Basic knowledge for tuning
Grasping the relative difference in the balance of low-range, mid-range and high-range sounds, humans perceive differences in sound. The low range is defined as sounds below 300Hz, the mid-range as 300Hz to 2kHz, and the high-range as above 2kHz. The range in which sound pressure drops the most on the Sound Frequency Characteristic Chart, from around 700Hz to around 1 kHz, is considered standard, and the sound image changes in accordance with differtial between sounds below and above this range.
For example, let's consider what happens when Filter A is affixed to the sound pipe. (Please refer to the Filter A Frequency Response Graph on "About the Sound Character for Each Filter " chapter below.) With no filter, if 700Hz to 1kHz is considered standard, the differential in sound pressure in the higher range is greater than that of the lower range. For that reason, it feels as though sound is drawn toward the high-range. As we apply Filters A-1 thru A-5 in sequential order, attenuation of sound in the mid-range and the high-range increases. However, the impact on low-range sound is soft, and so the sound seems to be drawn toward the lower range.
As we move to Filter A-6 and beyond, the constraint on the mid-range becomes greater than that of the other ranges, placing emphasis on low-range and the high-range sound. When tuning, if drawing sound toward the low-range is desired, rather than changing only the low-range, please keep in mind that changing the high-range as well will change the relative feel of the sound, and adjust the overall balance with reference to the Sound Frequency Characteristic Chart and the Frequency Response Graph and the Sound Image Distribution Chart.
[About the Sound Impression Distribution Chart]
This is a chart that represents the relative impact on sound impression of each filter with the initial setting at the time of purchase as the default. The default setting is at the center of the 2 axes. With the horizontal axis representing sensation of high-range sound and the vertical axis represents sensation of low-range sound, the position on the chart indicates the level of change with regard to higher or lower level sensation.
* These values are based on the evaluation of an internal company tester, so please understand that they may differ to the evaluations by individual customers.
[About the Frequency Response Graph]
The frequency characteristic of earphones and headphones measures the sound pressure emanated when a 1mW (milli watt) audio signal is input into the earphone or headphone at each frequency. The vertical axis represents the level of sound pressure in decibels (dB), the larger the value the louder the sound. The horizontal axis represents the corresponding frequency of the sound in Hertz (Hz), the larger the value, the higher the frequency of the sound. This characteristic provides the fundamentals for the sound impression of earphones and headphones, and so it can be said to be the most important characteristic. Several other elements contribute to the determination of sound, so even sound with the same frequency characteristic can differ in accordance with various other factors.
* The 1 kHz value of this frequency characteristic is what is represented as "sensitivity" in earphone and headphone specifications.
** For speakers, a straight line (flat) is said to be proper graph, but a completely different way of thinking is necessary for earphones and headphones. For details please refer to the last chapter of "Acoustics lecture for knowing earphones / headphones" page. Please access there from the following bottom.