Just got an avalanche 15..... now.... what?

Discussion in 'Home Theater Projects' started by AhsanR, Oct 7, 2005.

  1. AhsanR

    AhsanR Stunt Coordinator

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    So I just purchased an avalanche 15. From this board, I pretty much realized, I'd be an idiot if I didn't pick it up.

    I need your help though, I'm trying to make a 4 cu ft, sealed box for it.

    Trying to hit about 100db at 16 hz, which I can hopefully do.

    Trying to make it blend with my rocket 550s fronts.

    Anyone have any idea how to build a BOX????
     
  2. ThomasW

    ThomasW Cinematographer

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    Only if you use a LT circuit and a really BIG amp.
     
  3. AhsanR

    AhsanR Stunt Coordinator

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    What does that mean "LT circuit"?

    I may go bigger if you guys think I should...

    BTW i plan on using a 500 watt plate amp from BASH

    My room is 13 X 15
     
  4. AhsanR

    AhsanR Stunt Coordinator

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    If there is anyone who is experienced in box building who wouldnt mind giving me directions over AIM, i'd be more than grateful.
     
  5. ThomasW

    ThomasW Cinematographer

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    LT = Linkwitz Transform

    Below is a link to one of Dan Marx's designs, it's a good building guide. Scale your box size accordingly. The 4L is the 'net' volume inside the box after subtracting for the air displaced by the driver, the bracing, and anything else that takes up space

    His design is ported so he lines the sides of the box with foam. Sealed boxes are stuffed with damping material 0.5-1.5lbs/cu ft.

    http://www.danmarx.org/audioinnovation/tcsounds.html
     
  6. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    I think 100dB at 16Hz is pretty reasonable with 500 watts in this alignment. Throw in room gain, which should be considerable @16Hz, and you really should be able to meet this goal.

    LT is not strictly necessary to meet any specific X db @ Y loudness goal. Its used to alter the frequency response CURVE of a sub in order to meet your goals (in room). If you wanted 100dB at 16Hz and 100dB at 50Hz at the same gain setting, then you'd need LT or equalization to achieve that with your chosen box.
     
  7. AhsanR

    AhsanR Stunt Coordinator

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    This maybe a dumb question, but how do you tune a sub?

    I talked to Chad extensively before purchasing the driver. He said there really isn't much need for internal bracing, etc.


    I was thinking in a sealed box I could hit 16 hz at 100 db at 4 cu ft.
     
  8. ThomasW

    ThomasW Cinematographer

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    That's fine if you want less than optimal performance. Here's an interior view of the last box sub I built, obviously it was ported.

    [​IMG]

    BTW you might want to actually research a bit about subwoofer design. Here's a link to get you started.

    http://www.diysubwoofers.org/
     
  9. AhsanR

    AhsanR Stunt Coordinator

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    OK so here's the decision I made, tell me if its kosher or not.

    A) Going to use a 5.0 cu ft box in a 15 X 13 room.

    B) Bash Digital 500 Watt Amplifier

    C) Internally braced, somewhat like yours

    D) Polyfill used to stuff the insides.

    E) Sealed.


    And one more question, if its sealed will it still be able to move some air? I'm a little sucker for the pants flapping effect.


    DO I REALLY need some passive radiators?



    The one thing I'm worried about more than ANYTHING is the subwoofer being booomy. I just want it to be flat in response, and deeeeep.



    --
    BTW...What driver did you use?
     
  10. SteveCallas

    SteveCallas Second Unit

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    Typically, sealed subs have a better reputation for being more musical (tighter, less distortion). These drivers are clean and powerful enough that a well designed ported sub won't degrade the sound quality. You would get a smoother FR and more output down low near the tuning with ported. I'm not trying to sway you at all, if you were set on sealed, stick with sealed, but from your last post, it sounds like ported might be more of what you are after.

    I went ported with an 18" Avalanche and it is VERY clean and (I don't like using this adjective) tight, in no way boomy or one noted. I used a very large enclosure and a very large port.
     
  11. Travis_G

    Travis_G Agent

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    Ashan,

    A passive radiator is a substitute for a vent. If you want a sealed design then a passive radiator won't be necasarry.

    I second what Steve said, you can get deep bass from a sealed box but you need lots of amp power and either an EQ or LT. If you are tuning the box to ~ 18 Hz or so the sub is going to behave very similar to a sealed box from about 30 Hz on up anyways. This is where tight bass is most important.

    Travis
     
  12. AhsanR

    AhsanR Stunt Coordinator

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    The only reason I was going sealed is becuase I was under the impression that if I went ported, that it would sound horrible for music, and that the stories of "boomy" "slow" and "best buy sub" sounding horrors will be true.

    This is my first sub project, and I don't know too much about the audiophile world. I'll be honest, I never dreamt I would be in the DIY world, until I saw that I could purchase an Avalanche 15 for 225, and boy did I pick up on it.

    I'm decent at wood work, I just need to know what I'm doing. With all that said, I guess the general consensus around here is::

    *****If you get a ported, I wouldn't have to worry too much about EQ'ing, and I wouldn't worry too much about amp power.

    ***I am using a 500 watt bash amp, and if I were to make a ported 5.0 - 6.0 cu ft enclosure, I think, from what it sounds like, I'll cut the mustard.

