I'm getting a hissing noise from my speakers when the dial on the control pod is in the "off position" (the on/off switch on the subwoofer is still "on").  I understand that the speakers will hiss a little when they are on, but they shouldn't hiss when they're off, should they?  Has anyone else experienced this?  Are my speakers malfunctioning?  The hiss goes away when I unplug the DIN plug, but is unchanged when I unplug any of the other inputs/outputs.

Yes same here. I have got my system a week ago and there are a very noticeable (and anoying) hiss coming from the speakers even with the volume knob in the off position (and the line in not connected) which means the hiss is produced internally in the amp.

 My previous budget noname 2.1 system where dead silent. Im not sure this is what to expect from this price range of speakers? Are they faulty?

/Thomas in Sweden

Just got the same GMX A 2.1 speakers myself.  I too have the hissing sound problem.  I've tried other speakers in a comparison, looked at the trouble shooting and did every thing I could with the cables, the sound volume, etc to address it.  No luck, the hiss is definitely being produced by the speakers themselves, regardless of whether they're hooked up, turned on, or not.  The cultprit is the tweeter, must be receiving some signal from the sub-woofer amplifier. 

For me, it's tragic.  I really like these speakers, but I can't stand the white noise.  I have a new aluminum IMac that produces almost no fan noise, so the computer won't mask the sound of the hissing from the speakers.  I suppose I'll try to send them back.  I looked at the forum and found a lot of complaints about the noise - I guess I should have listened more carefully when I tried them out at a local store.  I'm very fortunate to have a very quiet house and office where the speakers are.  Some folks noted that they don't hear it, but I think it's likely still there for keen listeners in quiet locations.

Bottom line - these speakers really do sound great when they have a signal, but the hissing is constant - listening to quiet jazz, I could hear the hiss over and under the piano.  I put my headphones on - no hissing on the source recording - it's the speakers.

This might get better exposure in the GMX sub-forum...

http://forums.klipsch.com/forums/15.aspx 

I'm also getting a loud hissing noise on my ProMedia GMX 2.1 speakers.

It's audible from 6 feet away. My current set of speakers in question is a replacement for another set of ProMedia GMX 2.1 speakers which had exactly the same problem. I live in Denmark and had to order the speakers from Sweden due to no Danish retailers. I don't even know if the Swedish e-store will give me a full cash refund for these utterly useless speakers - it's so frustrating!

 And here's the irony: I replaced my old trusty Cambridge Soundworks speakers for this Klipsch system partially due to the fact that my old speakers had developed a slight hissing noise. While this noise was annoying, it was at most one tenth as loud as that of the Klipsch system.

it sounds to me like a software/hardware problem. have you tried listening to the speakers from another source like an MP3 player to see if it still hisses? to me it sounds pretty strange that 3 differant sets of speakers all had a hiss, as far as the Klipsch being worse than the Cambridge, maybe it was a frequency signal that the cambridge were not sensitive enough for, Klipsch have a very wide frequency range, which is why they sound as good as they do. Don't give up on Klipsch, I have several sets of Klipsch speakers/systems including the GMX Series and they all sound great in just about anything I play them through.

The problem is that the hiss is consistent without any source connected or even if the volume knob is in the off possition.

There IS a problem with these speakers or at least a large batch. check google on "klipsch hiss promedia"...  http://www.google.com/search?hl=en&q=klipsch+hiss+promedia&btnG=Google+Search

"2) Speaker hiss -- this is a well-known problem with most Klipsch speakers released sometime after the 2nd revision of the ProMedia 2.1 series. The speakers, when turned on at lowest volume (and without anything plugged into them as an input device), emit a very loud hissing noise. This haunts the GMX series as well. The problem is caused by Klipsch increasing the internal gain (amplification) of the speakers (thus making them louder). Since there's no way to adjust the gain, you end up with speakers requiring you to turn them completely off when not in use. Otherwise, white noise constantly bombards your ears."

"Pros: plays loud, sounds good when playing music Cons: hiss when no music is present is unacceptable"

 "Cons: nothing major. a slight hissing sound sound when there's nothing playing,  "

  "Also, both sets tended to hiss a bit when idle."

"Satellites hiss loudly when idle. Satellites prod..."

Yeah, i suppose i should read everything before posting, I thought you were talking about the ProMedia's, I did not realize we were talking about the GMX, all I have for the GMX is (2) of the GMX 5.1 systems, but both of them sound find, but then again, I use the digital inputs on them, I don't think I have ever even tried the analog inputs. do those systems have digital inputs? But yeah, after reading this post again, i see that you and others have the same problem, plus Google searching revealed the same, tisk tisk Klipsch. I love Klipsch, but I sure hope they came up with some kind of fix for you GMX 2.1 people. Amy Unger, if you read this, help these people out.