I have a 91 honda crx. I have 2 ssa evil 15's. And 2 american bass 500.1 the subs are dual 2 ohms. Each amp runs one sub at 1 ohm. Went to a show this weekend and found out it was not close to what i expexted. Had a 3 cube box with 2 4inch aero ports 18 inches long. The box efficiency was 98 percent but the box rise was 2.7 ohms at 50 hertz so the amps oonly were putting out a 1/3 of the power. Have zero guage wire ran. Was told to hook up both sides of amp also in future was also told need a larger port like a 10 inch port. Nothing is dynomated and yes i know i need a alternator. But had 4 batteries fully charged. Subs were at the b pillar and ports facing back. Only did a 144.7 resonant freq of vechile i believe is around 63 hertz from testing. Any i deas and help need this car at least to do 157 its for spl only. Box has to stay behind b pullar and 12 inches from highest point in ceiling.

 

get some deadener and make sure every thing is sealed up good. im also guessing your having alot of roof flex up at the window. usually the cars that are pulling above 155db I see a bar running from the top middle of the roof where the windshield meets the roof to somewhere in the middle of the center console. also play with your tuning I think your at 45hz now try higher/lower and see what affects your spl.
remove all carpet from your car replace with something rubber as well as your headliner
door opened>closed window down can also affect ur spl

i know this is a litte old but i just saw it

 

Will try thank you

 

i have a similar setup in my 323. i have subs firing forward with port back. im getting 148.3 i dont think im really doing much different i have three standard batteries nothing special. so id suggest what the other guy said and do deadening and lots of great stuff!

 

also it looks like your box is tuned around 33 hz

 

is your roof braced?

 

nope not a lick of deadening on the roof

 

but im using two 3000 watt amps and 1250 rms subs

 

Yea forget the deading and grab a 2x4 and wedge it between the back seat and at the top middle of ur roof(above rear view) make sure it's tight u should gain a couple to 5ish db even without deadener the roof is robbing sound pressure when it flexes

 

i have no backseat, but ill probably lean toward deadening before i do a stripper pole