Strangest hum in speakers... - AVS Forum
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post #1 of 36 Old 05-02-2012, 06:06 AM - Thread Starter
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I'll try to keep this as short as I can cause I have been at it for over 2 weeks and I'm at witts end in the cause.

Long story short...
I have a hum noise coming out of my Left and Right front speakers.
I also have a pretty good hum coming out of my 4x subs connected to a EP4000 (RCA to XLR monoprice cable)
I have a 7.2 channel receiver. When i connect to the sub1 channel the hum is pretty loud. When connected to sub2 channel the hum is reduced by about 70%

I disconnected EVERYTHING and still get a hum on my front speakers. (subs are now dead silent)

OK here's the weirdest now.
I have disconnected the front speakers and STILL get a hum!!!
I said WTF is that?

How can I still have a hum in my speaker when I disconnected (both + and - cable in the back of the speaker?

Please help!!!!!!


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post #2 of 36 Old 05-02-2012, 06:17 AM
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Wait...your speakers still hum and they are completely disconnected at the speaker terminals? Stupid question, but are you sure it's the speakers themselves making the hum? Feel the woofer cone to make sure. If they are humming, I'd leave the house and run like hell! Seriously, move them to another location and see what happens.

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post #3 of 36 Old 05-02-2012, 07:28 AM - Thread Starter
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My front speakers a 3-way speakers...
The midrange speakers hums all the time (No cable connected to speaker)
When I press the cone in the hum completely stops!
The woofers (2 of them) are dead silent!

I had to ask my kids to see if they heard it...they do! I thought I was loosing my marbles!

If I move the speaker around the hum diminishes but still present.
This is in a soundproof room.

I have been living in this house for 20 years!
I have never had this hum before...

Pictures of my setup


speaker close-up


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Equipment Speakers:
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post #4 of 36 Old 05-02-2012, 07:29 AM
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Originally Posted by Fatshaft View Post


How can I still have a hum in my speaker when I disconnected (both + and - cable in the back of the speaker?

You can't, unless you have it placed next to a very high density electro-magnetic source causing an induced current in the crossover coils.

Bill Fitzmaurice Loudspeaker Design

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post #5 of 36 Old 05-02-2012, 07:33 AM - Thread Starter
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The closest electrical circuit is the light bulb on the ceiling and/or the puck lights that work on 12VDC.
The right speaker is the loudest and maybe a foot away is the main water entrance copper pipe running from bottom to the top of the right side wall.

Not other electrical near by...nothing!


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post #6 of 36 Old 05-02-2012, 07:46 AM
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I got nothin' on this one! Dayum... Is there a resonance of some sort on your platform? Do the subs have a hum that isnt as audible that would possibly be vibrating the platform and coming through the mids?

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post #7 of 36 Old 05-02-2012, 08:26 AM
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I'm assuming your speakers aren't "self" powered, correct. They are passive.

Start throwing some of your breakers and see if the interference "hummmmm" is being generated from AC. It's entirely possible that it could be an FM signal as well, but I'd try the breakers first.

EDIT: You ask mentioned the water pipe. It's probable there's a ground issue there too.


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post #8 of 36 Old 05-02-2012, 08:57 AM
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Quote:
Originally Posted by garciab View Post

... If they are humming, I'd leave the house and run like hell!...

Can't ....

Stop...

Laughing!!
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post #9 of 36 Old 05-02-2012, 09:20 AM
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Remove the speakers from the room. If you still hear the noise coming from them, call a priest. If you still hear the noise in the room, it was never the speakers. If you no longer hear the noise, you must have a large motor (like an AC fan) right behind the wall.
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post #10 of 36 Old 05-02-2012, 11:10 AM
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Strange indeed...as Bill said, you must have some major source of em in the area. And I assume this just started, or are the speakers new to the room? It's gonna take some experiments to find the source, and even more to see if there's a cure. But do keep us posted as you go. I'd start by removing the midrange driver, disconnect it, check for hum with it free standing, then checking for voltage on the terminals.

bg
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post #11 of 36 Old 05-02-2012, 11:51 AM - Thread Starter
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Quote:
Originally Posted by garciab View Post

Strange indeed...as Bill said, you must have some major source of em in the area. And I assume this just started, or are the speakers new to the room? It's gonna take some experiments to find the source, and even more to see if there's a cure. But do keep us posted as you go. I'd start by removing the midrange driver, disconnect it, check for hum with it free standing, then checking for voltage on the terminals.

