yeah i just got one quick question. how would you figure out the spl for 2 12" subs if their efficiency rating is at 97dbs each sub. for the enclosure do you generally add bout 10dbs and type of car bout 7-8dbs. system will be 2000 rms 4000 peak. 1000 rms to each sub. thanks.
SPL is much more complex than that and there really is no way to figure it on paper as Jay mentioned. Keep in mind some of the factors that are involved: number of total speakers total power driver Xmech driver cone area cabin transfer point cabin sympathetic frequency enclosure design enclosure type enclosure location and position vehicle type and design charging system voltage and current supply ability which RTA or SPL meter you happen to use
these are just a few of the factors. There's really no way to tell, other than experience and eyeballing a guess, or getting it metered. for accurate results, use a Termlabs X RTA. that's the calibrated standard now.