When did acoustic suspension become infinite baffle?

[kelticwizard]

I never much liked "acoustic suspension"; it's more marketing speak than a descriptive term.

"Air suspension" would be much more accurate.

"Acousitic suspension" been used by Villchur since the early fifties when the idea of a box colume much smaller than the Vas first appeared. I believe Villchur was the one who specified the 3 to 1 ratio as well.

"Acoustic suspension is when the Vas/Vb ratio is less than 3. Infinite baffle is when the ratio is 3 or above."

Are you sure it's not Vb/Vas?

The acoustic suspension design, as outlined by Villchur, required a Vas/Vb ratio of 3 to 1 or greater.

Either way, I disagree. In science and engineering, "infinite" is used where increasing a value has no further significant effect.

Even at Vb = 3 Vas, the total stiffness is 3 parts from the air and 1 part from the driver, giving Fc = 1.15Fs.

Strictly speaking, you're entirely correct. but the volume requirements to implements an Infinite Baffle become so great, people started fudging. And even Fc = 1.15 Fs only means that you have raised Fs two tenths of an an octave.

To qualify as IB, I'd say Fc should be no more than 5% higher than Fs.

Not a bad standard to set. But to do it would require a box volume ten times the Vas. A 12 incher with a Vas of six cubic feet would require a box of sixty cubic feet to qualify. This is why people started fudging on the terminology.

 

[noah katz]

"I believe Villchur was the one who specified the 3 to 1 ratio as well."

Actually, that makes sense if the idea is that the air spring dominates over the mechanical stiffness.

"But to do it would require a box volume ten times the Vas. "

Well, that's what people get when you try to build something infinite

IB is more aptly applied when there is no box, like using an attic or garage space for the back volume.

 

[catapult]

In recent years, IB has taken on a specific meaning in the DIY community and it's not a small sealed box. Generally to be a "true" IB Vb should be at least 10x Vas although 4x will do in a pinch. Most IB installations these days are boxless and vent the backwave into an attic, basement, garage, etc.

Cult of the infinitely baffled

 

[poobah]

You should all know better

jeeze, you're talking words here....

and I'm scottish too...

 

[Tweeker]

If you have a better suggestion than talking words, please pipe up.

 

[poobah]

Geeze...

Foil hat...

 

[rcavictim]

If you have a better suggestion than talking words, please pipe up.

You could say it with flowers!