I have a lil old guitar amp that holds an 8" speaker. Would it be a good idea to take the speaker out and replace it with a sub? I might not need to replace the amp guts, just need a power inverter for the amp itself. Might it be worth trying? I think it'd look cool too

 

thats totally up to you but in my opinion i wouldnt do that because it may not sound great like your expecting

 

That probably will not sound too great

 

sounds like one of my ideas and most my ideas end badly.

 

try it. never know what you can end up with.

 

Is there a calculator for optimum sub box size? I wanna see how it does

 

The box size is sub specific.

Look up your exact model of your sub and it will tell you how big the box needs to be.