TL Tapering - quick question

[MJK]

Hi Navin,

does this mean that the more one tapers the line the smaller the TL will be (in length) but also one will get less output?

Yes, the more tapered the TL the shorter the length. Why do you think that the output would drop? I have not reached any conclusions on the output, Attachment C shows that the tapered TL's output is sufficient to match the driver's efficiency.

say my TL is 100" long. the fs of my woofer is 20Hz. i would have to have SL/SO = 0.1 that means a 10:1 taper. it also means Dz of 36.482!

Those values look about right.

also i dont see anywhere where there is a relation between Sd and area of the line. this area i assume is the start of the taper.

If you follow the sample problem on page 13, it demonstrates how to calculate the line areas as a ratio with Sd. You need the drivers T/S parameters and the values from reading the tables to perform this calculation. Be very careful to make sure you are using the correct units in the calculations.

Hope that helps,

 

[navin]

MJK, I get lost where So/Sd is calculated as per page 13.
i get a number that is 2236.618 and you get a number that is 2.872.

 

[navin]

oops. i punched the numbers wrong. Bl is in the denominator.

ok i get it.

my woofer's specs.
Fs=17Hz, Qts = 0.44, Sd= 0.044m2, BL= 7.8 Tm, Vas=380 liters.

If I tune the TL to 20Hz and have a SL/SO=0.1 I need 103". based on the above specs the So/Sd=3.

Now how do I detmine offset and stuffing?

 

[planet10]

Now how do I detmine offset and stuffing?

Offset is given as a ratio from the closed end... from memory 0.34 something on a 3:1 line... and i believe i asked Martin the question about stuffing and it was 0.25 lb/cu ft or about 4 g/liter (if my calc is right -- it is time to go to bed) but you could easily play with up to double that.

dave

 

[navin]

So/Sd=3. Sd=440cm2=70 sq. in.. so So=210 sq. in. ouch! that is huge! what happens if we retain length as 103" but reduce to So=Sd.

 

[MJK]

Now how do I detmine offset and stuffing?

For the alignment tables stuffing really needs to be done by ear. The other alternative is to put the alignment into the mathCad worksheest and further optimize the geometry and the stuffing.

So/Sd=3. Sd=440cm2=70 sq. in.. so So=210 sq. in. ouch! that is huge! what happens if we retain length as 103" but reduce to So=Sd.

Decreasing area reduces bass output, increasing area provides more bass output. If you really want to know how much smaller the enclosure could get, you need to model it in the worksheets. I do not predict an optimim design with the alignment tables, I just try and provide a good estimate for an enclosure that will produce TL type bass. Unfortunately, TL's tend to be bigger then was previously thought which is the conclusion I came to years ago with my Focal design.

 

[navin]

u can that again! TL's tend to be much bigger than thought.

presently the woofers i have are in 65liter sealed boxes. there is some boom. partly due to the high Qtc and partly due to the room.

my hope is to reduce the boom.