Hi all,
I just built a ~7 cu. ft. sealed enclosure for my new Dayton DCS380-4 15" sub. The box is sturdy (3/4" MDF, tons of wood glue, bracing, and joints sealed with caulk). I'm experiencing a weird rattling noise centered around 60Hz, and it's present at all volumes. The issue isn't the speaker itself, as I did not hear the rattling when I tested it in free air.
This is what it sounds like:
subwoofer rattle problem - YouTube
Any suggestions as to how to go about fixing this? What are the possible causes? There is no damping material inside the box - would adding this possibly help?
Thanks for any advice!
I just built a ~7 cu. ft. sealed enclosure for my new Dayton DCS380-4 15" sub. The box is sturdy (3/4" MDF, tons of wood glue, bracing, and joints sealed with caulk). I'm experiencing a weird rattling noise centered around 60Hz, and it's present at all volumes. The issue isn't the speaker itself, as I did not hear the rattling when I tested it in free air.
This is what it sounds like:
subwoofer rattle problem - YouTube
Any suggestions as to how to go about fixing this? What are the possible causes? There is no damping material inside the box - would adding this possibly help?
Thanks for any advice!
Great idea with the pillows for damping, but no dice. The sound is unchanged.
When I took it apart I noticed that the foam padding between the metal speaker frame and the box is extremely thin:
This is the back of the speaker. You can see the foam strip and a screw hole in this pic. This seems tantamount to there being no foam at all.
Is it likely that the lack of foam/damping between the speaker and my box is causing the problem? I've already ordered some foam gasking tape to add.
It sounds a lot like that 55-60Hz note is hitting the resonant frequency of the front panel of my speaker box. I might try adding some bracing to see if that changes the sound.
When I took it apart I noticed that the foam padding between the metal speaker frame and the box is extremely thin:
This is the back of the speaker. You can see the foam strip and a screw hole in this pic. This seems tantamount to there being no foam at all.
Is it likely that the lack of foam/damping between the speaker and my box is causing the problem? I've already ordered some foam gasking tape to add.
It sounds a lot like that 55-60Hz note is hitting the resonant frequency of the front panel of my speaker box. I might try adding some bracing to see if that changes the sound.
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Sounds like a dragging voice coil or perhaps tinsel lead flap, though tinsel lead flap should have been heard in an open air test.
Damping material won't fix either.
A dragging voice coil can be caused by too much heat, crud in the gap, or a uneven mounting surface distorting the frame.
Push on the cone evenly, if you hear a scraping noise the coil is dragging on something.
Tried pressing on the cone - no scraping noise. If this was indeed a dragging voice coil, wouldn't I have heard it in the open air test as well at all frequencies? My issue seems to be centered around 55-60Hz. The rattling comes on suddenly then fades away as you can hear in the video in my first post.
Dragging voice coils often only show as noise in a narrow band of frequencies.
You should be able to hear some noise if it is a dragging coil when you push on the cone, if there is no scraping that probably is not the problem.
Have you tried the sweep test outside?
Are you sure something else in the room is not rattling?
Using individual tones would give you more time to hear where the problem is originating.
Yeah, it's definitely not a dragging voice coil. I don't hear a thing when I press down on the cone.
The sweep test sounds just fine when the speaker is in free air.
When I began playing around with the screws that secure the sub to the box (loosening/removing), I started to alleviate the rattling sound coming from the box. The screws were never that tight in the first place, so I don't think I'm contorting the metal speaker frame. Is there any merit to the possible foam surround issue I mentioned before?
The sweep test sounds just fine when the speaker is in free air.
When I began playing around with the screws that secure the sub to the box (loosening/removing), I started to alleviate the rattling sound coming from the box. The screws were never that tight in the first place, so I don't think I'm contorting the metal speaker frame. Is there any merit to the possible foam surround issue I mentioned before?
Sounds like the frame is distorted, check the front panel with a known flat piece of plywood and see if it is true.
If the problem is a warped baffle, extra thick gasketing or window setting material, or clay may take care of the problem.
Can definitely still be that the voice coil becomes loose on the former or the former distorts when it warms up. I have a scan-speak at home which sounds great if you let it sit for a few months, but if you try to use it for a day it starts rubbing again when warm, then eventually keeps rubbing or amking noisees...needs a few more months of rest again...(replaced it eventually).
It doesn’t sound like a surround issue; sounds like metal on wood to me, or maybe the leads are hitting the cone as mentioned.
> Try mounting the woofer magnet out, maybe you can find something that you couldn’t see before.
> Try clamping the speaker box during testing, maybe add weights, etc.
