Match LC Circuit to Exponential Horn

Temperature	T		°F	22.2	°C	295.4	K
Speed of Sound	c	13564	in/s	344.5	m/s
Density of Air	ρ		lb/ft³	1.196	kg/m³
Size Factor	SF		(1:Free Space, 2:Half-space, 4:Quarter-space,…)
Horn Length	L_horn		in	0.718	m
Throat Diameter	d_throat		in	0.025	m
Throat Area	S_throat	0.785	in²	0.001	m²
Mouth Diameter	d_mouth		in	0.178	m
Mouth Area	S_mouth	38.485	in²	0.025	m²
Exponential Slope	m	0.138	1/in	5.424	1/m
Mouth Low Frequency Cutoff	f_mouth	617	Hz	3875	rad/s
Horn Fundamental Frequency	f_c	149	Hz	934	rad/s
Inductor	L		mH	0.077	H
Capacitor	C	14.802	μF	0	F
Capacitor Temperature Adjustment	ΔC/ΔT	-0.028	μF/°F	-0.05	μF/°C
Series Resistance	R_s		Ω
LCR Bandwidth	BW_LCR	10.3	Hz	64.6	rad/s

Reset to Defaults.

Enter the horn and inductor values to calculate the capacitance needed for electroacoustic resonance. Some samples follow.

Note the LC product needed is more sensitive to the air temperature than the calculated series resonance bandwidth suggests. In practice, if the (usually parasitic) series resistance is low, the capacitance needs to be within one-half of one percent of the needed value to achieve resonance and drop the total impedance significantly. A temperature change of less than 3°F (2°C) is often all that is needed to detune the system. Weird acoustic artifacts such as honking and ringing are often present when the electrical and acoustic resonance frequencies are mismatched.

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Series LC Circuit to Drive a Horn-loaded Piezoelectric Transducer