B&W dm4 speaker rattle, crackling noise at specific moments only?

[TrevorBarten]

So I know next to nothing about speakers. I have a pair of dm4s that I haven't looked at for years. Today I tried them and noticed that one of the speakers sounds kinda rattly at certain points. I also feel like the volume drops at times but I cannot confirm this. I also find it very hard to confirm the specific issue in general but I definitely think it doesn't sound quite right. Any clue what this could be ? I checked and all the screws are tight and the surface it's on is solid. I am planning on recapping both of these but I doubt that would resolve the rattling right?

 

[swechsler]

First step would be to figure out which driver is causing the rattling. You can do this with a frequency generator app on a smartphone hooked to your amp, and a toilet or paper towel roll tube to isolate each driver. Slowly increase the frequency until the rattle is constant. It should then be simple to figure out which driver is causing the issue. With that info we can proceed further.

 

[HamboneF18]

Or, you can just play music and put your ear to each driver. You’ll locate the noise.

Just 4 days ago I had a buzzing coming from one speaker (3-way). Played music. It was coming from the left woofer. I put my finger on the cone while music was playing. I found the buzzing. The woofer surround where it was glued to the basket rim had failed. Fixed it.

 

[TrevorBarten]

First step would be to figure out which driver is causing the rattling. You can do this with a frequency generator app on a smartphone hooked to your amp, and a toilet or paper towel roll tube to isolate each driver. Slowly increase the frequency until the rattle is constant. It should then be simple to figure out which driver is causing the issue. With that info we can proceed further.

Good tip, Couldnt locate it properly with just normal music playing. I'll try this asap and report my findings. I happen to have a pair of dm2 parts so I do have potential replacements.

 

[TrevorBarten]

Ok so I resolved the rattlinga s I noticed that the rubber ring on the woofer was loose in one spot. I did a temporary fix by using some electrical tape to hold it down and that fixes the issue so while I do some more research on how to properly repair that for now this will do. I have, however, ran into a different issue. I used my phone as a frequency generator and went through a sweep to diagnose the issue and I have noticed that for some frequencies (specifically around 500 hz but that is not the only frequency) the volume significantly drops on the same speaker that also has the woofer issue. Now that I know there is an issue I tried to do some sound tests with the amplifier in mono and noticed that that speaker is noticeably more bright than the other one. I do not know whether it's actually more bright or if it's just lacking midrange which honestly seems more likely considering the previously mentioned findings. Does anyone know what this could be? I checked around the rest of the rubber ring but did not notice any other spots where the adhesive has let loose. Could it be an issue with the filter? Seems easy enough to just replace the capacitors on those.

 

[HamboneF18]

A loose woofer surround can cause many problems. I doubt electrical tape can stand up to the mechanical forces of a woofer cone. I had phantom issues on my ‘65 AR speaker; the glue under the woofer surround that attaches it to the basket rim had begun failing. I wound up separating the entire surround and reglueing it. I used Gorilla Glue. All the phantom issues disappeared. I was getting dropouts, distortion, and a faint buzzing depending on the music.

 

[TrevorBarten]

A loose woofer surround can cause many problems. I doubt electrical tape can stand up to the mechanical forces of a woofer cone. I had phantom issues on my ‘65 AR speaker; the glue under the woofer surround that attaches it to the basket rim had begun failing. I wound up separating the entire surround and reglueing it. I used Gorilla Glue. All the phantom issues disappeared. I was getting dropouts, distortion, and a faint buzzing depending on the music.

How should I go about removing it?