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Old 1st October 2004, 01:55 AM   #1
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Default do stuffing, defeat box resonance?

I built a 122l sealed tempest to use for both HT and music but I could'nt enjoy it to much due to box resonance, is there anyway to defeat it.Btw I used 2 standard pillow(polyfill) for stuffing.
My volume set-up(HT) to the sub amp is 10 0'clock and in my receiver sub vol. is "0" and master vol. -18, from this set-up where most of box resonance appeared. Thank's and God blessed.
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Old 1st October 2004, 05:48 AM   #2
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anyone want's to enlightened me?
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Old 1st October 2004, 07:37 AM   #3
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Default Resonance

These are two different problems. Internal stuffing can reduce standing waves and other difficulties with uneven response from the sound bouncing off parallel surfaces, but it will do very little for box resonances caused from the panels rattling around.

You probably need to further brace the interior of the enclosure, if still accessible. If you want to check, use several pairs of woodworking clamps and clamp (4) solid 50mm x 100mm wood along the longest panel dimensions at uneven spacing (angled diagonally so the clamps reach) on all 4 sides. Careful with tightening the clamps - you can break the corner joints.

You may be able to add bracing externally by doubling the panels and screwing further braces to them.

Other possibilities - the Tempest woofer is no longer tight to the baffle, or the tuning/sealing of the box is wrong.

Tim

EDIT: 50mm x 100 x box height. Place a pad of carpet under the center.
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Old 1st October 2004, 02:25 PM   #4
rabbitz is offline rabbitz  Australia
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In addition to what has already been mentioned you can put some cleats in the inside corners (running from baffle to the back) as well as the bracing. Stiffeners glued to the sides running from baffle to the back make a big difference. Just don't put them on the centreline..... offset them a bit.

Need to be larger than shown in the pic as this is for a much smaller sub but gives you an idea.
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File Type: jpg corner cleats stiffener.jpg (39.1 KB, 125 views)
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Old 1st October 2004, 03:53 PM   #5
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Proper bracing, tight joints, stiff panels. Check for leaks. Another favorite trick of sub builders is to build a "box around the box". In other words, glue another layer of MDF or plywood around the existing box. This can be tricky but like any time you glue panels together there must be an air tight bond between them.
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Old 1st October 2004, 10:23 PM   #6
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Default Resonance

If desperate, you could also try drilling through the box about 1/3 of the way from the ends and running 18mm - 25mm thick wooden dowels entirely through the enclosure to connect opposing sides, then glue them in. Make sure they are much longer than you need so that they can be inserted easier. Cut them off with a small flush trim hand saw(about $6) after the glue has dried.

Tim
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Old 1st October 2004, 11:34 PM   #7
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thanks guys for the idea but I'm surely "sure" that I built the box properly I used to glue all the panels then screw it (3 1/2" interval for every screw 'coz I don't have any clamp) then I used
sealer to all internal corner then I checked the leak using a piece of tissue to see if theres a air coming out of course its turned on. also I used plastic foam (3/16" thick) in between the driver and to where to mount it. Oops wait a minute I used 18mm (thick) of mdf
its the only size available here do you think I got problem here?
Anyway how about If I used granite tiles in 8"x8" in size as internal damping but I'm afraid to loose internal volume required,
to result boominess. Thank's again, God Blessed.
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Old 2nd October 2004, 12:10 AM   #8
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Quote:
Originally posted by dranreb&*
thanks guys for the idea but I'm surely "sure" that I built the box properly I used to glue all the panels then screw it (3 1/2" interval for every screw 'coz I don't have any clamp) then I used
sealer to all internal corner then I checked the leak using a piece of tissue to see if theres a air coming out of course its turned on. also I used plastic foam (3/16" thick) in between the driver and to where to mount it. Oops wait a minute I used 18mm (thick) of mdf
its the only size available here do you think I got problem here?
Anyway how about If I used granite tiles in 8"x8" in size as internal damping but I'm afraid to loose internal volume required,
to result boominess. Thank's again, God Blessed.

Sorry, i think you might have missed what the posters were getting at. They're suggesting that the walls of your box are flexing. It's not a matter of leaks- it's all about how stiff the walls are. Braces can help, or something to make the walls stiffer.

Why not put the granite tiles on the outside? With a good adhesive, this could really improve sound- and I'm sure it will look nice. Whatever you decide to do, good luck!

Joe
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Old 2nd October 2004, 12:31 AM   #9
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Quote:
Sorry, i think you might have missed what the posters were getting at. They're suggesting that the walls of your box are flexing. It's not a matter of leaks- it's all about how stiff the walls are. Braces can help, or something to make the walls stiffer.
No i did not missed it, I absorved it. My reply is for general concern as you can see Timn8ster mentioned also about the leaks. Anyway thank's for the adviced but the box is too big already so If I add material on the outside it will looks more big. Thanks, God blessed
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Old 2nd October 2004, 05:02 AM   #10
FrankWW is offline FrankWW  Canada
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Hi,

If you can get into the speaker box this will work and preserve most of yuor internal dimensions.

You need some mass and some stiffness. So line it with thin, say 2mm, maybe even 1 mm, steel sheet. Glue, NOT screw, it on. Leave maybe 1 mm between them so they can't buzz and put sealer stuff between their edges.

Then line that with dense foam - it should have about the same amount of give as raw steak, maybe rare. GLUE it on. The foam might be about 5 to 10 mm thick And for overkill, glue some aluminum foil (or extremely thin sheet metal, thinner than that glued to the box) on the foam.

If you can't do the cutting yourself, get a local sheet metal shop to do it. You can probably get the steel sheet from them. Make sure you make the measurement allowance so the plates dont touch each other.

Get the kind of glue used for sticking metal and wood together and says on the label that it makes a flexible joint. You need to be able to spread it out evenly and use a hard roller on the metal sheet to make sure there are no air pockets.

If you have an automotive parts dealer near you he may carry something like this:

http://www.dynamat.com/

Same idea. Its used for damping body panels.It's very effective and you don't have to get the real thick stuff but it does have to have the metal on one side.


But i think you'rr better off going with the steel and glue because you need the mass and stiffnesss. You don't need thick steel because the lamination effect will make the box very strong for its weight - just like pywood or the new high tech foam sandwich materials. LIke a flattened I beam. And you don't want thick steel, anyway, because it's heavy and you want it to stay glued on.

What makes it work is the different density and thickness and elasticity of the materials.

The way it works is that when metal is stuck to a panel the vibration gets into the soft layer of glue and foam, and because the steel and aluminum foil is holding that middle layer surface stiff, sound can't vibrate it and gives up its energy by heating the foam and glue.

'Screwing the steel on will wreck the effect because IT has to flex, however microscopically.

It has to be glued.
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