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9. CAUTIONS CONCERNING HIGH-IMPEDANCE APPLICATIONS
To avoid damaging the HB-1 speaker in high-impedance applications (with the MT-S0601 matching
transformer installed), be sure to observe the following conditions:
1. Do not limit the input signal band using such devices as a low-pass filter, but instead drive the speaker with
the full-range signal.
2. Use a high-impedance amplifier with a power rating higher than the wattage tap selected on the matching
transformer.
Note
There is a low-frequency threshold for both the speaker matching transformer and the high-impedance
amplifier output transformer.
[Matching transformer low-frequency threshold]
If a signal with frequencies lower than the low-frequency threshold is applied at rated power, the transformer's
primary impedance (input impedance) decreases abruptly due to core magnetic saturation. With the MT-
S0601, the impedance begins to decrease at approximately 40 Hz for the rated input power of 60 W, and is
almost halved at 30 Hz. If the speaker is used under this condition, an increased load is put on the power
amplifier as well as the matching transformer, causing potential equipment damage.
The low-frequency threshold varies depending on the selected transformer tap, and the smaller the tap-
selected wattage, the lower the threshold.
[High-impedance amplifier low-frequency threshold]
When a full-range signal (not band-limited) is applied, the amplifier is not adversely affected. However, if the
signal is band-limited with a low-pass filter and driven with rated power, an increased load is put on the output
stage, causing potential amplifier damage.