> Mortile wetherstriping/caulking cord is a good for DIY projects; they sell it at HD.
There is always the obvious, maybe the speaker is simply not working properly.
E.G. Caulking Cord:
Mortite Weatherstrip And Caulking Cord BIC Warehouse
> Try mounting the woofer magnet out, maybe you can find something that you couldn’t see before.
> Try clamping the speaker box during testing, maybe add weights, etc.
> Mortile wetherstriping/caulking cord is a good for DIY projects; they sell it at HD.
There is always the obvious, maybe the speaker is simply not working properly.
E.G. Caulking Cord:
Mortite Weatherstrip And Caulking Cord BIC Warehouse
Thanks for all the help, everyone.
There was no issue with the dustcap backpressure - it appeared fully attached and removing the plate amp in the back of the box (thereby removing most of the pressure) did not change the rattling sound.
For those lurkers wondering how I ended up fixing it:
I added some serious bracing to the front panel of the box and that alleviated most of the issue. I can still faintly detect some rattling, but it doesn't bother me. Take-away for future builds: can't ever have enough bracing, especially for sealed builds. What's interesting is that I can slightly alter the amount of rattling by changing the torque applied to the sub's mounting screws (having this helps)--which just goes to show that warping the frame even to a minuscule extent is possibly of concern. Perhaps this wouldn't be the case with a more costly sub.
There was no issue with the dustcap backpressure - it appeared fully attached and removing the plate amp in the back of the box (thereby removing most of the pressure) did not change the rattling sound.
For those lurkers wondering how I ended up fixing it:
I added some serious bracing to the front panel of the box and that alleviated most of the issue. I can still faintly detect some rattling, but it doesn't bother me. Take-away for future builds: can't ever have enough bracing, especially for sealed builds. What's interesting is that I can slightly alter the amount of rattling by changing the torque applied to the sub's mounting screws (having this helps)--which just goes to show that warping the frame even to a minuscule extent is possibly of concern. Perhaps this wouldn't be the case with a more costly sub.
Gasketing - Splicing Tape
They sell a thick rubber tape at electrical supply stores, often called “bug tape”, it is used for field splices (then they wrap with standard tape). It doesn’t turn well, but it was fine for a 12” woofer.
I used the same tape (just over a 1mm thick) for a removable back the other day, it worked very well.
They sell a thick rubber tape at electrical supply stores, often called “bug tape”, it is used for field splices (then they wrap with standard tape). It doesn’t turn well, but it was fine for a 12” woofer.
I used the same tape (just over a 1mm thick) for a removable back the other day, it worked very well.
Attachments
Hey again... some more trouble.
Adding bracing to my front panel almost completely got rid of the rattle around 55-60Hz. But I'm now hearing the peak loudness of the rattle around 80-90Hz.
What's really odd to me is that I'm able to COMPLETELY get rid of the rattling by applying pressure to the woofer magnet in a specific direction. Here's a video of what's happening (80Hz tone playing). I'm completely baffled by this. Ideas?
Varying the tightness of the sub's mounting screws doesn't alter the rattling sound.
Thanks for any help!
Adding bracing to my front panel almost completely got rid of the rattle around 55-60Hz. But I'm now hearing the peak loudness of the rattle around 80-90Hz.
What's really odd to me is that I'm able to COMPLETELY get rid of the rattling by applying pressure to the woofer magnet in a specific direction. Here's a video of what's happening (80Hz tone playing). I'm completely baffled by this. Ideas?
Varying the tightness of the sub's mounting screws doesn't alter the rattling sound.
Thanks for any help!
One thing you could check is to see if the spider has partially become unglued on the outside from the magnet surround. I've experienced this with the Dayton QT385-4 15" subs.
It took a long time to track down what the actual cause was because only part of the spider was loose and that resulted in buzzing only at certain levels/frequencies.
Was easy to fix however with some plastic adhesive glue.
Probably worth a check out at this point in your adventure, good luck
It took a long time to track down what the actual cause was because only part of the spider was loose and that resulted in buzzing only at certain levels/frequencies.
Was easy to fix however with some plastic adhesive glue.
Probably worth a check out at this point in your adventure, good luck
Your driver has a manufacturing problem. What you hear is the resonance in some of the hardware parts of the loudspeaker. Probably the reason they come out on certain frequencies has to do with specific resonances in the cone in relation to Fs of the driver. These resonances are set out by nodal lines and nodal circles. I just made an overview of these nodal resonances for another thread.
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Since you have found the problem, you could wedge a piece of wood with a rubber foot contacting the magnet inside the cabinet to keep the woofer from rattling.
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