LsiM 705 Buzzing Sound

soundy

I noted a persistent buzzing sound that seems to come from the midrange woofer in my LsiM 705. I had a whole set of LsiM's for a few years now. The buzz has been there probably from the beginning. It is much more obvious with solo piano, at higher volume, but only seems to associate with certain keys & notes. Taking the grille off, I can feel the woofer vibrate strongly with the buzzing sound. Both left & right speakers do this. At low volume, it isn't as obvious.

I have searched under this issue extensively. While I saw many reports of similar issues of various speakers, some with LsiM, it isn't clear to me whether something is physically broken or simply LsiM does this from the get-go, by design.

Background: The speakers were bought new from Polk a few years ago (maybe still under warranty), powered by Parasound 5250 from front and side speakers, the rest by and via yamaha Rx-a2014.

Anybody has any suggestion on the cause and what to do about it?

pitdogg2

ground loop maybe. Do you have cable coming in anywhere in the chain?

soundy

I have an antenna cable signal coming into the receiver. But the buzzing noise with the solo pianos were heard when I played high-def good quality FLAC through the computer. The noise doesn't sound like ground loop humming noise. It's more like a mix of unclear buzzing, on and off, as you may have heard when certain piano notes are played. It happens more when certain keys in the kHz range (maybe) are pressed real hard ... I wish somehow I can describe it more accurately. Thanks!

tonyb

Is the buzzing sound there if your watching a movie or playing a cd ?

pitdogg2

If it comes and goes I'd look for something that is on the same circuit. I had a microwave and a fridge that drove me nuts trying to find the cause of my buzzing. Dirty line noise can affect certain frequency ranges or it can be there all the time. I ended up running a dedicated 20 amp outlet to my audio gear. Cheap thing is to buy some cheater ground adapters they are like .80cents throw a couple on your plugs to see if it does anything.

just something to think about I'm not saying this is what it is, but you do need to think outside the box sometimes.

DaveHo

Sounds like a defective driver. One of the mids in the first 705's Polk shipped me had a buzz like you are describing which was most evident on piano & keyboard notes.

soundy

Thanks for all your input. I am inclined to think this indicates a bad driver, for both speakers. I'm disheartened because I just realized this problem in the last week or two. I did a test with a known reference WAVE sound file and confirmed the presence of the buzzing noise not from bad music recording.

I haven't tested other feeding source, like CD player or playstation. I will try it. There are some occasional noise (with the sss .. sounds for example) when watching movies. For the past few years, I thought all those were from bad recordings or room treatment. I have some better than average treatments: sound panels at reflection points. The buzzing noise however is very clear at high volume with the piano pieces when I put my ears close to the speakers (1-2 ft). Once my mind got into it, it is very bothering ...

Well, I wish I could do more testing, much earlier.

DarqueKnight

One of the woofers on one of my 705s was bad. It made a buzzing sound on some bass notes.

pitdogg2

Call polk customer service they'll take care of you.