Mounting IB on rear deck


  • Member
    MetricMuscle on #1291

    I will hopefully be the proud new owner of an SBP15 soon with the intention of using it in a large sedan. The plan has been to just mount it horizontally on the rear deck facing upwards towards the back glass which is at a 20 degree angle to the rear deck. The fuel tank is located a few inches below the rear deck, up flush behind the back seat which has limited my mounting options. I like the idea of using the back glass as a sort of horn but am worried about sag being mounted horizontally.

    I do have room below the rear deck to install a wedge shaped manifold of sorts which would mount the SBP15 vertically and hanging down just to the rear of the fuel tank. I’m wondering if this would be a good idea as it would increase the length of the horn it is mounted in but I won’t be using any horn design parameters so may create new problems.

    Reasons I would even consider doing this-
    – Vertical mount of woofer, no sag issues.
    – Less exposure to sun.
    – Horns can have a positive effect on distortion IIRC.

    I’m not necessarily looking for any SPL increase but wouldn’t mind as long as it doesn’t bring along any new issues or distortion.
    I haven’t really found much discussion of how to go about this or what to do or not to. Any info or links would be greatly appreciated.


    Participant
    stryke on #11169

    Typically you never want to have a woofer firing up or down. Suspension will sag over time and as this happens it can begin to act non-linearly. Suspension sag is not something that can be covered under warranty. If you can do the manifold type design that would likely be a good idea for longevity of the woofer. I’m not sure the effects of the horn loading. That would really be something you would have to experiment with.


    Member
    MetricMuscle on #11170

    What would/should/could the manifold look like?
    Just a square cubical box enclosure below the rear deck with the top open into the cabin?

    A wedge shaped horn looking manifold would actually fit better under the deck so as to avoid the fuel tank which is also in this area.

    Are there any upsides/downsides soundwise to using a manifold?


    Participant
    stryke on #11171

    Fitting a manifold in a car is a little different than home theater, but this should give you an idea on some manifold ideas.

    http://home.comcast.net/~infinitelybaffled/page2IB-Gallery.html

    The main thing is keeping enough open area to not restrict the flow.


    Member
    MetricMuscle on #11167

    Is there much or any difference in performance if the front of the cone or the rear is facing into the listening space? If the woofer is mounted backwards so to speak, the cone facing into the trunk area, the basket into the listening space.


    Participant
    stryke on #11168

    There is very little difference at the lower frequencies either way. If it was in a system where you are playing up over 500hz then I would only want to use it front firing. Rear firing would be just fine for this application. Whatever makes it easier to work with.


    Member
    MetricMuscle on #11172

    So, if straight up vertical is the safest way to mount a subwoofer and flat horizontal is the worst, what is the most you can go off of perfectly vertical and still be OK? 30 degrees?

    Alot of folks mount behind the back seat which is not straight up but probably not a full 30 degrees either.

    I’m gonna have to get a little bit creative.


    Participant
    stryke on #11173

    The straighter you can mount them the better. The suspension is best to handle the effects of gravity that way. I don’t think there is really a set angle where it becomes bad, more that it is progressively worse as the angle increases. Many mount them up/down firing and still get years of use without issue. Work with what you can within reason.

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