John Sayers' Recording Studio Design Forum

So, I'm working in my new room, and my Genelecs are producing some 60 cycle hum. The weird thing is that if I shut them off and then turn them back on, the hum is gone (well, way less) and stays that way for awhile. Then at some point later (an hour? two?) I realize the hum is back.

I'm assuming it's some sort of power issue. But I'm pretty clueless. We set up the electrical with a sub panel in the studio, and added a ground pole to the whole system (there wasn't one prior). I've got pretty much the whole studio running from a Furman conditioner (PL-PLUS). Though to test it, I plugged one of the Genelecs directly into the wall (bypassing the Furman), and it does the same thing.

Thoughts?

Does the hum come and go? Maybe when a fridge is running or HVAC unit is running?

Is the input to the Genelec's balanced or unbalanced?

Is your source (console or ??) balanced and grounded?

Is the console/source on a different phase or leg than the monitors?

I just took another look at the room.

Are those halogens in the ceiling? Are they on a dimmer switch?

Hey Aaron,

Everything's balanced.

Yes halogens, but no dimmers.

It doesn't come and go once the hum has built up, it stays constant. Constantly annoying.

The source is a StudioComm 50/51 set up. It's balanced, and it's on the same Furman as the rest of the studio. Side note... the Studiocomm's rack piece where all the cables connect has been making a similar hum. But it's actually coming from the rack itself. But, if I pull the plug on the StudioComm, that hum quits, but the speakers still hum (assuming they're already humming).

Do they still hum w/ the input cables unplugged from them? Let's narrow it down to power or ground loops or issue's w/ monitors.

Still hums with the cable disconnected. So, power or something's up with the monitors.

Have someone start flipping breakers to everything in the house while you're listening and see if the noise goes away, get's quieter or...

Just a thought here.
Your speakers are not sheilded like computer speakers are.
That big beautiful LCD or Plasma above the speakers might be creating your hum. Especially if you see a warble in the screen closest to the speaker.
The only problem I ever had with hum was an ac/dc power converter for my DI. All I had to do was move them away from the rest of the gear and it solved the prolem
And that easy move took a few months to find.
Good luck
Tom