For critical audio monitoring, here are some characteristics to look for in a monitor loudspeaker:
- Full audio bandwidth of 20 Hz to 20 kHz. The very low frequencies are often handled by one or more external sub-woofers, especially with surround sound systems.
- A smooth frequency and phase response, both on-axis and off-axis, over the audio bandwidth. Look especially at the frequency and phase response plots at the crossover region, where the audio signal transitions from one driver to another (from one frequency band to another). Listen critically in the crossover frequency ranges. This is where anomalies often occur.
- A smooth off-axis response (smooth polar response). Most loudspeaker systems by design are directional, that is, sound pressure level decreases as you move around the loudspeaker from on-axis to off-axis. However, the higher frequencies are more directional than the lows. In fact, the very low frequencies tend to be fairly omni-directional. This means the farther off-axis you listen, the more the highs will decrease compared to the low frequencies, resulting in a more bass-heavy sound (frequency response). A good monitor loudspeaker will have a fairly uniform frequency response, even off-axis, especially over the coverage angle of interest.
(c)2005 Mary C. Gruszka