Axiom Home Page Forums General Discussion Technical Questions Buzzzz from speakers multiple subs.

Well, I am finishing up a few minor things and should have my remodeling of the Plex done soon. Hope to take a few snapshots asap.

Anyway, last night I was taking a few initial sweeps from the primary seat to get an idea of how each of my subs individually (distance/levels) will have to be set before doing all 8 sweeps.

Whenever I plug in my 350 I get a buzzing sound coming out of all my speakers. It is loud enough to be annoying. I have a good idea that it has to do with it being on a different circuit than the rest of the equipment, but I have no options. Eventually, I might bring down my other 350 to have both of them on the opposite wall of the 600 to follow Toole's papers. (2 350's opposite the 600)

When I enclosed in the theater portion from the rest of the recroom, I added a rear and side entrance wall. I was unable to tap into the existing HT circuit, and had to extend off a circuit that powers the rest of the recroom. If that tells you anything.

Anyway, I found an article that Alan did about eliminating this annoying buzz and will try to troubleshoot, just looking for ideas.

http://www.ecoustics.com/electronics/products/articles/180767.html

I don't have satellite/cable in this room yet as the article mentions, but do have a HTPC that is hooked to an external over-the-air antenna, don't think that would be the problem.

Here is my setup for now, still need to bring the Bluray player back down that is being used upstairs...

Denon 3808ci
Sanyo Projector (hooked to HDMI out on Denon)
HTPC (hooked to HDMI in on Denon)
Outlaw 7700 amp (hooked to Denon preouts using RCA)
Axiom EP600, 80's, 180, Qs8s (hooked to speaker jacks on amp)

Tripplite HT Powerbar Surge/Isobar - all equipment is hooked to this, which is hooked to outlet on 20amp circuit. The EP600 is plugged into an outlet on the same circuit in the room.

So, I still think it has to do with the 350 being on a different AC circuit. Just trying to figure out where to start. Maybe one of these gizmos that Alan mentions in his article will help.

thanks for listening, Randy

The HTPC could definitely be the source of the ground loop.

So why do you think being on a different AC circuit would cause buzzing on your other speakers? Feedback through the coax connection between the sub and AVR? Have you looked at a product called powerbridge? I used several of them so I can located all my power connections in one area. The powerbridge allows you to run romex through the wall and have plugs on each end. I did this so the power conditioner that services my a/v stack of equipment would also service my TV. Check out powerbridgesolutions dot com. I really don't see how putting your sub on one AC circuit and your other components on another circuit would cause AC hum or ground loop from the first circuit to get into the othe speakers. The HTPC could be resonating at a freq that is causing some interference. Turn it off while doing the sweeps and see it goes away.

Update, after completely removing/unplugging all the equipment except the receiver and amp, I still had a transformer type buzz emitting from all the speakers once I added the 350 into the equation.

So I thought....I wonder if I put the EP600 back there, same thing, the buzz was not as loud but still there...soooo I removed the ground screw from the back of the EP600,

annnnnnnnnnnnnnnnnnnnnd


wait for it.................. dead silence...

So, not sure what that tells us, but I am going to leave the EP600 standing up along the back wall, not exactly centered, but close.

I also have both my 350's up front spread out, and the VP180 resting on top of them, looks pretty cool.

The 180 is not as high as I would like it, but works for now. Probably need to raise it about 6-9 inches once I figure out how.

Will have pics asap.

Randy, what removing that screw does is to cut the connection between the grounded sub amp chassis and the shield in the sub cable. Normally, having them connected can slightly reduce the noise level by having the shield also using the chassis ground to drain off noise. If there's a ground loop present however, with them connected it also feeds into the cable and then to the receiver. The difference in the electrical voltage potential between two different electrical circuits can cause a hum current to flow through the amplifier and be audible in the speakers. Removing the screw(which still leaves the sub amp chassis grounded)might slightly raise the ultimate noise floor, but doesn't feed the ground loop hum into the sub cable.

As to positioning the subs, having the two EP350s up front supporting the VP180(possibly flipped upside down to project more upward?)and just left and right of center is very little different from having one sub at the midpoint of the front wall from the standpoint of the room mode minimization placement suggested by Dr. Toole and others. Having the EP600 as close as possible to the midpoint of the back wall would therefore form the midpoint of front and back wall arrangement and should work quite well.

thanks John for explaining the grounding issue. The 350's are spread out as far as I could and still be able to support the rubber feet on the bottom of the 180, I actually got longer bolts and have 3 rubber feet on the front to help with the upward angle. I could probably fit another 350 in that gap.

No need to be concerned with spreading the EP350s far out, as long as they support the VP180 and look good. Having both as close to the front wall center as possible is better.

I'm trying to picture how it looks - can't wait for the pics Randy!

I will try and get some pics by this week or weekend. I need to figure out how to get the 180 a little higher, but in time.

I got a guy who can photoshop it higher for you, Randy ;-) Just kidding - looking forward to seeing them!