Funny you say that...

Had a friend come over to try and make logic of this...we can't
Anyways...
Took the speaker out of the room and NO HUM
Put left speaker on the right side and it hums.
Took 2 tower speakers and placed it same place and they ALL hum!!!
There is something weird about this corner.

A little info about this right corner.
In the back of the right side wall and the front wall is earth. That's right earth! In the back of these 2 foundation walls is front yard and balcony and driveway.
There are NO fans of any kind. The closest electrical is the street light pole which is about 100ft away.

On the floor above that right corner, (Room upstairs) I have a PC and speakers connected and an aquarium.

Don't forget! I completely shut-off my main breaker and the speaker still hums!

Now my biggest concern is to find the hum that's on my subs as that is driving me CRAZY!!!!

BTW I've tried grounding the water pipe and nothing changed.
Both my friend and I are baffled! I have no clue where it's coming from and I work in the electrical world!


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8x subs: 4x FTW21's and 4x SI18's
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post #12 of 36 Old 05-02-2012, 12:00 PM
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Try grounding each of your components' chassis to each other in your signal chain with a piece of wire. I had a nasty hum in my setup, and that was all it needed to clear up my ground loop.

Sam Carter
Custom Sounds NW
Custom enclosures, service and installation of mobile electronics and home theater equipment.
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post #13 of 36 Old 05-02-2012, 12:26 PM
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You mentioned what's upstairs and what's outside the walls but not what's underneath. There may be some buried power lines running nearby.

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post #14 of 36 Old 05-02-2012, 01:17 PM
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You mentioned what's upstairs and what's outside the walls but not what's underneath. There may be some buried power lines running nearby.

That's a possibility, call Dig Safe to find out.

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post #15 of 36 Old 05-02-2012, 01:17 PM
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i would get some 6 ft copper ground rods and 10ga copper wire. pound the rods into the ground near each speaker until only an inch or so sticks out, then use the 10ga wire to connect the rods to the negative terminal on each speaker.

the friction caused by pounding the rod through concrete and earth will created a quad-fluxed parabolic magnetic field that should protect each speaker from not only each other, but whatever universal RF emittance diodes may be present in your room's atmosphere.

report back after you've done this.
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post #16 of 36 Old 05-02-2012, 01:28 PM
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Quote:
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quad-fluxed parabolic magnetic field

I need to get me one of those! Sounds absolutely awesome!
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post #17 of 36 Old 05-02-2012, 01:39 PM
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i would get some 6 ft copper ground rods and 10ga copper wire. pound the rods into the ground near each speaker until only an inch or so sticks out, then use the 10ga wire to connect the rods to the negative terminal on each speaker.

the friction caused by pounding the rod through concrete and earth will created a quad-fluxed parabolic magnetic field that should protect each speaker from not only each other, but whatever universal RF emittance diodes may be present in your room's atmosphere.

report back after you've done this.

Mind = blown

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post #18 of 36 Old 05-02-2012, 01:39 PM
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If you have access to an oscilloscope, see what you are getting at the speaker terminals. If the cone is moving, there has to be a signal. The shape and frequency of that signal might offer some clues.

I'm not into "thumbs upping" or "liking". Don't take it personally. Just assume that I found your post helpful. Unless it wasn't.
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post #19 of 36 Old 05-02-2012, 01:43 PM
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Thinking out loud: what else could cause this?

A vibrating floor? Does it still hum if you pick up the speaker?

Vibrating air? It seems like you would hear this if it was present, but maybe it is right at a resonant freq of the driver. Try covering vents, opening/closing doors, etc.

-Max
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post #20 of 36 Old 05-02-2012, 09:14 PM
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try surrounding the speaker or at least the humming drivers with a piece of sheet metal. That should shield it from any kind of interference.

