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Interesting Box design problem

Discussion in 'Subwoofer Box and Custom Fabrication' started by zps2004, Sep 7, 2010.

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  1. Ranger SVO

    Ranger SVO Full Member

    I also enjoyed it, its a really cool thread
     
    Ranger SVO, Sep 12, 2010
    #21
  2. zps2004

    zps2004 Full Member

    I was actually thinking on mounting the box that way just so I can throw stuff in the back of the car and not worry about damaging the speaker. Should the port be facing down on a downfire or can it be out one of the sides? I was also thinking on just having some 2"X2" squares holding the box up, not having the big surround over 3 sides. If I did that it would be like a bandpass box.

    I see in your parameters it has a 3" port that is 8.2" long. Is that correct? Winisd gives huge port volumes. I would like to have a round port, but in winisd it says I need a really long one like 25" or so. that is why I was thinking of a slotted port with rounds because I can get the longer length easier. Also with the 3" port, the velocity is really high. Then again you were probably just using that for the response, not to have a reasonable velocity. Either way I think the 1.5ft3 with 35hs is the way to go.

    I need to make a cardboard box to resemble the size for the 10" and put it in the car to see what the best way to mount it would be. I know there is some wasted space in the back corners I would love to use. a 12" would be nice but I think it would take up too much space in the back. I do have a 2nd set of wheels in the back from time to time so having the space would be nice.
     
    zps2004, Sep 12, 2010
    #22
  3. Ranger SVO

    Ranger SVO Full Member

    I like the downfire box just for the reason you stated. I can throw things in the back of the car and the woofer is protected. Also the performance is awesome.

    The port should face the same direction as the woofer for best performance. Also you do need close off 3 sides. If you have opposite sides open, there will be some sound cancellation and performance will suffer. Been there, done that, won't do it again.

    Also the opening needs to face something in the car. In my case it faces the rear hatch. But it could have faced the side (bigger opening better sound????). Thanks for bring that up, I may do a redesign.!!!!

    I agree the vent velocity with the 3-inch is a little high. Try a port opening around 12 sq inches. See if that helps. Only problem I see is that a small box with a tuning around 35 hZ will require a long port. The port would need to be around 16-inches long. Also remember that port volume is ADDED to the box volume. In other words your box volume will be 1.5 cu ft PLUS the port volume.

    But if space is a problem try a sealed downfire box, they work and the sound is incredible. My box is only 0.45 cu ft, so yours should work in a 0.75 to 1.0 cu ft. Firing it down will fix any low frequency problems we usually encounter with small sealed boxes.

    Something to think about.
     
    Ranger SVO, Sep 12, 2010
    #23
  4. zps2004

    zps2004 Full Member

    I might initially mount it as a downfire, and then try it on it's side to see if I notice any difference. Maybe a rear fire with having the speaker facing the rear hatch, but be only 2-3 inches away, leaving the top open? I am not worried about the port length because I am planning on making the box wide. My initial plan is to have the inside volume 10"tall 9" deep and 29" wide. Once I make a cardboard cutout and put it in the car i'll go from there to see if I can find a place to make it more square then rectangular.

    I looked really quick at a 12" and it would perform awesome but the box would have to be almost twice the size than the 10".

    Oh and looking back at it the cabin gain makes a bunch of sense. In my first post I mentioned that the speakers I have in the CRX right now don't have as much bass as when it was on my other car which is a Miata. It makes sense now since the Miata has such a small cabin, that the gain would be greater thus having more bass.
     
    zps2004, Sep 13, 2010
    #24
  5. Ranger SVO

    Ranger SVO Full Member

    I think you got it.

    My Ranger PU really sounds good. But the bass performance could be better. If I open a window the bass really improves. Small Cabin.

    My Yaris has a ton more bass output at lower frequecies. Both vehicles use a 10-inch woofer, both vehicles use a 300-watt RMS amp. The Rangers box is larger, which means it should have better output. Cabin size means alot.
     
    Ranger SVO, Sep 13, 2010
    #25
  6. TE5LA

    TE5LA Guest

    Ranger is correct. Your graph is very peaky. This is an inherit trait of ported enclosures. You will almost always have that spike. A proper sealed enclosure will be very smooth and fall off gradually.

    And tuning to 27 is way too low. You should shoot for something like 35-40 Hz because CDs are mastered to roll-off around there anyway, unless you just want to use some of the special bass demo discs to impress friends.

    Some basic porting info:

    • Ports should optimally be spaced a minimum of the port's diameter (cylindrical port) from the woofer itself, from any adjacent walls, and from the wall behind the port.
    • Rectangular ports should have a width not exceeding 7 times the height. So a 1x12 port is not good.
    • The edges of ports should be rounded off (not sharp) to help avoid a high mach speed (vent noise).
    • The larger the port diameter, the longer the port will be.
     
    Last edited by a moderator: Oct 9, 2010
    TE5LA, Oct 9, 2010
    #26
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