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Thread: Ideal amount of dampening material? |
    
New member Username: Plenk
Post Number: 5
Registered: Apr-06
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| Posted on Tuesday, September 05, 2006 - 02:35 pm: |
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I am going to make a sub box 1.75 ft^3. At that size it has the ideal frequency response I am looking for. I was going to add some type of dampening material inside the box, but I read that the box acts larger after you do that. Should I then make my box smaller to account for the acoustic dampening material, or not even worry about using any of this? Thanks. |
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Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1075
Registered: Dec-03
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| Posted on Tuesday, September 05, 2006 - 03:30 pm: |
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Vented or sealed?
Vented subs usually don't need acoustic filler of any kind unless you're referring to cabinet resonance damping which is a different matter. I've used acoustic fill in bass reflex cabinets to limit the amount of high frequency information getting to the port tube. Not really an issue with subwoofers. Don't use it in vented boxes unless you have a good reason for doing so.
Sealed boxes benefit for the reason you've stated, however, don't include this into your volume calculations. Get the correct size from whatever program you're using and add damping material afterwards. Cabinet volume has the most impact on performance while filler is for fine tuning. Start with about 8 ounces per cubic foot of internal volume, listen to it for a while and go up from there. Using 1 lb. per cubic foot is not unheard of. My 8 cu. ft. sealed sub uses about 3 pounds of filler. |
New member Username: Plenk
Post Number: 6
Registered: Apr-06
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| Posted on Tuesday, September 05, 2006 - 05:00 pm: |
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Thanks for the help. Im doing a ported enclosure and its for a sub as I stated. I didnt know if the port was going to pick up unwanted crossed sound waves from inside the box, so I was thinking using some filler would eliminate the problem. |
New member Username: Plenk
Post Number: 7
Registered: Apr-06
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| Posted on Tuesday, September 05, 2006 - 05:03 pm: |
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Also, does the location of the port on the sub box make any difference? I have looked at several high end subs that had them in various locations. |
Gold Member Username: Timn8ter
Seattle,
WA
USA
Post Number: 1076
Registered: Dec-03
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| Posted on Tuesday, September 05, 2006 - 07:22 pm: |
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The idea behind the port is to create a low frequency air mass inside the port at a point in the box that has the greatest gathering of that frequency. Very similar to small room acoustics; sides and corners. The farther from the back of the cone the better and near one of the side walls. In a subwoofer a filter is typically used that limits it to 100Hz or much less. This makes it a bit different than a standard bass reflex full range speaker. If you're concerned about high order harmonics inside the box mucking up the port sound the usual solution is to put "egg crate" foam on the hard surfaces inside the box. |
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