    **Is there any way for me to find out what my sub will be tuned to at 5.0 or 6.0 cu ft?

    ---

    I do know one thing, I have an 8 inch, noname brand sub sitting in my house powered by a 50 watt amp thats definetely not cutting it.
    --



    One more thing, thanks alot to the memebers who have chimed in, I didn't expect anyone to help me whatsoever, I've already changed my plans, went to drawing board twice, and been in conversation about what type of finish I will use.

    Once this thing is made, you can BET pictures will be up [​IMG]
     
  13. AhsanR

    AhsanR Stunt Coordinator

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    OH - and if anyone has plans that they know work with this driver, I would be more than obliged to follow those. It would save me a world of a headache trying to play Speaker Designer.

    Currently, I was going to go with a modified version of the link posted above with 6 inch port holes, maybe bigger.... this is where all the big AIR comes out of right ?


    My email is [email protected]
     
  14. Travis_G

    Travis_G Agent

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    Ported subwoofers can sound boomy and slow because they rely on stored sound energy that is released through vent, so there is some delay. Most sealed subs also rely on stored energy as well and they are not immune to sounding boomy and slow. As long as you keep group delay below 33 milliseconds at 30 Hz and below 16 milliseconds at 60 Hz I don't think you will have a problem. It is easy to do with a good speaker and a program like Win ISD that you can download for free off the internet.

    You can tune any sized ported box to any frequency. But with a smaller box, you either need to make the port longer or smaller in diameter. This can be a problem because the port either gets so small that you can hear the air rushing in and out or it gets so long that it won't fit inside the box. That is why people often use PR's on small enclosures.

    Travis
     
  15. AhsanR

    AhsanR Stunt Coordinator

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    Travis this is the enclosure I'm going to make, however, the changes I am making are, I'm going to use two 6 inch ports instead of the two 4 inch ports he is using. I am also extending the sub 6 inches on all sides length, width, and height.

    I also am wondering how to figure out what the sub will be tuned to in that size box.


    Do you agree these plans, with my alterations, and a Bash Amp will be able to do my sub justice?

    http://www.danmarx.org/audioinnovation/tcsounds.html


    You guys have got me really excited. As soon as you guys give me the ok, I'm building this thing!
     
  16. SteveCallas

    SteveCallas Second Unit

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    Download WinISD or Unibox so you can start playing around with the numbers. You have a good plan for a box design there, you might just wanna change a few dimensions to make the box larger or smaller to mate better with 2 6" ports. Otherwise, I think you're on your way.

    I realize you're excited, but don't be in a hurry to put this thing together until you optimize the design. You will be much happier that you did in the long run. You want to get the FR as flat as possible, maximize spl, minimize group delay, minimize port velocity, and allow the driver to go as low as possible without exceeding its excursion limits. You have to juggle all these things together to reach the best compromise. The larger a box you go with, the easier it will be to do all these things.
     
  17. Travis_G

    Travis_G Agent

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    It's a good design Ashan but Steve is using a different speaker. If you use the same box you will get a peak 1-2 dB peak in frequency response and you won't be getting the deepest bass possible for your speaker.

    If you lengthened the ports to 30" it would smooth out the frequency response and give you deeper bass, but you would need to change the box dimensions because 30" vents won't fit in that box (unless they stuck out the front [​IMG] ). Hey, if you have an understanding spouse you might get away with it. [​IMG]

    Even if you copied his design it would still sound better than anything you could buy for the same price, but why put all that work into it and do it half way? You will get more for your money if you download Win ISD and ask the folks here whenever you need help.

    Otherwise you could start a new thread and ask if anyone has plans for an avalanche 15 that you could copy.

    Travis
     
  18. Ben Ch

    Ben Ch Agent

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    I can attest to Thomas W's 15" ported design, I built one with a Blueprint Designs BP-1503 15 inch high excursion driver and never regretted it ...

    It's powered with an Adire Audio ADA 1200, it's an astounding design, a bit heavy (260 pounds with driver and amplifier, but theft won't likely be a problem.) and just dissapears into the music (untill it's called upon to let you know it's there - then there is absolutley no mistaking that there is something very potent creating the low bass).

    ht tp://img.photobucket.com/albums/v234/tneB/IMG_0415a.jpg

    something is amiss with the forum - I can';t post a picture, so just remove the space from the above http/.. and you're good to go.
     
  19. Travis_G

    Travis_G Agent

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    Thomas used a different driver though Ben. Tempest possibly? It may sound great with an Avalanche 15 but then it may not. There is no way of telling unless you model it's response before you build it.

    Travis
     
  20. ThomasW

    ThomasW Cinematographer

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    First, the box in the picture was designed for the HE-15, not a Tempest.

    Second, a ported design is reasonably 'generic'. So actually one can copy the box design, and drop in a different driver if most of the pertinent T/S parameters are similar.

    The HE-15 and the BP1503 were very similar drivers. The major difference between the Ave 15 and the HE-15/BP1503 is that Ave has a much higher Vas
     

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