Hum problem, not a ground loop... ?

[mulester7]

.....ThA, I humbly submit you need to throw that splitter in the trash, move both subs up front in the corners, doesn't matter if they're front-firing or down-firing, and Y the sub-signal to both subs via much shorter cable for one of them....of course, this will necessitate moving the AV-rack wherever you can make it work in the front soundstage, or moving it down the side-wall 4-6 feet....yes, you would incur some costs for cables and longer runs of speaker-wire, but we're talking about your Home Theater's sound and effectiveness....you can also find locally, 10/3 extension cords with triple-heads in various lengths that are thick as a nickel...."BUT THEY'RE ORANGE!!!"....so spray-paint them whatever color you wish....

.....ThA, if you feel like you've just GOT to keep one sub behind the listening position, disregard ALL the above....I can understand if you feel that way....many guys put down-firing subs out in the room....but where is the TV located?....is the TV not, the window to the movie?....where is it located?....the front soundstage....then where should the sound come from, only being widened and brought a bit closer by surrounds?....the front soundstage....I personally don't want rears....they bring the front soundstage MUCH closer, tend to muddy the overall, and once again, where is the TV?.....

 

[Rickster71]

I hate troubleshooting long distance, it's so much easier being there, and seeing the room.
I forgot to ask if there is a dimmer circuit in this room?

Okay, this may be easier than we thought.
You don't need redundant grounds on the subs. So since they have ground pins on their power plugs, (that's all you need)you have two different ground potentials, with the ground in the signal cable.

Let's try this test:
Temporarily move the rear sub, up next to the front sub.


Use a shorter RCA cable (that you can sacrifice) and run it between the subs as the jumper.
Test them to hear if the short cable made a difference.

If not, try the next step:
The center pin of the RCA cable is the signal, and the outer ring is ground.
We want to get rid of that ground on one end of the cable, closest to the second sub.
So, first strip 1" of the ground shielding away just before the RCA plug, as it goes into the second sub.
Or better yet, use tin snips and make a few cuts in the outer ground plug and spread it apart, maybe cover the ground with electrical tape. Do whatever you have to do to isolate the ground.

Tell us how that goes. Isn't this fun?

I do like Mulester's idea of the two subs up front. Just a thought.

 

[highfigh]

I hate troubleshooting long distance, it's so much easier being there, and seeing the room.
I forgot to ask if there is a dimmer circuit in this room?

Okay, this may be easier than we thought.
You don't need redundant grounds on the subs. So since they have ground pins on their power plugs, (that's all you need)you have two different ground potentials, with the ground in the signal cable.

Use a shorter RCA cable (that you can sacrifice) and run it between the subs as the jumper.
Test them to hear if the short cable made a difference.

If not, try the next step:
The center pin of the RCA cable is the signal, and the outer ring is ground.
We want to get rid of that ground on one end of the cable, closest to the second sub.
So, first strip 1" of the ground shielding away just before the RCA plug, as it goes into the second sub.
Or better yet, use tin snips and make a few cuts in the outer ground plug and spread it apart, maybe cover the ground with electrical tape. Do whatever you have to do to isolate the ground.

I'm pretty sure a dimmer would cause a buzz, not a hum. Dimmers, beer (or other) neon and florescent signs and lights and computers/monitors can inject noise into audio circuits but it's always a buzz, not a 60Hz hum.

A second audio cable and a wire held onto the two center conductors will do the job if one that can be snipped isn't available. As far as the redundant grounds on the subs- if the shield of the second sub is connected to the electrical ground, it puts both at the same potential, which is why I recommended it and it sometimes works in car audio, too (done it many times). Generally, improving the ground (decreasing any resistance between two devices) works best.

 

[highfigh]

Hey guys... I've recently hooked up all my new equipment with a new set of cables from BJC and have been battling a bad hum between my two subs.

I know this issue normally reeks of a ground loop, but I have done my research, changed a few things here and there and still cannot seem to isolate it. I am not one to beg for help, but I've pretty much exhausted my bag of tricks on this one.

All cables run in wall through 2 inch wiring conduit along with the BJC 10 white speaker cables, and the wiring conduit does pass by one electrical wire inside the wall, but they cross at a 90 degree angle to each other and with about 3 to 4 inches of seperation between them.

All the equipment at the front of the room is connected into my APC H15 power conditioner, however the sub at the back of the room is obviously not. It is plugged straight into the wall on the dedicated circuit. (This is one of my last remaining ideas as to what is causing the hum, could it be that the sub that is not being surge protected / AC line filtered be the culprit?) I am fairly confident that subs shouldn't hum just because they are not plugged into a power conditioner, as any sub I have owned in the past were never connected to one, but I've seen crazier things happen.

As I mentioned to you, I have properly grounded the incoming TV coax cable to the shared ground on the cold water pipe that comes into my house. I know that often these problems are a ground loop problem, but I assure you I have done my research and this does not seem as such.

I noticed on the 37' sub cable that there are copper strands sticking out of the top of the crimped connection and they make contact with the plug itself. I am not sure if this makes a difference or not, as if you have the shielding braid strands contacting a signal conductor on coax TV cable you get massive noise, but when this sub cable is connected just by itself there is no issue.

That's all I can think of at this time, I just wanted to stress that I only get loud unwanted noise when both cables are both connected to the splitter at the same time.

Any help you guys can offer me would be greatly appreciated, as I am at my wit's end troubleshooting this mess.

Just a couple of additional thoughts- if your TV or anything else came with those ferrite beads that are supposed to be snapped over a cable, put one on the cable feeding the second sub. This will be a good indicator of whether it's a radiated noise issue or grounding.

 

[Rickster71]

I'm pretty sure a dimmer would cause a buzz, not a hum. Dimmers, beer (or other) neon and florescent signs and lights and computers/monitors can inject noise into audio circuits but it's always a buzz, not a 60Hz hum.

A second audio cable and a wire held onto the two center conductors will do the job if one that can be snipped isn't available. As far as the redundant grounds on the subs- if the shield of the second sub is connected to the electrical ground, it puts both at the same potential, which is why I recommended it and it sometimes works in car audio, too (done it many times). Generally, improving the ground (decreasing any resistance between two devices) works best.

Agreed.

Doing this long distance makes it all the more of a pain in the ***.
One man's buzz is another's hum.