V output is a gimmick.
I’m not sure what you’re trying to show me. I had no problem getting a wonderful Dirac measurement with this subwoofer. It produced an ideal sound for my apartment and fit perfectly into my decor.

My issues were: 1. Keeping the sub from going to sleep at low volumes, 2. A wicked turn on pop when coming out of standby, and 3. A hum which was intrusive enough to be heard. That’s why I had to unfortunately return it.
 
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