i'm sorry guys, but if someone wants a mid-scooped tone who are we to say that it's "wrong"? markbass prides itself in its VPF and VLE, which are mid scoop and low pass filter controls. seymour duncan's paranormal has a "slap contour" which is a mid scoop and bass boost.
sure, mids can help you cut through the mix. but if that's the only way you are going to be heard in the mix, your tone is gonna be one-dimensional. and while the grit is good for rock, nobody ever thought of asking what genre of music being played. you can also boost the highs for your tone to have presence. what happens when you boost bass, mids and highs? you need more power.
at the end of the day, mids cannot substitute actual power.
if the guitar amps are stacks, they are probably 100w of solid state power. preferably you would need 300w of power to amplify the lows. remember that different frequencies need different amounts of power to be amplified. past a certain point, all you are increasing is the highs, while the lows get stuck or worse, start to distort.
now you don't need that kind of power in a jam session. but the reason why jam studios do this may not be because of power, it may be because of tone, and a certain tone you get when you push the guitar amp at a certain level.
you can crank up the gain on the bass amp, but as we all know, the tone starts to deteriorate past a certain point on all solid state amps. there is absolutely no way a 15" combo is going to provide that kind of power. if there are 2 heavy guitars in your band, nothing below 150w is going to be heard, unless at the expense of tone. and let us not go into highly complex discussions of the overall volume level of 1 vs 2 guitar amps.
to quote a talkbass user, "mids will get you by when you are broke, but i prefer the good stuff"
anyway, regarding studios, i played at fourtones once where there was a hartke 3500 into a 4x10.
