Ok, for this question let's say you have One JL12w3

JL says the recommended sealed enclosure should be 1.00-1.5 cubic feet.

Now, let's assume it is running off of a 300w amp in each of the 3 scenarios:

1. 12in goes into 1.0 cubic ft enclosure
2. 12in goes into 1.25 cubic ft. enclosure
3. 12in goes into 1.5 cubic ft. enclosure


So, what happens to sound(both quality and volume) when the exact same sub is placed in each various size? Is there an optimum size? Does a larger or smaller size give you a tighter sound and less boom? Or vice versa?

How does this all work?

 

http://www.bcae1.com/spboxad2.htm

It is a very complex function without a simple rule of thumb.

Any sub box is a high pass filter. The smaller the box the higher the high pass filter effect. The larger the box the lower the high pass filter effect - AT MICROSCOPIC volumes.

At higher volumes, the performance of the speaker is dictated by the size of the box, because the air in the box is an air spring that is working with the suspension of the driver.

Basically, the sound difference you are likely to hear within that rainge is minimal. Outside that range you would hear more difference. You would probably get a slightly lower note with the larger box but not enough to disqualify using the smaller box.

 

Given the limited space in a G35C trunk I am trying to go on the smaller size so I can maintain functionality. So basically you are saying if I were to go with a 1.0cubic ft box for a jl12w3 it wouldn't be so bad since JL recommends between 1.0-1.5, correct?

 

Correct, they tell what will make them look good. If your amp has a parametric bass EQ **** you might use it to get back a hint of the sub bass you might lose.