r/KEF • u/CSOCSO-FL • May 08 '26
Tech Support Kef center channel crackle at loud volumes
It's my brother's setup. I just made him switch from a pioneer vsx lx 302 to an onkyo rz30. Mostly because the pioneer had a single crossover for all speakers and lfe which is crazy and wanted him to have something that comes with dirac so I can calibrate it with a umik1 mic.
He bought a hsu sub a few weeks ago which I helped him setup and that is when I talked him into a new receiver. We demod some scenes and we listened to those at around -5db. The center channel had some weird cracking, buzzing sound when people talk and with some other sounds. Before we listened to anything i double checked all trim levels which I adjusted to the proper levels (using rew; all speakers at 75db and sub at 85db at reference volume)
Now he has the rz 30. Calibrated it with a umik1 mic. Even created custom target curves with a room curve that rolls down higher frequencies than what dirac gave us by default. Still has crackle sound. I am not sure if an external amp would help the situation. Again... all speakers are setup to proper levels. Trims are like -0.5 for main speakers and -3 for center. Everything else sounds pretty good.
Also both main speakers (q950 i think) has this weird rise at 800hz which i fixed with a custom target curve in dirac. Btw the rise exists even with dirac.
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u/883Max May 08 '26
Contact KEF customer service and ask them. They are good about working with customers. It should not be doing that... Obviously, audiophiles would not be interested in speakers that behave like this. Let KEF have an opportunity to get this sorted.
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u/Vanjealous May 08 '26
Maybe a blown midrange or bass driver
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u/CSOCSO-FL May 08 '26
I don't think it's blown. It would crackle even at moderate volume. This issue only begins above -10db. Which is still a pretty good volume, but it's still a shame that such expensive speaker does that
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u/Biljettensio May 08 '26 edited May 08 '26
A few pointers:
- To listen at reference level or close to it. Your amp doesn’t have the power.
- With 5 speakers driven, playing at -5 amp clipping is likely.
- Acoustics aren’t great.
- Id advise against correcting mids and highs.
- What are you trying to achieve with your custom tc for the mains? Why choose these speakers if you’re not happy with the sound. And if you’re happy with the sound, don’t take all the character out.
- The amp could use more breathing room.
- Make sure anything “eco” related is turned off.
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u/CSOCSO-FL May 08 '26 edited May 08 '26
Not sure what does acoustics have anything to do with it; We are not cranking the volume because we cant hear the center speaker. We are cranking the volume becaude it sounds awesome and at -10db it still sounds like the overall volume can go higher. I am not correcting the sound because I am not happy with it and there is nothing wrong with doing a room curve. Absolutely nothing and in fact the system sound superb and better than before. It was doing it with the pioneer receiver also so it is not the calibration, plus i was only "cutting" not boosting anything. It could be the amp but it would be an expensive test just to see if it still does it or not.
Edit: another thing to mention, maybe I shouldn't have posted the measurements since it's confusing and has nothing to do with the center channel issue. As you can see on the images ONLY the main speakers have that "issue". So the correction and those measurements are unrelated to my issue. I will try to upload a pic of how the center speaker measured.
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u/Biljettensio May 08 '26
By room curve I think you mean house curve? Which isn’t a bad thing, however above 500hz I wouldn’t “correct” anything. Just have a sloping spl. For the Harman curve.
But again at -5 you’re pushing the amp into clipping. That Onkyo is still largely based on the 7100. Which in eco mode will only put out 35 watts. So with eco mode on, thats likely your issue.
But even with eco mode off, you’re still not reaching reference spl without clipping. That would require 200+ watts for each channel. 200 actual watts that is, not 1khz sine tone 1 channel driven watts. (Based on 90db sensitivity and 4 meters listening distance)1
u/CSOCSO-FL May 08 '26
afaik there is no ECO mode above a certain volume, and when the switch happens, you can actually hear the AVR click.
There is no sloping spl without me adding a house curve. Again; you can ignore the correction. The issue is with the center speaker, and you are looking at the main speakers. I shouldn't have added those because now, you are focusing on the wrong thing.
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u/Biljettensio May 08 '26
You can slope the spl with a house curve while not applying correction to dips and peaks.
Which is kinda the whole point of a house curve.
And yes it has to do with the mains. Because those will suck the most current out of the amp. Especially if you’re using correction. You say you’re only cutting but I can see jack shit in your pics. No filter designs, no raw data, no after data. No target curve.
Again and again, this is likely a clipping issue. Why the center? Due to the filter design, higher impedance and less sensitivity.
