Need help with new sub

Discussion in 'Home Theater Projects' started by ScottDIY, Dec 20, 2004.

  1. ScottDIY

    ScottDIY Agent

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    Ok, I need some input. I built a sealed 75lt DPL12 last Feb. It has been working great, but I would like to make, it or something else, better. My goal, to get cleaner lower base. I have a couple of thoughts. Either an infinite baffle with at least two tempest, a phoenix type dipole using two dpl12 (http://sho.mystarband.net/BBContent/BBBass.html) or a push pull type transmission line (http://www.teresaudio.com/haven/subs/subs.html)

    Any thoughts, I am leaning towards the dipole of tl because I already have one DPL12. But, I do have a perfect location for an infinite baffle too. I don’t have a sub EQ yet so, can one of these run relatively well without one.
     
  2. ThomasW

    ThomasW Cinematographer

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    You'll need roughly 4 times the displacement for a dipole compared to an IB.

    A dipole also needs much more EQ than an IB.
     
  3. ScottDIY

    ScottDIY Agent

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    Hi Thomas, do you think that two tempest would do a fair job. Remember that I am running only a single sealed DPL12 and I have adequate base, I just would like to clean it up a little and expand the usable frequency range. It does fairly well down to low 30’s and starts dropping by 27 and falls quickly past 25. I thought about getting a plate amp with a 4db boost @ 25 or an EQ, that would extend the base but what about quality. Back to two Tempest. The area I have for the IB is next to my entertainment system and would vent in an empty basement next the concrete wall. So I only have three sides to work with. I believe the it has to be symmetrical so I can only go with two or maybe two over two, I can’t utilize the other two sides of the combustion chamber.
     
  4. stephanX

    stephanX Stunt Coordinator

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    Did you ever think of buying another DPL and trying a DPL IB? Or even a vented DPL in a larger vented box. In a low tuned box, the DPL is a wicked low bass machine. Although if you really want to do IB and have money to spend, the tempests would be jaw dropping.
     
  5. ThomasW

    ThomasW Cinematographer

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    There are numerous dual 15" IB's in operation. Some people have discovered that one must be careful not to overpower the drivers. It's probably a good idea to make a manifold that has expansion potentional for an additional pair of drivers, just in case....
     
  6. ScottDIY

    ScottDIY Agent

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    Ok, how about two DPL12 in an IB. I know the output wouldn’t be the same as two Tempest, but I have enough output from the one sealed DPL. I would just like to reach a little lower and cleaner. A vented DPL 12 would go lower, but I don’t think it would be a quick and clean as the sealed box, isn’t that correct. Also, would the IB system take more or less power to operate than a sealed unit.
     
  7. ThomasW

    ThomasW Cinematographer

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    My 'small' IB uses 4 DPL-12's, it sounds very good. The room is 12'X18' with a cathedral ceiling.

    If you haven't already done so why don't you wander around the FAQ section of the IB forum. That might provide so additional info to help with your decision.

    One option would be to make an expandable manifold. Start with a pair of driver add more later if needed.
     
  8. ScottDIY

    ScottDIY Agent

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    Thanks for the FAQ link Thomas.

    We had 40cm of snow and 80km/hr winds the other day, so I decided to experiment. I built this IB with my one DPL12 to see how it sounds. Because of the concrete wall the box is only expandable to two. For music it sounds great, it does take a little more power than the seald unit, but not much. will th addition of another DPL increase the DB level or just create a cleaner base?

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  9. Rob Bird

    Rob Bird Agent

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    Personally, I'd just add a touch of eq down low. It will go a long way, and a BFD just isn't expensive. Add that to the IB and voila, instant happiness.
     
  10. Geoff L

    Geoff L Screenwriter

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    Scotty

    Have you taken room freq/spl measurments of the IB and compared them to your old sub, both at the seating postion???

    Adding a BFD will help no doubt in controling any modes you may have along with a tiny bit of boost down low possibly if needed.

    Adding a second driver should clean up the sound a touch at the same given spl.. (Less cone travel for same spl)

    Should add 3db min ~{if when adding a driver in an IB operates the same as standard subs alignments while carrying the same ohm load to the amp..
    Where the baffle loads/opens into the room can have a bearing, I'm sure, on how much db extra gain you receive on top of the normal 3db..

    It will require more power naturaly to reach max clean spl as your powering 2 drivers as opposed to one now...

    Thomas W the (IB cult king) and others are much more qualified to deal with IB questions than I,,, most "certainly".!

    Regards
    Geoff ¥
     
  11. ScottDIY

    ScottDIY Agent

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    thanks, I am going to do a search on BDF. What unit are most people using and do they have one with an active crossover?
     
  12. Chris Bates

    Chris Bates Stunt Coordinator

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    Have you thought about a passive radiator? Here is a link to one of adire's designs.

    http://www.adireaudio.com/Files/PR15...12ComboKit.pdf


    I put it through BassBox Pro and it looks good. Personally I like PR's better than ports. You get the same increase in db's over a sealed enclosure without the risk of port noise.
     
  13. ThomasW

    ThomasW Cinematographer

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    Scotty,

    Additional drivers mean more output and lower overall distortion

    You want to be careful with EQ. In an IB, the driver will bottom more quickly than if it was in a different alignment.

    It looks like you have 2 more available sides and the bottom. All those surfaces can be used to mount additional drivers if the budget permits.

    Most people are using the LFE output on their pre/pro.

    Behringer makes a couple low buck active crossovers. I don't know about their sound quality. They don't make a unit where a BFD is combined with a XO. I tend to keep the XO separate from the EQ
     
  14. ScottDIY

    ScottDIY Agent

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    Ok, Thanks for the help guys. Thomas, I thought that the drivers had to be in pairs and facing each other. Expanding to three sounds like a great idea, but I that will have to wait. I am thinking that an EQ might be money well spent. I had to set the driver/s down ~ 12in to clear the floor joist and I didn't like the driver so far down in the manifold. So, I thought I would make a few changes. Until I can expand, I came up with other idea based from the FAQ threads (Jon Foulks 'outie' IB). Here are a couple of photos of my Mini Sub, had to get out the shoehorn for this one, well more like a wood chisel. I am going to double up the top layer to deaden some of the vibration. It sounds fine, but I think the more weight the better, any suggestions.


    [​IMG]
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    from underneath
     

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