11.5: Procedure

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1. The circuit of Figure 11.4.1 can be thought of as a pair of frequency dependent voltage dividers. \(X_L\) increases with frequency, thus attenuating high frequency signals reaching R2. Similarly, \(X_C\) increases with a decrease in frequency, thus attenuating low frequency signals reaching R1. (R2 takes the place of the woofer while R1 takes the place of the tweeter). The crossover frequency is the frequency where R1 = \(X_C\) and R2 = \(X_L\) (normally the same frequency for both). Using C = 250 nF, L = 100 mH, and R1 = R2 = 620 \(\Omega\), determine the crossover frequencies and record in Table 11.6.1.

2. Using the voltage divider rule and \(E_{in}\) = 2 V p-p, determine and record the theoretical voltage at output one (R1) for each frequency listed in Table 11.6.2. Be sure to include both magnitude and phase.

3. Build the circuit of Figure 11.4.1 using R1 = R2 = 620 \(\Omega\), L = 100 mH, and C = 250 nF. Place one probe across the generator and another across output one (R1). Set the generator to a 2 V p-p sine wave at 50 Hz. Make sure that the Bandwidth Limit of the oscilloscope is engaged for both channels. This will reduce the signal noise and make for more accurate readings.

4. Measure and magnitude and phase shift of the output with respect to the input and record in Table 11.6.2. Repeat the measurements for the remaining frequencies in the table.

5. Repeat Steps two through four using the second output (R2) and Table 11.6.3.

6. On a single graph plot the magnitude response of both outputs with respect to frequency. On a separate graph plot the phase response of both outputs with respect to frequency.