Importance of box dampening... - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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post #31 of 34 Old 03-08-2012, 02:38 PM
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Originally Posted by JohnnyWash1 View Post

In my mind, air stiffness is a layman's explanation for air pressure. An increase in air pressure would be similar in concept to "stiffer" air, as the air presses with more force on the cone.

Could also be a non-native english person speaking, like me...
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post #32 of 34 Old 03-08-2012, 03:07 PM
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Originally Posted by gperkins1973 View Post

Hi Bill,

I was refering to my ported sub with being in a 15 cu ft instead of a 30 cu ft box which is optimum size. It was more thinking that stuffing could make the alignment better by way off boosting the bottom end without EQ thus making the driver think it is in a bigger box.

Word has it that stuffing doesn't work in a VB the way it does in a sealed. I can't say with certainty how it works in a VB as I've never tried/measured it. And even in a sealed box stuffing doesn't boost the bottom end, that's one of the myths about stuffing. It lowers Qtc, which can tame a response bump. Only a larger box can give more actual low end extension.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
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post #33 of 34 Old 03-08-2012, 03:17 PM
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Maybe time for some new drivers then I guess which their alignment would be better suited to my 15 cu ft boxes. The FI SP4 models significantly better in the same enlcosure when compared to my old Q18's. I don't think I have the energy to build new boxes just yet. LOL.
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post #34 of 34 Old 03-08-2012, 06:08 PM
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Originally Posted by madlim View Post

When you put stuffing in a box it does two things:

First of all, it introduces an often desirable resistive loss and secondly it increases
the apparent volume of the box. In this second part thermodynamics comes in:

In a empty box, you get a adiabatic process, meaning that when the cone move
inwards it raises the box pressure and hence the temperature. A gas with increasing
temperature tries to expand which will cause an increased suspension stiffness and
raised resonant frequency as a result.

When adding stuffing you move toward a isothermal process, the stuffing cools the
raising air temperature in the box and give a less increased suspension stiffness then
in the adiabatic case, and a lower resonant frequency as a result.

In other words, yes the prefix is thermo, and it got everything to do with it!

Hope I made myself understood, my english is a little rusty...

Well if this is indeed true (not disputing it) then my understanding of why box stuffing works is wrong and thermodynamics does apply. I seem to have put my foot in my mouth here....
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