Akabak & stuffing

[Henkjan]

has anyone found a way to model stuffing in Akabak?

I see the "AcouResistance" parameters, but am not sure on how to translate 50 grams of polyester to this...

[Henkjan]

just slight offtopic in my own thread.... I compared the akabak scripts for a tapped horn with 2 drivers, 1 with the 2 assumed at the same location (as it is in Hornresp) and 1 with the 2 drivers at separate locations (as the real thing)

this is with 1 shared location

[Henkjan]

and this is with 2 separate locations

[Henkjan]

in other words.. not much difference..

[Henkjan]

Originally posted by Henkjan
has anyone found a way to model stuffing in Akabak?...

no-one any experience with this?

[applehorn]

Hi,

I suggest that you look at Martin Kings site http://www.quarter-wave.com . There is also an important paper by George Augspurger that showed that the important points are not the stuffing but the Qts of the driver and the pipe shape. Maybe someone can give properties for Dacron, Long Hair Wool etc.

Iain.

[Henkjan]

I know MJK's sheets, but thanks anyway...

I started to look more into Akabak because it is able to simulate stuff even Martin's sheets cannot do, like a tapped horn and systems with mulitple drivers. (+ that Martin has withdrawn his sheets from the public domain, which leaves us with only Hornresp in combination with Akabak)

I also asked this question to Joerg panzer, the author of the program, and this is his reply:

Hm, difficult question. You see, the simulator Akabak assumes a more
abstract level. You can take into account losses by lowering the quality
factors as provided in the Enclosure and Duct components. However, the
correspondence between the effect of material and these quality factors is
not provided. Typically it is regarded as a difficult issue and in many
cases best controlled by your experience. The isothermal effect can be
taken into account by slightly increasing the volume of the component.
Theoretically the upper bound is 1.4.

Rule of thumb: Run the simulation with low losses in order to see
resonances clearly. Then play with the quality factors to learn about the
sensitivity of the response to these parameters.

PS: yes, line shape and driver parameters are more important, but the location and amount of stuffing can be the key to success, especially with a full range application

[geitmans]

I did some simulations in akabak using damping. See th-spud thread

I used multiple duct elements with a larger viscosity to approximate a waveguide. If I compare the calculated impedance plots with the reality it seems it gives better resemblance.

[Henkjan]

thank!

Duct 'D3' Node=4=5 HD=24.5cm WD=13cm Len=50cm visc=50
Duct 'D4' Node=5=6 HD=24.5cm WD=14cm Len=50cm visc=1

to how much (grams/volume) stuffing did the visc=50 and visc=0 correspond?

[geitmans]

The standard viscosity is 1. When using a larger number you increase the viscosity.

I lined the throath and first section of the horn with polyester batting of around 2 cm thickness. When comparing the measured results with the calculations the 50 setting gave the best results. I also used a small amount of stuffing in the mouth area (20)

With these setting you can see a little bit the effect of the damping but as always you have to check the reality.