Elementary Noob Question of the Day: How tightly should you pack wool in an enclosure?

[tubelectron]

Looks an aweful lot like the Bonded Logic UltraTouch recycled cotton i use.

dave

It is called "Métisse" here (a French product), and it is used for thermal / acoustic insulation of buildings, available in 45mm and 100mm thickness. And of course yes : I'm sure that there's an equivalent product in USA / Canada. 😉

The Métisse is no comparison with fiberglass or rockwool in terms of pleasure to work, plus it is harmless, both for people, animals and last but not least : for speakers ! 😎

The reduction in the pressure changes is the equivalent of the compliance of the air-spring being increased. This reduces the frequency of resonance defined by the cone mass and the total compliance experienced by the cone.

Yes. That's true : a few hertz lowering can be noted, plus a more gentle resonant peak amplitude. At least, that's what I measured (sorry, no recordings were done... I should have 😕 !)

The addition of convenient damping material in the enclosure provides an increasement of the acoustic volume of theoretically 41%, but usually 15% to 20% are obtained (J. D'Appolito / "Testing Loudspeakers"). Personally, I tend to consider an increasement of 15% (M.Colloms / "High Performance Loudspeakers"). This increase is considered for a "100% filling" of the volume (V. Dickason / "Loudspeaker CookBook"), that is to say like what I presented on post #14 above.

T

 

[planet10]

Agree with all your points on the cotton. Wonderful stuff.

dave

 

[kgrlee]

Nice to see one with periods instead of sec as the depth axis. A much better format for examining ringing.

Q are displayed in the same manner, and you are looking for a series of “parallel” lines as the DUT rings down.

Mark, which software are you using?

We were the first to do this in the early 80s. We called them PAFplots, after Peter Fryer, as opposed to KEFplots, which are the common or garden 'waterfall' today.

 

[kgrlee]

As a pedant, I feel duty bound to correct your use of the term "adiabatic" - it should read "isothermal" (i.e. a process where temperature doesn't change, which is the effect of the stuffing acting as a heat sink).

I stand corrected Pedant Keith. I apologise for my sole remaining brain cell that has serious problems wid dem polysyllabic words.

My 'method' was to stuff a sealed box until the measured 'driver in box' resonance stops dropping. You can usually get 20% apparent increase in apparent box volume with Fibreglass or Rockwool. 15% is good with lesser materials. Alas, I could never specify Fibreglass for a commercial product for fear of being lynched by the factory.

 

[Arthur Jackson]

“Adiabatic process, in thermodynamics, change occurring within a system as a result of transfer of energy to or from the system in the form of work only; i.e., no heat is transferred. A rapid expansion or contraction of a gas is very nearly adiabatic.” https://www.britannica.com/science/adiabatic-process

 

[markbakk]

Mark, which software are you using?

We were the first to do this in the early 80s. We called them PAFplots, after Peter Fryer, as opposed to KEFplots, which are the common or garden 'waterfall' today.

I use ARTA, now sadly EOL, and REW from time to time. I think most of us do here these days.

 

[geoffkait]

What I found is that a small grapefruit or baseball size ball of hollow fiber wool is best, better tighter bass, more open and more dynamic than other solutions. No need to suffocate the sound by over-stuffing.