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Port length, through a decklid

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=82207
Printed Date: May 13, 2024 at 8:11 PM


Topic: Port length, through a decklid

Posted By: dxplicitone
Subject: Port length, through a decklid
Date Posted: August 29, 2006 at 2:37 AM

Thank you in advance for anybody helping me out with this one. Ok this might be a very elementary question but im really needing to do this properly the first time through so please bare with here. The vehicle i am working with is a 02 Lexus IS300... i recently ripped out my Diamond Audio / Kicker setup because it was really kind of a temp setup with only a single 10" sub ported through the ski pass in the rear seat. This time around i will be doing a 3 sub configuration and im currently shopping subs. The Rockford Stage 3's, JL 10W6V2's, and the Eclipse SW7000's all in a 10" were catching my eye. But i am very open and would like to hear feedback on those who might have had experiences with them or any other sub that might be in this range or slightly better for performance.
Ok to my real question since the IS300 is a trunk vehicle and it actually has a piece of metal between the seats and the trunk i wanted to port the subs into the deck lid to bring them more into the cabin of the vehicle. Now after calculations of port lengths and diameters, is the length that is called for for each application the length of the port that runs "inside" the box or is it the "total" length of the port as if lets say my setup called for a 4" Dia with a 10" length but i had 4" between where the top of my box meets the deck lid. Would i A. make a total 10" port and have only 6" of it inside the actual enclosure and the extra 4" running up to the deck lid? Or would i B. make a 14" port so that i have 10" in the actual enclosure and then the 4" to the top of the deck lid? Im sorry for the detailed and looong question but i figured i should be as detailed as possible.



Replies:

Posted By: stevdart
Date Posted: August 29, 2006 at 5:42 AM

The total length of a port is what decides tuning frequency;  it doesn't matter whether it's inside the box or outside.  If you extend the length to reach the deck, you will lower the tuning frequency.  But that is not what is best here anyway....

The ports should open into the same cavity (in this case, the trunk) as the subs.  That is, all drivers and port openings open into the same airspace and from the same plane.  It is the blended sound of the drivers and ports that you wish to hear more clearly in the cabin, not just the sound from the ports.  You should make a passive hole through the sheet metal that separates the cabin from the trunk, which will combine the airspaces of the two.



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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.




Posted By: dxplicitone
Date Posted: August 29, 2006 at 4:50 PM
Thanks for the information. Looks like ill be taking a different approach with this whole trunk now. And this is why i came and asked here simply looking for an answer like that... to correct my improper way of thinking.





Posted By: cloak559
Date Posted: August 29, 2006 at 9:44 PM

I have this same problem with my Mercedes, except I have a gas tank in between the rear seats and the trunkposted_image

Im not really familiar with the IS300...But if there is only a piece of metal between the rear seats and the trunk, I would say cut it out.  Weld in a center support bar(if needed), then just build a normal vented enclosure. and your set...

The other route you could take(which is what I am doing with my car) is use a normal vented anclosure, and cut a large opening in the rear shelf.  Cover the hole with cloth and you're done...



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'89 Mercedes-Benz 300E
Pioneer DEH-5900UB
(2)RE Audio SX 10"s
(1)US Amps MD3D
3ft^3 @ 37Hz

Blowing up in a car accident doesnt worry me, as long as I'm putting out some major dB's when I die...





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