[quote name='squire5' post='1217517' date='May 2 2011, 01:42 PM']I still think that since starting to use the Squier P5,that this has been a major contributor to the problem.I use the low 'B' quite a lot,so having the 15" will actually cushion,or help to cushion the wear and tear on the 4x10.Time will tell,I guess.[/quote]
Whether you use a 1x15, 2x10 or another 4x10 with your existing cab, it's still gonna get the exact same amount of bass to it. Adding a 15" wont cushion anything but it will do the following (& maybe more) things, 1) make everything louder as you'll be moving more air & thus won't need to turn it up so far. 2) cancel out certain frequencies due to different sized drivers putting out different sized soundwaves (Sometimes has a positive effect, often has a negative effect).
Your new 10" drivers should be able to handle whatever you're throwing at them & I really doubt that your low B will harm them at all. But do let your ears be the judge of that.