DIY Subwoofer Enclosure Help

Discussion in 'Archived Threads 2001-2004' started by Robert N., Sep 16, 2002.

  1. Robert N.

    Robert N. Auditioning

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    I'm a regular over at www.caraudioforum.com
    I'm planning a very simple home theatre setup for either my basement or my room...I haven't decided yet...
    In any case, I'm going to have a Cerwin Vega! VEGA car audio sub lying around after I get done messing around with it in a SPL box for my car...just for kicks...when I get bored with that I want to use it for my HT...now..I know it isn't the best type of woofer for a home theatre but I think it might do the job well enough...I'd like to couple it with a plate amp...maybe from partsexpress or adire audio...if the VEGA just doesn't work at all I might sell it later and replace it with a Shiva or Tempest...
    I'm looking for some help on the enclosure design for my VEGA...I know how to design a box well enough, as I am from the car audio realm...but I'm not sure what kind of tuning freq is good for HT...I'm new to all this, could someone please help??
     
  2. Robert N.

    Robert N. Auditioning

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    Could someone please help me??
     
  3. Cees Alons

    Cees Alons Moderator
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    Robert,
    Welcome to the forum. No need to bump up your post so soon. You will get help, eventually!
    The optimal tuning frequency of a ported sub is mainly determined by the characteristics of the driver. So an important question to start with is: which driver do you have exactly? Do you know the T-S parameters of that driver?
    From there you could give it a start by using a program like, say, WinISD.
    Have a good start!
    Cees
     
  4. Robert N.

    Robert N. Auditioning

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    Sorry, CAF's quick responce time has spoiled me [​IMG]
    In any case, I do have Win ISD and I do know how to use it fairly well...
    Problem is, I'm really not sure the kind of responce is optimal for a Home Theatre subwoofer...I'll post what peramiters I have in a minute...let me dig them up...
     
  5. Robert N.

    Robert N. Auditioning

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    Okay, I got those peramiters:

    This is all that Cerwin Vega has on file...

    VEGA 124 Specifications

    Diameter: 12”

    Number of Voice Coils: 1

    Sensitivity(1W @ 1m): 94DB

    RMS Power Handling: 400 Wrms

    Frequency Response: 20-500hz

    Nominal Impendence: 4ohms

    Voice Coil Diameter: 3.0”

    Mounting Diameter: 11” (278.4mm)

    Mounting Depth: 5.625” (142.9mm)


    T/S Parameters

    Fs 23hz
    Qts 0.330
    Qms 4.31
    Qes 0.358
    Vas 2.85 cubic feet
    Xmax 19mm
    Revc 3.3ohms
    Volume Displacement: .13 cubic feet


    Any ideas?
     
  6. Wayne A. Pflughaupt

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    Robert,
    I suggest re-posting your topic at the
    DIY and Advanced Projects section of this forum. A lot of DIY speaker building-types hang out there, and they’ll be glad to point you in the right direction.
    Regards,
    Wayne A. Pflughaupt
     
  7. Robert N.

    Robert N. Auditioning

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    Hello, I'm new to this forum...but I'm a regular over at www.caraudioforum.com so...I'm not exactly a newbie to DIY enclosures...
    Problem is, I'm not sure what type of enclosure is optimal for HT use...I plan to have a Cerwin Vega! VEGA subwoofer lying around after I get done playing with it in a SPL enclosure, seeing what it can do...I would like to take it and use it as a HT sub...I know it's not the best type of woofer for this situation...but...I work with what I've got, as I'm poor [​IMG]
    So, I could really use some suggestions, I do have the specs for the woofer and I do know how to use Win ISD fairly well...I'll post the specs and maybe someone can help me with some kind of rough layout or something? Any help would be appriciated
    VEGA 124 Specifications
    Diameter: 12”
    Number of Voice Coils: 1
    Sensitivity(1W @ 1m): 94DB
    RMS Power Handling: 400 Wrms
    Frequency Response: 20-500hz
    Nominal Impendence: 4ohms
    Voice Coil Diameter: 3.0”
    Mounting Diameter: 11” (278.4mm)
    Mounting Depth: 5.625” (142.9mm)
    T/S Parameters
    Fs 23hz
    Qts 0.330
    Qms 4.31
    Qes 0.358
    Vas 2.85 cubic feet
    Xmax 19mm
    Revc 3.3ohms
    Volume Displacement: .13 cubic feet
    I might end up with the 15" version, I'm not sure yet...but for arguments sake lets assume I go with this 12" version...I plan to power it with a Plate amp from Adire or Partsexpress...unless someone has a better (cheaper [​IMG] ) idea??
    Thanks everyone!
     
