Subwoofer Rattling - SDX12

[Genesis Boy]

Hello.

A year ago I built a pair of 24" cube ported subwoofers using SDX12 drivers. They are powered by a Crown XLS2500 amp.
Just tonight, after listening to some music, I turned off all my speakers and left the subs on (they are usually the last things I turn off) but noticed the left one making a rattling sound. I tested it several times using a signal generator and a few songs, and it sounds to me that right past the cone is the source of the rattling.

It seems to be the spider, but I wouldn't know. I am very worried for my subwoofer driver as it was pretty expensive.. Can someone please let me know what is wrong and what I can do to fix it?
It's a little strange to me that only one of my subwoofers is having issues. Maybe an insect or spider crawled in through the port and went somewhere vital?

If you require my complete setup, let me know and I will oblige.

The following link is a picture of the subwoofer having this issue. http://imgur.com/OyRYGSO
(The green mark is just masking tape.)

 

[tyhjaarpa]

Do you have kids/pets that could put things inside from the ports? This would be first thing to check.

 

[Genesis Boy]

Do you have kids/pets that could put things inside from the ports? This would be first thing to check.

No kids (that I know of.. lol jk). I have cats, but the port is in the top right corner in the back (curved downwards) so I kind of doubt my cats could have managed to put something in it. Even at low volumes it still makes the rattling noise. I did a slow sweep of 20Hz-30Hz and it sounded like around the 25Hz tones was when the rattling occurred.

 

[tyhjaarpa]

No kids (that I know of.. lol jk). I have cats, but the port is in the top right corner in the back (curved downwards) so I kind of doubt my cats could have managed to put something in it. Even at low volumes it still makes the rattling noise. I did a slow sweep of 20Hz-30Hz and it sounded like around the 25Hz tones was when the rattling occurred.

Well I have even heard rodents to store seeds inside of subwoofers from the ports so I wouldn't rule cat out at all. It could be something else, but this one is pretty easy to check out.

 

[GO-NAD!]

I've had a couple of SDX 12 subwoofers in a PR configuration (Quartet12XC) for over 3 years now and they have been working perfectly - and I've had them punching out some pretty deep LFE at elevated volumes. Have you removed the driver to examine it and/or to have a look inside the enclosure?

 

[TLS Guy]

It sounds like a classic case of starting cone voice coil separation to me.

 

[Genesis Boy]

Well I have even heard rodents to store seeds inside of subwoofers from the ports so I wouldn't rule cat out at all. It could be something else, but this one is pretty easy to check out.

I have taken the port out and shone a bright inside to see if there's anything there. I didn't see anything but I noticed when I took the port out it stopped making the noise. I put the port back in and held it with my hand and it still didn't make the noise. I then screwed the port in and it still didn't make the noise, so I pushed the sub back (I had pulled it about 3" away from the wall and turned it 45 degrees for easy access to the port) and it started making the noise again.
I then pulled the sub back about half an inch and the noise seems to have stopped, but it will very rarely make the rattling.. It's very strange. It doesn't affect the bass at all, but I'm worried about continued use of this sub in fear that it will escalate into a more serious issue.

I've had a couple of SDX 12 subwoofers in a PR configuration (Quartet12XC) for over 3 years now and they have been working perfectly - and I've had them punching out some pretty deep LFE at elevated volumes. Have you removed the driver to examine it and/or to have a look inside the enclosure?

I have not removed the driver but I did remove the port (see my response in the previous paragraph). I do not want to remove the driver because I put a square piece of MDF between the magnet and the bottom of the enclosure (using foam lining where the MDF comes into contact with the magnet) so that the magnet isn't being suspended and thus crating extra strain on the baffle (which is 2 layers of 3/4" MDF), and also so the driver doesn't somehow warp under its own weight..

I hope this isn't the issue. I checked and found that it is a very tight fit. The piece of MDF under my other sub driver's magnet has fallen loose and is now lying flat on the inside of the enclosure but it doesn't cause any issues at all, doesn't vibrate or anything.

It sounds like a classic case of starting cone voice coil separation to me.

How can I check to be able to say for sure that this is the issue, and if it is, what can be done to fix it?




Thank you all for your replies thus far.

 

[MR.MAGOO]

ported subwoofers / speakers. Maybe a small dead carcass of a rattling set of bones. Sorry, couldn't resist.

