Stray Hum in Midrange.

[RT FAN]

Yesterday morning as I walked by my Chorus II's I heard a strange hum coming from my right speaker. It was coming from the midrange & sounded like a ground loop or something similiar. It was confined to 1 speaker only & just from the mid. No components were on, I disconnected the speaker cable yet the sound was still there. I turned off my Belkin power center, which is always on, no change. I am baffled as to what this is, I played some music which lessened the hum, I also gave the speaker the obligatory rap on the side. So what would cause the Midrange to give off a hum with no compnents on, & the speaker wire disconnected? The hum is around half of what it was yesterday morning, but still noticeable, any suggestions, like pulling the mid & checking the connections, etc would be appreciated. Thanks.

[tube fanatic]

So you're saying that the hum was present with the leads disconnected from the speaker? Sounds like something is inducing either a magnetic or electrical field into the speaker voice coil or crossover. Did you try moving the speaker a few feet away from its usual position, and did that make any difference? Did you try placing the speaker from the other channel in the same location to determine if it too had any hum? What's on the other side of the wall from the speaker? Any AC wiring running in the wall directly behind the speaker? Did you try shorting the terminals on the back of the speaker with a short jumper, and if so, did it eliminate the hum?

[Don Richard]

This was discussed a couple of years ago:

http://community.klipsch.com/forums/p/126972/1285216.aspx#1285216

It surprised me that a speaker could be so sensitive that it could pick up EMI so easily.

[LarryC]

My bet is on the crossover coils picking it up much more than the voice coils. The speaker's high efficiency then magnifies it. Tube fanatic's post lays out good diagnostic and therapeutic steps. Hopefully you can move the speaker far enough away if that's what it takes.

I'll bet your other drivers may also have the hum, just not as loud. Put your ear next to their output to see.

Oh, yes, check out dimmer switches, even if on other circuits! Especially if you have transformer-based halogen lights. If you do, take off the switch face plate, look at the flange on the edge of the switch, and see if it says it's for "incandescent" lights. It MUST be "for electronic transformer loads only" if that's what you have! Not all lighting stores are up on this.

[RT FAN]

Thanks for the replies, some helpful info here.

Tube Fanatic: The first thing I did was disconnect the speaker wire, then made sure all the components were off. I then turned off the power center that everything is plugged into. The hum was still very obvious. I have been in the house for 13 years & this was the first noticeable occurence. My LCD tv is fairly close, as is the Dish receiver, perhaps I will isolate those pieces on a seperate power center as they are not plugged into the PC that has my 2 channel rig. The speakers are pulled away from the wall to allow the passive radiator room to breath, & there is a closet on the other side of the wall. My thermostat is 6-8 feet away from the speaker, I will check the wiring, perhaps there is a stray wire.

Don Richards: thanks for the link to the previous post, it gives me some stuff to work on this weekend.

LarryC: I checked all of the drivers closely & it was limited to the one midrange. I also have an Academy & a pair of KG 1.5's hooked up to the system & there was no interference coming from any of those speakers. The Crossover is a relatively new Crites one, which has worked perfectly since I dropped it in. I couldn't do too much with it this weekend as it is leaf raking time here in the northeast, but I will have some time to devote to it this Saturday. I will post any changes regarding the interference. Thanks again guys, Stephen.

[pzannucci]

I had speakers with external crossovers and if the inductor/choke was too close to a power supply, such as a transformer or other high voltage source, there would be a fair amount of hum. Shut off the power to the amp, still hum... thought I was crazy when I disconnected the speaker cables and it was still there.

The coils appear to pick up the stray EMI/EMF and the closer the crossover is to the source (transformers from a power conditioner), the higher the output.

[LarryC]

LarryC: I checked all of the drivers closely & it was limited to the one midrange.

Thanks, Stephen. In my case, a hum on one side (the other side wasn't affected) came from the outside electrical service entrance on the exterior wall immediately outside where that K-horn sat. While the hum seemed to come only from the bass horn, I could hear very faint higher freq components from the mid-horn and even the tweeter as well. I didn't notice it until I got very close to the horn mouths of those two. Hum only from one driver seems unlikely since EMI has to impact the entire crossover.

I was surprised how low-level that hum was, given how close the K-horn was to the outside entry.

And don't forget the dimmer switch if you have transformer-based trak lights. It took me a few years to find that one out! Putting in the right dimmer switch took care of that combo hum and buzz in a flash. That problem mostly affected the other K-horn from the hum, BTW.

Larry

[tube fanatic]

Interesting case! The first thing I would try if I had such a problem is to shut the main breaker at the entrance panel to see if the hum goes away. If it does, then turn it back on, but shut all the breakers and then turn them back on one at a time to isolate the individual circuit which may be causing the problem. That said, it's entirely possible that the source isn't even in your house! Having spent decades hanging out with insane ham operators who are always blamed for any kind of interference, I've seen cases where rain gutters were picking up a field from a neighboring house and coupling the EMI/RFI into the wiring of the house with the problem (especially if Romex is used as opposed to BX cable). Things like doorbell transformers, especially if they're very old, can cause all kinds of weird effects such as what you're describing (and it could be blocks away), the wiring of the house with the transformer in question acting as an antenna. So, you'll need to do a bit of detective work and I'm sure you'll figure it out. But, it would be worth putting your other speaker in exactly the same location to note if it exhibits the same behavior.

Maynard

[noway1]

...But, it would be worth putting your other speaker in exactly the same location to note if it exhibits the same behavior.

Maynard

+1. That's what I would try first.

[RT FAN]

...But, it would be worth putting your other speaker in exactly the same location to note if it exhibits the same behavior.

Maynard

+1. That's what I would try first.

I'll get the handtruck!

[mustang guy]

Is there a leprichan inside the speaker that is humming because he doesn't know the words?

[RT FAN]

So I disconnected the TV, Dish receiver & light in the bookcase from the outlet nearest my speaker. I then plugged them into a separate Power Center which I have connected to an outlet further away from the speaker. No change, still got the hum. I did however notice that when I turned on the halogen track lights in the kitchen the hum intensified, those light are on a dimmer switch. I have had those lights for 4 or 5 years with no problem & they were installed by an electrician. I will remove the faceplate on the dimmer switch & check to see if they are set to "electronic transformer loads only" as Larry C suggested. Could it be that the track lighting, which consists of 4 rows of 4 small spotlights, is drawing too much juice for the circuit thus causing the hum? I have noticed the wall plate is warm to the touch if the track lights have been on for a while. Thanks again, guys.

[djk]

Phase-controlled light-dimmers have problems with asymmetry in their triacs firing in the 4th quadrant, this can cause various problems

Does it hum/buzz with the track-lights turned off?

If so, you may want to install a small Variac instead of using a dimmer.

If you live in a large multi-unit dwelling there may be a problem with power-line harmonics causing excessive current in the neutral that is inductively coupling into the autoformer on your Klipsch.

If you move the speaker next to the other does it clear up?

[LarryC]

faceplate on the dimmer switch & check to see if they are set to "electronic transformer loads only" as Larry C suggested

That would be OK; an incompatible kind of switch would be "incandescent only." DJK's suggestion to switch off the track lights and see if the hum goes away is what I did.

[RT FAN]

With the lights off the hum is still present just much lower, when the lights are on the hum is more noticable. When music is playing you cannot hear the hum at all. This is a single family house. I haven't had the chance to move the speaker as the living room has been run over by Christmas decorations.