Suppose the passive crossover in a pair of speakers is dumping everything below 100 Hz, but they do receive the full range from the amplifier. However none of the low frequencies are being reproduced by the speakers. In such a csse is the amplifier under the normal load, or under reduced load, as the low frequencies are not being reproduced by the speakers ??
The amplifier is being fed the full range signal and therefore must reproduce the full range signal, it knows no better than to do as it is told. However, it will not be affected by the demands of the speaker's voltage and current draw, based upon impedance swings, at the frequencies the speaker is not reproducing. The stress on the amplifier has been lowered but not eliminated and the amplifier will still clip the large voltage low frequency demands of the signal if you ask too much of the amplifier. Reproducing signals from 100Hz upward still leaves a lot of the speaker's reactive load in place on the amplifier's outputs.
So I understand that the amplifier will definitely not be bearing the load of the frequencies the speaker is not reproducing, even though the amplifier itself is being fed the full range signal.
Yes, but as I said, the amplifier is still being asked to reproduce those low frequencies. Since the lowest three octaves require the most power to reproduce, the amplifier will still be under some strain if you ask too much of the power supply.