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Discussion Starter · #1 ·
Hi, I need a little advice on subs. size(s) brand and box type, size etc.. I would like to use about 2.2 cu.ft. net or less, but could use a little more space if necessary. Any size sub or subs up to 12" can be used in this setup. It's a Mercedes sedan and goes in the trunk, with really no openings to cabin. It's hard to get sound through to cabin as You know, but I have faith in You Guys to put something together. I Would like punchy, not boomy bass just good all around bass. This is the basics. I'm using in the front doors Focal 3way active and in the rear doors Hertz 2way passive all on a amp/dsp. The sub source is out of the dsp, so it does have full crossover/eq tuning. The center speakers etc.. are running off the cars original amp and I will up grade them also. I do have a Alpine Pdx 1200 mono amp and a JL 12w7 but not sure that's the best sub setup for this car. I'm not stuck on the JL/ Alpine setup it's just something I have already. Please, remember I don't know all the lingo and have no where near the knowledge of most of Y'all. Please, don't roll me under the bus and use abbreviations etc... Ok, I'm old. I enjoy the site and want to Thank You for all Your advise, direction and ideas. Thanks, BubbaB
 

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The prime candidate with 1200W is going to be the Brahma12 - if you wanted to run more power and get a few more dB then the SQL12 but you'd need roughly double the power to gain anything substantial over the Brahma and it won't need a 2.2 cuft box if you run sealed. About 1 cuft net after displacement on 1200W is all you'd need. Will be much more musical than the 12W7 in roughly half the enclosure volume and still have plenty of punch. Now if you're up to the adventure you can run bandpass and run the port tubes up through the rear deck (if you have one, you didn't state which Merc you have) if you really want to get bumping. But bass is omnidirectional and with the DSP you can tune it to what you want even with the rear seat in the way.
 

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Discussion Starter · #3 ·
Thanks for the quick response! I have a e550 w212 chassis with rear window shade etc... The bandpass how big would the box need to be and how big ports into rear deck? Thanks
 

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Bandpass would be a bigger box as you're basically building two boxes but in general around 2.2 - 3 cuft total net airspace and that's internal so the external dimensions would be 2.5 to around 3.5 gross. The particulars would have to be figured out in a deeper discussion about port length and actual finished size you could stand but the Brahma responds better to 6th order bandpass or series tuned bandpass (6th with an additional port between the two halves) so figure on at least 2 x 4" round port tubes. If you can live with a -3dB reduction in output and more limited bandwidth then 4th order bandpass will work at about 1.5 cuft net internal and one 4" port. (Port diameters all modeled to less than or equal to 40 meters per second at 1200W.)

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I'd run the w7 in a ported box. You should have plenty of space to work with for a low tuned ported box. I don't see any point in buying a new sub at all.
 

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My BMW trunk was also fully sealed from cabin. I cut my own ski pass and did a trunk IB setup. Even if using a box, it would allow bass to enter the cabin with much more ease. I noticed a HUGE improvement after cutting the hole.

I recently put a 12w7 in the trunk baffle too, have yet to put it through it’s paces, but so far so good.
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I'd run the w7 in a ported box. You should have plenty of space to work with for a low tuned ported box. I don't see any point in buying a new sub at all.
For a proper SQ tuned ported alignment for the 12W7 you need at least 4 cuft (preferably 5) net airspace and that's after port displacement. It's a big box - been there done that - but now the Trunk Baffle mentioned below is the ultimate and the 12W7 is not "bad" in that alignment but there are better and if he's doing an E-Class I'd think he wants to do it right... :cool:
 

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For a proper SQ tuned ported alignment for the 12W7 you need at least 4 cuft (preferably 5) net airspace and that's after port displacement. It's a big box - been there done that - but now the Trunk Baffle mentioned below is the ultimate and the 12W7 is not "bad" in that alignment but there are better and if he's doing an E-Class I'd think he wants to do it right... :cool:
That's a big box, I'm curious to know what it would model like in 2 cubes. An IB setup would be excellent, sell the W7 and buy an SBP15, or just give the W7 a try.
 

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That's a big box, I'm curious to know what it would model like in 2 cubes. An IB setup would be excellent, sell the W7 and buy an SBP15, or just give the W7 a try.
Ran 2 x 12W7 sealed for years cause the ported box was way too big for my cargo area...

Pink is 5 at 22.6 (HP = 15Hz LR24)
Green is 2 at 32 (Same HP - not horrible if you only want Boom and Slam)
Blue is sealed at 2 cuft
Yellow is sealed at 20 cuft (pseudo IB - also requires HP at 15Hz LR24)
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Modeled with cabin gain on 1,000 Watts each:
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And yes the 12W7 is below xmax in this model at 1,000 Watts with the Infrasonic filter active:
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Discussion Starter · #10 ·
The IB system sounds interesting. I need to see if I can pull the rear arm rest back out. I can get another sub(s) if the W7 isn't going to workout.
 

