Last time I played a rumble, it wasn't the 75w model you have. It was not a flat response sound. It was on the boomy side. That's with a stock 15" speaker it had.
You can see specs of a speaker at the manufacturers website. However it's a bit complex as no one spec will mean much alone especially without the cabinet specs, interior volume and port sizing (if ported)
If you can get that turbosound 12" cheaply it will work. Any speaker in your rumble will have a different sound. It will sound like a bass amp. Nothing random will be perfect. The original speaker will not be perfect. It will be like a preset eq. You can use the amps eq to flavour it just like you would if it was the stock speaker.
If you want a perfect sound (I.e your personal preference) then it is unlikely to be achieved with random selection.
You can see specs of a speaker at the manufacturers website. However it's a bit complex as no one spec will mean much alone especially without the cabinet specs, interior volume and port sizing (if ported)
If you can get that turbosound 12" cheaply it will work. Any speaker in your rumble will have a different sound. It will sound like a bass amp. Nothing random will be perfect. The original speaker will not be perfect. It will be like a preset eq. You can use the amps eq to flavour it just like you would if it was the stock speaker.
If you want a perfect sound (I.e your personal preference) then it is unlikely to be achieved with random selection.