Originally Posted by
Ruediger
You should 1st design the crossover network, and decide which series coil You can afford. The DC-resistance of that coil will determine the resulting Qt of the driver. According to the TS-params table the driver alone has a Qt of 0.21, with a series coil it will get larger.
The formula for Qt is:
1/Qt = 1/Qa + (1/Qe) [Re/(Rg + Re)]
Re is the DC-resistance of the speaker's voice coil.
Rg is the "generator" resistance: Output impedance of amplifier (8 Ohm / 200 or better), cable resistance and series resistances in the crossver.
TS-params for the 2215 from the table:
fs = 20 Hz, Qt = 0.21, Vas = 736 ltr,
Qm = 5.5, Qe = 0.22, Re = 5.7 Ohms
In the Technical References Thread (General Audio Discussion) there is the Thiele paper. In table I there are the alignments.
Say Your drivers Qt would become 0.259 (3rd entry in table), then
f3 = fs * 1,77,
f3 / fb = 1.25,
Vab = Vas / 4.46
f3 would be 35.4 Hz, Vab would be 165 ltrs
Other alignments with a not ideally flat response curve are possible, but the 1st thing You need to do is to estimate the effect of the crossovers DC-resistance (see the table in the papers and experiment a bit), and then let somebody with a PC-program do the calculation for You.
Let him do the calculations with the corrected Qt!
Ruediger