Has anyone ever seen this kind of loudspeaker's crossovers in this picture?
It looks like there are two second-order low-pass filters cascading. I'm not sure if it is aimed for creating the half-way system or not, i.e., 2.5 or 3.5-way speaker system.
If it is meant for the half-way system, then, are there any formula for calculating those L1, C1, L2, C2 parameters? Assume WF#1 and WF#2 are identical.
It looks like there are two second-order low-pass filters cascading. I'm not sure if it is aimed for creating the half-way system or not, i.e., 2.5 or 3.5-way speaker system.
If it is meant for the half-way system, then, are there any formula for calculating those L1, C1, L2, C2 parameters? Assume WF#1 and WF#2 are identical.
It's the same formula like for every LPF, just the input of it is already filtered. And, ofc, the Qtc of the 2nd driver will be increased because of the additional Rdc of the L2 (many folks even forget to include the L1 Rdc to their simulation). Usually a 2.5 or 3.5 speaker is just using a 1st order LP for the 2nd driver since in most cases the 6dB drop/rise fits better in most cases. That, of course, depends if the .5 is used to compensate for the baffle step or 'just' to get a deeper bass. So the values of the parts is much more dependent of the actual speaker, baffle dimensions, tuning etc than the formula itself.
E: For the 2nd order LPF to actually work as intended, an impedance compensation (flattening of the fs impedance peak) is often needed - which makes it quite expensive.
E: For the 2nd order LPF to actually work as intended, an impedance compensation (flattening of the fs impedance peak) is often needed - which makes it quite expensive.
You really need to start using simulation tools! Formulas are not useful for real loudspeakrs.
I second that. It's useful to get a starting point for the values but you usually end up with completely different values unless you've got drivers with exceptioally linear impedance (AMT, magnetostats, ribbons, plasma etc) and no baffle step is in effect in their frequency range.
E: I.e. for woofers, a rule of thumb is to double the inductance to get closer to a realistic value.
It could be. It's also likely especially if the woofers are the same.