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post #21 of 36 Old 05-02-2012, 09:34 PM
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Quote:
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try surrounding the speaker or at least the humming drivers with a piece of sheet metal. That should shield it from any kind of interference.

An impromptu faraday cage/shield? I like the way you think...
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post #22 of 36 Old 05-02-2012, 09:44 PM
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i would like to see a video of the speakers moving not plugged in.
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post #23 of 36 Old 05-03-2012, 05:42 AM
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An impromptu faraday cage/shield? I like the way you think...

An EMI source strong enough to do what the OP claims isn't going to be stopped by a bit of sheet metal. Perhaps 1/4" thick mu-metal, which would be a considerable investment. Finding the cause is the better option.
As to if this is happening, if the cone is moving there will be an induced voltage that can be read on the input terminals with an AC volt meter/DMM.

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post #24 of 36 Old 05-03-2012, 08:02 AM
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Mind = blown

hehe.. i like to bring some humor to these otherwise dry and boring discussion topics.
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post #25 of 36 Old 05-03-2012, 08:04 AM
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I admire and advocate humor in most cases. I feel often enough some of mine gets lost in translation, but regardless I enjoy a good laugh just about anytime. Ive gotten some great ROFL's off this site over the last year.

(European models do not accept banana plugs.)

 

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post #26 of 36 Old 05-03-2012, 08:28 AM
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Quote:
Originally Posted by thaddeussmith View Post

i would get some 6 ft copper ground rods and 10ga copper wire. pound the rods into the ground near each speaker until only an inch or so sticks out, then use the 10ga wire to connect the rods to the negative terminal on each speaker.

the friction caused by pounding the rod through concrete and earth will created a quad-fluxed parabolic magnetic field that should protect each speaker from not only each other, but whatever universal RF emittance diodes may be present in your room's atmosphere.

report back after you've done this.

DAMN! If I just had my Flux Capacitor working!

Seriously, the only reason that driver (mid range) is "humming" is because that's the frequency the interference is "at". It's not your driver - you solved this by trying the other speaker in that area. I completely agree that it's probably buried power outside your home. Call your local utility company for a free test of what's buried out there. It's probably not under your house, but beside it (just outside the wall that your speaker is on). I also agree with Bill about the metal shielding. It's just a "band aide" to put over the problem. You should really look into what's causing the problem. Which brings me to my earlier post. Throwing the breakers most likely won't solve your problem because I now believe it's the power outside your home, not inside.


Good luck,
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post #27 of 36 Old 05-03-2012, 08:46 AM - Thread Starter
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Regarding having a Power line outside my home.

I know for a fact that there's no power lines anywhere near my house.
I know because about 10 years ago, we changed the the main waste drain from my house (it's right under my right speaker) to the city's drain and replaced it with ABS. it was a total of about 90 ft.
Looking at the corner of my room. the drain pipe goes on a 45 degree angle to the city's pipe.

There is NO power lines anywhere near outside of my home.

You cannot hear it unless you stick your ear against the mid range speaker (no the speaker is not moving)
I might borrow my friends DB meter and take pictures.

Right now I need to find the source of my hum and eliminate it from my subs.
This is what is driving me nuts for now.


I did not have this hum before...here's what I have also found out.
When source is PCM MULTI, I have WAY more hum.
When source is other then PCM MULTI, hum almost disappears.

Also when I connect my sub to sub1 it is twice as loud as the sub2 output.
I'm thinking something is wrong with my HK 7550HD receiver.

Thanks all for your suggestions BTW.

Regards,


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post #28 of 36 Old 05-03-2012, 09:03 AM
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If the EM interference is enough to get sound out of a speaker, it is certainly strong enough to inject interference into line level cables. The cause for both could be the same.
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post #29 of 36 Old 05-03-2012, 09:16 AM
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so what was added to your setup just prior to the hum starting? and recent maintenance work around or in your house? any major storms recently?
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post #30 of 36 Old 05-03-2012, 09:19 AM
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Quote:
Originally Posted by garciab View Post

If they are humming, I'd leave the house and run like hell! Seriously, move them to another location and see what happens.

Perhaps THE BEST advice I've yet to read on this forum..... Classic and signature worthy
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