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New subwoofer suggestions?

Discussion in 'Home Theater Projects' started by Vaughan Odendaal, Dec 18, 2003.

  1. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Greetings all.I'm busy building a subwoofer, and I want to use the Tempest driver.

    Basically, I've almost finished constructing the enclosure.I want to go sealed.So I'm going to provide you with the dimensions of the enclosure that I'm going to build, and then if you would be so kind, you could tell me if its a good choice.

    The dimensions are : 28" H X 18" W X 32" D.I think that this is a very big subwoofer enclosure.Who do you think? Is this a good size for a single sealed Tempest subwoofer? What type of extension would I achieve in this size enclosure? Thanks.

    Any problems, then please let me know.
     
  2. Jeremy Stockwell

    Jeremy Stockwell Supporting Actor

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    Vince,

    I don't know what you're design goals are, but in that size enclosure, with a Tempest, I'd go with a vented allignment. Perhaps a modified Adire Alignment? Download LspCAD and play around with different tunings with the box you've got. You can also see what it looks like sealed, if you want.

    JKS
     
  3. Joseph Sabato

    Joseph Sabato Stunt Coordinator

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    Vince,

    From your dimensions, you have a 218 L cabinet before subtracting braces etc. 237L models as a bessel alignment (Q=.577) which will give you real tight bass. Although you are a little undersized, stuffing the cabinet with polyfill will give the "appearance" of a bigger cabinet, and it should work quite well. I have a 120L sealed Tempest (Q=.707) which works very well, I have another one on the way (should arrive on Monday) and I will either clone my first (using old AR cabinets) or go the Infinite Baffle route if I can convince my wife to let me cut a hole in the wall. Good luck with your project!
     
  4. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Thanks for the replies.Yes, I don't want ported.I just want a sealed subwoofer, albeit quite large, that will be exquisite for music, as well as for movies.Thats why I want the very large size.

    Could you please tell me what type of extension I would be looking at? Ie, how low in-room? Thanks.
     
  5. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Just for clarification, these dimensions are WITHOUT the driver, the amp or the braces.Actually, I'm not sure what the volume of this enclosure is.I'm not sure what cubic size this enclosure is, but I'm guess around 7 cu feet.

    Is there anything inherently wrong with using a sealed subwoofer at this size with a single Tempest? Or is it the best sized enclosure for a sealed Tempest? The enclosure is already build save for the few extra things I need.I repeat, I repeat, a ported subwoofer is not an option.I only want sealed chacteristics.About the stuffing, I'm not sure how much would effect anything, the tuning frequency etc?
     
  6. Jack Gilvey

    Jack Gilvey Producer

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    Out of curiosity, how did you arrive at this size box while having none of the anwers to the questions you're asking?


    And they would be (in your experience)? I repeat, I repeat, it's an rather staunch position you've taken with very little information.
     
  7. Joseph Sabato

    Joseph Sabato Stunt Coordinator

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    Download LSP Cad for Adire from Adire Audio's site and input the information about your box, your room and listening position etc. That will give you an idea of what kind of response you will get from the sub and at your listening position, assuming your room is rectangular and without a sloped ceiling. How low you go in room is highly dependent on the size of the room, the sub's location and the seating location; it is impossible to get an answer without modeling it.
     
  8. Frank Carter

    Frank Carter Screenwriter

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    Stuffing makes the woofer act like it's in a larger box and there is no tuning frequency in a sealed box.
     
  9. ThomasW

    ThomasW Cinematographer

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    Oops wrong...the tuning frequency can be measured with the same method as is used to test a ported box. The difference is that instead of a dip in voltage at the tuning frequency there is a spike.
     
  10. Frank Carter

    Frank Carter Screenwriter

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    I knew that I just wasn't thinking...I'm just so set on thinking tuning frequency = port tuning.

    What actually happens with a sealed sub at this point?
     
  11. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    By the looks of your comment, you sound aggitated.You shouldn't assume that I have little information about the sound of the subwoofer that I'm looking for.First, I've heard many ported designs.I just don't like the sound of ported subwoofers.

    There are drawbacks with each design, and I still enjoy sealed more.The transient response is not up to the standards of a big sealed box, IMO.I have friends that have built DIY subwoofers, and the bass is noticeably cleaner and more natural sounding that the ported variations that I've heard, both DIY and commercial.

    Thats not to say that you can't built a great ported box, but a sealed box is far easier to build, while still granting you the excellent characteristics that sealed designs are known for.

    I just want a sealed design thats all.I'm also trying to play safe as it were.

    Can anyone be so kind and find out what the tuning frequency would be in this size enclosure.The in-room response as well.Again, thanks for your comments guys.
     
  12. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Guys, just for further help regarding the enclosure size, I emailed Adire.

    The response is as follows(hope I am allowed to post this?)

