small sealed vs. large sealed, spl

[2kchevy06civic 5,000+ posts]

The sub would act like IB if the box volume far exceeded Vas //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I r the n00b ;P. lol

 

[audioholic 5,000+ posts]

The definition of Vas is "Vas/Cms--------Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker" or more simply as "equivalent air compliance". So why would it take 3X or 10X this number to reach an infinite baffle situation? Vas is defined as the amount of air volume that equals the same compliance as the speaker's suspension, therefore anything over this number will result in no measurable resistance on cone travel. IB is anything over Vas, not a multiple of it.

 

[squeak9798 5,000+ posts]

The definition of Vas is "Vas/Cms--------Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker" or more simply as "equivalent air compliance". So why would it take 3X or 10X this number to reach an infinite baffle situation? Vas is defined as the amount of air volume that equals the same compliance as the speaker's suspension, therefore anything over this number will result in no measurable resistance on cone travel. IB is anything over Vas, not a multiple of it.

Per the loudspeaker design cookbook:

"A closed-box loudspeaker becomes an acoustic-suspension speaker when the compliance of the air volume inside the box is less than the compliance of the woofer by a factor of three or more."

Previous to that, Vance explains how there are two types of closed-box systems; Infinite baffle (IB) and acoustic suspension (typical sealed enclosure).

 

[audioholic 5,000+ posts]

Per the loudspeaker design cookbook:
"A closed-box loudspeaker becomes an acoustic-suspension speaker when the compliance of the air volume inside the box is less than the compliance of the woofer by a factor of three or more."

Previous to that, Vance explains how there are two types of closed-box systems; Infinite baffle (IB) and acoustic suspension (typical sealed enclosure).

I have quotes too. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

"An infinite baffle speaker design is defined as an enclosure that contains a greater volume of air than the Vas requirement of the driver. An infinite baffle system can easily be applied to an automobile. This is accomplished by mounting the speakers on a board and using the trunk of the vehicle as the other walls of the enclosure. It is important that the enclosure be tightly sealed such that no air moves from the front to the back of the cone. Look for speakers where the Qts is greater than .6, and a Vas figure lower than the volume available, when selecting a woofer for an infinite baffle system." - http://www.electronixwarehouse.com/education/glossary/I.htm

"An infinite baffle design is defined as an enclosure that contains a greater volume of air than the Vas of the driver." - MTX Audio - http://mtx.com/caraudio/education/enclosureDesign.cfm

"Vas stands for acoustical suspension volume

Vas is basically the maximum amount of airspace needed for an acoustical suspension in a sealed box. Anything beyond that would be considered infinite baffle." - Jmac - http://forums.caraudio.com/vb/showthread.php?t=20115&highlight=%22infinite+baffle%22+vas

So a quote doesn't explain it. Ive read the speaker design cookbook also, albeit many years ago. //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif But as you can see, Ive found quotes, from experts and even just from knowledgeable people on this board, stating IB is anything beyond Vas, not a multiple of it. Clearly there is some confusion even within the industry.

Again, Vas as defined: "the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker"

Seemingly by definition of Vas, being merely greater than it, not by a factor of 3, would offer compliance less than that of the suspension itself. Why would we need to go 3x beyond this point before enclosure air volume compliance becomes a non-issue? Quoting one source simply stating it is does not prove one way or the other.