OK. So I want to tune the TL to 40hz. This is an attainable tuning and should suit the driver very well, giving me plenty of deep bass without over stretching.
I have also decided to go with an untapered line for 2 reasons. The first reason is it allows me to fit 3 folds instead of the 2 I had before into my standmount giving a much longer line without making the design excessively deep. The second is that it will just be a lot easier to put together and thats no bad thing.
To attain the desired tuning frequency with an untapered line I need a length of 210cm. The box height will therefore be increased to 55cm giving a line length of 208cm.
I ahve also decided to reduce the width of the box to 18cm for reasons that Zaph describes in his ZD5 design.
The final part is where I really need help - choosing the area of the line.
According to Martin King, the optimum area is:
S0 = ((rho)*c*DZ*DR*Re)/(B^2*l^2)
I will go with a value of 460 for rho*c (acoustic impedance) unless someone can suggest a value better taking into account stuffing of the line.
Sd = 95
DZ = 38.858 for my tuning and taper (from tables)
DR = 0.14 (from tables)
This leaves me trying to work out B and l where B is the flux density in the voice coil air gap and l is the length of wire in the voice coil air gap.
My first guess was that these would simply by the Bl value quoted for the driver, especially since the units match, but it gives a silly answer so I must be wrong. Can anyone offer any help here?
Thanks
I have also decided to go with an untapered line for 2 reasons. The first reason is it allows me to fit 3 folds instead of the 2 I had before into my standmount giving a much longer line without making the design excessively deep. The second is that it will just be a lot easier to put together and thats no bad thing.
To attain the desired tuning frequency with an untapered line I need a length of 210cm. The box height will therefore be increased to 55cm giving a line length of 208cm.
I ahve also decided to reduce the width of the box to 18cm for reasons that Zaph describes in his ZD5 design.
The final part is where I really need help - choosing the area of the line.
According to Martin King, the optimum area is:
S0 = ((rho)*c*DZ*DR*Re)/(B^2*l^2)
I will go with a value of 460 for rho*c (acoustic impedance) unless someone can suggest a value better taking into account stuffing of the line.
Sd = 95
DZ = 38.858 for my tuning and taper (from tables)
DR = 0.14 (from tables)
This leaves me trying to work out B and l where B is the flux density in the voice coil air gap and l is the length of wire in the voice coil air gap.
My first guess was that these would simply by the Bl value quoted for the driver, especially since the units match, but it gives a silly answer so I must be wrong. Can anyone offer any help here?
Thanks
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