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Sub and box crackling (Read 3123 times)
Purvis11
Ex Member



Sub and box crackling
11/19/05 at 03:41:46
 
I finished my box and was all pumped to play it.  But when i did i noticed it rattled at a low volume.  I found some air leaks and no more, but there is still a  "Womp, womp, blump" crackly sound at a volume that should not have any problems like that. Cry

Any help, tips, or advice are appreciated,

Purvis
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gexter
Ex Member



Re: Sub and box crackling
Reply #1 - 11/19/05 at 04:40:13
 
See if you can isolate it to one driver or both.
power only one side up at a time.
crackley sounds like a voice coil but unlikely with new sub or ones you used before.
did you use any damping at all?
possibley a wire buzzing against the basket, again not likely.
thats a start anyway.
Others may have other ideas
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Purvis11
Ex Member



Re: Sub and box crackling
Reply #2 - 11/19/05 at 15:41:16
 
Im pretty sure its not the drive.  No i didn't use any dampening material.  Should I?  What should I use for it?

Purvis
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bassman
Ex Member



Re: Sub and box crackling
Reply #3 - 11/19/05 at 17:05:16
 
Did you solder the wires to the speaker. Mine made a noise like that when I tested them by just wrapping the wire around the terminal. When I soldered them it was gone. Also make sure the frame or basket is solid against the baffle. Once again had some noise from mine because I over tightened the screws and bent the mounting flange just enough for it to rattle. Just my experiences. Good luck.
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lunarlab
Ex Member



Re: Sub and box crackling
Reply #4 - 11/19/05 at 19:39:06
 
Hi....I used a 2 inch screw spacing on my newer WO's and industrial adhesives on every join....Depending on your drivers you may want to use some bracing in the sealed side.  My first cabinet shook like a leaf and needed to be up off my hard floor in my studio on carpet to not rattle.  After many re builds and mods and mega bracing I have a solid and heavy box....  :'( http://lunarlab.greenbtn.com/music/pics/woplan.jpg ....over 390 screws....88 or so in each lid.  It makes a huge difference on the performance to have a well assembled and sealed box.
Question....what crossover frequency are you using ? are your drivers centered,  flush and tight ? Did you goo all your joins with silicone around the inside of the box ? Is your lid seal sealed ? How much damping did you use ?....
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« Last Edit: 11/19/05 at 19:48:47 by lunarlab »  
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DirtDawg
Ex Member



Re: Sub and box crackling
Reply #5 - 11/19/05 at 21:28:37
 
Nice work lunarlab,

It looks like your findings are the same as mine when it comes to the WO cabs. The doubling of the throat panel really helps to stop the gargling!

Did you use a thicker top and bottom or ribs on the outside to stop the flex in that area? I ended up using a "+" brace inside on mine to tie all 4 sides together. Mine was probably not as easy to do.

It's nice when some else independantly re-confirms my obssessions. I don't feel crazy!
Smiley
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lunarlab
Ex Member



Re: Sub and box crackling
Reply #6 - 11/19/05 at 21:56:09
 
[quote author=DirtDawg  link=1132375306/0#5 date=1132435717]Nice work lunarlab,

It looks like your findings are the same as mine when it comes to the WO cabs. The doubling of the throat panel really helps to stop the gargling!

Did you use a thicker top and bottom or ribs on the outside to stop the flex in that area? I ended up using a "+" brace inside on mine to tie all 4 sides together. Mine was probably not as easy to do.

It's nice when some else independantly re-confirms my obssessions. I don't feel crazy!
Smiley [/quote]
well you are crazy... but aren't we all.  just kidding.  Obsessive... yes.  Crazy, maybee a little... but in answer to your question...I thought of cross braces in both the sealed and ported side.  I also tossed around the idea of bracing in the horn mouth.  Although mine seem to be ok with just one brace tying the sides to the center in both chambers.  Perhaps some bracing attached to the lid to stiffen it a bit.  Two 1.5 or 2 inch strips running edgewise along the top and bottom as stiffening ridges.... I think just brace the snot out of it till it doesn't bomp anymore Cheesy
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Purvis11
Ex Member



Re: Sub and box crackling
Reply #7 - 11/19/05 at 21:56:33
 
Should I use and dampening material and what kind?

Im going to try and doubling the thickness of the baffle and the rest of the rattle seems to be coming from the last angle piece at the throat where there is the 2 inch opening.  Should I double that thickness to?