    "It's overly large - for a sealed box Tempest, we typically don't recommend over 5 cubic feet, since larger doesn't audibly increase bass tightness, and doesn't gain you any more extension. In other words, there's a point of diminishing returns, beyond which you gain nothing from the larger box.

    The 8 cubic foot box would have an F3 of 36 Hz; a 5 cubic foot box would have an F3 of 35 Hz
    "

    Now I'm just confused.The enclosure size is fixed, and I have no desire of going ported.That doesn't mean that ported wouldn't be good, as I'm sure that it would be exceptional, but ported enclosures have drawbacks, just like sealed enclosures have drawbacks.I want to use a high excursion Tempest, and actually, I was thinking of using the Maelstrom but the enclosure is already 18" wide so that won't be able work.

    About the F3 of 36hz, isn't that a little high? Why would a smaller enclosure, as stated above, produce a slightly lower F3? What type of in-room response would I get in this enclosure? I was thinking around 16-18hz extension, is that more or less what the extension would be like, or am I missing some details? Thanks again for the responses.
     
  13. Dan Hine

    Dan Hine Screenwriter

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    Not for sealed designs. In fact, that's pretty good for a sealed enclosure. To be quite honest you went about this 100% backwards. You should have designed your box around your woofer...not built a box and hope the woofer works for it. As for the frequency response in YOUR room, well that is pretty much impossible to tell since all rooms are different. You could have dips where someone else has peaks and vice versa.

    Vince, winISD is FREE. How come you haven't downloaded it?

    - Dan Hine
     
  14. GrahamT

    GrahamT Supporting Actor

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    "Oops wrong...the tuning frequency can be measured with the same method as is used to test a ported box. The difference is that instead of a dip in voltage at the tuning frequency there is a spike."

    I think you meant impedance, not voltage.
     
  15. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    You know, I am an idiot[​IMG].Some of you guys have built large sealed subwoofers with Tempests, and I thought that using a big enough enclosure would improve performance -- transient response, low bass performance.

    I had time to waste, so I just started building a large enclosure.I understand that I should have used proper software.All that I really wanted to know was if my enclosure dimensions were okay, and it seems like its marvelous for the application that I would like to use it for.I'll try to download this program, and mess around with it.

    BTW, does anyone have a ballpark figure at what type of low frequency extension this subwoofer would put out? My room is just a rectangle, 3000 cubic feet in size.I don't expect a pinpoint answer.

    Once again, thanks for replies.
     
  16. Dan Hine

    Dan Hine Screenwriter

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    Well, as Adire said you have and F3 of about 36hz. So in room response..hmmm...probably useable response down to around 20hz or so (that's the approx. F10). But, if I understand things correctly, since that is your F10, if you get it to a usable level then freqs up around 35hz and higher will be 10db louder which may drive you nuts! Maybe I'm wrong...

    Definitely consider getting some type of EQ in there too.

    - Dan Hine
     
  17. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Thanks for your help.
     
  18. Jack Gilvey

    Jack Gilvey Producer

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  19. Vaughan Odendaal

    Vaughan Odendaal Second Unit

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    Guys, I just downloaded WinISD 0.44.Very interesting program to be sure.

    I have some questions.I added my Vb of 210 L, but the program gives the optimum size to be 25" W X 39" H X 15" D! That is different to my 27" H X 18 W" X 32" D.My dimensions are the external measurements.Its already made with 1" thick MDF, with a 2" front baffle.Stupid question time: Does it matter that the width of the programs optimum size is much bigger than mine, considering that my existing enclosure makes up for it in the depth area? Or is the end overall size regardless of whether the program calculates in different proportions the main consideration? Just want to be completely sure.

    Another question, does WinISD calculate SPL with room gain, or is it strictly an anechoic response? At 20hz, it gives me 95db's.This output level is at 3 metres away, with 300 watts of power.Is that good or not?

    I'm still not sure what type of extension I would expect in my 3000 cubic foot room.I want extension to at least 20hz, but if at all possible, to around 17hz.

    Am I doing something wrong here? You guys have already told me that my enclosure size is very good for a sealed subwoofer.I take it because its not everyday that you see a sealed enclosure at almost 8ft.Given that I have provided the dimensions of my subwoofer enclosure, should I now get the driver, make the driver cutouts and purchase the amplifier and expect brilliant sound? Is there anything more that I must do?

    Another question that I have is about the stuffing.I now understand that stuffing will increase the apparent size of the enclosure.Can I just use the inside of pillow stuffings for this, or do I need to buy other stuff? Generally, how much would you guys recommend me to use in this size enclosure? Again, I would like to have 20hz extension but preferably lower for movies and music.Are things okay at present, or are there details that I'm missing? Thank you very much for your time guys!
     
  20. ThomasW

    ThomasW Cinematographer

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    One can use the same technique for a sealed sub; but instead of a dip in the measured voltage there will be a spike at the tuning point.
     

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