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-   -   Sound dampening inside the box (http://www.diyaudio.com/forums/multi-way/188011-sound-dampening-inside-box.html)

lup31337 28th April 2011 10:54 AM

Sound dampening inside the box
 
I got some car speakers and i want to use them in the house. I'm gonna make a ported box. I want to use some sound dampening material (that sponge looking kind) on the walls (all of them except the side with the speakers and bass-reflex port (all of these are on the front side) ... so its sound dampening material on all sides expect the front one. I calculated the box volume and added the extra volume from crossovers, speaker magnets etc. Do i have to add to the box volume, the volume displaced by this material also ? Or because is so light and "airy" it doesn't affect the overall volume of the box. Simply put : do i need to add the volume of the sound dampening material to the box volume or do leave it the way it is ?

Inductor 28th April 2011 11:44 AM

Quote:

Originally Posted by lup31337 (Post 2554129)
...Or because is so light and "airy" it doesn't affect the overall volume of the box. Simply put : do i need to add the volume of the sound dampening material to the box volume or do leave it the way it is ?

You have a good point. You don't need.

speaker dave 28th April 2011 01:56 PM

For crossovers and magnet structures, etc. be sure to subtract volume rather than add. Good stuffing material, actually adds some apparent volume, up to an extra 40% for the stuffing volume.

Standard fiberglass material is far and away the best material for cabinet stuffing. It absorbs more mid frequency standing waves and will give a slight effective volume increase (assume +20 %).

Worst material: dacron fluff (pillow stuffing).

David

lup31337 28th April 2011 04:32 PM

I'm not talking about stuffings. That is used for sealed enclosures. I'm talking about something that you put on the walls. Like this : AUDIO ALCHEMY (first few pics) . Does that affect the volume which the speaker needs (as in i need to make the enclosure bigger to compensate the lost volume because of the displaced volume by this dampening material) or it doesn't affect it and i leave the enclosure as it is ?

Arty 28th April 2011 07:12 PM

notice, fieberglass + ported design may not be healthy. can eject very small galss particles via the vent. ->at least i would not use it anyways for other than sealed box <-

speaker dave 28th April 2011 08:10 PM

Quote:

Originally Posted by lup31337 (Post 2554531)
I'm not talking about stuffings. That is used for sealed enclosures. I'm talking about something that you put on the walls. Like this : AUDIO ALCHEMY (first few pics) . Does that affect the volume which the speaker needs (as in i need to make the enclosure bigger to compensate the lost volume because of the displaced volume by this dampening material) or it doesn't affect it and i leave the enclosure as it is ?

Okay, stuffing would be filling the box vs. lining which is putting a layer around the perimeter. In both cases you do not need to subtract the volume of the stuffing or lining material. It is a compressible medium and does not diminish the apparent cabinet volume (as stated, it actually increases it slightly but not enough to make much difference).

Fiberglass can blow out the port but I find that it if you cut it carefully this is minimal and most of the loose particles blow out in the first few days. There is also a material called duct lining which is used in HVAC (I'll let you guess what for) and is basically fiberglass with a skin, preventing it from fragmenting.

Fiberglass is the universally used material in room acoustics, since it has the greatest sound absorption for a given thickness of any practical material.

David

David


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