THanks fot all your help and advice

Purvis
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DirtDawg
Ex Member



Re: Sub and box crackling
Reply #8 - 11/19/05 at 21:59:32
 
[quote author=Purvis11  link=1132375306/0#0 date=1132371706] ..... "Womp, womp, blump" ......
Purvis [/quote]
Soldering the wiring is crucial to stop the cracklies!
What's your XO freq?

MOD:
The baffle needs to be double! Every joint has to be rock solid and glued, screwed, sealed.
I have no filling in mine and they are low and solid crossed at 40Hz for canned music.
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« Last Edit: 11/19/05 at 22:09:53 by DirtDawg »  
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DirtDawg
Ex Member



Re: Sub and box crackling
Reply #9 - 11/19/05 at 22:21:47
 
[quote author=lunarlab  link=1132375306/0#6 date=1132437369]..... I also tossed around the idea of bracing in the horn mouth.  :D [/quote]
The horn mouth was fine after I braced the insides. Believe me, I went all over this cab with a pair of mics and headphones with test tones going until I found every weakness and the result is a flat response that continues to impress me. I've never heard a 4th order cab that comes even close to the sound I'm getting.
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lunarlab
Ex Member



Re: Sub and box crackling
Reply #10 - 11/19/05 at 22:28:44
 
[quote author=Purvis11  link=1132375306/0#7 date=1132437393]Should I use and dampening material and what kind?

Im going to try and doubling the thickness of the baffle and the rest of the rattle seems to be coming from the last angle piece at the throat where there is the 2 inch opening.  Should I double that thickness to?

THanks fot all your help and advice

Purvis [/quote]

Hello...yes indeed use some damping.  I use the low itch white fiberglass.  Most commonly you would use poly-stuff from an audio supplier.  It has nice sonic quality and no itch , otherwise non toxic and some are fire-retardant. Fiberglass also has good properties for acoustic stuffing and makes a good damping material. It can be torn into different thicknesses and as long as you wear gloves and a dustmask it is ok to work with.  I line all my sub boxes with a one inch matt of fiberglass and loose fill with torn apart chunks.  You may have to play with the amount of damping until you find the right ratio.  Too much can seriously muffle the sound and too little can give a bit of box noise.  I have also used thin eggshell foamies for years for damping behind the cone or in ported boxes where otherwise pieces of loose poly or worse fiberglass can be blown out of the port.   I also suggest damping for higher crossover frequencies with this box...it can sound a bit wild over 120 Hz or so but I found damping cures that up nice.  I run at about 50-75Hz cutoff depending on the material I am listening to ,and have a loose stuff about 75 % of the volume of the sealed box.  You can get up to 30 % more apparent volume to the driver with a full poly stuff  .  Check to the Vb of your driver...closer to 2 cubic feet and you may concider stuffing.  WO sealed section is around .7 cubic feet, so a full stuff will make it around 1.   Also note that some driver manufactures suggest damping for their drivers and others do not....I guess it depends on the woofer and x'sover point.
Also on the doubling of the baffle...yes double it up,  double up the port, and any other join you double wont hurt.... screw and glue the hell out of it till it doesn't rattle.
Angry
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« Last Edit: 11/19/05 at 22:46:03 by lunarlab »  
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lunarlab
Ex Member



Re: Sub and box crackling
Reply #11 - 11/19/05 at 22:30:20
 
[quote author=DirtDawg  link=1132375306/0#9 date=1132438907]
The horn mouth was fine after I braced the insides. Believe me, I went all over this cab with a pair of mics and headphones with test tones going until I found every weakness and the result is a flat response that continues to impress me. I've never heard a 4th order cab that comes even close to the sound I'm getting.
[/quote]

no kidding...you should hear four of them... Undecided
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DirtDawg
Ex Member



Re: Sub and box crackling
Reply #12 - 11/19/05 at 23:59:53
 
Oh, yeah! Or 16? Cheesy
I'm new to the WO, but my PA experience tells me that stacking big folded horns out smarts the 3dB rule every time.
Four stacked as one unit (latch them together!) will be more than 3dB increase over two cabs. I've measured 6 to 10dB better at the low end.
I guess a better coupling to the surrounding air results in a larger effective mouth area and lower horn loading. (?) I don't know if the WO will "gang up" that way, but I'd love to be there when you try it. But, 3dB? you can put that in the bank and write a check on it! Grin
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« Last Edit: 11/20/05 at 00:05:42 by DirtDawg »  
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