I currently own a cheapy Ibanez seven string guitar that I want to upgrade the pickups for. I'm interested in putting active EMG's in but am wondering if I can add six string EMG in a seven string guitar? I currently don't use the low B string.
Having tried this (I have 2 7-string guitars: an Ibanez and a BC-Rich Warlock) I can confirm that although you will still get signal out from each sting, the signal levels will not be consistent, so it will sound wrong. Some strings will sit between two pole pieces, so the signal from them will be very low.
You could make a six string pickup fit the top six strings, but you may need to angle it, because as Tim pointed out, the spacing will be different.
If you like the EMG pickups, the simplest option is to buy an EMG 7 string pickup. They are a little bit more expensive, but not dramatically so.
The problem is going to be the spacing of the pole pieces. If you want to use 6 instead of 7, or any other change, then the poles of the pups need to be spaced accordingly. As in, each string needs its own pole piece, directly under each string. It will depend a lot on the string spacing of each individual guitar, so I don't know exactly for yours. The bridge will give clues - maybe that needs changing too, which puts extra problems into the equation.
I know with 5 string basses, there are at least two different string spacings, so even changing pups on one of those is fraught with problems.
Best left as is, and obtain the right instrument for the job you want it to do.
To the two geniuses that answered: EMGs dont have pole pieces, they use bar magnets. So yeah, it would work. BUT: Id wonder how youd fit them onto your guitar since the mounting holes arent placed for six string pups. Also itd probably look somewhat weird.. So WOULD it work? Yes. SHOULD you do it? Nah.