old Tline program-valid?

[mikee12345]

is this program any use at all thesedays?

i was looking that the 'magic' deathboxes over at car audio forums,and magic'snailshells' that hit 140db with 6.5" speakers,and i saw this loading on the cone in this program with a little compliance behind the speaker ....could be different things,,no one seems to know enough to say any facts..


a larger compliance shifts the frequency of 'booming ' in this case (high Q speaker) downwards.

PROGRAM DESCRIPTION


TLBOXMOD is a computer model of a transmission-line
loudspeaker system that uses the acoustic model proposed by
Bradbury (The Use of Fibrous Materials in Loudspeaker
Enclosures, JAES, vol. 24, pp. 162-170, 1976). In addition
it has provisions for tapering the line, inserting a coupling
volume between the driver and line, and for a line
cross-section different than the driver piston area. Also,
the air speed in the line is selectable as is the porosity of
the line filling.

 

[mikee12345]

compare with same speaker in ported box 55l
the Tline shows much higher loading at a very specific point

 

[MJK]

In my opinion, the TLBOXMOD program does not work. It is based on the moving fiber theory proposed by radbury which was in favor at the time. This theory assumed dramatic reductions in the speed of sound at low frequencies as the fibers coupled with the air and effectively increased the moving mass. I tried using this theory for years and was never able to correlate it against test data, it was always way off at low frequencies.

Bullock wrote an AES paper where he tried to correlate his program against test data. If I remember correctly, he concluded that the correlation was poor.

 

[mikee12345]

Thanks for shedding some light on this

i thought it maybe some retro not understood or well implemented idea.

cheers!