Relation between Vas and Enclosure volume

[tda]

For the moment I left the big box and I built another enclosure with a 6’’ driver. This time I follow MJK advises, the enclosure 1 m long, the top and bottom area are just 260 cm^2. The result is excellent. The response is almost exactly as the MathCAD sheets predicts it. The volume of the enclosure is around 26 l and the Vas of the driver is 9 l…so is 3 times smaller, but in this kind of enclosure it seems that the rule of VAS for ported and sealed enclosure is not applying. MJK has the answer for the behavior of quarter wave’s designs, and most probably he’s right.

[tda]

I just finished all the nearfield and farfiled measurements for my new system. On nearfield measurements everything is corresponding to MathCAD sheets, the results are smooth between 45 Hz and 2000 Hz. In farfield measurements, the baffle step is almost exactly like the Excel Baffles Step Simulator predicts it, so I’m very happy with the results…with only one exception….the maximum power applied to the system is around 8-10 W. If I increase the power, the speaker excursion became large, over XMAS specifications, and the sound at low frequency is distortional.
Of course, I can build a Subwoofer and make a crossover at 100 Hz, but then what is the sense of the Transmission line? I can put my 6’’ driver in closed box instead of a TL large enclosure…I’m curious if anybody faced the same problem. I read a MJK reply on this forum and he doesn’t seem to be concerned about cone excursion. He used in one of his project 6’’ ½ drivers… I wonder if he faced the cone excursion problem.

[MJK]

I read a MJK reply on this forum and he doesn’t seem to be concerned about cone excursion. He used in one of his project 6’’ ½ drivers… I wonder if he faced the cone excursion problem.

Hi tda,

I have not really had any cone excursion problems. This might be a function of the music I like and the volume level it is played at. I listen to acoustic music, almost exclusively old mainstream jazz. I have pushed some of my speakers very hard on occasion but have not noticed any real degradation of the sound. If I watch the driver I do not see large excursions.

Somewhere in my CD collection I have the Telarc 1812 disc which I have used on occasion when a visitor wants a real thrill. I used to have a big Focal 3 way speaker and did manage to bottom the ported 10" woofers very hard a couple of times. I put that disc away and don't play it through my Lowther or Fostex systems.

Maybe your reproduction needs are more severe then mine,