My SWR Silverado Special (300 watts, 2x12 combo) is having speaker issues when I play loud low notes, the bottom speaker makes horrible rattling/farting/grinding sounds. When I push my finger against the speaker (not the cone) and play, the noise pretty much goes away. Has this speaker been blown? My suspicion is that it has, since the upper speaker seems to be just fine. If I have to replace the speaker ( have no problems replacing and wiring it myself), is it worth it to get a SWR replacement, or is it more cost effective to purchase a different speaker? Also, if I replace one with a different speaker, should I also replace the upper speaker or should I replace both? Thanks in advance for the help.