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Something Really Odd Happening With Forte II's...


kevco
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Last night, I leaned down to plug in a lamp..while doing so, my head came close to the face of one of my Forte II's. I heard a buzzing sound coming from the speaker, but none of the amplification was powered up. I removed the grill and the sound was definately coming from only the mid-range driver. On inspection, the other speaker (8 feet away) was doing the same. The stereo has not been used in three days. I disconnected the speaker wires and shut off power to my amps...the noise continued. I pulled plugs throughout the house, wall warts, space heaters, all off. I even went so far as to shut off the main breaker to the house...the noise continues through BOTH mid-range drivers, and is still happening this morning! I'm thinking I've got some kind of radio frequency or electromagnetic interference happening or perhaps static electricity (the air is very dry and if I pet my cat, he gets zapped, much to his dismay). I am not near any radio towers, high tension lines, sizeable transformers or cell phone antennas...Any thoughts here would be greatly appreciated. I have had no trouble driving these speakers with less than 2 watts of single-ended triode power, so I figure the amount of juice to cause those drivers to emit a buzz from 6-8 inches away is pretty miniscule, but it definately never happened before as my head has been in that air space plenty of times!

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This reminds me of an interference case I helped solve many years ago with a ham operator buddy. I suggest you try moving one of the speakers (with cables disconnected, and the main breaker of your house turned off) to another location as many feet away from its usual spot as possible (even take it outside if feasible). If the buzz changes (either increasing or decreasing), I'd start looking at possible causes coming from a neighbor's house, or powerlines/telephone lines. A number of things come to mind: 1) someone can have a bad bell transformer, light dimmer, fish tank heater, etc, which is emitting all kinds of hash which is being literally transmitted by their house wiring (assuming that it's Romex, and not BX cable); 2) a possible bad connection going to any kind of antenna (do you by chance have a TV or other antenna at your house?); 3) do you get any kind of interference on a portable AM radio (you may need to tune the entire band to find it, if it's there)? If so, take the radio for a walk around the neighborhood. Doing so may help you to isolate the cause. If there are overhead powerlines, there could be leakage around an insulator or at a transformer. Believe it or not, even metal rain gutters can cause interference by radiating any kind of "signal" to which they are exposed. The wiring inside the speakers can easily act as an antenna which is picking up such interference. I'm anxious to hear of your results. Please post again!

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The neighborhood is 60-odd years old, the houses close together, the power transmitted atop short, rickety poles, but they're about 70 feet from the speakers with a brick house in-between, yes it could be generated anywhere. My home has been mostly rewired with Romex, but God only knows what's hiding in my neighbors walls! I have no antennas, so that can be ruled out. I'm going to try the AM radio trick as soon as the rain stops and see what happens. Thanks for the idea, Tube Fanatic! Oh, and the lamp stays..it wasn't plugged-in in the first place.

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Sounds like an X-File episode, too strange. Why don't you try something simple first. Wrap the mid drivers 100% in tin foil and then use an insulated wire with a small alligator clip at each end to attach the tinfoil wrap to the speakers negative (ground terminal. If that fails to work you could always try adding a series resistor or even a resistor and cap to filter out the noise. Might be worth a try as this is RF pick up so a shield ought to work and this would be way cheaper and less intrusive than power line conditioners for your gear. Good luck buddy.

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Might be worth a try as this is RF pick up so a shield ought to work and this would be way cheaper and less intrusive than power line conditioners for your gear.

I think his speaker wires are unhooked and noise still persists. I don't think a shielding on any wire will work. It is likely being picked up by the crossover or drivers themself (internal to the speaker).

A little scary that their is that much noise though hopefully it is just radio frequency or something, not a health hazzard.

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A Klipsch employee (possibly Trey Cannon) mentioned that they experienced that with many pairs of Forte IIs.

Same thing happened to me only my Forte IIs were in my wife's car being transported to a wedding reception to DJ the dance. Heard a buzzing from the back of the car and realized it was coming from my Forte IIs even though they weren't hooked up to anything.

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Any ham radio operators in your area? This is supposed to be a source of EMI.

I think you're right to look for EMI rather than RFI sources, but it can't hurt to try the aluminum foil idea.

What about other power coming into your house that's not affected by your mains switch? For example, power to telephones? I don't know how it works or if it's an EMI source, but land lines seem to be always powered even when household power has been knocked out.

Here's a source of EMI, but only when household power is on: halogen lights dimmed via transformers! I was finally told I had to use light switches marked "for halogen lights" and NOT "for incandescent lights." Odd, but switching the switches took care of most of a long-standing buzz in my speakers!

Good luck.

