Audio

General frequently asked questions about audio products.

1.What is "Frequency Response"?　
Frequency response is the measure of any system's response at the output to a signal of varying frequency (but constant amplitude) at its input. It is usually referred to in connection with electronic amplifiers and similar systems. The frequency response is typically characterized by the magnitude of the system's response, measured in dB, versus frequency.
The frequency response of a system can be measured by:

Applying an impulse to the system and measuring its response (see impulse response)
Sweeping a constant-amplitude pure tone through the bandwidth of interest and measuring the output level
Applying a maximum length sequence

Once a frequency response has been measured (e.g., as an impulse response), providing the system is linear and time-invariant, its characteristic can be approximated with arbitrary accuracy by a digital filter. Similarly, if a system is demonstrated to have a poor frequency response, a digital or analog filter can be applied to the signals prior to their reproduction to compensate for these deficiencies.

Frequency responses curves are often used to indicate the accuracy of amplifiers and speakers for reproducing audio. As an example, a high fidelity amplifier may be said to have a frequency response of 20 Hz - 20,000 Hz +/- 1dB. This means that the system amplifies all frequencies within that range within the limits quoted. "Good frequency response" therefore does not guarantee a specific fidelity, but only indicates that a piece of equipment meets the basic frequency response requirements.

Human beings are capable of hearing between 20Hz to 20kHz. Frequencies at or even above and below this may be relevant (sub bass, high harmonics).

2.What is Amplifier?　
A component that increases the gain or level of an audio signal.

3.What is Bass?　
Low frequencies; those below approximately 200 Hz.

4.What is Bi-Wiring?　
A method of connecting an amplifier or receiver to a speaker in which separate wires are run between the amp and the woofer and the amp and the tweeter.

5.What is Coaxial?　
A speaker typically with one driver in the middle of, and on the same axis as, another driver.
An audio or video cable with a single center pin that acts as the hot lead and an outer shield that acts as a ground.

6.What is Decibel (dB)?　
A logarithmic measurement unit that describes a sound's relative loudness, though it can also be used to describe the relative difference between two power levels. A decibel is one tenth of a Bel. In sound, decibels generally measure a scale from 0 (the threshold of hearing) to 120-140 dB (the threshold of pain). A 3dB difference equates to a doubling of power. A 10dB difference is required to double the subjective volume. A 1dB difference over a broad frequency range is noticeable to most people, while a 0.2dB difference can affect the subjective impression of a sound.

7.What is Impedance?　
A measure of the impediment to the flow of alternating current, measured in "ohms" at a given frequency. Larger numbers mean higher resistance to current flow.

8.What is Sensitivity?　
A measurement (in dB) of the sound-pressure level over a specified frequency range created by a speaker driven by 1 watt (2.83V at 8 ohms) of power with a microphone placed 1 meter away.