Hello,
I want to build a 1x12 cab for my jensen jet tornado 100, i d like to use the tl806 plan but i know that a ported cab must be carefully planned.
There is a program to calculate the cabinet volume and vent area, this one http://www.linearteam.org/
I don t have a pc and i was wondering if any of you already used this program.
Here the speaker specs
I did, i also found an online calculator, and here is the result
I understand i can now come out with the measures of the cabinet to match the volume. What i don t understand is the vent, in the result it is shown as a sort of pipe, while on the tl806 there are three chambers underneath the speaker.
Mikante wrote: ↑Sat Jun 07, 2025 1:08 am
Yes, exactly, how can i calculate the size of the shelf port?
The diameter of the vent is 4 inches in the drawing.
It might be time to purchase speaker cab design software.
Tube junkie that aspires to become a tri-state bidirectional buss driver.
It is a one time project, i m not going to buy a dedicated program for that.
I will build the cabinet according to the cabinet volume suggested by the free program and adjust the vent on the going.
I don t need to tune the cabinet to 50hz, the speaker doesn t go that low. The tl806 cab is tuned around 70hz with the vent fully opened which is exactly how far my speaker goes.
the idea behind the 3-component shelf port in the EV TL series cabs was that you could install a port cover in the middle (across the two braces) to reduce the port area and change the port tuning to change the cab's frequency response. The EV data sheets refer to this as "step down mode,"
I know, with the vent cover on, the cabinet is tuned around 55hz, without it is tuned around 70hz.
One thing i don t really understand. When i do the calculation according to my speaker specifications, the cabinet volume suggested by the program is almost three times bigger than the tl806, 127 liters to be precise.
The program uses thiele-small parameters, so how did they do the calculation?
I know that an hi-fi cabinet is different and it is designed to not alter the sound.
If i enter the evm12l speaker specifications the program gives me a suggested cabinet volume that is much bigger than the tl806 too.
Hello, yes, the program gives you parameters for open, closed and ported cabinets.
About the vents, you can only chose the diameter, so it is for pipe vented cabinets.
The result is the drawing i previously posted, 4 inches diameter.
It looks like you can adjust tube size in this program.
On the TL806 drawing, take the port measurements and calculate total port area. Then calculate circle size with same area. Put this number into program and volume should be closer to TL806 volume.
IIRC port length is also a factor for volume calculation. If this can be changed in program then do so.
To be honest I'm going off memory of when I made some boxes myself while in my teens in the early 1980's. I was doing the calculations by hand using a book from Radio Shack as a reference.
Now my curiosity is peaked, I'll look deeper into this when I get a chance.
I know fo sure port size (cross sectional area) mattered and am pretty sure port length mattered too. I want to say its the flow restriction the port presents to the volume of air in the cabinet as it moves due to speaker cone movement that really matters. As port cross section decreases so does length (to keep flow restriction constant) but too small of cross section results in "whooshing or whistling" on lower frequencies.
I'll let you know what I dig up or hopefully someone better versed will enlighten us.
It looks like it doesn't matter with this online program, it does not change the cabinet volume according to the vents parameters. That is why i was unconvinced in the first place.
A guy in another forum posted some result using my speaker specifications, he s using Winlsd on window. 55 liters for the cabinet volume and one 10cm diameter pipe 10cm long is the suggested playground, not very close to my results
Anyway, thank you for sharing and partecipating