 

[TLS Guy]

I have taken the port out and shone a bright inside to see if there's anything there. I didn't see anything but I noticed when I took the port out it stopped making the noise. I put the port back in and held it with my hand and it still didn't make the noise. I then screwed the port in and it still didn't make the noise, so I pushed the sub back (I had pulled it about 3" away from the wall and turned it 45 degrees for easy access to the port) and it started making the noise again.
I then pulled the sub back about half an inch and the noise seems to have stopped, but it will very rarely make the rattling.. It's very strange. It doesn't affect the bass at all, but I'm worried about continued use of this sub in fear that it will escalate into a more serious issue.



I have not removed the driver but I did remove the port (see my response in the previous paragraph). I do not want to remove the driver because I put a square piece of MDF between the magnet and the bottom of the enclosure (using foam lining where the MDF comes into contact with the magnet) so that the magnet isn't being suspended and thus crating extra strain on the baffle (which is 2 layers of 3/4" MDF), and also so the driver doesn't somehow warp under its own weight..

I hope this isn't the issue. I checked and found that it is a very tight fit. The piece of MDF under my other sub driver's magnet has fallen loose and is now lying flat on the inside of the enclosure but it doesn't cause any issues at all, doesn't vibrate or anything.



How can I check to be able to say for sure that this is the issue, and if it is, what can be done to fix it?

Thank you all for your replies thus far.

You seem to have a lot of issues.

Your driver could be vibrating against the MDF board. I think that was a bad plan. No driver worth having or cabinet will deform under the weight of the driver.

Next did you model this enclosure, especially vent velocity? I would highly doubt one round port is adequate for this driver, and this may well be port noise.

If the driver is separating then it has to be removed to see if you can create any movement between, the cone and VC. If there is separation then the driver needs reconing.

 

[Swerd]

I have taken the port out and shone a bright inside to see if there's anything there. I didn't see anything but I noticed when I took the port out it stopped making the noise. I put the port back in and held it with my hand and it still didn't make the noise. I then screwed the port in and it still didn't make the noise, so I pushed the sub back (I had pulled it about 3" away from the wall and turned it 45 degrees for easy access to the port) and it started making the noise again.
I then pulled the sub back about half an inch and the noise seems to have stopped, but it will very rarely make the rattling.. It's very strange. It doesn't affect the bass at all, but I'm worried about continued use of this sub in fear that it will escalate into a more serious issue.

It is possible that the noise you hear is caused by the port tube vibrating against the cabinet. Fixing that should be simple and inexpensive. Remove the port, and do one of three things:

• Apply a bead of 100% silicone caulk around the rim where the port mounts to the cabinet. Remount the port.
  
• Use self-sticking weather stripping instead of silicone caulk.
• Use Speaker Gasketing Tape. This has closed cell foam.

If any of these work, you can rule out more expensive solutions.

 

[Genesis Boy]

You seem to have a lot of issues.

Your driver could be vibrating against the MDF board. I think that was a bad plan. No driver worth having or cabinet will deform under the weight of the driver.

Next did you model this enclosure, especially vent velocity? I would highly doubt one round port is adequate for this driver, and this may well be port noise.

If the driver is separating then it has to be removed to see if you can create any movement between, the cone and VC. If there is separation then the driver needs reconing.

Thank you for letting me know about the unlikeliness of deformation. This is my first time building subwoofers so I was worried that the 40lb driver, no matter how good quality, would deform unless it was installed in an upright or upside down orientation. Now I know to remove the piece of MDF supporting the magnet and just let it support itself from the screws in the baffle, which I will do if I continue having issues.
It's not damaging the driver, is it? If it is, I'll remove it immediately..

It is possible that the noise you hear is caused by the port tube vibrating against the cabinet. Fixing that should be simple and inexpensive. Remove the port, and do one of three things:

• Apply a bead of 100% silicone caulk around the rim where the port mounts to the cabinet. Remount the port.
  
• Use self-sticking weather stripping instead of silicone caulk.
• Use Speaker Gasketing Tape. This has closed cell foam.

If any of these work, you can rule out more expensive solutions.

Thank you for your suggestions. I already have self-sticking weather stripping lining the inside edge of the port (where it comes into contact with the enclosure).
In fact, I did not want to glue the lid of my enclosure on in case I would need to open it for some reason (in a case where the size of the driver or port holes would not suffice) so I lined the entire area where the lid comes into contact with the enclosure (including the brace down the middle of the enclosure) with weather strip and used 4 wood screws on each side.
I will tighten the screws if I continue hearing rattling.