Focal Kanta No. 2 Speakers hum with speaker with speaker cable disconnected

Thanks for the reply... No there isn't any in close proximity to the house.  

Thanks for the suggestion, no home alarm either.

It’s specifically the left speaker, even with no speaker cable connected. It being the left speaker makes it a bigger issue, as it’s closest to the analog setup. So any noise generated by the speaker (plugged/unplugged) is causing a sort of feedback with the phono.

Right speaker is dead silent, even when connected to the amp. Is it safe to assume that this rules out any power leakage from the power amp (Parasound JC-5) to the speakers?

SKW OCC speaker cables, QED reference 40 RCA and XLR interconnects

@mofojo the hum is independent of the phono. I did unplug the phono’s power and umbilical cord, so zero power. I think this hum is what’s causing the phono to hum in the first place.

@erik_squires Thanks Erik! I give it a try.

@gs5556 You might be onto something, the electrical wiring is indeed 240v and running through the wall approximately the same height same as the speaker terminals. Maybe the power line is emitting RFI/EMI in this instance, and the speaker is picking it up. Left speaker is around 3ft. off the back wall and 2.5ft off the side wall.

Yeah it's troubling to hear that even speakers at Wilson's price point can have design flaws that cause it to pickup interference. 

I think @erik_squires nailed it. I shorted the speaker terminals and indeed the hum dissipates completely. I'm not knowledgeable enough to make a diagnosis, but this kind of points to an internal issue, possibly a leaky/noisy cap? By shorting it, I guess it's being discharged, so no humming. The phono hum is hopefully going to be resolved if this is sorted. Right speaker is silent, so it's just limited to a single speaker.

Thank you all for the suggestions and help. It wouldn't have occurred to me to try out some of proposed tests. I'll reach out to my dealer and update him on this, hopefully he can source a new crossover and install it.

Regards,

Faisal

Fair enough... It might be too early to start celebrating. Though I did move the Left speaker to a different spot in the house, far away from the listening room and the hum was still there but disappeared when shorted. No high-voltage or transmission lines within a few miles of the house. No radio towers/cell towers close by either, and I believe they operate at a much higher frequency range (MHz/GHz) than the speaker can pickup. If that was the case, wouldn't both speakers be affected equally? Right speaker hasn't been moved at all and doesn't hum, whether connected to amplifier or not. No large electrical equipment.

I'd like to point out that the hum is not heard at all unless your press your ear to the woofer/tweeter, even then it's very faint. If it didn't cause any interference with the phono, I wouldn't have noticed or cared about it. Unfortunately the quieter/more sensitive the phono is, the more these issues are noticeable/annoying.

Thanks Erik for the detailed response, and all the others who contributed.

I moved the speaker far away to see if it's a location based issue, and it didn't appear to be the case. Shorting seems to completely stop the humming any where it's been placed, so there's that tidbit.

I'll try what you suggested with speaker placement, and rotation, and I'll swap Right and Left speakers as suggested. Speaker is admittedly heavier than what the specs suggest :)

Best,

Faisal

The DC output is something I considered and tested for when troubleshooting the phono hum. I purchased the DC blocker adapter that plugs between the IEC socket and power cable, no change. The Puritan Mains conditioner does a great job at filtering all nasty stuff coming in the power line, not that it's that bad to begin with. Measured the EMI/RFI interference out of the Puritan sockets and it's between 11-16mv or 0.011v - 0.016v seems negligible.

Dealer told me about a speaker he owned a few years back that kind of had similar issues with humming. Took him a while to find out the cause: oil-filled caps leaked and shorted or corroded something.

Tried measuring with a multimeter, it's super basic model, and it's measuring no DC current at the mV setting. So either my amp is 100% not leaking any DC (unlikely), or the meter is misleading, which what I think is happening.

Sorry Eric, the timeline of the posts have me answering in reverse order.

If I un-short the speaker the hum comes back, whether in the listening room or elsewhere, doesn't matter. If it's EMF and a wonky something in that speaker only, then yeah your explanation fits the bill. The only thing is, that the right speaker exhibits none of this, connected to the amp or not, so that kind of excludes the amp outputting DC, no?

I unplugged every piece of gear that emits WiFi/Bluetooth (Playstation, Apple TV, TV, Router, Philips Hue/Bridge, and even disabled the WiFi on my AV receiver, but it didn't seem to do anything with the hum. The phono is canary in the coalmine so to speak, it's amplifying whatever is being emitted by the speaker. Many orders of magnitude louder than the original hum level.

Thanks Erik for clearing up the mix-up. The measurements quoted above are the amp’s DC offset, I chose the right speaker binding posts but the left should be the same, no? I’ll try again when I get a new meter. Forgot to ask what’s an acceptable range of values for DC offset? I saw 100mV as the maximum acceptable value on the web, any truth to this?

In the meantime, I’ll contact my dealer and Focal, and swap the right and left speakers to confirm it’s just the one speaker. Based on the what’s been mentioned above, it’s seems that there is definitely something wonky with the speaker’s crossover. Caused by their "Neutral inductance Circuit" not working as intended as @gs5556 has kindly brought up, or a malfunctioning component. So far I can’t find anything that leads me to suspect an environmentally induced hum. Quite the head-scratcher this had been.

Again, thank you all for the help!

Edit: Typo