[SonicDawg]

Recently I purchased a vintage Kenwood integrated amp, and I tried the Koss phones out of the phone output of the amp. But stupidly I forgot to turn down the dial, and for a split second of LOUD( I torn off the headphones cringing) music going through the phones, I played them again with the right volume and there's buzzing noise whenever strong low frequency notes are played (e.g. double bass). I RMAed them to Koss claiming that their drivers were blown. Few weeks later they returned with new cable (which I really appreciate of Koss), but the buzzing still persists. Anyone has any idea how to remedy this problem? I don't want to do the RMA again...

 

[b0dhi]

First thing to check is whether the loud music dislodged a hair stuck inside the driver. Blow into it at various angles to see if it comes out.

 

[nc8000]

I get the same thing with my A250's on occasion. The sound is a bit like standing under overhead high voltage electric cables on a damp day. The sound is not loud and can only be heard during quite passages but it's deffinately there

 

[kramer5150]

They are pretty cheaply made IMHO so any number of things could have managed to work their way loose.


I doubt its anything in the headband, but that deserves a look over anyways.

They are easy to take apart.

Carefully remove the earpad cushions. They are an elastic-vinyl, stretch-over type of design. Carefully peel back each corner of the foam driver screen to expose the 4 driver-plate attachment screws. Remove the screws.

The driver baffle plates should just fall out, once the screws are removed.

Carefully inspect the internals for any debris or loose parts. Make sure the driver is securely glued to the baffle, a little hot melt glue can be used to secure the driver if it has managed to loosen.

Inspect the perforated mesh grilles on the earcups. They should be securely heat-staked in place. Mine managed to fall apart. I had to re-glue them with some epoxy.

Other than that, theres not much else you can do. The divers have been out of production for over a decade. Theoretically you could have caused the coils to separate from the diaphragm, I don't think thats a DIY fix.

 

[jinx20001]

yep certainly sounds like driver damage

 

[jinx20001]

i must say ive been following a few threads that kramer has contributed to and im very impressed by his thorough explanation's handy guy to have around here on head fi

 

[Nagasaki_Kid]

coil seperating from driver I hate when that happens I had 2 mac/5 and a td/61 do that on me. after that I learnt to listen at lower olumes

 

[SonicDawg]

Thanks for all the info. I will try to take about the earcup carefully for inspection. I will report back when I find something interesting.

 

[SonicDawg]

Well, here's the update after an afternoon of tempering and tinkering:

First, I took off the driver forms. Boy, they were sagging! They were caved in from my ears that the drivers also suffered the same problem of creasing. They (Koss) literally did not even bother to stretch the forms at all when taping them in

Fortunately I have a solder sucker, with which I carefully sucked the drivers back in shape. Now that the forms were in a crumbled and torn state, I replaced them with some speaker cloth. I hot-glued them onto the pads' interior and cut them into the right sizes befitting the earcups. Everything well done, they fit perfectly and much less abrasive to the tips of my ears!

Best thing of this "mod", is that:

1) The buzzes are gone.

2) The frequency response of the phones seem to "mellow" out: more prominent bass, and less strigent trebles.

I am pleasantly surprised by this mod that I pulled off in less than 20 mins. The Koss are sounding a lot less harsh but smoother! Not to mention the increased warmth and bass quantity! Last but not least, the buzzing problem is resolved. But just what the Koss service was thinking...

 

[facelvega]

did you happen to take any pictures of the process, by any chance?

 

[SonicDawg]

Not really. But I can probably take some pictures of the innards and mods later