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Thread: 318is. Subwoofer on the trunk. Ideas??

  1. #1
    Join Date
    Jul 2004
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    Costa Rica
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    328i 99

    318is. Subwoofer on the trunk. Ideas??

    Hi Fellows,

    Some weeks ago I changed the head unit and speakers... now I want to go deeply and install an sub and amp...

    My target at this moment is:
    Two 10 inch p-series orion subs (www.orioncaraudio.com) and
    600W RMS directed amp. (www.directed.com )

    Now the important questions...

    What do you think of that configuration?

    Sealed or vented box?

    Will I need to open holes from trunk to cabin? some experiences here?

  2. #2
    Join Date
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    NG SAAB 9-5
    I never do a complete box as this adds too much weight on the back end. What I do is use the trunk space as part of the box, picture this:

    You're standing in back of your car facing the open trunk. Measure inside, wheel well to wheel well across, just where the parcel shelf ends, then measure top to bottom. Get a rectangular piece of 3/8 inch plywood that size, cut out two holes for your woofers and mount your amp (I usully screw it to the back of one of the rear seats). Thus you are only adding 1 piece of wood & utilizing the trunk as the rest of the box, the back of the seats being the back of the box, the sides of the trunk, the sides, etc. The vents in the parcel shelf & small spaces around the wood (if you don't have a flush fit with the wood) will serve as air holes & you will get that rich bass thump in the cabin via the parcel shelf vents. This making any sense? You may choose to cover the plywood with 'speaker carpet' which will make for a snug, squeak-free fit (you can just wedge it in & take it out whenever you need the space. I find this 'wedge method also serves as some sort of brace, as if you had a rear shock tower brace). I've done this in both of my Getta's with excellent results. On my E30 w/rear firewall, I cut holes in the firewall & cut away some of the rear seat foam & also got good sound, but nothing is better than the rear fold-down seats & for extra cabin bass you can fold down one of the seats. I'm about to do the same thing with my E36 318is.

    The result? Great thump with minimal weight.

  3. #3
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    Thanks bigbris1,

    Do you have a picture?

    AC

  4. #4
    Join Date
    Aug 2003
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    Portland, OR USA
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    07.328cic & 13.x1M
    Woah dude, DO NOT follow BigBris's advice, that's terrible!!! You HAVE to have a sealed enclosure. Random cracks and whatnot are not ports. They are not tuned. It will sound like the biggest piece of poo you've ever heard. Really. NO ONE and I mean NO ONE will use this method unless they are installing free air subs and don't give one iota about quality.

    Seriously BAD advice.

    Whether sealed or ported is entirely a question YOU have to answer yourself. Do you like SQ (quality) or SPL (loudness)? Ported will generally give you a lower range but sealed will give you the tight punch/clarity. And if you don't care about quality and just want it as low as it can go, you want bandpass.

    R
    07 Japan Red 328cic
    ...sport/cold/prem, convience, black trim...

    11 Omni Blue Element
    ...work, ski, camp...

    13 Valencia Orange x1 2.8
    ...nav/Msport/sat, convenience...

    Quote Originally Posted by LinearX
    In the future we'll be like... man, I miss OBD2... OBD57 is so hard to tune.
    :

  5. #5
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    Jul 2004
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    Thanks Davbret

    Now, I like more the Idea of a sealed box... quality... and that takes me to my initial question...

    The trunk seems like a sealed structure on this car. what happens with sound when placing a sealed sub box inside an almost sealed trunk? If the air can not flow to then cabin, part of it will move trought the structure of the car as a mechanical wave. I do not think it will sound nice.

    Is good option to make holes, and place some exit tubes?
    How near to a 4th order box it will be?

    WinISD (from http://www.linearteam.dk ) looks like a helpful tool to make some graphs and try to predict sound power output, but power is not everything.. I want to hear some opinions from real world
    Last edited by acoto; 08-07-2004 at 02:40 AM.

  6. #6
    Join Date
    Mar 2004
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    WA - U.S.
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    1994 325is
    actually, it seemed to me that bigbris1 was talking about an IB (infinite baffle) setup which would totally work. its the principle that the jl steathboxes work on and many other people have done it one their bimmers.

    check out aus' install if you want pictures of what bigbris1 was talking about. aus has a page on sounddomain.

    just buy a sub that works well IB and its a great sounding install that leaves you with lots of trunk space. im actually going to be doing this myself if my subs ever arrive.

    i will say that if you do this dont lay down the seats or it will kill the IB principle. you have to keep the front and rear sound waves seperated, which is the point of the baffle board. oh and use 3/4" medium density fiberboard (mdf) instead of plywood.

  7. #7
    Join Date
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    99' Cosmos ///M3
    u could remove the rear speakers.....and cut holes in the rear deck if u want. and do u have fold down rear seats? if not....punch out the skihole...that will help as well.

  8. #8
    Join Date
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    Georgia
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    2001 325i
    Pretty sure he was talking about infinite baffle... but usually in IB, you seal off parts of the trunk better...
    Dreams are what you make of them

  9. #9
    Join Date
    Aug 2003
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    New Jersey
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    TSX
    backseat dont fold down on 318s....i gota 92 318i....i got a 10 inch phoenix gold carbon fiber sub with a JVC 550w (only using 225 of it)...i gota the sub in a sealed box.....if u stand outside the car with all the doors closed u wont here no thumping outside the car (which is what i like)....but inside...thats some seriousness....i was worried bout the "sealed" trunk not alowing and good bass to go into the car but dont worry it bumps pretty nice....i wokrin on a rack now to mount the amp and attach the sub cause right now everything sliding around the back...
    ________
    ford popular history
    Last edited by e36; 02-09-2011 at 11:26 AM.

  10. #10
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    ab325is, thank you.

    I admit I'm not the authority when it comes to audio but I do know what has worked for me. I have tried many set-ups including the one where you just dump a sealed box in your trunk & this has not worked for me. So you know, my main objective was toward sound enrichment. I could care less about people outside my car being able to hear my system.

    With the correct placement of the 'board' & quality speakers you can acheive great sound quality by using the space in the trunk.

    e36, the rear seat folds down on the 318is models. Since you have an 'i' you have a rear firewall (sucks, don't it?)

    themuchacho, I have done this & aside from everyone being able to see the speakers in the rear deck, the sound quality (to me) was far worse as the whole trunk becomes 'the box.'

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