ok i am a big time noob to box's, but i do know ported is more spl and sealed is LSQ. For a BL you need to go ported. But for a ported box which would be the loudest out of the 4 combinations, small box small port, big box small port, small box big port, smal box small port? all i am concerned about is spl/loudness. (it is for a 15 BL.) thx.

It depends on MANY factors...

How much space do you have to work with? Loudest depends on range, tuning, power and other factors. You will gain efficiency in a larger box than over small... this is great for lower power, but there is a point where the smaller box will handle more power (mechanically) and might take over in overall output as well since you can dump more into it. Too small of a port will result in compression and lack of the port coupling with the surrounding air (and noise).

Let us know space wise what you have and we can try to optimize things for it.

Thanks,

Scott