Noise coming from subwoofers and centre channel

Here's one for $130

OP:  Some of my recommendationsi were well under $100

OP: Well my recommendation of an HDMI isolator is still the best way to go, but another HDMI cable may help and be a cheap solution.

It would really only help if the ground was significantly better... so for sure dont' spend money on boutique cables.  Buy an affordable one that's as short as possible but looks well made.

OP:  Not sure how portable your projector is, but can you move it close and use a very short HDMI cable?  If that fixes the issue, a better (not more expensive) cable may be a good option.

@soix Yes, you are missing the reason the AC cable has a ground wire.  It's to trip the fuse.

The ground wire on equipment (amp, refrigerator, any) is there to ground the metal shell so in the event of a fault where the incoming hot shorts to the outer shell the current should flow through the ground wire in the power cord at a high enough rate to trip a breaker or fuse.  The idea is to trip the fuse before a person or pet touches it and electrocutes themselves.

The problem is signal ground wires (shields) can't safely conduct that much current leaving two bad options:

1.  High resistance, which leaves the chassis hot and dangerous

2.  Melts and causes a fire

That's why cheater plugs are in all cases not safe. 

I’m a huge fan of Furman power conditioners, but I can almost guarantee no conditioner will solve a ground loop problem, no matter how much you spend on it.

Cheater plugs will work, at a high safety risk. What you really want is to isolate the signal ground that causes the loop, not the AC ground.

While there’s nothing in a Furman or megabuck power conditioner that will solve a ground loop, moving all AC plugs to the same strip sometimes is a solution, but it’s not a matter of any circuitry but rather that the grounds are so close.

The OP has already moved everything to the same outlets.  He's pretty much demonstrated that what he needs is an HDMI isolator.

OP: The coax only matters if it’s plugged into a device in your rack and can create a new ground path. Coaxial ground loop eliminators are cheap and plentiful. Honestly everyone should use them just in case.

Having an antenna or cable TV cable grounded outside your home by a grounding block is code,and not by itself a problem. The problem is when that cable is connected inside to a set top box and that set top box is connected to your stereo. The outer shield in the coax now creates a very long and separate ground path.

By the way, we don’t have the same issues with Ethernet because Ethernet is inherently isolated. Mostly. For this reason we don’t have ground loops when your cable Internet is connected to devices inside via Ethernet.

PS - If the coax isn't used, make sure it's disconnected outside.  Even though there may be no equipment at the provider side that long coax can function as an antenna and bring in lightning surges into the home.  Leave the grounding block in place.

PS - I did find direct HDMI to optical isolators at around $750 a pair, so the options above are a lot cheaper.

Also, double check you don't also have a coaxial cable coming in somewhere, those are often hum sources, and relatively easy to fix.

It is risky to use a cheater plug.  The correct answer here is you want an HDMI isolator, and one way to achieve this isolation is to use HDMI to Ethernet converters...

https://amzn.to/3OyueZU

OP: 

It does sound like a ground loop is forming.  If you disconnect the video cable from your projector does the noise go away? 

I was going to suggest could it be the projector has another ground path??  Try turning it on without any video cables attached.

Put the projector on the same circuit