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Shiva sub in sonotube in trunk of my Subaru. Questions.

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#1 of 2 OFFLINE   Shawn Shultzaberger

Shawn Shultzaberger

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  • Join Date: Dec 02 2000

Posted February 18 2004 - 07:44 PM

Currently I'm in the planning phase of putting a sub in the trunk of my car. I've never owned a car that had a sub in the trunk. I've always had minivan's, trucks or hatchbacks with subs. The back seat in my Subaru Impreza does not fold down and is solidly mounted. It consists of the normal seat foam with a very thin 1/4" fiber board as a backer in the trunk.

I was looking to put a Shiva Mark IV into a sealed or ported sonotube. The sealed tube would be 14"w x 14"t for a volume of 1.24cu.ft. If I go with the ported it will be 16"w x 30"l for a volume of 3.48cu.ft. Reason for 16"wide is for (what I think is) a 3" x 10" port on the same side as the sub.

I can only guess at the volume of my trunk but it's probably around 25cu.ft.

My questions are:

1. Being that the sub will be in the extremely small trunk am I going to lose the cabin gain that I would get if the sub were in the cabin with me? Or will it be vice versa and I'll get more gain because of the smaller enclosed area the sub is in?

2. The sub will be pointed directly at the back of the back seat. Will the seat foam absorb a lot of the bass and basically muffle the sound?

3. Because of the seat foam and small trunk area which sub alignment would you suggest I go with?

4. Will a solid 300w RMS be enough for what I'm looking to do?

My music tastes are eclectic. They run from Country, to Metallica, to Electronica/Techno, to extremely Bass Heavy like Techmaster PEB (for the ultra low fix I need sometimes), to my Telarc classical CD's.

I've had MTX subs that were kinda muddy with kick drums but would shake your cheeks during the really low stuff. I've also had Infinity Beta 12's that did a kick drum justice but just wouldn't go low enough for me.

I appreciate any and all input.
"A human being is part of the whole called by us the Universe. We experience ourselves, our thoughts and feelings as something separated from the rest --a kind of optical delusion of consciousness. This delusion is a kind of prison for us, restricting us to our personal desires and to affection...

#2 of 2 OFFLINE   Gary Johnson

Gary Johnson


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Posted February 19 2004 - 05:47 AM

Shawn- I have done car audio for about 20 years and you are correct in most of your assumptions. I own a Forester, which I got because I could put the sub in the cab with me. I am very close to trading in for a WRX STI, which of course has the trunk with no fold down rear seat, so I'm am starting to investigate haw to implement the sub. The problem is you loose alot of bass output with the sub in the trunk. If you crack the trunk lid, you will get a tremendous increase in bass. This is because you are basically building a bandpass enclosure with your trunk acting as the second chamber. The only way I have ever found to really get good sound is to vent ALL the bass into the cabin. Usually this means building a bandpass box with the output port being fed up through the rear deck(usually through one of the rear speaker openings since you remove the rears because they're worthless.)sealing as well as you can around the port. Downside to all this is the box is harder to make and will probably take up more space than a conventional box. Upside is if it done right, you will have very good bass and will eliminate your questions 1,2 and 3. Gary

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