What increases cabinet volume size and what decreases it?

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tone?

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Joined 2022
#1
Does wool felt decrease the volume?
does foam increase it?
does wadding increase it?

im confused. If all the material is absorbing standing waves inside , then shouldn’t they all increase the cabinet volume?

cheers
 
#2
That's not what is happening.
  • Each material of course occupies some physical space and thus reduces the actual cabinet volume.
  • When the woofer moves in/out it compresses/expands the air in the box which heats/cools slightly.
  • Some materials by interacting with the air change this heating/cooling from adiabatic to isothermal (or maybe vice-versa, I always forget which is which). This makes the cabinet seem like a larger, unstuffed cabinet as far as the woofer is concerned.
  • Materials also absorb midrange frequencies, how well depending on the material.
  • My recollection is unfaced fiberglass is king, pillow stuffing not very effective, things like Acousta-Stuff somewhere in between. And the foams absorb midrange but I don't think increase the box volume.
AFAIK the most extensive testing is in Vance Dickason's excellent Loudspeaker Design Cookbook (7th edition I think is the latest)
 
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#3
head_unit said:
That's not what is happening.
  • Each material of course occupies some physical space and thus reduces the actual cabinet volume.
  • When the woofer moves in/out it compresses/expands the air in the box which heats/cools slightly.
  • Some materials by interacting with the air change this heating/cooling from adiabatic to isothermal (or maybe vice-versa, I always forget which is which). This makes the cabinet seem like a larger, unstuffed cabinet as far as the woofer is concerned.
  • Materials also absorb midrange frequencies, how well depending on the material.
  • My recollection is unfaced fiberglass is king, pillow stuffing not very effective, things like Acousta-Stuff somewhere in between. And the foams absorb midrange but I don't think increase the box volume.
AFAIK the most extensive testing is in Vance Dickason's excellent Loudspeaker Design Cookbook (7th edition I think is the latest)
Click to expand...

i actually found this and it explains it a bit

http://www.troelsgravesen.dk/ports.htm
 
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