I'm giving a respectful response, despite being called Sommer******. Shall I
start calling you Anuson?


It's been done. William Michael Watson Dayton-Wright built
conventional dynamic speakers with bags of SF6 in the woofer box.

** For what advantage ?

The speed of sound is about half in SF6 but that is no help in a sealed
box where resonance depends only on the stiffness of the volume of
gas trapped behind the woofer.
The smaller the volume or the larger the woofer, the stiffer it becomes.

The lower speed of sound makes the bag appear to have a larger acoustic
volume than the air it replaces.

** You have simply ignored the question, which is the stiffness of a fixed
volume of gas.

Take a look at Boyle's Law (PV = k)

As Michael Flanders put it... "The greater the pressure, the larger the volume
of hot air."

I found the spec sheet. He describes the SF6 as performing a linearizing
function. He says nothing about increasing the cabinet's "apparent" volume.
I'll call a friend who designs speakers and have him put me right -- if such
needs be done.

http://www.dayton-wright.com/WATSON-10_.html


Really. The bass cabinet was about 20" by 20" by 12".

** That is not a "small cabinet" at circa 50 litres internal volume.

I consider it "small", as it was the bottom structure of a floor-standing
speaker. That's not a large enclosure for a speaker that gets to 20Hz and
lower with low distortion.


Had an 15 inch woofer fitted -- did it ?

Nope. Two oddball 10" drivers -- with pie plates glued to them! See the photo.


At 16Hz, there was no /audible/ output from the speaker, but everything
loose in the room was rattling.

** Standing waves are a real bitch...

Oh, I walked around to see if I could hear any subsonic output. There was
none. Assuming you believe the spec sheet, note the ridiculously low LF
distortion.


Ever heard his SF6-filled electrostatics?

** Now that was done for an entirely different reason.