Strange hiss loop noise on HEDD Type 07 Speakers

[Proximus]

Hi guys,

I recently bought a pair of HEDD Audio Type 07 (MK1) monitors and got strange hiss problem. Except hiss pink noise that is common with those speakers, i have this strange loop noise that sound like oscillator. My room is quiet and i can clearly hear this sound from 5ft away.

Both speakers behave the same even though nothing is connected, only power cord. Level of hiss is same and it behaves as the same loop sound on both speakers in sync.

I tried most of the outlets in the house as well as the garage, everywhere is the same. I live in a new house built 2 years ago, so I think the electrical installations are ok.

I recorded it with my iPhone at a distance of a few centimeters.

Can a Power Conditioner device maybe reduce this problem? What else I can try? I didn't test them in time and now I can't return them to the previous owner.

Listen to the audio HERE

 

[AnalogSteph]

That's weird. With it being in sync on both you have to assume that it's some sort of external interference. Does shorting the inputs with a piece of wire (pins 2+3) make any difference?

 

[Proximus]

No difference after shorting 2 and 3 pins

 

[Curvature]

Did you try contacting HEDD?

 

[Berwhale]

Looks like the main tone is around 5KHz, but there's one a bit higher as well...

You can paste the URL of the M4A file in the Choose File dialog here: https://academo.org/demos/spectrum-analyzer/

 

[Proximus]

Did you try contacting HEDD?

Yes,

they answered me this:

Hey,
thank you for reaching out.
What a unique issue!
Since it appears on both speakers equally it has to come from the outside.
Our guess are electromagnetic waves/radio waves from a nearby station (or anything alike).

It is annoying but to test the theory it´s best to take one of the speakers anywhere else (a few miles/kilometers maybe next time you visit a friend/family) and check there. Only then we will know if this is actually the root of this issue.

 

[Curvature]

Yes,

they answered me this:

It makes sense but I would imagine your other speakers/microphones/headphones would show the same issue, so it's strange it only came up now.

I would be very interested in understanding the source of the issue.

If it really is interference and you aren't planning to move, you will have to get EMI/RFI shielded speakers. I think aluminum body Genelecs may work. You could install shields on your walls, but that feels impractical.

 

[Proximus]

I have Monitor Audio Bronze 500 6G hifi speakers and Cambridge audio CXA80 amp in the room next to this one without any problems.