SPL loss when hatch closed

I am currently in a situation that makes me think that my biggest mistake was to remove the back seat for nothing.I am currently running 1 Massive audio P3000.1 amp running at 4 ohms onto 2 Atomic apocalypse SPL 15s in a 7.5 cubic feet per box(sub) tuned at 50hz,I have this installed in a 1990 VW Golf,And it is totally noticeable that when I have the hatch open the bass hits harder and deeper for sure. I have the subs and ports pointing towards the front of the car.I was thinking that maybe I have to isolate around the front of the box to the back of the hatch area.
I would greatly appreciate any help.Thanks again.
Alex B.

is it truly an SPL loss (tested with a meter) or does it just "sound" quieter? just because it sound quieter doesnt mean the SPL is less, it might actually be more.

Thanks for the reply, It isnt just quieter but it sounds like if the subs where out of phase even,im no physics pro but im thinking that maybe the front pressure is bouncing off the front windshield and coming back towards the hatch area enough to cancel ttself out a little.Any more advice would be greatly much appreciated.

I posted a thread on this recently. You want your subs to be further away from you and not point at you, but away from you, 180 degrees away. Point them at the back of your car and be done.

yes, you get better response with the subs facing away from you. your best bet would be to try it, i know its gonna be hard with a 7.5^3 box but it will be worth it.

Thanks for the replies guys,I guess Im going to have to try them pointing them back into the hatch area,like most are advising me to do.I still dont understand why then most spl competitors have them directly behind them,like pointing towards the front. I guess trial and error I think. Man this is going to be a pain in the ass to do lol.The whole box measures 28"X36"X34" made out of 1" MDF.
Thanks again guys,does any one else thinks the same way? Or should I try something else.

i dunno, but all i know is i love the old golfs, and that sounds like a bad ass system. I once had a pair of old Atomic 10's and they had mad excursion [for 10's]... any pics of it? i would love to see this beast Pofke13@sbcglobal.net

I dont know quite what SPL competitors you have seen or talked to.   But I know all of my vehicles have some sort of reflection for the ports.

The only vehicles that should be firing at your is a complet walled off setup (modified setup)

All our vehicles fire away, My crx is ports back subs up. Our civic coupe is subs up ports up, in the trunk firing at the lid.

The Mazda mini, scion xb, and blazer extream are all subs up ports up.

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

Scores from those cars....

CRX 158+   not telling quite where it is, USACi finals is a few weeks away
Civic coupe 153.5

Mazda 152.1
Extreame 152.0
scion 151.0

All those except the CRX are using (2) Kicker L7 12's on (2) Kicker KX1200.s

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2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR
2007 USACI World Champion
2007 World Record
2006 USACI Finals 2nd Place

so Jeff the Civic is louder than the Xb? damn..... seat folded down right? do you have any opening in the rear deck or just the seats folded down?

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Shaking The Neighborhood