I would use Mac’s play without amplification suggestion and see if the E and B strings still have lower volume. If they do before buying anything else I would change strings keeping the same gauge but maybe a different brand. I have had the same problem with some packages of strings, i.e. for some reason the E and B strings were DOA out of the package.

You didn’t say what gauge or brand of strings you are using but I have heard the same problem on many of my students’ guitars, acoustic and electric, when they use ultra-light strings 8s, 9s or 10s. Maybe the next gauge up will solve the problem.

Older strings have a propensity to exhibit the same problem, especially if you don’t wipe the strings down after every time you play. Could that be the problem.

I hope this helps and good luck.

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