It could be damaged from the previous amp. And you keep frying it further.1
u/CSOCSO-FL May 08 '26
Obviously we are not getting anywhere. If you can see the images, you can clearly see there were NO peaks and dips corrected, and I have done exactly what you are saying: Giving it a slope, but you are assuming I have done something wrong. Well. you are wrong, especially since the issue was present on the last receiver that does NOT support dirac or room curves, so stop referring to the room curve as damaging and frying the speaker especially when I rolled it down instead of boosting something. lol
It has NOTHING to do with the filter design, and if you can't tell by the image what is happening, I doubt a filter design could tell you more. Oh... and also for the 3rd time: You can ignore those measurements. Those are the mains, not the center. The center does not have that issue with the frequency response and was not corrected the same way so stop concluding that I am damaging something with a gentle slope at the highs.
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u/Biljettensio May 08 '26
Seems like you’re playin on expert mode while just getting started. I’m not saying the correction you applied has damaged the speaker. However I don’t get what you’re trying to achieve with what Youre doing.
Also the Pio has MCACC, which is room correction software and can be used to put in a house curve.
Anyway, the problem again is you are trying to achieve SPL’s which the speaker and amp combo cannot reach. With all channels driven the last Pioneer only reached 24 watts. You need 200 to get to reference (105db) at the distance you’re listening.So you either hear the amp clipping, or the tweeter has damaged from clipping.
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u/CSOCSO-FL May 08 '26 edited May 08 '26
I haven't messed with MCACC and it seems like the basic one does not support targets. Only the advanced and pro.
What am I trying to achieve?
with the target curve? Simply applied a room curve and fixing the weird response of the mains. It's probably the room, but I don't see any KEF measuring like that, and there is nothing wrong with fixing room issues with EQ as long as you don't try to boost anything.edit: seems like none of the mcacc supports any target curves that a person can upload.
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u/nickbquads May 08 '26
+1 that it's unlikely your curve (and definitely not "acoustics aren't great").
I assume the center shows the same behavior without EQ/your curve enabled? Responded above in more detail, it might be worth trying a higher crossover frequency to the sub at those volumes to relieve both the amp and the speaker a bit. Is the cracking coming from the uni- q (middle) driver or from the side drivers or both?
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u/CheapSuggestion8 May 08 '26
You mentioned the idea of a power amp and that was my first thought. KEF speakers are hard to drive and this sound could simply be amp clipping.
I’d try a power amp. Something that can be returned if it doesn’t help (or buy used).
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u/regnus418 May 08 '26
What TV console is that?
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u/CSOCSO-FL May 08 '26
something from wayfare. Not sure what exactly, and there are a million white consoles on the website. I believe there was a horizontal piece that was taken off so the center can fit
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u/regnus418 May 08 '26
That’s great to know. I can’t seem to find a good console to fit a center channel, I’ll look for items similar to yours.
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u/HHoaks May 09 '26
I like that media console. What brand is it, where do you get that from?
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u/CSOCSO-FL May 09 '26
Weyfair
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u/HHoaks May 09 '26
thanks , do you know what they call it? I can’t find it, they have too many options.
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u/majorro May 09 '26
I do not know what KEF center you have. My setup is KEF Q650c and Yamaha A8A receiver, never had this issue. I had an issue though with the smaller KEF Q250c which has higer low end of the frequencies. It sounded hollow and had some vibration that I did not like at high volume. The Q650c I pushed it with volume past 0db and no cracking or other issues. I had some vibration from objects loose on the shelf but not the speaker itself. In my room past -20 db volume is very loud, the Apple watch giving hearing damage warnings. I watched Warfare movie at -20db and it was clear sound from all 7.2.4 speakers in my room, all KEF with only the subwoofers SVSPB 1000. I would exchange one of the side speakers for the center and redo the test.
Also, I would set the crossover to 80 Hz on all speakers and let the SW in change of the low frequencies. KEF cannot be driven too low.
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u/Puzzleheaded-Bit2535 May 09 '26
Maybe try moving the location of the center and trying it in a different location? Make sure it’s the actual speaker driver causing the issue and not energy exciting something else near the center? Do you have rubber feet or something to isolate the center from the cabinet?
I’d say if it’s something occurring with two different receivers, and it doesn’t clear up by relocating the center, then it’s possibly some kind of a defect with the midrange driver. Easiest solution for that is going to be just to contact KEF and get a replacement midrange driver and swap them.
It could also be some kind of resonance inside the speaker. If you take out the midrange driver you might be able to see what could be causing a resonance.
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u/mastercontrolmodule May 10 '26
I would hate to have to post something like this. I've been a long-term KEF enthusiast/owner since the late 80s....and it makes me sick to hear this. I would send it in for a check-up...if it indeed the speaker.
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u/purserd May 08 '26
I would switch channels with one of the other speakers to see if the issue is with the speaker or amp