Advice regarding rear shelf infinite baffle setup

[insainiii]

Hi. I just made and account to make this post. I have a w211 mercedes sedan with non-folding rear seats so the cabin is pretty well sealed from the trunk. The vehicle has harmon kardon logic 7 system from factory but it is basically garbage. I added a 5 channel pioneer amp as well as a JL 12W0V3 Subwoofer in a ported box in my trunk. I ran the stock harmon kardons in the cabin through the pioneer amp and ran the highpass filter higher than factory through them and got much better sound out of them. Sub wise the I was running the 300w JL on 350w RMS and I blew it after a few months(Im stupid I know..). After running the JL on 350rms it sounded great when I opened my trunk and stood outside it but inside the cabin since the trunk is so well sealed from the car I barely got anywhere near the bass I wanted. I also want to mention my amp can run 350w at 4ohm and 600w at 2 ohm. My new plan was to just get a 12 inch pioneer champion sub rated at 500wrms and run it in the ported box in the trunk again at 500w rms on my gain lowered with a voltmeter. After thinking about my issue with the bass barely making it into the cabin I thought maybe a subwoofer in my rear deck would maybe be better at providing bass in the cabin. After doing some research on infinite baffle subwoofers I found the AE IBU12 interesting but its very expensive at 500$. I also read on some forums that using regular subwoofer in this application may require me to run the subwoofer at half its rated power to ensure I dont bottom out the sub. I am also aware a Qts close to 0.7 is good and a low Fs is good and a high Xmax is good. The pioneer champion subwoofer has a Qts of 0.73, Fs of 38, and Xmax of 11.3mm. I am now in a dilemma of if I should run the subwoofer in my trunk with a ported box at 500w at 2ohm or run it on my rear shelf as infinite baffle at 2/3ish the power rating at 300ishw rms at 4 ohm (since my amp can do 350 at 4 or 600 at 2) Im not sure which method to go with. I just want good quality bass inside my cabin and am not sure what method to go with. Also the subwoofer comes in 4ohm SVC and DVC so if I do the 300 at 4ohm I would buy the SVC and if I did 500 at 2ohm I would buy the DVC. If anyone has any advice with a similar vehicle like this or any tips regarding any of this I am open to everything. My budget for my subwoofer is <200 usd. And I can fit upto a 12 inch in my rear deck. The amplifier I am running is the Pioneer GM9705. Thank you

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[1aespinoza 10+ year member]

Thank you

I have seen four methods for this exact issue. 1)IB mounted on a 3/4 panel . 2) Port of box extending into the cabin. 3)Box built to height of rear deck, sub up with a foam ring to seal trunk from cabin. 4)Remove deck speakers or cut a hole to let the bass into the cabin.
The one that sounded best IMO was the sub up with the foam ring. It was in a sealed box so it played pretty wide. After that, the IB sounded clean. It was a 10" mounted with 6x9s on either side. The other two were just plain brutal. So loud that IMO it defeated the purpose of pouring into the cabin. You would have heard them if you put them in the trunk of a separate car.

 

[insainiii]

Alright so I modelled the pioneer in WinISD and my trunk is 15cubic ft. I found that as long as I am underpowering the 500watt sub at 350watts and I use a subsonic filter at 40Hz... my subwoofer cone safely stays below the Xmax. Now my issue is my amp doesnt have a subsonic filter option and I dont have a dsp. Is there any budget/simple way to do this?

 

[Jimi77 5,000+ posts]

Your problem may not have been the trunk, but where and how the subwoofer was oriented.

Installer.com technical and historic papers

Car Audio installation Technical and historic Papers

www.installer.com

If indeed you have bass trap trunk, I'd suggest a 4th bandpass ported into the cabin or ported enclosure vented into the cabin via a "manifold." Kinda like a blowthru in a pickup truck.

 

[1aespinoza 10+ year member]

via a "manifold."

This just reminded of the Coustic Bass Pump.

 

[Jimi77 5,000+ posts]

This just reminded of the Coustic Bass Pump.

You could construct something similar pretty easily.

 

[1aespinoza 10+ year member]

You could construct something similar pretty easily.

Yes, just watched a video by the universally loved Patrick C. I have an '05 Stratus I could try that on.

 

[Grimmjoww]

I just built a system not long ago in my 2008 C300. I actually cut out the partition behind the arm rest in the rear seat to act like a port. I had an american bass 10xd in placed all the way back in the drivr corner of the trunk in a small 1 cube ported box. Kind of acted like a 6th order in a way. I used lizard skin under every panel that would come off easily. It sounded pretty dang good, night and day from being sealed in the trunk. Wish I had took some pics before I sold it, I trimmed the hole back out with some nice wood strips after I cut it out.