I have an iMac, but the speakers are from my old PC setup. Nothing special about the little ones sitting on either side of my Mac. They are those typical ones that come with computers, but they have controls for bass and treble. But I also have an Altec Lansing powered subwoofer sitting under the desk and it makes a huge difference in adding depth to the sound. At work, I have two simple little speakers, with no treble/bass control (and even if there was bass control....), with no subwoofer. The sound is way, way better on the home system. On some concerts there is pretty good stereo seperation and the bass comes through. The Electric Flag late show is particularly good, as you can hear Harvey Brooks providing the bottom and the horns are nicely balanced. Miles drumming is too prominent on some pieces and Bloomfield's guitar goes in an out for some reason, but when it's all together like in "Ain't No Doctor", it's very, very rockin'.
The sound crews in those days were not working with much compared to now and it must have certainly been the case that some of them were in very altered states and thought things sounded OK at the time. Also, there were not monitors in front of the those singing until sometime in the late 1960's, so to hear bad harmonies is common. This fact is verified by The Bear, also known as Augustus Owsley, the reknowned maker of most of the LSD for the Acid Tests and many of the musicians heard in the Vault (personal supplier for the Dead, Big Brother, the Airplane, and Hendrix -- and some of his purple barrel ended in my mouth for my first trip in 1967, but I digress). When Bear got out of jail, he became the sound man for the Dead and other groups. His webpage is interesting -- he lives off the grid somewhere in Aussieland - and in one place he tells of the sound challenges they had back then.