Thiele's Alignment based on Q_t

Thiele's method is to choose an alignment based on QT.
Alignment				Box design
Order	No	Type	Ripple(dB)	f3/fs	fB/fs	VB/VAS	QT
Quasi Third Order	1	QB3	---	2.68	2.000	0.0954	0.180
	2	QB3	---	2.28	1.730	0.1337	0.209
	3	QB3	---	1.77	1.420	0.2242	0.259
	4	QB3	---	1.45	1.230	0.3390	0.303
Fourth Order	5	B4	---	1.000	1.000	0.7072	0.383 optimally flat
	6	C4	---	0.867	0.927	0.9479	0.415
	7	C4	0.13	0.729	0.829	1.372	0.446
	8	C4	0.25	0.641	0.757	1.790	0.518
	9	C4	0.55	0.600	0.716	2.062	0.557
	9.5	C4	1.52	0.520	0.638	2.60	0.625

Example: fs = 30.4 Hz Vas = 125.9 liters Qe = 0.249 Qm = 3.9934 Rs = 7.4 ohm EBP = fs/Qe = 122 --> vented With 0.5 Rext external, QT = 0.249 Looking at the table, this QT suggests alignment No3 ( QB3 ), giving: Vb = 28.23 liters fb = 43.2 Hz f3 = 53.8 Hz   Calculator: fs [Hz] : Vas [liters] : Vas [cu.ft.] : Qe [] : Qm [] : Re [ohms] : Rext [ohms] : Calculations: EBP [] : QT [] : Vb [liters] : Vb [cu.ft] : fb [Hz] : f3 [Hz] :   Port calculations   Dv : [cm] Lv : [cm] Pa : [cm2]   Dv : [inches] Lv : [inches] Pa : [sq.inches]   If you change the pipe diameter [Dv], click on 'Port' to recalculate Port length. GLOSSARY OF SYMBOLS fs - resonance frequency of driver in free air Vas - volume of air having same acoustic compliance as driver suspension Qe - Q of driver at Fs considering system electrical resistance only Qm - Q of driver at Fs considering system nonelec-trical resistances only Re - dc resistance of driver voice coil Rext - dc resistance of crossover-filter-coil and speakercable EBP - efficiency bandwidth product QT - total Q of driver at fs including all system resistances Vb - net internal volume of enclosure fb - Helmholtz resonance frequency of vented box f3 - alignment (-3dB) cutoff frequency Dv - Diameter of the bass reflex pipe Lv - Length of the bass reflex pipe Pa - Area of the bass reflex pipe

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