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The IB system sounds interesting. I need to see if I can pull the rear arm rest back out. I can get another sub(s) if the W7 isn't going to workout.
I would go the IB route, as well. The mercedes trunks are well built, and trying to run "punchy/tight" bass without venting into the cabin is never good.

If you can find a spot, even 8x12 inches, to cut an opening into the cabin, you will have much better bass response.

You also keep almost the entire trunk space, as evidenced by Ali-323's install photo.
Another benefit to I.B./free air subs is, they play very deep. You'll want a sub with a Qts around .6 or greater for this job. In my own BMW, I cut my ski pass out, as Ali-323 has. And in my older BMW, I did the same thing.

The sound quality from the right 12" or 15" sub running free air is excellent, especially in a well sealed German trunk.
 

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The IB system sounds interesting. I need to see if I can pull the rear arm rest back out. I can get another sub(s) if the W7 isn't going to workout.
You'll definitely have the best Sound Quality running Trunk Baffle (make the distinction between Trunk and Infinite Baffle since most trunks aren't big enough to qualify as truly IB for actual IB Subs) and the 12W7 will suffice till you can get a 15 or 18 IB Sub from AE, Fi or SI (that SI link is for the 24 but Nick at Stereo Integrity will happily make you one in a 15 or 18 - whatever will fit for you) and you want the opening to be (at a minimum) 75% of the Sd (Surface Area of the Cone) of the driver. The 12W7 has an Sd of 84 sqin so 75% of that would be 63 sqin or an 8" square hole.
 
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Discussion Starter · #13 ·
I don't think anything bigger then a 12" will fit. I'm not sure if I can remove the back of the arm rest. If not will just mounting behind seat still work? I will post some photos later and try to pull seat this weekend. Thanks!
 

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Correct me if I'm wrong but the E Series has fold down rear seats with an open pass through to the trunk when the rear seats are folded down?
 

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Discussion Starter · #15 ·
Yes, You are correct, some do have folding seats, unfortunately this one doesn't. The way the trunk is made it gets smaller directly behind the rear seat. Its only about 12.5" in height ( it's slightly more due to the angle of the rear seat) and 39" in width +/_ a inch on width. I pretty sure that a wall can be installed behind the seat and sealed off good. I'm not sure about getting the arm rest backing out. I will try tomorrow night or this weekend. I'm in South Louisiana and luckily we missed the full fury and destruction of the recent hurricane. We're still busy bring supplies and helping those who weren't as lucky, not to mention running my businesses. Hopefully I can't get to it Friday sometime or this weekend . If the rear seat arm rest backing can't be removed to open up a hole, would the following work ok? Behind the rear seat make like a plenum a inch or two deep to allow speakers not to hit rear seat.
I could put a pair of 12"s and kick them hard . The amp which I could use, (I have others and willing to purchase others if needed) is Alpine PDX I think 1200watts [email protected] 2ohm and [email protected] 4 ohm. Not 1 ohm stable. The rear seat on each side of the arm rest is kinda thin. Just where the arm rest is feels like there a plate or something. I really appreciate all the information and direction. Y'all have been great!!
 

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It all depends on what you find back there - if there's a finished back to the seat backs that provides it's own support to the seatbacks and isn't dependent on whatever is behind the seatback for support then that could work. But if the seatbacks are installed onto the Sheetmetal that creates the wall between the trunk and the passenger space then it might be a different story.

Here's an E Class with the fold down seats where the installer made a manifold further into the trunk where the load floor is lower and let the back of the subs extend over that shorter section you're talking about...

Then it becomes a matter of simply sealing the manifold to the sides of the trunk space and letting the back side of the cones excite the cabin space.
 
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Discussion Starter · #17 ·
Very similar. When the seat is down it looks the same. His subs facing rear. If ours is facing forward pushing on rear seat would that make a difference? The back of rear seat isn't that thick and I don't think there's a metal wall on seat back.
 

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I don't think anything bigger then a 12" will fit. I'm not sure if I can remove the back of the arm rest. If not will just mounting behind seat still work? I will post some photos later and try to pull seat this weekend. Thanks!
Not sure what you mean by removing the back of the arm rest, in my case I had to cut a hole to create the access path.

Without having the hole, i wouldn’t mount the sub directly to the seat back firing against it.
 

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In this pic you can see my cuts, they get hidden when I put the trim piece in place (which I also vinyl wrapped in CF).
 

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Discussion Starter · #20 ·
Hi, Think I can cut a vent through like Ali-323i has shown in above post. I checked with Ae and Fi web sites. Ae is showing 2 models IB12au-4 or SBP12. Fi shows, the IB312v2 but is out of stock. Which one would be the best choice. I can get a opening around 8" buy 11" through rear seat arm rest. Do I wait and try for Fi or another brand, or go with Ae, and which model. Thanks
 
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