  8. Cees Alons

    Cees Alons Moderator
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    Robert,
    Low is better in this case [​IMG].
    But I'm not sure how large your cabinet can be.
    Personally, I think I would try to tune that one to 20.80Hz (will need a volume of approx. 4 cubic feet).
    If that cabinet would be too large for you, you could try tuning to 23.6 and use a volume of 2.5 cubic feet.
    Disclaimer: I hope I converted your cubic feet well to the liters and meters units I'm used to, and back (1 feet = 3.048 liters - that's what I used).
    Cees
     
  9. Robert N.

    Robert N. Auditioning

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    Can anyone help me? Please??
     
  10. Cees Alons

    Cees Alons Moderator
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    Robert,

    I merged your threads into one: this one. And see my reply (originally in the other thread) above.

    Cees
     
  11. Robert N.

    Robert N. Auditioning

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    Ahhh...okay...LoL
    I was looking at it thinking "What is going on here??" [​IMG]
    Cabinet size is not any kind of a problem in my house as it can be in car audio...and I think with a 250rms plate amp there shouldn't be any kind of risk of bottoming out the driver...but...is it a good idea to tune below the woofer's Fs? I have heard that it is not recomended...perhaps this is misinformation..??
    Do you feel that this woofer will be sufficent for a home theatre application? I'd hate to spend alot of time on it and then have it end up sounding like crap...Cerwin Vega isn't exactly known for their.."Sound quality" atributes...but I will admit that I am somewhat of a basshead, as is typical in the car audio realm [​IMG]
    Hmmm...
    Any thoughts?
     
  12. Cees Alons

    Cees Alons Moderator
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    Robert,
    A 400 Watt (RMS) is very reasonable for a sub [​IMG].
    The low tuning freq. (just below the driver's own res.) will give you much more of that "thumb .. thumb". Of course the group-delay will be much higher (compared to a version with 28Hz tuning freq.), but that has never been a real problem with a typical HT application. You have the driver for "free", so why not try something grand?
    Cees
     
  13. Robert N.

    Robert N. Auditioning

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    Alrighty...
    One last question...those enclosure sizes that you recomended...are they before or after port displacment? That is going to have to be one extreamly long port for 20hz...so it's kinda important [​IMG]
     
  14. Cees Alons

    Cees Alons Moderator
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  15. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Have you modeled a sealed enclosure, looks pretty good with a 15"X12"X12" external 3/4" box with all insides damped esp with a room rise of 6dB per oct below 50Hz. This driver might be a good candidate for passive radiator as the port size gets weird. Also my software is flagging the spl as incorrect for the other T/S parameters.
     
  16. Robert N.

    Robert N. Auditioning

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    I didn't realize that a sealed enclosure was a viable option in a Home Theatre setup...so no, I hadn't modeled that up...

    Also, exactly how does a passive radiator work? I realize they are an alternative to porting but I don't understand how a desired tuning frequency is achieved...

    This is all fairly new to me, as passive radiators arn't widley used in Car Audio as they are in Home Audio for whatever reason...

    Could someone explain?
     
  17. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Here is a thread about PRs (passive radiators)
    http://www.hometheaterforum.com/htfo...threadid=95246
    Also This speaker would be an excellent candidate for a Linkwitz Transform active circuit. I am using or will be using one for a new sub that I will be building. So your next question is what the h*ll is a Linkwitz Transform circuit. It was conceived by Linkwitz of the crossover fame to be an active eq circuit for a sub woofer. A sealed sub has a slow roll off as you go down in frequency. This curve is described by the Qts of the sub/speaker/box combo. The LT (Linkwitz Transform) circuit changes the curve to a flat response of a different curve(Q). So you can use a sealed sub in a small box and have response curve like a tuned ported or PRed sub! However nothing is free you have to have the X-max and allot of power ( if you want real loud or real low ). [​IMG] An LT can be added later also. I would build a sealed sub and play around with that, esp if you have the driver! A pe plate amp would work well with the LT also I think you could get 108 dB at 20 Hz with no room gain using an LT!
     

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