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sure the pick up could just as easily be at the criossover and it could also be wrapped as well as long as you used a plastic bag to insulate the foil from the components.Once the speakers are connected to the amp then there is a ground. You would want to insure that the components don't get too hot in the bag. Might be worth trying just to see if it makes for a fix. Weird science at work in his house. A guy does not need a microwave where he lives. Flash "Dead speaker designer invents free power source (also doubles as a mid range horn)" Best regards Moray James.

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rule out rats, biting at your woofers suspension system inside the fortes cabinets Confused

No rats thankfully. I haven't had time yet to remove the back covers to try the foil idea yet. A general search of AM band showed no sign of interference that could be linked to the buzzing of the drivers, but moving the speakers shows more noise the closer I get to my next door neighbors house! I guess it's time to knock on her door... I listened to two records last night while having dinner and sound isn't noticeably effected in any way. That's good. I must say that I am a bit concerned that my home is being bombarded with enough amplitude to cause this. I hope I am not exposed to anything that could harm me or my family. Anybody know how much juice is required to get those drivers to buzz loud enough to be heard when my head is 6-8 inches away?

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rule out rats, biting at your woofers suspension system inside the fortes cabinets Confused

No rats thankfully. I haven't had time yet to remove the back covers to try the foil idea yet. A general search of AM band showed no sign of interference that could be linked to the buzzing of the drivers, but moving the speakers shows more noise the closer I get to my next door neighbors house! I guess it's time to knock on her door... I listened to two records last night while having dinner and sound isn't noticeably effected in any way. That's good. I must say that I am a bit concerned that my home is being bombarded with enough amplitude to cause this. I hope I am not exposed to anything that could harm me or my family. Anybody know how much juice is required to get those drivers to buzz loud enough to be heard when my head is 6-8 inches away?

If you could get your neighbor to let you shut the main breaker for a few seconds you may have your answer. I'll be surprised if it doesn't turn out to be the bell xfmr, or a light dimmer, given the continuous nature of the buzz. I would not be concerned about being exposed to anything harmful. It takes very little radiated energy to cause what you describe.

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I haven't had time yet to remove the back covers to try the foil idea yet. A general search of AM band showed no sign of interference that could be linked to the buzzing of the drivers, but moving the speakers shows more noise the closer I get to my next door neighbors house!

Exhaust other possibilities before trying foil, since RFI seems very unlikely in the absence of electronics. Horns are very efficient and "magnify" base-level buzzes and hums that are picked up by crossover coils, making them audible. I wonder if the physical layout of the xovers affects the amount of EMI?

Is your neighbor's house detached from yours or at least not too close? Moving your speaks a short distance in comparison shouldn't make much difference. Perhaps you're moving them closer to a telephone transformer; doorbell transformers, for example, are sometimes tacked up just underneath the main floor.

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The neighbor hasn't been home, she's a nurse and works odd shifts. I think she also spends much of her free time at her boyfriends place. Her house is detached, but only about 16 feet from mine. My speakers are placed so that one is on the wall closest to her house and the other is is on the perpendicular wall facing the street. The stereo field bridges the corner between the two walls. Although both speakers are buzzing right now, the one closest to her home is twice as loud. If I switch them, whichever is closest to her house is louder. I am not aware that the buzzing has stopped since my first post.

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you can look to see if you have noise sources in your place such as halogen lamp transformers, mercury reed switches as used in thermostats waterbed heaters, compact floursents lamps could also make RF noise anything with a switching supply or old motors on a pump or furnace might be a source as could be loose make / break electrical connections. Any new cell towers in your area? Best of luck. Regards Moray James.

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The neighbor hasn't been home, she's a nurse and works odd shifts. I think she also spends much of her free time at her boyfriends place. Her house is detached, but only about 16 feet from mine. My speakers are placed so that one is on the wall closest to her house and the other is is on the perpendicular wall facing the street. The stereo field bridges the corner between the two walls. Although both speakers are buzzing right now, the one closest to her home is twice as loud. If I switch them, whichever is closest to her house is louder. I am not aware that the buzzing has stopped since my first post.

The fact that the speaker closest to the neighbor's house buzzes more loudly does suggest that something is getting radiated from over there. However, where does the powerline and telephone line attach to your house and hers? Do either of these run down the sides that face each other? If so, something could be happening from those. While waiting for the neighbor to be around, take a look at your metal rain gutters and try moving them around a bit, especially where any sections connect. Almost anything metallic can act as a detector (very much like a detector/diode in a radio) which will then radiate the energy. You already mentioned shutting your main breaker and still hearing the buzz, so that rules out anything in your house as being the cause. Can you take your AM radio and walk around the neighbor's house to see if anything is picked up there? If all of this fails to isolate a cause, you may want to contact a local ham radio club. Hams are very accustomed to tracking down all kinds of interference from different causes (particularly since they usually get blamed for it even when they are not on the air!), and are always willing to help out people in the community.

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