There are a host of reasons this sort of thing can occur and it usually is a combination of factors including, bad speaker design, defective driver, bad amp/speaker match and room acoustics.
A peak at 100-130 Hz is going to make a system with what I call wet bass. I like my bass dry and always put a 2 dB notch there. What you describe is usually too much energy in the 2 kHz to 4 kHz region which makes a system difficult to listen to at volume and very sibilant. This is a very common room problem.
Listening to a multidriver system near field is a very bad idea as you start to hear the individual drivers. If you want to get an idea what the speaker sounds like in an anechoic environment take it outside and place the speaker on a 5 foot ladder on soft ground. What a PITA that is.
DEQX solves the problem by taking a very near field measurement of each driver at 6 inches then measurements from the listening position. From these measurements it can extrapolate what is due to the room and correct for just that and not the sound of the speaker which you do with EQ to taste. This is what your father's system needs, a DEQX Pre 8. Then he can make it sound however he likes.