Sealing the trunk off? Need Help

I have a little dilema. I built my subwoofer to fire into the cabin of my car. It doent seem as loud as it should be. So I asked the one guy I know who has sort of the same setup. He says that what rear waves that get generated from the sub reflect off of the trunk and cause the destructive interference with the front wave. So in order to cancel that he said i needed the seal the trunk off from the cabin of the vehicle or to port the trunk so it all has somewhere to go. I did notice that when i open my trunk that it does get louder and more defined in the vehicle, even when the windows are open. So does anybody have any hints or tips on helping get rid of my problem? here is a link to my pictures of it so you know a little about what im talking about : http://www.cardomain.com/memberpage/430050/2

It sounds like cancellation big time to me. Try putting that sub in a proper sealed box and see if it sounds better. Or, if you wanted to keep your fiberglass front you made you could just build a box behind it and you'd be done.

the fiberglass front is just that. a front. i have the sub in a sealed enclosure attached to the rear of it and the sub pokes through.  its in the proper size enclosure and that was a little bit of my first problem and thought that could have solved it. it helped a little but wasnt enough obviously. you said build a box behind it. do you mean to have an enclosure go around the sub enclosure? i was thinking something like that and packing it with a deadening material. or do you think i can just cover the sub enclosure in the deadening material instead.  ive always had my stereos with the subs in the trunk. im new to having them this way. since my seats fold down in this car id figured i try soemthing new.

Im pretty sure he means to completely seal the sub in its own enclosure. Maybe even somehow attaching it to the existing fiberglass work , nice job on the entire system by the way. I dont know if it will make any difference at all but I was going to suggest reversing the polarity just for a few moments to see if that made any difference. I dont think it should in an IB set up but its all I could think of rather than adding the extra enclosure. Keep us posted.99 F-one fitty

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the sub is in an enclosure already and the enclosure is attached to the front fiberglass piece. so its not an IB setup. alot of people think that lol i can remove the enclosure from the fiberglass piece if i ever needed to. i tried reversing the polarity, both by physically switching the wires or by using the reverse phase option on my hu. but to no avail there wasnt a difference in the sound.

No, switching the phase won't work in this case.  The rear waves are travelling far enough back to the rear of the car, then reflecting toward the cabin to cause a noticeable 180 degree phase cancellation wave.  The two waves (front and rear) are cancelling each other out.  When you opened the trunk and found it to be louder, that proved it.  The open trunk allowed the rear waves to escape the vehicle, so only the front waves arrived and were unimpeded.  http://www.installer.com/tech/aiming.html identifies this problem.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

"I did notice that when i open my trunk that it does get louder and more defined in the vehicle, even when the windows are open." The reason that it got louder is because you created what resembles an Infinite Baffle. Meaning the Air movement created by the front of the cone does not meet the Air Movement created by the rear of the cone. A few subs perform best in Infinite Baffles, or really large boxes. I don't think that your problem is Phase cancellation. Trunks are usually irregular shapes (Not squares). This causes the sounds waves to Not "bounce" directly back at the Cone. For the sound waves to cancel each other out, they would have to be approximately 180 Degrees phase of each other. With the irregularities of a trunk, this does not usually occur. Annyway... I would suggest that you better insulate the Cabin from the trunk space. This should prevent any, if there is any, cancelation from occuring I think the problem is that you have an improperly sized "enclosure". To fix this, you could measure the entire volume of the trunk space

stevdart wrote: No, switching the phase won't work in this case.  The rear waves are travelling far enough back to the rear of the car, then reflecting toward the cabin to cause a noticeable 180 degree phase cancellation wave.  The two waves (front and rear) are cancelling each other out.  When you opened the trunk and found it to be louder, that proved it.  The open trunk allowed the rear waves to escape the vehicle, so only the front waves arrived and were unimpeded.  http://www.installer.com/tech/aiming.html identifies this problem.

thanks for the link. so, this is what i got from it. since there is better response with the sub in the back of the trunk becuase the rear waves dont travel as far and dont end up being 180* out of phase. so, that being said if i built a wall behind the enclosure, sealing it off 95% from the rest of the trunk, it would more than likely react the same way that it would if the enclosure was farther back in the trunk? is that correct? my amp rack is going to be a wall right behind the enclosure to help with trunk space, so if what i asked was true i should be able to use this as part of the wall to seperate the enclosure from the rest of the trunk. since the back wave wont travel as far and hit off of something (wall/amp rack) before it gets to the rear of the trunk.

I think you're on the right track, as that is what I was thinking as well.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

stevdart wrote: I think you're on the right track, as that is what I was thinking as well.

Ok cool. at least we're getting somewhere. lol and poormanq45, im going to dynamat the entire rear deck area and seal off any holes that i may see and and use some minumum expanding foam for the smaller ones that are hard to reach. that way was the one thing i was told to do first. since im finding these different ways ill do em both. anyone else have tips?