CAT CAT Amplifiers and Loudspeakers 2 — Questions and Answers
Question 1: What type of amplifier topology is most commonly used in modern high-power commercial audio amplifiers due to efficiency?
- Class D (switching) (Correct answer)
- Class A
- Class B push-pull
- Class AB linear
Correct answer: Class D (switching)
Class D switching amplifiers can achieve efficiencies above 90%, making them the dominant choice for high-power commercial applications where heat management and power draw are concerns.
Question 2: What is the significance of a loudspeaker's Thiele-Small parameter Fs?
- The free-air resonant frequency of the driver (Correct answer)
- The frequency at which cone breakup begins
- The maximum safe input frequency for the driver
- The -3 dB point in the enclosure response
Correct answer: The free-air resonant frequency of the driver
Fs is the free-air resonant frequency where the driver cone oscillates most easily; it is fundamental to enclosure design calculations.
Question 3: When bi-amping a speaker system, which driver typically receives the amplifier with higher power output?
- The low-frequency (woofer) driver (Correct answer)
- The high-frequency (tweeter) driver
- Both drivers receive equal power
- The midrange driver
Correct answer: The low-frequency (woofer) driver
Woofers require significantly more power to move air at low frequencies, so the high-power amplifier channel is assigned to the LF driver in an active bi-amp configuration.
Question 4: What does the term 'impedance dip' refer to in loudspeaker specification?
- A frequency at which the speaker impedance drops below its nominal rated value (Correct answer)
- A drop in efficiency due to voice coil heating
- Loss of sensitivity caused by cabinet resonance
- A reduction in crossover filter slope at high frequencies
Correct answer: A frequency at which the speaker impedance drops below its nominal rated value
An impedance dip is a frequency region where the speaker's impedance falls below its nominal rating, potentially causing the driving amplifier to deliver more current than intended.
Question 5: What is the function of a limiter in a commercial amplifier or processor?
- To prevent the amplifier output from exceeding a set ceiling to protect speakers (Correct answer)
- To boost gain when signal levels fall below a threshold
- To reduce hum and noise in the system
- To equalize the frequency response of the power stage
Correct answer: To prevent the amplifier output from exceeding a set ceiling to protect speakers
A limiter clamps the signal at a defined maximum level to prevent clipping and excessive power that could damage loudspeaker voice coils.
Question 6: In a line array system, what acoustical behavior occurs when individual elements are properly coupled?
- Cylindrical wave propagation with slower SPL loss over distance (Correct answer)
- Spherical wave propagation identical to a point source
- Increased horizontal dispersion at high frequencies
- Total cancellation of off-axis reflections
Correct answer: Cylindrical wave propagation with slower SPL loss over distance
When line array elements are closely spaced relative to wavelength, they sum coherently and radiate as a cylindrical wave, losing approximately 3 dB per doubling of distance instead of 6 dB.
CAT CAT Amplifiers and Loudspeakers 2
What type of amplifier topology is most commonly used in modern high-power commercial audio amplifiers due to efficiency?