I joined this site to ask this question...

I am upgrading my subs from two 10" alpine to two 15" subs, not sure what kind yet..however I cannot be persuaded to a certain brand so save your breath. The only advice I am asking you people maybe laughable to the versed car audio individual....but here goes. I drive a custom car. The trunk is almost completely fiberglass (major structures and mechanics aside) and I don't want to encourage my trunk walls to flex, bend, alter, warp, or MOVE. BUT, the trunk is not sealed...In the front seat of my car I can look and see the very back of the trunk. Would it make sense for me to buy a sealed box or a vented box? (keeping the request of having minimal flex in my trunk walls in mind) My dim witted logic tells me that a vented box pushes more air around and would encourage the fiberglass trunk structure to move around more. BUT, because the trunk isn't sealed would the air pressure dissipate to the rest of the chamber/cabin of my vehicle and not be an issue? Should I dynamat and get the subs in a sealed box? I need your 5 cents here, folks. I don't want my fiberglass trunk walls to move..sealed or vented?

No matter what you do, even with an open trunk, it will still pressurize, your best answer would probably be a trunk wall, the subs would seal off into the cabin behind the rear seats and minimize pressure buildup in the trunk itself.

Ported or not depends mainly on space/design constrictions, most cars wouldn't be able to fit the ~8 Cubes a pair of ported 15's would need to breathe properly.

2 15s is going to flex the shit out of it either way. I'd recommending using CLD tiles (dynamat or similar) on the back of the fiberglass if possible

2 /12 in Daytons in a sealed enclosure, with min rms power might be alright

Yea with 2 15" you are going to have flex. unless you only use about 300 watts. and you still will have some minor flexing.

I do have the abililty to seal the trunk area if I want, but wouldnt that make more pressure (smaller space)? So you are recommending a sealed box with a sealed trunk?

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Originally Posted by billsburgundy

I do have the abililty to seal the trunk area if I want, but wouldnt that make more pressure (smaller space)? So you are recommending a sealed box with a sealed trunk?

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I'm assuming behind the back seats you have a large hole? if so, this is what I mean.

http://img.photobucket.com/albums/v2...7/DSCN1381.jpg

The box is port and subs firing forward, into the cabin, completely sealed off from the trunk itself.

I have two sealed 15 inch radio shack pieces of junk on 300 watts rms in the trunk of my car and there is FLEX.

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Originally Posted by UnderFire

I'm assuming behind the back seats you have a large hole? if so, this is what I mean.

http://img.photobucket.com/albums/v2...7/DSCN1381.jpg

The box is port and subs firing forward, into the cabin, completely sealed off from the trunk itself.

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^^that^^

jes 42...that would be very similar to my setup...do you get more trunk flex when the backseat lid is up or down?

or, is the lid always down...kindve looks that way....

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Originally Posted by billsburgundy

or, is the lid always down...kindve looks that way....

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Most of them will fold up just fine and work like stock, I would prefer to mount the amp in the trunk rather then on the seat directly in front of the port though.

seriously people?

op, fiberglass is used in the construction of subwoofer enclosures fairly often. It's very stiff stuff unless it's a large flat panel, but even then you can stand on a quarter inch thick piece, lol... If it's strong enough to be part of a vehicle, then it will hold up fine to a system.

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Originally Posted by av83

seriously people?

op, fiberglass is used in the construction of subwoofer enclosures fairly often. It's very stiff stuff unless it's a large flat panel, but even then you can stand on a quarter inch thick piece, lol... If it's strong enough to be part of a vehicle, then it will hold up fine to a system.

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I wouldn't want constant flex on fiberglass, if it's anything like a boat hull, it may be very stiff, but fiberglass is very prone to stress cracks.

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Originally Posted by UnderFire

I wouldn't want constant flex on fiberglass, if it's anything like a boat hull, it may be very stiff, but fiberglass is very prone to stress cracks.

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fiberglass car body panels are thicker than boat hulls. They are also smaller, which increases the resistance to vibration caused by sound.