series parrallel for 3 subs

Yup, with this diagram using 4 ohm voicecoils your amplifier load will be at 12 ohms. You wont have as much headroom if you ran them in parrallel, but at least you wont wreck any of your equipment.

I was afraid that was the case. I appreciate all the help. I have another sub that I can add to the equation. I just had the enclosure for the 3. I guees I can build a new box. Thanks again for all your help.a life without christ is a life that is never fixed-kj52

Sounds like a 4 speaker box is too big for your trunk. Considder constructing a 2 speaker box with 4 subs (isobaric), where 2 subs are facing each other in a clamshell. Wire the outside speakers in reverse so they pull instead of pushing. Your box will only need to be 1/2 of the calcualted volume on an isobaric setup. This way you can run a series parallel load with all 4 speakers putting 4 ohms at the amp.

You should nix thoughts of trying your hand at isobaric loading.  Forget you ever heard about it.  Drop your sub total to two, build a fine enclosure with all the volume those subs want, face the enclosure for optimal sound and power the subs with proper amp power.  More is not necessarily better.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

I ran some isobaric stuff back in the early 90s. I just had the 3 sub enclosure from another car and it fit nicely. I have plenty of room for 4 10s, I just didnt want to build another enclosure. Thank you all for your kindness.a life without christ is a life that is never fixed-kj52