All speakers create sound based on a Bell Curve (yes, math!). With subwoofers they range from inaudible pressure waves to a manly man's voice. Tweeters will range from high notes on a guitar to making dogs howl.
Right in the middle of those ranges is the resonant pitch. That's the single most powerful and loudest frequency (note) for an equitable amount of power to other frequencies (notes).
For some subs, that's at 60Hz, for others it's at 47Hz, others 100Hz etc. That's where you get the most 'punch'. With your old speakers, those had a different resonant frequency for each of the included speakers. They might have had mediocre bass, strong mids, weak highs, and then your new speakers might have stronger bass, stronger mids, mediocre highs.
Which is going to change the sound table you are used to listening to. This is what an Equalizer is for, whether software or physical, to change the amplitude of the source particular frequencies which can add or subtract to the volume of any one note. So if the speaker sounds too 'tinny' for your liking, you can take a little of that out, if it sounds too 'muddy', you can clear it up, by enhancing or detracting the amplitudes of certain frequency ranges.
Most software equalizers have presets, like 'Pop' or 'Rock' or 'Jazz', but some will also include sound affects like 'Concert Hall' or 'Open Field', 'small Room' etc.
Put on your favorite music, or talk show or something you are very familiar with and know exactly how you like to hear, then adjust the equalizer to make that happen. On my pc, my new speakers had way too much highs and not enough bass, so I turned the speaker to face the wall 6inches away instead, thereby changing the sound stage. Got more bass and less highs.
Sound is a sine wave (yes, math again!). The most volume or punch will be at the top of the wave, looses power at the bottom, comes back to zero. A 60Hz bass wave is physically 15ft long sine wave. So to get the most 'punch' your head should be about 4ft away. In a car, that's awkward, so you place the sub to catch the 'next' wave at 15ft + 4ft, 19ft is easily do-able. For some, that means facing the sub towards the back of the trunk, for some it downward, or upwards or facing the driver.
Physical location, direction, refracted sound from objects or walls can play a massive role in exactly how you perceive the sound at the location of your ears.
Sound reproduction is highly subjective. It all depends on the individual tastes of the listener. Getting that 'right' sound can be a real pain as it often involves changing speakers, changing speaker locations or directions, lots of time messing around on the equalizer etc.