Well i am Liam from England been into car audio for 4 years now i have had the car from standard to what it looks like today all work has been done/paid for by me. The main aim for the car was a streetbasser that competes in propper droppers which is a format over here that tests how flat your system plays between 20Hz and 40Hz they test the system with the termlab on the passenger headrest and a window or door open, they test 20,25,33,40Hz and your peak then you get an average i am currently the loudest system in walled under 6,000rms.  
I have had 4 walled systems in the car over the last 2 years. 6 12s flat wall, 8 budget 12s ported tunnel then replaced the budget subs with some better subs and now i have the 18s. Current aim for the car is to keep my title on propper droppers and to make a low powered 149.9 bass racer

sounds system:
pioneer deh-p7100bt
audiocontrol epicenter
10x JBL: GTO-837 8" coaxial speakers
2x Genesis Profile 4
4x JBL: GTO-1201.1 Mono Amplifier (4,400rms total)
2x fi btl neo 2 18s with smd baskets fully loaded
2x XS power D3100
250amp @ 14.1 alternator
20m of 0gauge power cable
50m of speaker cable
20m 4gauge power cable
17cu:ft box made out of mdf, birch and steel sealed in with 10 cans of expanding foam
1" mdf roof with 3" of expanding foam topped with a 1mm steel sheet to cover sunroof
60 sq:ft of 2mm ivanhoe (roof, rear bench/boot floor, doors(inner and outer skin), rear quaters)
20 sq:ft of 4mm Silent Coat Extra Door Kit (foot wells and wheel wells)

Mods to the car:
custom center console for phone and gauge
custom door builds
15" white alloys
wide mouth grill
lowered 100mm front (coilovers) 100mm+ back
4-2-1 manifold
carbon fiber vinyl roof
full vt kit fitted and colour coded
fogs and front toeing eye smoothed and grill widened
side badges smoothed in
front grills black meshed
relocated immobiliser keypad
custom built keyles/fobles entry system

upgrade from standard 80amp alternator to a 250amp one 


Sunroof removed:



Door build:


The subs:






Build progress: was a rush job to get the 18s in and playing

















hairtricks





still got lots of things todo things todo next is flares and then im looking at upping the power time for some numbers

these number where the day after a weekend show where i had been playing with engine off so batteries where flat. did a 151.2 @ 41hz dB drag style
31hz tunning
Total average 152.5dB
peak 154.4 @ 33hz
40hz 152.5
33hz 154.4
25hz 153.5
20hz 147.7

with blockers 27hz tunning
Total average 152.6dB
peak 154 @ 33hz
40hz 151.9
33hz 154
25hz 153.5
20hz 149.8

Score from my old systems

ported tunnel tuned to 27hz with the 8 jbl gt5 12s did 150.1db @ 31hz dB drag style and the propper dropper scores where
total average = 152.1  
peak 153.5 @ 32hz
40=151.5            
33=152.6
25=153
20=149.9
 
then upgraded to the Ground Zero RW12-AL's did 148.6 @ 31hz db drag style and the propper droppers scores where
Total average 151.4
peak  153 peak @ 27hz
40hz 151.2
33hz 152.5
25hz 151.7
20hz 148.7

even thou ground zeros had better xmax more power handling and more of a solid cone the scores where down but to the ear it sounded alot smoother and cleaner
pictures of the ground zeros