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A4 saloon - getting good bass from boxed sub in sealed boot?!

Discussion in 'In-Car Entertainment' started by A4 stu, Jun 13, 2013.

  1. A4 stu
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    A4 stu Member

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    [Jun 13, 2013]
    I have a saloon B5 with no ski hatch - I am looking at getting the best SQ bass from the car. ideally without cutting or modifying the car.

    I have a 12 inch Pioneer sub in a sealed box and a Kenwood mono amp which will easily drive it to its max if needed, but I would like advice on how best to set up a boxed sub in a sealed boot.

    Previously, my cars have been hatchbacks so this hasn't been an issue or Mercedes 190's where I have built custom boxes, sealed so the driver fires straight through into the cabin through a large metal hole in the rear shelf. In both cases the bass was driven straight into the cabin and a sealed 10" sub easily gave me enough lows and volume.

    My initial choice was to cut through the Ski hatch hole and fix a sub behind it in an IB set-up. But, this car is the main family car and to be honest I do think I need the option of being able to remove the sub if needed.

    Has anyone got any experience/photo's/opinions of:

    1. Boxed sub positioned to fire through the ski hatch after its been cut through - so its still removable?

    2. Boxed sub in boot - did you remove the rear speakers to let air into the cabin, or remove them and seal the holes. Where should the box be positioned and what direction should the sub fire?

    3. IB type setup where the sub is suspended under the rear shelf, the rear speakers are removed and the bass comes through the speaker holes?

    Stu
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  3. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Jun 13, 2013]
    There's more than enough leaks from the boot area to easily let through the bass, you might just need a little more power than a hatchback is all. Normal wedge enclosure up against the seat backs firing to the rear is fine. I found the sound was actually much tighter with a semi sealed boot than when I had the seatbacks down
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  4. dualmono21
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    dualmono21 Well-Known Member

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    [Jun 14, 2013]
    saloons and convertibles are the two hardest vehicles to get decent bass in
    because essentially the bass is trapped in another cabinet

    the ski hatch method does work well , but try not to place the driver so close to the rear seat as you will get some reflections from the seat and phase cancellation
    if you removed the rear speakers from the shelf and then fired the sub upwards from a sealed enclosure this would also work well

    you could if you wished mount the drivers in the actual parecl shelf but it would need substantially re-inforcing before doing so
    but once done would give very very good bass response as essentially the boot is the enclosure
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  5. A4 stu
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    A4 stu Member

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    [Jun 15, 2013]
    I could remove the rear speakers and suspend my sub (one at the moment but could expand to two as I understand more cone area is better for IB?) on a shelf underneath the rear deck. With the rear speakers removed the bass air would flow trough the speaker holes.

    If I'm clever enough I could even make the shelf removable, maybe even slide in and out or the occasions I need the boot space?

    Andy - I suppose the only thing I can do is plug it in and see, but if you have even able to get a good response from the sealed boot then that's a good start for me. Did you find you needed a certain size sub or power of amp to get enough volume?

    stu
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  6. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Jun 15, 2013]
    Subwoofers only work in a sealed or ported enclosure with the correct internal volume. They definately don't work hanging from the rear shelf in free air - the boot area is not a sealed enclosure
    I had a 10" Alpine in a ported enclosure running with a 400wrms amp and never had any issues with lack of bass
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  7. dualmono21
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    dualmono21 Well-Known Member

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    [Jun 15, 2013]
    sorry andy but they do work , there just not to everyones taste

    the method of mounting the woofer and using the boot as the enclosure is called "infinite baffle"
    google it or wikipedia it will explain how things work

    like all methods it has advantages and disadvantages personally for me it has too many disadvantages
    this method requires substantially more power to control the woofer properly
    the frequency response from the woofer is not as flat as a sealed enclosure and the woofer requires a subsonic filter to stop the cone from over exertion
    the woofer has no protection from whatever else it is in the boot being banged against it
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  8. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Jun 15, 2013]
    Haha, always makes me laugh when people talk about infinite baffle - as the name suggests it doesn't actually exist unless you have an infinately large piece of MDF, or to get round this impracticality you fold the baffle round the back of the speaker, which I think is then called a sealed enclosure, oooh now where was that mentioned?
    I know what an infinite baffle is and it isn't the boot of an A4 - too many leaks, and as a suggestion on here, you said it yourself, has too many disadvantages, so it doesn't really work
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  9. dualmono21
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    dualmono21 Well-Known Member

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    [Jun 15, 2013]
    fact is andy whatever you or i call it or however much we may dislike it ... it does work
    you mention sealed or ported enclosures as the only two methods which work but isnt ported just an infinite baffle with a hole in it ... the same as a piece of wood strapped to the undershelf of the leaky boot of an a4 ??? you may not like , i may not like it but theres no argueing it does actually work

    the purpose of the baffle is to stop the front wave of the speaker interacting with the back wave but in certain applications like ported that is actually encouraged not discouraged

    there are literally hundreds of differant mounting and loading methods for speakers but for simplicity and best sound quality you cannot beat a sealed enclosure
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  10. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Jun 15, 2013]
    The one difference being a ported enclosure is tuned and the back wave has to travel a defined distance before it reaches the hole, somehow I don't think the boot of an A4 is tuned!
    So "simplicity and best sound quality you cannot beat a sealed enclosure " - think that's essentially what I said a few hours ago
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  11. dualmono21
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    dualmono21 Well-Known Member

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    [Jun 15, 2013]
    no andy what you stated exactly is that it didnt work !!!

    when in fact the principle is exactly the same as a ported enclosure
    a portion of the backwave re-inforces the sound from the front wave ... how far it travels and how much of the backwave re-inforces the front only alter a small portion of frequency and phase response of the woofer

    you state above that you know what infinite baffle is and that the boot of an a4 isnt such
    well actually it is !!!

    infinite baffle is a generic term for large enclosure which is exactly what the boot of an a4 is
    it refers to anything thats stops the rear wave of the speaker interacting with the front wave
    ie. seats ,wings ,boot floor
    not just the size of the actual baffle itself

    the rear wave of the speaker travelling through the holes in the cabin could be classed as the port
    this would be the holes that leak from the boot to the main cabin
    these dont have to be a specific tuned length or indeed amount , but any amount can influence the sound of the woofer
    either by altering the frequency response or in deed the phase response
    which will be why earlier on in the thread you state that you prefer the sound with a semi sealed boot
    a portion of this sound will be re-inforcing a frequency making the sound more pleasing to your ear
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  12. A4 stu
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    A4 stu Member

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    [Jun 16, 2013]
    Er........

    I'm going to try the following over the next few weeks and see which I prefer and why:
    1. Boxed sub in boot
    2. Sub in free air application through ski hatch
    3. Boxed sub firing through ski hatch

    Thanks for the replies.

    Stu.
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  13. dualmono21
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    dualmono21 Well-Known Member

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    [Jun 17, 2013]
    stu
    be mindfull if your going to try firing the woofer through the ski hole that you need some distance between the woofer and the actual hatch
    if you try and put the woofer bang next to it you will damage the woofer as it has no where to go when the voice coil extends
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