Rattle in CMT-340

[The Onion Man]

Hi everybody,


I have been the happy owner of a set of CMT-340s (center and mains) for just over a year now. Recently, though, one of the mains developed a nasty rattle. At first it seemed to get better after just re-securing the front cover, but after listening closely I noticed that there was definitely still a rattle (but not as bad) coming from the lower woofer. I switched it with the other main in my 3.1 system and sure enough, the problem stayed with the same speaker, so I am pretty confident that I can rule out anything wrong with the cables or the receiver.

I'm still very new to A/V stuff and am not sure what to do. I didn't want to force anything but I did notice that if I lightly touched the dome of the affected woofer, the rattle seems to go away, though it comes back almost immediately. Might this be a dust problem? An electronics problem? How to tell? Am I maybe going to have to make a warranty claim?


Thanks in advance for all your help!

[Mag_Neato]

Do you have kids? If so is it possible someone may have dropped something in the port and it could be stuck to the drivers magnet and is then vibrating against the woofer? I would remove the woofer and check that first.

[The Onion Man]

No kids but I can check the port. How do I remove the woofer (besides "carefully")?

[Mag_Neato]

Just remove the 4 screws around the mounting flange. If the woofer sticks put your hand over it and face the speaker downward and it should fall into your hand.

[davef]

Hi everybody,


I have been the happy owner of a set of CMT-340s (center and mains) for just over a year now. Recently, though, one of the mains developed a nasty rattle. At first it seemed to get better after just re-securing the front cover, but after listening closely I noticed that there was definitely still a rattle (but not as bad) coming from the lower woofer. I switched it with the other main in my 3.1 system and sure enough, the problem stayed with the same speaker, so I am pretty confident that I can rule out anything wrong with the cables or the receiver.

I'm still very new to A/V stuff and am not sure what to do. I didn't want to force anything but I did notice that if I lightly touched the dome of the affected woofer, the rattle seems to go away, though it comes back almost immediately. Might this be a dust problem? An electronics problem? How to tell? Am I maybe going to have to make a warranty claim?


Thanks in advance for all your help!

If you haven't been able to resolve the issue from the suggestions here, simply give us a call at the office :)

[The Onion Man]

So I unscrewed the woofer and took a look inside. When I took out the speaker, the central "rocket tip" shaped thing (magnet?) fell out! Just to be sure I lightly touched the magnet up top and no, it was quite secure. Seems to be a glue failure of some kind.

[Mag_Neato]

So I unscrewed the woofer and took a look inside. When I took out the speaker, the central "rocket tip" shaped thing (magnet?) fell out! Just to be sure I lightly touched the magnet up top and no, it was quite secure. Seems to be a glue failure of some kind.

Sounds like it's time to invoke the 5-year warranty!

[davef]

Hi Onion...

I am a bit confused here. Your initial post was this:


So I unscrewed the woofer and took a look inside. There wasn't any obvious detritus, but it was fairly dusty, and after blowing lightly to clear the dust the problem seems to be resolved. I say "seems" because I want to make absolutely sure, but if the problem still exists it's not nearly as bad. So, probably dust.

Is there a good way to prevent dust from getting inside the port in the future?


You then changed it and mentioned that somehow the phase plug (the rocket shaped item) broke off the speaker assembly. Did you accidentally drop the woofer or speaker? It would take a very considerable amount of force to actually break the phase plug off the woofer. That said, please send me a few pics of the woofer.

Thanks in advance!

[The Onion Man]

Hi Dave,


Sorry about the confusion. When I initially went to remove the woofer from the case, the phase plug actually fell out. But it happened so smoothly that I thought it must have been designed to do that, and I noticed small grooves on it, which made me think that it screwed into place. (As I said, I am very ignorant about all of this stuff). That's when I made the first post you quoted.

After trying and failing to screw the phase plug back in, I noticed that it doesn't actually screw in at all, and also noticed some whitish residue that seemed to be from the glue. I gently tugged on the other phase plug but, as you indicate, it is quite secure. So I figured that the problem must be with the adhesive used to secure the phase plug to the woofer, and made the second post, the one that's still up.

Just to be clear, I never dropped the speaker or anything. And I actually already sent some photos to Dina at customer service--she's extremely helpful, thanks so much!--and she is sending me a replacement woofer tomorrow. But for future reference, and whoever might find this post someday, I will attach the photos that I sent to Dina here. You will see the speaker housing is undamaged, the phase plug in my hand, and a closeup where you can see the whitish residue that I presume to be from the adhesive.


http://i.imgur.com/aGytQjC.jpg

http://i.imgur.com/zPcP4Xh.jpg

http://i.imgur.com/W1Usvo7.jpg

[davef]

Hi Dave,


Sorry about the confusion. When I initially went to remove the woofer from the case, the phase plug actually fell out. But it happened so smoothly that I thought it must have been designed to do that, and I noticed small grooves on it, which made me think that it screwed into place. (As I said, I am very ignorant about all of this stuff). That's when I made the first post you quoted.

After trying and failing to screw the phase plug back in, I noticed that it doesn't actually screw in at all, and also noticed some whitish residue that seemed to be from the glue. I gently tugged on the other phase plug but, as you indicate, it is quite secure. So I figured that the problem must be with the adhesive used to secure the phase plug to the woofer, and made the second post, the one that's still up.

Just to be clear, I never dropped the speaker or anything. And I actually already sent some photos to Dina at customer service--she's extremely helpful, thanks so much!--and she is sending me a replacement woofer tomorrow. But for future reference, and whoever might find this post someday, I will attach the photos that I sent to Dina here. You will see the speaker housing is undamaged, the phase plug in my hand, and a closeup where you can see the whitish residue that I presume to be from the adhesive.



Thanks for the clarification. I am not sure if I have ever seen that before - it looks like the bond between the pole piece and phase plug somehow failed. Dina gave me a bit more detail and she has arranged to send you a replacement woofer under warranty. You should have it soon.

Thanks again!