Subwoofer box rattle issue - diyAudio
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Old 27th December 2011, 11:01 PM   #1
qa9b is offline qa9b  United States
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Default Subwoofer box rattle issue

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!
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Old 27th December 2011, 11:48 PM   #2
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Yes Damping would assist, and may cure this, try a pillow or two first, to see if it changes the sound.
Cheers / Chris
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Old 28th December 2011, 01:03 AM   #3
qa9b is offline qa9b  United States
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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:

Click the image to open in full size.

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.

Last edited by qa9b; 28th December 2011 at 01:08 AM. Reason: image broke tables
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Old 28th December 2011, 01:31 AM   #4
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Quote:
Originally Posted by qa9b View Post
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!
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.
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Old 28th December 2011, 02:39 AM   #5
qa9b is offline qa9b  United States
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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.
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Old 28th December 2011, 03:00 AM   #6
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Quote:
Originally Posted by qa9b View Post
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.
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Old 28th December 2011, 04:47 AM   #7
qa9b is offline qa9b  United States
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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?
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Old 28th December 2011, 05:02 AM   #8
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The rattle could manifest itself from the dustcap when the driver is placed in the enclosure due to backpressure ,whether it be a sealed or(less likely) from a vented box. I've had a dustcap vibrate with just 1"of it detached from the cone. Just a thought
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Old 28th December 2011, 05:05 PM   #9
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Quote:
Originally Posted by qa9b View Post
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?
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.
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Old 28th December 2011, 07:16 PM   #10
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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).
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